@chapter Filtering Introduction
 @c man begin FILTERING INTRODUCTION
 
 Filtering in FFmpeg is enabled through the libavfilter library.
 
 Libavfilter is the filtering API of FFmpeg. It is the substitute of
 the now deprecated 'vhooks' and started as a Google Summer of Code
 project.
 
 Audio filtering integration into the main FFmpeg repository is a work in
 progress, so audio API and ABI should not be considered stable yet.
 
 In libavfilter, it is possible for filters to have multiple inputs and
 multiple outputs.
 To illustrate the sorts of things that are possible, we can
 use a complex filter graph. For example, the following one:
 
 @example
 input --> split --> fifo -----------------------> overlay --> output
             |                                        ^
             |                                        |
             +------> fifo --> crop --> vflip --------+
 @end example
 
 splits the stream in two streams, sends one stream through the crop filter
 and the vflip filter before merging it back with the other stream by
 overlaying it on top. You can use the following command to achieve this:
 
 @example
 ffmpeg -i input -vf "[in] split [T1], fifo, [T2] overlay=0:H/2 [out]; [T1] fifo, crop=iw:ih/2:0:ih/2, vflip [T2]" output
 @end example
 
 The result will be that in output the top half of the video is mirrored
 onto the bottom half.
 

 Filters are loaded using the @var{-vf} or @var{-af} option passed to

 @command{ffmpeg} or to @command{ffplay}. Filters in the same linear
 chain are separated by commas. In our example, @var{split, fifo,
 overlay} are in one linear chain, and @var{fifo, crop, vflip} are in
 another. The points where the linear chains join are labeled by names
 enclosed in square brackets. In our example, that is @var{[T1]} and

 @var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points

 where video is input and output.
 
 Some filters take in input a list of parameters: they are specified

 after the filter name and an equal sign, and are separated from each other
 by a colon.

 There exist so-called @var{source filters} that do not have an
 audio/video input, and @var{sink filters} that will not have audio/video
 output.

 
 @c man end FILTERING INTRODUCTION
 
 @chapter graph2dot
 @c man begin GRAPH2DOT
 
 The @file{graph2dot} program included in the FFmpeg @file{tools}
 directory can be used to parse a filter graph description and issue a
 corresponding textual representation in the dot language.
 
 Invoke the command:
 @example
 graph2dot -h
 @end example
 
 to see how to use @file{graph2dot}.
 
 You can then pass the dot description to the @file{dot} program (from
 the graphviz suite of programs) and obtain a graphical representation
 of the filter graph.
 
 For example the sequence of commands:
 @example
 echo @var{GRAPH_DESCRIPTION} | \
 tools/graph2dot -o graph.tmp && \
 dot -Tpng graph.tmp -o graph.png && \
 display graph.png
 @end example
 
 can be used to create and display an image representing the graph

 described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be
 a complete self-contained graph, with its inputs and outputs explicitly defined.
 For example if your command line is of the form:
 @example
 ffmpeg -i infile -vf scale=640:360 outfile
 @end example
 your @var{GRAPH_DESCRIPTION} string will need to be of the form:
 @example
 nullsrc,scale=640:360,nullsink
 @end example
 you may also need to set the @var{nullsrc} parameters and add a @var{format}
 filter in order to simulate a specific input file.

 
 @c man end GRAPH2DOT
 

 @chapter Filtergraph description
 @c man begin FILTERGRAPH DESCRIPTION
 
 A filtergraph is a directed graph of connected filters. It can contain
 cycles, and there can be multiple links between a pair of
 filters. Each link has one input pad on one side connecting it to one
 filter from which it takes its input, and one output pad on the other
 side connecting it to the one filter accepting its output.
 
 Each filter in a filtergraph is an instance of a filter class
 registered in the application, which defines the features and the
 number of input and output pads of the filter.
 
 A filter with no input pads is called a "source", a filter with no
 output pads is called a "sink".
 

 @anchor{Filtergraph syntax}

 @section Filtergraph syntax
 

 A filtergraph can be represented using a textual representation, which is
 recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}

 options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the

 @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in

 @file{libavfilter/avfiltergraph.h}.

 
 A filterchain consists of a sequence of connected filters, each one
 connected to the previous one in the sequence. A filterchain is
 represented by a list of ","-separated filter descriptions.
 
 A filtergraph consists of a sequence of filterchains. A sequence of
 filterchains is represented by a list of ";"-separated filterchain
 descriptions.
 
 A filter is represented by a string of the form:
 [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
 
 @var{filter_name} is the name of the filter class of which the
 described filter is an instance of, and has to be the name of one of
 the filter classes registered in the program.
 The name of the filter class is optionally followed by a string
 "=@var{arguments}".
 
 @var{arguments} is a string which contains the parameters used to
 initialize the filter instance, and are described in the filter
 descriptions below.
 
 The list of arguments can be quoted using the character "'" as initial
 and ending mark, and the character '\' for escaping the characters
 within the quoted text; otherwise the argument string is considered
 terminated when the next special character (belonging to the set
 "[]=;,") is encountered.
 
 The name and arguments of the filter are optionally preceded and
 followed by a list of link labels.
 A link label allows to name a link and associate it to a filter output
 or input pad. The preceding labels @var{in_link_1}
 ... @var{in_link_N}, are associated to the filter input pads,
 the following labels @var{out_link_1} ... @var{out_link_M}, are
 associated to the output pads.
 
 When two link labels with the same name are found in the
 filtergraph, a link between the corresponding input and output pad is
 created.
 
 If an output pad is not labelled, it is linked by default to the first
 unlabelled input pad of the next filter in the filterchain.
 For example in the filterchain:
 @example
 nullsrc, split[L1], [L2]overlay, nullsink
 @end example
 the split filter instance has two output pads, and the overlay filter
 instance two input pads. The first output pad of split is labelled
 "L1", the first input pad of overlay is labelled "L2", and the second
 output pad of split is linked to the second input pad of overlay,
 which are both unlabelled.
 
 In a complete filterchain all the unlabelled filter input and output
 pads must be connected. A filtergraph is considered valid if all the
 filter input and output pads of all the filterchains are connected.
 

 Libavfilter will automatically insert scale filters where format
 conversion is required. It is possible to specify swscale flags
 for those automatically inserted scalers by prepending
 @code{sws_flags=@var{flags};}
 to the filtergraph description.
 

 Follows a BNF description for the filtergraph syntax:
 @example
 @var{NAME}             ::= sequence of alphanumeric characters and '_'
 @var{LINKLABEL}        ::= "[" @var{NAME} "]"
 @var{LINKLABELS}       ::= @var{LINKLABEL} [@var{LINKLABELS}]
 @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
 @var{FILTER}           ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]
 @var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]

 @var{FILTERGRAPH}      ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]

 @end example
 
 @c man end FILTERGRAPH DESCRIPTION
 

 @chapter Audio Filters
 @c man begin AUDIO FILTERS
 

 When you configure your FFmpeg build, you can disable any of the

 existing filters using @code{--disable-filters}.

 The configure output will show the audio filters included in your
 build.
 
 Below is a description of the currently available audio filters.
 

 @section aconvert
 
 Convert the input audio format to the specified formats.
 
 The filter accepts a string of the form:

 "@var{sample_format}:@var{channel_layout}".

 @var{sample_format} specifies the sample format, and can be a string or the
 corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p'
 suffix for a planar sample format.

 
 @var{channel_layout} specifies the channel layout, and can be a string

 or the corresponding number value defined in @file{libavutil/audioconvert.h}.

 
 The special parameter "auto", signifies that the filter will
 automatically select the output format depending on the output filter.
 
 Some examples follow.
 
 @itemize
 @item

 Convert input to float, planar, stereo:

 @example

 aconvert=fltp:stereo

 @end example
 
 @item

 Convert input to unsigned 8-bit, automatically select out channel layout:

 @example

 aconvert=u8:auto

 @end example
 @end itemize
 

 @section aformat
 
 Convert the input audio to one of the specified formats. The framework will
 negotiate the most appropriate format to minimize conversions.
 
 The filter accepts the following named parameters:
 @table @option
 
 @item sample_fmts
 A comma-separated list of requested sample formats.
 
 @item sample_rates
 A comma-separated list of requested sample rates.
 
 @item channel_layouts
 A comma-separated list of requested channel layouts.
 
 @end table
 
 If a parameter is omitted, all values are allowed.
 
 For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
 @example
 aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo
 @end example
 

 @section amerge
 

 Merge two or more audio streams into a single multi-channel stream.

 The filter accepts the following named options:
 
 @table @option
 
 @item inputs
 Set the number of inputs. Default is 2.
 
 @end table

 
 If the channel layouts of the inputs are disjoint, and therefore compatible,
 the channel layout of the output will be set accordingly and the channels
 will be reordered as necessary. If the channel layouts of the inputs are not
 disjoint, the output will have all the channels of the first input then all
 the channels of the second input, in that order, and the channel layout of
 the output will be the default value corresponding to the total number of
 channels.
 
 For example, if the first input is in 2.1 (FL+FR+LF) and the second input
 is FC+BL+BR, then the output will be in 5.1, with the channels in the
 following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
 first input, b1 is the first channel of the second input).
 
 On the other hand, if both input are in stereo, the output channels will be
 in the default order: a1, a2, b1, b2, and the channel layout will be
 arbitrarily set to 4.0, which may or may not be the expected value.
 

 All inputs must have the same sample rate, and format.

 
 If inputs do not have the same duration, the output will stop with the
 shortest.
 
 Example: merge two mono files into a stereo stream:
 @example
 amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
 @end example
 

 Example: multiple merges:

 @example
 ffmpeg -f lavfi -i "
 amovie=input.mkv:si=0 [a0];
 amovie=input.mkv:si=1 [a1];
 amovie=input.mkv:si=2 [a2];
 amovie=input.mkv:si=3 [a3];
 amovie=input.mkv:si=4 [a4];
 amovie=input.mkv:si=5 [a5];

 [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv

 @end example
 

 @section amix
 
 Mixes multiple audio inputs into a single output.
 
 For example
 @example

 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT

 @end example
 will mix 3 input audio streams to a single output with the same duration as the
 first input and a dropout transition time of 3 seconds.
 
 The filter accepts the following named parameters:
 @table @option
 
 @item inputs
 Number of inputs. If unspecified, it defaults to 2.
 
 @item duration
 How to determine the end-of-stream.
 @table @option
 
 @item longest
 Duration of longest input. (default)
 
 @item shortest
 Duration of shortest input.
 
 @item first
 Duration of first input.
 
 @end table
 
 @item dropout_transition
 Transition time, in seconds, for volume renormalization when an input
 stream ends. The default value is 2 seconds.
 
 @end table
 

 @section anull
 
 Pass the audio source unchanged to the output.
 

 @section aresample
 
 Resample the input audio to the specified sample rate.
 
 The filter accepts exactly one parameter, the output sample rate. If not
 specified then the filter will automatically convert between its input
 and output sample rates.
 
 For example, to resample the input audio to 44100Hz:
 @example
 aresample=44100
 @end example
 

 @section asetnsamples
 
 Set the number of samples per each output audio frame.
 
 The last output packet may contain a different number of samples, as
 the filter will flush all the remaining samples when the input audio
 signal its end.
 
 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
 separated by ":".
 
 @table @option
 
 @item nb_out_samples, n
 Set the number of frames per each output audio frame. The number is
 intended as the number of samples @emph{per each channel}.
 Default value is 1024.
 
 @item pad, p
 If set to 1, the filter will pad the last audio frame with zeroes, so
 that the last frame will contain the same number of samples as the
 previous ones. Default value is 1.
 @end table
 
 For example, to set the number of per-frame samples to 1234 and
 disable padding for the last frame, use:
 @example
 asetnsamples=n=1234:p=0
 @end example
 

 @section ashowinfo
 
 Show a line containing various information for each input audio frame.
 The input audio is not modified.
 
 The shown line contains a sequence of key/value pairs of the form
 @var{key}:@var{value}.
 
 A description of each shown parameter follows:
 
 @table @option
 @item n
 sequential number of the input frame, starting from 0
 
 @item pts
 presentation TimeStamp of the input frame, expressed as a number of
 time base units. The time base unit depends on the filter input pad, and
 is usually 1/@var{sample_rate}.
 
 @item pts_time
 presentation TimeStamp of the input frame, expressed as a number of
 seconds
 
 @item pos
 position of the frame in the input stream, -1 if this information in

 unavailable and/or meaningless (for example in case of synthetic audio)

 
 @item fmt
 sample format name
 
 @item chlayout
 channel layout description
 
 @item nb_samples
 number of samples (per each channel) contained in the filtered frame
 
 @item rate
 sample rate for the audio frame
 
 @item checksum

 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame

 
 @item plane_checksum

 Adler-32 checksum (printed in hexadecimal) for each input frame plane,
 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3} @var{c4} @var{c5}
 @var{c6} @var{c7}]"

 @end table
 

 @section asplit
 

 Split input audio into several identical outputs.
 
 The filter accepts a single parameter which specifies the number of outputs. If
 unspecified, it defaults to 2.

 
 For example:
 @example

 [in] asplit [out0][out1]

 @end example
 

 will create two separate outputs from the same input.
 
 To create 3 or more outputs, you need to specify the number of
 outputs, like in:
 @example
 [in] asplit=3 [out0][out1][out2]
 @end example

 @example
 ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT

 @end example
 will create 5 copies of the input audio.
 

 @section astreamsync
 
 Forward two audio streams and control the order the buffers are forwarded.
 
 The argument to the filter is an expression deciding which stream should be
 forwarded next: if the result is negative, the first stream is forwarded; if
 the result is positive or zero, the second stream is forwarded. It can use
 the following variables:
 
 @table @var
 @item b1 b2
 number of buffers forwarded so far on each stream
 @item s1 s2
 number of samples forwarded so far on each stream
 @item t1 t2
 current timestamp of each stream
 @end table
 
 The default value is @code{t1-t2}, which means to always forward the stream
 that has a smaller timestamp.
 
 Example: stress-test @code{amerge} by randomly sending buffers on the wrong
 input, while avoiding too much of a desynchronization:
 @example
 amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
 [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
 [a2] [b2] amerge
 @end example
 

 @section atempo
 
 Adjust audio tempo.
 
 The filter accepts exactly one parameter, the audio tempo. If not
 specified then the filter will assume nominal 1.0 tempo. Tempo must
 be in the [0.5, 2.0] range.
 
 For example, to slow down audio to 80% tempo:
 @example
 atempo=0.8
 @end example
 
 For example, to speed up audio to 125% tempo:
 @example
 atempo=1.25
 @end example
 

 @section earwax
 
 Make audio easier to listen to on headphones.
 
 This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
 so that when listened to on headphones the stereo image is moved from
 inside your head (standard for headphones) to outside and in front of
 the listener (standard for speakers).
 
 Ported from SoX.
 

 @section pan
 
 Mix channels with specific gain levels. The filter accepts the output
 channel layout followed by a set of channels definitions.
 

 This filter is also designed to remap efficiently the channels of an audio
 stream.
 

 The filter accepts parameters of the form:
 "@var{l}:@var{outdef}:@var{outdef}:..."
 
 @table @option
 @item l
 output channel layout or number of channels
 
 @item outdef
 output channel specification, of the form:
 "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
 
 @item out_name
 output channel to define, either a channel name (FL, FR, etc.) or a channel
 number (c0, c1, etc.)
 
 @item gain
 multiplicative coefficient for the channel, 1 leaving the volume unchanged
 
 @item in_name
 input channel to use, see out_name for details; it is not possible to mix
 named and numbered input channels
 @end table
 
 If the `=' in a channel specification is replaced by `<', then the gains for
 that specification will be renormalized so that the total is 1, thus
 avoiding clipping noise.
 

 @subsection Mixing examples
 

 For example, if you want to down-mix from stereo to mono, but with a bigger
 factor for the left channel:
 @example
 pan=1:c0=0.9*c0+0.1*c1
 @end example
 
 A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
 7-channels surround:
 @example
 pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
 @end example
 

 Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system

 that should be preferred (see "-ac" option) unless you have very specific
 needs.
 

 @subsection Remapping examples
 
 The channel remapping will be effective if, and only if:
 
 @itemize
 @item gain coefficients are zeroes or ones,
 @item only one input per channel output,
 @end itemize
 
 If all these conditions are satisfied, the filter will notify the user ("Pure
 channel mapping detected"), and use an optimized and lossless method to do the
 remapping.
 
 For example, if you have a 5.1 source and want a stereo audio stream by
 dropping the extra channels:
 @example
 pan="stereo: c0=FL : c1=FR"
 @end example
 
 Given the same source, you can also switch front left and front right channels
 and keep the input channel layout:
 @example
 pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
 @end example
 
 If the input is a stereo audio stream, you can mute the front left channel (and
 still keep the stereo channel layout) with:
 @example
 pan="stereo:c1=c1"
 @end example
 
 Still with a stereo audio stream input, you can copy the right channel in both
 front left and right:
 @example
 pan="stereo: c0=FR : c1=FR"
 @end example
 

 @section silencedetect
 
 Detect silence in an audio stream.
 
 This filter logs a message when it detects that the input audio volume is less
 or equal to a noise tolerance value for a duration greater or equal to the
 minimum detected noise duration.
 
 The printed times and duration are expressed in seconds.
 
 @table @option
 @item duration, d
 Set silence duration until notification (default is 2 seconds).
 
 @item noise, n
 Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
 specified value) or amplitude ratio. Default is -60dB, or 0.001.
 @end table
 
 Detect 5 seconds of silence with -50dB noise tolerance:
 @example
 silencedetect=n=-50dB:d=5
 @end example
 
 Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
 tolerance in @file{silence.mp3}:
 @example
 ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
 @end example
 

 @section volume
 
 Adjust the input audio volume.
 
 The filter accepts exactly one parameter @var{vol}, which expresses

 how the audio volume will be increased or decreased.

 
 Output values are clipped to the maximum value.
 

 If @var{vol} is expressed as a decimal number, the output audio

 volume is given by the relation:
 @example
 @var{output_volume} = @var{vol} * @var{input_volume}
 @end example
 
 If @var{vol} is expressed as a decimal number followed by the string
 "dB", the value represents the requested change in decibels of the
 input audio power, and the output audio volume is given by the
 relation:
 @example
 @var{output_volume} = 10^(@var{vol}/20) * @var{input_volume}
 @end example
 
 Otherwise @var{vol} is considered an expression and its evaluated
 value is used for computing the output audio volume according to the
 first relation.
 
 Default value for @var{vol} is 1.0.
 
 @subsection Examples
 
 @itemize
 @item
 Half the input audio volume:
 @example
 volume=0.5
 @end example
 
 The above example is equivalent to:
 @example
 volume=1/2
 @end example
 
 @item
 Decrease input audio power by 12 decibels:
 @example
 volume=-12dB
 @end example
 @end itemize
 

 @section volumedetect
 
 Detect the volume of the input video.
 
 The filter has no parameters. The input is not modified. Statistics about
 the volume will be printed in the log when the input stream end is reached.
 
 In particular it will show the mean volume (root mean square), maximum
 volume (on a per-sample basis), and the beginning of an histogram of the
 registered volume values (from the maximum value to a cumulated 1/1000 of
 the samples).
 
 All volumes are in decibels relative to the maximum PCM value.
 
 Here is an excerpt of the output:
 @example
 [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
 [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
 [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
 @end example
 
 It means that:
 @itemize
 @item
 The mean square energy is approximately -27 dB, or 10^-2.7.
 @item
 The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
 @item
 There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
 @end itemize
 
 In other words, raising the volume by +4 dB does not cause any clipping,
 raising it by +5 dB causes clipping for 6 samples, etc.
 

 @section asyncts
 Synchronize audio data with timestamps by squeezing/stretching it and/or
 dropping samples/adding silence when needed.
 
 The filter accepts the following named parameters:
 @table @option
 
 @item compensate

 Enable stretching/squeezing the data to make it match the timestamps. Disabled
 by default. When disabled, time gaps are covered with silence.

 
 @item min_delta
 Minimum difference between timestamps and audio data (in seconds) to trigger

 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
 this filter, try setting this parameter to 0.

 
 @item max_comp

 Maximum compensation in samples per second. Relevant only with compensate=1.
 Default value 500.

 @item first_pts
 Assume the first pts should be this value.
 This allows for padding/trimming at the start of stream. By default, no
 assumption is made about the first frame's expected pts, so no padding or
 trimming is done. For example, this could be set to 0 to pad the beginning with
 silence if an audio stream starts after the video stream.
 

 @end table
 

 @section channelsplit
 Split each channel in input audio stream into a separate output stream.
 
 This filter accepts the following named parameters:
 @table @option
 @item channel_layout
 Channel layout of the input stream. Default is "stereo".
 @end table
 
 For example, assuming a stereo input MP3 file
 @example

 ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv

 @end example
 will create an output Matroska file with two audio streams, one containing only
 the left channel and the other the right channel.
 
 To split a 5.1 WAV file into per-channel files
 @example

 ffmpeg -i in.wav -filter_complex

 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
 side_right.wav
 @end example
 

 @section channelmap
 Remap input channels to new locations.
 
 This filter accepts the following named parameters:
 @table @option
 @item channel_layout
 Channel layout of the output stream.
 
 @item map
 Map channels from input to output. The argument is a comma-separated list of
 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
 @var{in_channel} form. @var{in_channel} can be either the name of the input
 channel (e.g. FL for front left) or its index in the input channel layout.
 @var{out_channel} is the name of the output channel or its index in the output
 channel layout. If @var{out_channel} is not given then it is implicitly an
 index, starting with zero and increasing by one for each mapping.
 @end table
 
 If no mapping is present, the filter will implicitly map input channels to
 output channels preserving index.
 
 For example, assuming a 5.1+downmix input MOV file
 @example

 ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav

 @end example
 will create an output WAV file tagged as stereo from the downmix channels of
 the input.
 
 To fix a 5.1 WAV improperly encoded in AAC's native channel order
 @example

 ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav

 @end example
 

 @section join
 Join multiple input streams into one multi-channel stream.
 
 The filter accepts the following named parameters:
 @table @option
 
 @item inputs
 Number of input streams. Defaults to 2.
 
 @item channel_layout
 Desired output channel layout. Defaults to stereo.
 
 @item map
 Map channels from inputs to output. The argument is a comma-separated list of
 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}

 can be either the name of the input channel (e.g. FL for front left) or its

 index in the specified input stream. @var{out_channel} is the name of the output
 channel.
 @end table
 
 The filter will attempt to guess the mappings when those are not specified
 explicitly. It does so by first trying to find an unused matching input channel
 and if that fails it picks the first unused input channel.
 
 E.g. to join 3 inputs (with properly set channel layouts)
 @example

 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT

 @end example
 
 To build a 5.1 output from 6 single-channel streams:
 @example

 ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex

 'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE'
 out
 @end example
 

 @section resample
 Convert the audio sample format, sample rate and channel layout. This filter is

 not meant to be used directly.

 @c man end AUDIO FILTERS
 

 @chapter Audio Sources
 @c man begin AUDIO SOURCES
 
 Below is a description of the currently available audio sources.
 

 @section abuffer
 
 Buffer audio frames, and make them available to the filter chain.
 
 This source is mainly intended for a programmatic use, in particular
 through the interface defined in @file{libavfilter/asrc_abuffer.h}.
 
 It accepts the following mandatory parameters:

 @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}

 
 @table @option
 
 @item sample_rate
 The sample rate of the incoming audio buffers.
 
 @item sample_fmt
 The sample format of the incoming audio buffers.
 Either a sample format name or its corresponging integer representation from
 the enum AVSampleFormat in @file{libavutil/samplefmt.h}
 
 @item channel_layout
 The channel layout of the incoming audio buffers.
 Either a channel layout name from channel_layout_map in
 @file{libavutil/audioconvert.c} or its corresponding integer representation
 from the AV_CH_LAYOUT_* macros in @file{libavutil/audioconvert.h}
 
 @end table
 
 For example:
 @example

 abuffer=44100:s16p:stereo

 @end example
 
 will instruct the source to accept planar 16bit signed stereo at 44100Hz.

 Since the sample format with name "s16p" corresponds to the number
 6 and the "stereo" channel layout corresponds to the value 0x3, this is

 equivalent to:
 @example

 abuffer=44100:6:0x3

 @end example
 

 @section aevalsrc
 
 Generate an audio signal specified by an expression.
 
 This source accepts in input one or more expressions (one for each
 channel), which are evaluated and used to generate a corresponding
 audio signal.
 
 It accepts the syntax: @var{exprs}[::@var{options}].
 @var{exprs} is a list of expressions separated by ":", one for each

 separate channel. In case the @var{channel_layout} is not
 specified, the selected channel layout depends on the number of
 provided expressions.

 
 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
 separated by ":".
 
 The description of the accepted options follows.
 
 @table @option
 

 @item channel_layout, c
 Set the channel layout. The number of channels in the specified layout
 must be equal to the number of specified expressions.
 

 @item duration, d
 Set the minimum duration of the sourced audio. See the function
 @code{av_parse_time()} for the accepted format.
 Note that the resulting duration may be greater than the specified
 duration, as the generated audio is always cut at the end of a
 complete frame.
 
 If not specified, or the expressed duration is negative, the audio is
 supposed to be generated forever.
 

 @item nb_samples, n
 Set the number of samples per channel per each output frame,
 default to 1024.
 
 @item sample_rate, s
 Specify the sample rate, default to 44100.
 @end table
 
 Each expression in @var{exprs} can contain the following constants:
 
 @table @option
 @item n
 number of the evaluated sample, starting from 0
 
 @item t
 time of the evaluated sample expressed in seconds, starting from 0
 
 @item s
 sample rate
 
 @end table
 
 @subsection Examples
 
 @itemize
 
 @item
 Generate silence:
 @example
 aevalsrc=0
 @end example
 
 @item
 

 Generate a sin signal with frequency of 440 Hz, set sample rate to

 8000 Hz:
 @example
 aevalsrc="sin(440*2*PI*t)::s=8000"
 @end example
 
 @item

 Generate a two channels signal, specify the channel layout (Front
 Center + Back Center) explicitly:
 @example
 aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
 @end example
 
 @item

 Generate white noise:
 @example
 aevalsrc="-2+random(0)"
 @end example
 
 @item
 Generate an amplitude modulated signal:
 @example
 aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
 @end example
 
 @item
 Generate 2.5 Hz binaural beats on a 360 Hz carrier:
 @example

 aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"

 @end example
 
 @end itemize
 

 @section anullsrc
 

 Null audio source, return unprocessed audio frames. It is mainly useful
 as a template and to be employed in analysis / debugging tools, or as
 the source for filters which ignore the input data (for example the sox
 synth filter).

 It accepts an optional sequence of @var{key}=@var{value} pairs,
 separated by ":".

 The description of the accepted options follows.
 
 @table @option

 @item sample_rate, s
 Specify the sample rate, and defaults to 44100.
 
 @item channel_layout, cl
 
 Specify the channel layout, and can be either an integer or a string
 representing a channel layout. The default value of @var{channel_layout}
 is "stereo".

 
 Check the channel_layout_map definition in

 @file{libavcodec/audioconvert.c} for the mapping between strings and
 channel layout values.

 
 @item nb_samples, n
 Set the number of samples per requested frames.
 

 @end table

 
 Follow some examples:
 @example

 #  set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
 anullsrc=r=48000:cl=4

 
 # same as

 anullsrc=r=48000:cl=mono

 @end example
 

 @section abuffer
 Buffer audio frames, and make them available to the filter chain.
 
 This source is not intended to be part of user-supplied graph descriptions but
 for insertion by calling programs through the interface defined in
 @file{libavfilter/buffersrc.h}.
 
 It accepts the following named parameters:
 @table @option
 
 @item time_base
 Timebase which will be used for timestamps of submitted frames. It must be
 either a floating-point number or in @var{numerator}/@var{denominator} form.
 
 @item sample_rate
 Audio sample rate.
 
 @item sample_fmt
 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
 
 @item channel_layout
 Channel layout of the audio data, in the form that can be accepted by
 @code{av_get_channel_layout()}.
 @end table
 
 All the parameters need to be explicitly defined.
 

 @section flite
 
 Synthesize a voice utterance using the libflite library.
 
 To enable compilation of this filter you need to configure FFmpeg with
 @code{--enable-libflite}.
 

 Note that the flite library is not thread-safe.
 

 The source accepts parameters as a list of @var{key}=@var{value} pairs,
 separated by ":".
 
 The description of the accepted parameters follows.
 
 @table @option
 
 @item list_voices
 If set to 1, list the names of the available voices and exit
 immediately. Default value is 0.
 
 @item nb_samples, n
 Set the maximum number of samples per frame. Default value is 512.
 
 @item textfile
 Set the filename containing the text to speak.
 
 @item text
 Set the text to speak.
 
 @item voice, v
 Set the voice to use for the speech synthesis. Default value is
 @code{kal}. See also the @var{list_voices} option.
 @end table
 

 @subsection Examples

 
 @itemize
 @item
 Read from file @file{speech.txt}, and synthetize the text using the
 standard flite voice:
 @example
 flite=textfile=speech.txt
 @end example
 
 @item
 Read the specified text selecting the @code{slt} voice:
 @example
 flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
 @end example
 
 @item
 Make @file{ffplay} speech the specified text, using @code{flite} and
 the @code{lavfi} device:
 @example
 ffplay -f lavfi flite='No more be grieved for which that thou hast done.'
 @end example
 @end itemize
 
 For more information about libflite, check:
 @url{http://www.speech.cs.cmu.edu/flite/}
 

 @c man end AUDIO SOURCES
 

 @chapter Audio Sinks
 @c man begin AUDIO SINKS
 
 Below is a description of the currently available audio sinks.
 

 @section abuffersink
 
 Buffer audio frames, and make them available to the end of filter chain.
 
 This sink is mainly intended for programmatic use, in particular

 through the interface defined in @file{libavfilter/buffersink.h}.

 It requires a pointer to an AVABufferSinkContext structure, which
 defines the incoming buffers' formats, to be passed as the opaque
 parameter to @code{avfilter_init_filter} for initialization.

 @section anullsink
 
 Null audio sink, do absolutely nothing with the input audio. It is
 mainly useful as a template and to be employed in analysis / debugging
 tools.
 

 @section abuffersink
 This sink is intended for programmatic use. Frames that arrive on this sink can
 be retrieved by the calling program using the interface defined in
 @file{libavfilter/buffersink.h}.
 
 This filter accepts no parameters.
 

 @c man end AUDIO SINKS
 

 @chapter Video Filters
 @c man begin VIDEO FILTERS
 

 When you configure your FFmpeg build, you can disable any of the

 existing filters using @code{--disable-filters}.

 The configure output will show the video filters included in your
 build.
 
 Below is a description of the currently available video filters.
 

 @section alphaextract
 
 Extract the alpha component from the input as a grayscale video. This
 is especially useful with the @var{alphamerge} filter.
 
 @section alphamerge
 
 Add or replace the alpha component of the primary input with the
 grayscale value of a second input. This is intended for use with
 @var{alphaextract} to allow the transmission or storage of frame
 sequences that have alpha in a format that doesn't support an alpha
 channel.
 
 For example, to reconstruct full frames from a normal YUV-encoded video
 and a separate video created with @var{alphaextract}, you might use:
 @example
 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
 @end example
 
 Since this filter is designed for reconstruction, it operates on frame
 sequences without considering timestamps, and terminates when either
 input reaches end of stream. This will cause problems if your encoding
 pipeline drops frames. If you're trying to apply an image as an
 overlay to a video stream, consider the @var{overlay} filter instead.
 

 @section ass
 
 Draw ASS (Advanced Substation Alpha) subtitles on top of input video
 using the libass library.
 
 To enable compilation of this filter you need to configure FFmpeg with
 @code{--enable-libass}.
 

 This filter accepts the syntax: @var{ass_filename}[:@var{options}],
 where @var{ass_filename} is the filename of the ASS file to read, and
 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
 separated by ":".
 
 A description of the accepted options follows.
 
 @table @option

 @item original_size
 Specifies the size of the original video, the video for which the ASS file
 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
 necessary to correctly scale the fonts if the aspect ratio has been changed.

 @end table

 
 For example, to render the file @file{sub.ass} on top of the input
 video, use the command:
 @example
 ass=sub.ass
 @end example

 @section bbox
 
 Compute the bounding box for the non-black pixels in the input frame
 luminance plane.
 
 This filter computes the bounding box containing all the pixels with a
 luminance value greater than the minimum allowed value.
 The parameters describing the bounding box are printed on the filter
 log.
 

 @section blackdetect
 
 Detect video intervals that are (almost) completely black. Can be
 useful to detect chapter transitions, commercials, or invalid
 recordings. Output lines contains the time for the start, end and
 duration of the detected black interval expressed in seconds.
 
 In order to display the output lines, you need to set the loglevel at
 least to the AV_LOG_INFO value.
 
 This filter accepts a list of options in the form of
 @var{key}=@var{value} pairs separated by ":". A description of the
 accepted options follows.
 
 @table @option
 @item black_min_duration, d
 Set the minimum detected black duration expressed in seconds. It must
 be a non-negative floating point number.
 
 Default value is 2.0.
 
 @item picture_black_ratio_th, pic_th
 Set the threshold for considering a picture "black".
 Express the minimum value for the ratio:
 @example
 @var{nb_black_pixels} / @var{nb_pixels}
 @end example
 
 for which a picture is considered black.
 Default value is 0.98.
 
 @item pixel_black_th, pix_th
 Set the threshold for considering a pixel "black".
 
 The threshold expresses the maximum pixel luminance value for which a
 pixel is considered "black". The provided value is scaled according to
 the following equation:
 @example
 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
 @end example
 
 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
 the input video format, the range is [0-255] for YUV full-range
 formats and [16-235] for YUV non full-range formats.
 
 Default value is 0.10.
 @end table
 
 The following example sets the maximum pixel threshold to the minimum
 value, and detects only black intervals of 2 or more seconds:
 @example
 blackdetect=d=2:pix_th=0.00
 @end example

 @section blackframe
 
 Detect frames that are (almost) completely black. Can be useful to
 detect chapter transitions or commercials. Output lines consist of
 the frame number of the detected frame, the percentage of blackness,
 the position in the file if known or -1 and the timestamp in seconds.
 
 In order to display the output lines, you need to set the loglevel at
 least to the AV_LOG_INFO value.
 
 The filter accepts the syntax:
 @example
 blackframe[=@var{amount}:[@var{threshold}]]
 @end example
 
 @var{amount} is the percentage of the pixels that have to be below the
 threshold, and defaults to 98.
 
 @var{threshold} is the threshold below which a pixel value is
 considered black, and defaults to 32.
 

 @section boxblur
 
 Apply boxblur algorithm to the input video.
 
 This filter accepts the parameters:

 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}

 
 Chroma and alpha parameters are optional, if not specified they default
 to the corresponding values set for @var{luma_radius} and
 @var{luma_power}.
 
 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
 the radius in pixels of the box used for blurring the corresponding
 input plane. They are expressions, and can contain the following
 constants:
 @table @option
 @item w, h

 the input width and height in pixels

 
 @item cw, ch
 the input chroma image width and height in pixels
 
 @item hsub, vsub
 horizontal and vertical chroma subsample values. For example for the
 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
 @end table
 

 The radius must be a non-negative number, and must not be greater than

 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
 and of @code{min(cw,ch)/2} for the chroma planes.
 
 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
 how many times the boxblur filter is applied to the corresponding
 plane.
 
 Some examples follow:
 
 @itemize
 
 @item
 Apply a boxblur filter with luma, chroma, and alpha radius
 set to 2:
 @example
 boxblur=2:1
 @end example
 
 @item
 Set luma radius to 2, alpha and chroma radius to 0
 @example
 boxblur=2:1:0:0:0:0
 @end example
 
 @item
 Set luma and chroma radius to a fraction of the video dimension
 @example
 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
 @end example
 
 @end itemize
 

 @section colormatrix
 
 The colormatrix filter allows conversion between any of the following color
 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
 and FCC (@var{fcc}).
 
 The syntax of the parameters is @var{source}:@var{destination}:
 
 @example
 colormatrix=bt601:smpte240m
 @end example
 

 @section copy
 
 Copy the input source unchanged to the output. Mainly useful for
 testing purposes.
 

 @section crop
 

 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}

 The @var{keep_aspect} parameter is optional, if specified and set to a
 non-zero value will force the output display aspect ratio to be the
 same of the input, by changing the output sample aspect ratio.
 
 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
 expressions containing the following constants:

 
 @table @option
 @item x, y
 the computed values for @var{x} and @var{y}. They are evaluated for
 each new frame.
 
 @item in_w, in_h

 the input width and height

 
 @item iw, ih
 same as @var{in_w} and @var{in_h}
 
 @item out_w, out_h

 the output (cropped) width and height

 
 @item ow, oh
 same as @var{out_w} and @var{out_h}
 

 @item a
 same as @var{iw} / @var{ih}
 
 @item sar
 input sample aspect ratio
 
 @item dar
 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
 
 @item hsub, vsub
 horizontal and vertical chroma subsample values. For example for the
 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
 

 @item n
 the number of input frame, starting from 0
 
 @item pos
 the position in the file of the input frame, NAN if unknown
 
 @item t
 timestamp expressed in seconds, NAN if the input timestamp is unknown

 @end table

 The @var{out_w} and @var{out_h} parameters specify the expressions for
 the width and height of the output (cropped) video. They are
 evaluated just at the configuration of the filter.

 The default value of @var{out_w} is "in_w", and the default value of
 @var{out_h} is "in_h".

 The expression for @var{out_w} may depend on the value of @var{out_h},
 and the expression for @var{out_h} may depend on @var{out_w}, but they
 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
 evaluated after @var{out_w} and @var{out_h}.

 The @var{x} and @var{y} parameters specify the expressions for the
 position of the top-left corner of the output (non-cropped) area. They
 are evaluated for each frame. If the evaluated value is not valid, it
 is approximated to the nearest valid value.

 The default value of @var{x} is "(in_w-out_w)/2", and the default
 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
 the center of the input image.
 
 The expression for @var{x} may depend on @var{y}, and the expression
 for @var{y} may depend on @var{x}.
 
 Follow some examples:

 @example

 # crop the central input area with size 100x100
 crop=100:100
 
 # crop the central input area with size 2/3 of the input video
 "crop=2/3*in_w:2/3*in_h"
 
 # crop the input video central square
 crop=in_h
 
 # delimit the rectangle with the top-left corner placed at position
 # 100:100 and the right-bottom corner corresponding to the right-bottom
 # corner of the input image.
 crop=in_w-100:in_h-100:100:100

 # crop 10 pixels from the left and right borders, and 20 pixels from

 # the top and bottom borders
 "crop=in_w-2*10:in_h-2*20"

 # keep only the bottom right quarter of the input image
 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
 
 # crop height for getting Greek harmony
 "crop=in_w:1/PHI*in_w"
 
 # trembling effect
 "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
 

 # erratic camera effect depending on timestamp

 "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
 
 # set x depending on the value of y
 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
 @end example

 @section cropdetect
 
 Auto-detect crop size.
 
 Calculate necessary cropping parameters and prints the recommended
 parameters through the logging system. The detected dimensions
 correspond to the non-black area of the input video.
 
 It accepts the syntax:
 @example

 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]

 @end example
 
 @table @option
 
 @item limit
 Threshold, which can be optionally specified from nothing (0) to
 everything (255), defaults to 24.
 
 @item round
 Value which the width/height should be divisible by, defaults to
 16. The offset is automatically adjusted to center the video. Use 2 to
 get only even dimensions (needed for 4:2:2 video). 16 is best when
 encoding to most video codecs.
 
 @item reset
 Counter that determines after how many frames cropdetect will reset
 the previously detected largest video area and start over to detect
 the current optimal crop area. Defaults to 0.
 
 This can be useful when channel logos distort the video area. 0
 indicates never reset and return the largest area encountered during
 playback.
 @end table
 

 @section decimate
 
 This filter drops frames that do not differ greatly from the previous
 frame in order to reduce framerate.  The main use of this filter is
 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
 it could in theory be used for fixing movies that were
 inverse-telecined incorrectly.
 
 It accepts the following parameters:
 @var{max}:@var{hi}:@var{lo}:@var{frac}.
 
 @table @option
 
 @item max
 Set the maximum number of consecutive frames which can be dropped (if
 positive), or the minimum interval between dropped frames (if
 negative). If the value is 0, the frame is dropped unregarding the
 number of previous sequentially dropped frames.
 
 Default value is 0.
 
 @item hi, lo, frac
 Set the dropping threshold values.
 
 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
 represent actual pixel value differences, so a threshold of 64
 corresponds to 1 unit of difference for each pixel, or the same spread
 out differently over the block.
 
 A frame is a candidate for dropping if no 8x8 blocks differ by more
 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
 meaning the whole image) differ by more than a threshold of @var{lo}.
 
 Default value for @var{hi} is 64*12, default value for @var{lo} is
 64*5, and default value for @var{frac} is 0.33.
 @end table
 

 @section delogo
 
 Suppress a TV station logo by a simple interpolation of the surrounding
 pixels. Just set a rectangle covering the logo and watch it disappear
 (and sometimes something even uglier appear - your mileage may vary).
 
 The filter accepts parameters as a string of the form
 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
 @var{key}=@var{value} pairs, separated by ":".
 
 The description of the accepted parameters follows.
 
 @table @option
 
 @item x, y
 Specify the top left corner coordinates of the logo. They must be
 specified.
 
 @item w, h
 Specify the width and height of the logo to clear. They must be
 specified.
 
 @item band, t
 Specify the thickness of the fuzzy edge of the rectangle (added to
 @var{w} and @var{h}). The default value is 4.
 
 @item show
 When set to 1, a green rectangle is drawn on the screen to simplify
 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
 @var{band} is set to 4. The default value is 0.
 
 @end table
 
 Some examples follow.
 
 @itemize
 
 @item
 Set a rectangle covering the area with top left corner coordinates 0,0
 and size 100x77, setting a band of size 10:
 @example
 delogo=0:0:100:77:10
 @end example
 
 @item
 As the previous example, but use named options:
 @example
 delogo=x=0:y=0:w=100:h=77:band=10
 @end example
 
 @end itemize
 

 @section deshake
 
 Attempt to fix small changes in horizontal and/or vertical shift. This
 filter helps remove camera shake from hand-holding a camera, bumping a
 tripod, moving on a vehicle, etc.
 
 The filter accepts parameters as a string of the form
 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
 
 A description of the accepted parameters follows.
 
 @table @option
 
 @item x, y, w, h

 Specify a rectangular area where to limit the search for motion

 vectors.
 If desired the search for motion vectors can be limited to a
 rectangular area of the frame defined by its top left corner, width
 and height. These parameters have the same meaning as the drawbox
 filter which can be used to visualise the position of the bounding
 box.
 
 This is useful when simultaneous movement of subjects within the frame
 might be confused for camera motion by the motion vector search.
 
 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
 then the full frame is used. This allows later options to be set
 without specifying the bounding box for the motion vector search.
 
 Default - search the whole frame.
 
 @item rx, ry
 Specify the maximum extent of movement in x and y directions in the
 range 0-64 pixels. Default 16.
 
 @item edge
 Specify how to generate pixels to fill blanks at the edge of the
 frame. An integer from 0 to 3 as follows:
 @table @option
 @item 0
 Fill zeroes at blank locations
 @item 1
 Original image at blank locations
 @item 2
 Extruded edge value at blank locations
 @item 3
 Mirrored edge at blank locations
 @end table
 
 The default setting is mirror edge at blank locations.
 
 @item blocksize
 Specify the blocksize to use for motion search. Range 4-128 pixels,
 default 8.
 
 @item contrast
 Specify the contrast threshold for blocks. Only blocks with more than
 the specified contrast (difference between darkest and lightest
 pixels) will be considered. Range 1-255, default 125.
 
 @item search
 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
 search. Default - exhaustive search.
 
 @item filename
 If set then a detailed log of the motion search is written to the
 specified file.
 
 @end table
 

 @section drawbox
 
 Draw a colored box on the input image.
 
 It accepts the syntax:
 @example
 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}
 @end example
 
 @table @option
 
 @item x, y
 Specify the top left corner coordinates of the box. Default to 0.
 
 @item width, height
 Specify the width and height of the box, if 0 they are interpreted as
 the input width and height. Default to 0.
 
 @item color
 Specify the color of the box to write, it can be the name of a color
 (case insensitive match) or a 0xRRGGBB[AA] sequence.
 @end table
 
 Follow some examples:
 @example
 # draw a black box around the edge of the input image
 drawbox
 
 # draw a box with color red and an opacity of 50%
 drawbox=10:20:200:60:red@@0.5"
 @end example
 

 @section drawtext
 
 Draw text string or text from specified file on top of video using the
 libfreetype library.
 

 To enable compilation of this filter you need to configure FFmpeg with

 @code{--enable-libfreetype}.
 
 The filter also recognizes strftime() sequences in the provided text
 and expands them accordingly. Check the documentation of strftime().
 
 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
 separated by ":".
 
 The description of the accepted parameters follows.
 
 @table @option
 

 @item box
 Used to draw a box around text using background color.
 Value should be either 1 (enable) or 0 (disable).
 The default value of @var{box} is 0.

 @item boxcolor
 The color to be used for drawing box around text.
 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
 The default value of @var{boxcolor} is "white".

 @item draw
 Set an expression which specifies if the text should be drawn. If the
 expression evaluates to 0, the text is not drawn. This is useful for
 specifying that the text should be drawn only when specific conditions
 are met.
 
 Default value is "1".
 
 See below for the list of accepted constants and functions.
 

 @item fix_bounds
 If true, check and fix text coords to avoid clipping.

 
 @item fontcolor
 The color to be used for drawing fonts.
 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
 (e.g. "0xff000033"), possibly followed by an alpha specifier.
 The default value of @var{fontcolor} is "black".
 

 @item fontfile
 The font file to be used for drawing text. Path must be included.
 This parameter is mandatory.

 @item fontsize
 The font size to be used for drawing text.
 The default value of @var{fontsize} is 16.

 @item ft_load_flags
 Flags to be used for loading the fonts.
 
 The flags map the corresponding flags supported by libfreetype, and are
 a combination of the following values:
 @table @var
 @item default
 @item no_scale
 @item no_hinting
 @item render
 @item no_bitmap
 @item vertical_layout
 @item force_autohint
 @item crop_bitmap
 @item pedantic
 @item ignore_global_advance_width
 @item no_recurse
 @item ignore_transform
 @item monochrome
 @item linear_design
 @item no_autohint
 @item end table
 @end table
 
 Default value is "render".
 
 For more information consult the documentation for the FT_LOAD_*
 libfreetype flags.
 

 @item shadowcolor
 The color to be used for drawing a shadow behind the drawn text.  It
 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
 The default value of @var{shadowcolor} is "black".
 
 @item shadowx, shadowy
 The x and y offsets for the text shadow position with respect to the
 position of the text. They can be either positive or negative
 values. Default value for both is "0".
 

 @item tabsize
 The size in number of spaces to use for rendering the tab.
 Default value is 4.

 @item timecode
 Set the initial timecode representation in "hh:mm:ss[:;.]ff"

 format. It can be used with or without text parameter. @var{timecode_rate}

 option must be specified.
 

 @item timecode_rate, rate, r
 Set the timecode frame rate (timecode only).
 

 @item text
 The text string to be drawn. The text must be a sequence of UTF-8
 encoded characters.
 This parameter is mandatory if no file is specified with the parameter
 @var{textfile}.
 
 @item textfile
 A text file containing text to be drawn. The text must be a sequence
 of UTF-8 encoded characters.
 
 This parameter is mandatory if no text string is specified with the
 parameter @var{text}.
 

 If both @var{text} and @var{textfile} are specified, an error is thrown.

 
 @item x, y
 The expressions which specify the offsets where text will be drawn
 within the video frame. They are relative to the top/left border of the
 output image.
 
 The default value of @var{x} and @var{y} is "0".
 

 See below for the list of accepted constants and functions.

 @end table
 

 The parameters for @var{x} and @var{y} are expressions containing the

 following constants and functions:

 
 @table @option
 @item dar
 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
 
 @item hsub, vsub
 horizontal and vertical chroma subsample values. For example for the
 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
 

 @item line_h, lh
 the height of each text line

 @item main_h, h, H
 the input height

 @item main_w, w, W
 the input width

 @item max_glyph_a, ascent

 the maximum distance from the baseline to the highest/upper grid
 coordinate used to place a glyph outline point, for all the rendered
 glyphs.
 It is a positive value, due to the grid's orientation with the Y axis
 upwards.
 
 @item max_glyph_d, descent
 the maximum distance from the baseline to the lowest grid coordinate
 used to place a glyph outline point, for all the rendered glyphs.
 This is a negative value, due to the grid's orientation, with the Y axis
 upwards.
 

 @item max_glyph_h
 maximum glyph height, that is the maximum height for all the glyphs
 contained in the rendered text, it is equivalent to @var{ascent} -
 @var{descent}.
 
 @item max_glyph_w
 maximum glyph width, that is the maximum width for all the glyphs
 contained in the rendered text
 

 @item n
 the number of input frame, starting from 0
 

 @item rand(min, max)
 return a random number included between @var{min} and @var{max}
 

 @item sar
 input sample aspect ratio
 

 @item t
 timestamp expressed in seconds, NAN if the input timestamp is unknown

 @item text_h, th
 the height of the rendered text
 
 @item text_w, tw
 the width of the rendered text

 
 @item x, y
 the x and y offset coordinates where the text is drawn.
 
 These parameters allow the @var{x} and @var{y} expressions to refer
 each other, so you can for example specify @code{y=x/dar}.

 @end table
 

 If libavfilter was built with @code{--enable-fontconfig}, then
 @option{fontfile} can be a fontconfig pattern or omitted.
 

 Some examples follow.

 @itemize
 
 @item
 Draw "Test Text" with font FreeSerif, using the default values for the
 optional parameters.

 
 @example

 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"

 @end example
 

 @item

 Draw 'Test Text' with font FreeSerif of size 24 at position x=100

 and y=50 (counting from the top-left corner of the screen), text is
 yellow with a red box around it. Both the text and the box have an
 opacity of 20%.

 @example
 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
           x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
 @end example
 

 Note that the double quotes are not necessary if spaces are not used
 within the parameter list.
 

 @item
 Show the text at the center of the video frame:
 @example

 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"

 @end example
 
 @item
 Show a text line sliding from right to left in the last row of the video
 frame. The file @file{LONG_LINE} is assumed to contain a single line
 with no newlines.
 @example

 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"

 @end example
 
 @item
 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
 @example

 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"

 @end example
 
 @item
 Draw a single green letter "g", at the center of the input video.
 The glyph baseline is placed at half screen height.
 @example

 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"

 @end example
 

 @item

 Show text for 1 second every 3 seconds:
 @example
 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\\,3)\\,1):text='blink'"
 @end example
 
 @item

 Use fontconfig to set the font. Note that the colons need to be escaped.
 @example
 drawtext='fontfile=Linux Libertine O-40\\:style=Semibold:text=FFmpeg'
 @end example
 

 @end itemize
 

 For more information about libfreetype, check:

 @url{http://www.freetype.org/}.

 For more information about fontconfig, check:
 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
 

 @section edgedetect
 
 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
 
 This filter accepts the following optional named parameters:
 
 @table @option
 @item low, high
 Set low and high threshold values used by the Canny thresholding
 algorithm.
 
 The high threshold selects the "strong" edge pixels, which are then
 connected through 8-connectivity with the "weak" edge pixels selected
 by the low threshold.
 
 @var{low} and @var{high} threshold values must be choosen in the range
 [0,1], and @var{low} should be lesser or equal to @var{high}.
 
 Default value for @var{low} is @code{20/255}, and default value for @var{high}
 is @code{50/255}.
 @end table
 
 Example:
 @example
 edgedetect=low=0.1:high=0.4
 @end example
 

 @section fade
 
 Apply fade-in/out effect to input video.
 
 It accepts the parameters:

 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]

 
 @var{type} specifies if the effect type, can be either "in" for
 fade-in, or "out" for a fade-out effect.
 
 @var{start_frame} specifies the number of the start frame for starting
 to apply the fade effect.
 
 @var{nb_frames} specifies the number of frames for which the fade
 effect has to last. At the end of the fade-in effect the output video
 will have the same intensity as the input video, at the end of the
 fade-out transition the output video will be completely black.
 

 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
 separated by ":". The description of the accepted options follows.
 
 @table @option
 
 @item type, t
 See @var{type}.
 
 @item start_frame, s
 See @var{start_frame}.
 
 @item nb_frames, n
 See @var{nb_frames}.
 

 @item alpha
 If set to 1, fade only alpha channel, if one exists on the input.
 Default value is 0.

 @end table
 

 A few usage examples follow, usable too as test scenarios.
 @example
 # fade in first 30 frames of video
 fade=in:0:30
 
 # fade out last 45 frames of a 200-frame video
 fade=out:155:45
 
 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
 fade=in:0:25, fade=out:975:25
 
 # make first 5 frames black, then fade in from frame 5-24
 fade=in:5:20

 
 # fade in alpha over first 25 frames of video
 fade=in:0:25:alpha=1

 @end example
 

 @section fieldorder
 
 Transform the field order of the input video.
 
 It accepts one parameter which specifies the required field order that
 the input interlaced video will be transformed to. The parameter can
 assume one of the following values:
 
 @table @option
 @item 0 or bff
 output bottom field first
 @item 1 or tff
 output top field first
 @end table
 
 Default value is "tff".
 
 Transformation is achieved by shifting the picture content up or down
 by one line, and filling the remaining line with appropriate picture content.
 This method is consistent with most broadcast field order converters.
 
 If the input video is not flagged as being interlaced, or it is already
 flagged as being of the required output field order then this filter does
 not alter the incoming video.
 
 This filter is very useful when converting to or from PAL DV material,
 which is bottom field first.
 
 For example:
 @example

 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv

 @end example
 

 @section fifo
 
 Buffer input images and send them when they are requested.
 
 This filter is mainly useful when auto-inserted by the libavfilter
 framework.
 
 The filter does not take parameters.
 

 @section format
 
 Convert the input video to one of the specified pixel formats.
 Libavfilter will try to pick one that is supported for the input to
 the next filter.
 

 The filter accepts a list of pixel format names, separated by ":",
 for example "yuv420p:monow:rgb24".

 Some examples follow:

 @example

 # convert the input video to the format "yuv420p"
 format=yuv420p

 # convert the input video to any of the formats in the list
 format=yuv420p:yuv444p:yuv410p
 @end example

 @section fps
 
 Convert the video to specified constant framerate by duplicating or dropping
 frames as necessary.
 
 This filter accepts the following named parameters:
 @table @option
 
 @item fps
 Desired output framerate.
 
 @end table
 

 @section framestep
 
 Select one frame every N.
 
 This filter accepts in input a string representing a positive
 integer. Default argument is @code{1}.
 

 @anchor{frei0r}

 @section frei0r
 
 Apply a frei0r effect to the input video.
 
 To enable compilation of this filter you need to install the frei0r

 header and configure FFmpeg with @code{--enable-frei0r}.

 
 The filter supports the syntax:
 @example

 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]

 @end example
 
 @var{filter_name} is the name to the frei0r effect to load. If the
 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
 is searched in each one of the directories specified by the colon
 separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r
 paths, which are in this order: @file{HOME/.frei0r-1/lib/},
 @file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}.
 
 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
 for the frei0r effect.
 
 A frei0r effect parameter can be a boolean (whose values are specified
 with "y" and "n"), a double, a color (specified by the syntax
 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
 description), a position (specified by the syntax @var{X}/@var{Y},
 @var{X} and @var{Y} being float numbers) and a string.
 
 The number and kind of parameters depend on the loaded effect. If an
 effect parameter is not specified the default value is set.
 
 Some examples follow:

 
 @itemize
 @item
 Apply the distort0r effect, set the first two double parameters:

 @example
 frei0r=distort0r:0.5:0.01

 @end example

 @item
 Apply the colordistance effect, takes a color as first parameter:
 @example

 frei0r=colordistance:0.2/0.3/0.4
 frei0r=colordistance:violet
 frei0r=colordistance:0x112233

 @end example

 @item
 Apply the perspective effect, specify the top left and top right image
 positions:
 @example

 frei0r=perspective:0.2/0.2:0.8/0.2
 @end example

 @end itemize

 
 For more information see:

 @url{http://frei0r.dyne.org}

 @section gradfun
 
 Fix the banding artifacts that are sometimes introduced into nearly flat

 regions by truncation to 8bit color depth.

 Interpolate the gradients that should go where the bands are, and
 dither them.
 

 This filter is designed for playback only.  Do not use it prior to
 lossy compression, because compression tends to lose the dither and
 bring back the bands.
 

 The filter takes two optional parameters, separated by ':':
 @var{strength}:@var{radius}
 
 @var{strength} is the maximum amount by which the filter will change
 any one pixel. Also the threshold for detecting nearly flat
 regions. Acceptable values range from .51 to 255, default value is
 1.2, out-of-range values will be clipped to the valid range.
 
 @var{radius} is the neighborhood to fit the gradient to. A larger
 radius makes for smoother gradients, but also prevents the filter from
 modifying the pixels near detailed regions. Acceptable values are
 8-32, default value is 16, out-of-range values will be clipped to the
 valid range.
 
 @example
 # default parameters
 gradfun=1.2:16
 
 # omitting radius
 gradfun=1.2
 @end example
 

 @section hflip
 
 Flip the input video horizontally.
 

 For example to horizontally flip the input video with @command{ffmpeg}:

 @example
 ffmpeg -i in.avi -vf "hflip" out.avi
 @end example
 

 @section hqdn3d
 
 High precision/quality 3d denoise filter. This filter aims to reduce
 image noise producing smooth images and making still images really
 still. It should enhance compressibility.
 
 It accepts the following optional parameters:
 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
 
 @table @option
 @item luma_spatial
 a non-negative float number which specifies spatial luma strength,
 defaults to 4.0
 
 @item chroma_spatial
 a non-negative float number which specifies spatial chroma strength,
 defaults to 3.0*@var{luma_spatial}/4.0
 
 @item luma_tmp
 a float number which specifies luma temporal strength, defaults to
 6.0*@var{luma_spatial}/4.0
 
 @item chroma_tmp
 a float number which specifies chroma temporal strength, defaults to
 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
 @end table
 

 @section hue
 
 Modify the hue and/or the saturation of the input.
 

 This filter accepts the following optional named options:

 @table @option
 @item h
 Specify the hue angle as a number of degrees. It accepts a float
 number or an expression, and defaults to 0.0.
 
 @item H
 Specify the hue angle as a number of degrees. It accepts a float
 number or an expression, and defaults to 0.0.
 
 @item s
 Specify the saturation in the [-10,10] range. It accepts a float number and
 defaults to 1.0.
 @end table
 

 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
 following constants:
 
 @table @option
 @item n
 frame count of the input frame starting from 0
 
 @item pts
 presentation timestamp of the input frame expressed in time base units
 
 @item r
 frame rate of the input video, NAN if the input frame rate is unknown
 
 @item t
 timestamp expressed in seconds, NAN if the input timestamp is unknown
 
 @item tb
 time base of the input video
 @end table
 

 The options can also be set using the syntax: @var{hue}:@var{saturation}
 
 In this case @var{hue} is expressed in degrees.
 
 Some examples follow:
 @itemize
 @item
 Set the hue to 90 degrees and the saturation to 1.0:
 @example
 hue=h=90:s=1
 @end example
 
 @item
 Same command but expressing the hue in radians:
 @example
 hue=H=PI/2:s=1
 @end example
 
 @item
 Same command without named options, hue must be expressed in degrees:
 @example
 hue=90:1
 @end example
 
 @item
 Note that "h:s" syntax does not support expressions for the values of
 h and s, so the following example will issue an error:
 @example
 hue=PI/2:1
 @end example

 
 @item
 Rotate hue and make the saturation swing between 0
 and 2 over a period of 1 second:
 @example
 hue="H=2*PI*t: s=sin(2*PI*t)+1"
 @end example
 
 @item
 Apply a 3 seconds saturation fade-in effect starting at 0:
 @example
 hue="s=min(t/3\,1)"
 @end example
 
 The general fade-in expression can be written as:
 @example
 hue="s=min(0\, max((t-START)/DURATION\, 1))"
 @end example
 
 @item
 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
 @example
 hue="s=max(0\, min(1\, (8-t)/3))"
 @end example
 
 The general fade-out expression can be written as:
 @example
 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
 @end example
 

 @end itemize

 @subsection Commands
 
 This filter supports the following command:
 @table @option
 @item reinit
 Modify the hue and/or the saturation of the input video.
 The command accepts the same named options and syntax than when calling the
 filter from the command-line.
 
 If a parameter is omitted, it is kept at its current value.
 @end table
 

 @section idet
 
 Interlaceing detect filter. This filter tries to detect if the input is
 interlaced or progressive. Top or bottom field first.
 

 @section lut, lutrgb, lutyuv
 
 Compute a look-up table for binding each pixel component input value
 to an output value, and apply it to input video.
 
 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
 to an RGB input video.
 
 These filters accept in input a ":"-separated list of options, which
 specify the expressions used for computing the lookup table for the
 corresponding pixel component values.
 
 The @var{lut} filter requires either YUV or RGB pixel formats in
 input, and accepts the options:
 @table @option

 @item c0
 first  pixel component
 @item c1
 second pixel component
 @item c2
 third  pixel component
 @item c3
 fourth pixel component, corresponds to the alpha component

 @end table
 
 The exact component associated to each option depends on the format in
 input.
 
 The @var{lutrgb} filter requires RGB pixel formats in input, and
 accepts the options:
 @table @option

 @item r
 red component
 @item g
 green component
 @item b
 blue component
 @item a
 alpha component

 @end table
 
 The @var{lutyuv} filter requires YUV pixel formats in input, and
 accepts the options:
 @table @option

 @item y
 Y/luminance component
 @item u
 U/Cb component
 @item v
 V/Cr component
 @item a
 alpha component

 @end table
 
 The expressions can contain the following constants and functions:
 
 @table @option
 @item w, h

 the input width and height

 
 @item val
 input value for the pixel component
 
 @item clipval
 the input value clipped in the @var{minval}-@var{maxval} range
 
 @item maxval
 maximum value for the pixel component
 
 @item minval
 minimum value for the pixel component
 
 @item negval
 the negated value for the pixel component value clipped in the
 @var{minval}-@var{maxval} range , it corresponds to the expression
 "maxval-clipval+minval"
 
 @item clip(val)
 the computed value in @var{val} clipped in the
 @var{minval}-@var{maxval} range
 
 @item gammaval(gamma)
 the computed gamma correction value of the pixel component value
 clipped in the @var{minval}-@var{maxval} range, corresponds to the
 expression
 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
 
 @end table
 
 All expressions default to "val".
 
 Some examples follow:
 @example
 # negate input video
 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
 
 # the above is the same as
 lutrgb="r=negval:g=negval:b=negval"
 lutyuv="y=negval:u=negval:v=negval"
 
 # negate luminance

 lutyuv=y=negval

 
 # remove chroma components, turns the video into a graytone image
 lutyuv="u=128:v=128"
 
 # apply a luma burning effect
 lutyuv="y=2*val"
 
 # remove green and blue components
 lutrgb="g=0:b=0"
 
 # set a constant alpha channel value on input
 format=rgba,lutrgb=a="maxval-minval/2"
 
 # correct luminance gamma by a 0.5 factor
 lutyuv=y=gammaval(0.5)
 @end example
 

 @section mp
 
 Apply an MPlayer filter to the input video.
 
 This filter provides a wrapper around most of the filters of
 MPlayer/MEncoder.
 
 This wrapper is considered experimental. Some of the wrapped filters
 may not work properly and we may drop support for them, as they will
 be implemented natively into FFmpeg. Thus you should avoid
 depending on them when writing portable scripts.
 
 The filters accepts the parameters:
 @var{filter_name}[:=]@var{filter_params}
 
 @var{filter_name} is the name of a supported MPlayer filter,
 @var{filter_params} is a string containing the parameters accepted by
 the named filter.
 
 The list of the currently supported filters follows:
 @table @var
 @item denoise3d
 @item detc
 @item dint
 @item divtc
 @item down3dright
 @item dsize
 @item eq2
 @item eq
 @item field
 @item fil
 @item fixpts
 @item fspp
 @item geq
 @item harddup
 @item hqdn3d
 @item il
 @item ilpack
 @item ivtc
 @item kerndeint
 @item mcdeint
 @item noise
 @item ow
 @item palette
 @item perspective
 @item phase
 @item pp7
 @item pullup
 @item qp
 @item rectangle
 @item sab
 @item softpulldown
 @item softskip
 @item spp
 @item telecine
 @item tile
 @item tinterlace
 @item unsharp
 @item uspp
 @item yuvcsp
 @item yvu9
 @end table
 
 The parameter syntax and behavior for the listed filters are the same
 of the corresponding MPlayer filters. For detailed instructions check
 the "VIDEO FILTERS" section in the MPlayer manual.
 
 Some examples follow:

 @itemize
 @item
 Adjust gamma, brightness, contrast:

 @example
 mp=eq2=1.0:2:0.5
 @end example

 
 @item
 Add temporal noise to input video:
 @example
 mp=noise=20t
 @end example

 @end itemize

 
 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
 

 @section negate
 
 Negate input video.
 
 This filter accepts an integer in input, if non-zero it negates the
 alpha component (if available). The default value in input is 0.
 

 @section noformat
 
 Force libavfilter not to use any of the specified pixel formats for the
 input to the next filter.
 

 The filter accepts a list of pixel format names, separated by ":",
 for example "yuv420p:monow:rgb24".

 Some examples follow:

 @example

 # force libavfilter to use a format different from "yuv420p" for the
 # input to the vflip filter
 noformat=yuv420p,vflip

 # convert the input video to any of the formats not contained in the list
 noformat=yuv420p:yuv444p:yuv410p
 @end example

 
 @section null
 

 Pass the video source unchanged to the output.

 @section ocv

 Apply video transform using libopencv.

 
 To enable this filter install libopencv library and headers and

 configure FFmpeg with @code{--enable-libopencv}.

 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
 
 @var{filter_name} is the name of the libopencv filter to apply.
 
 @var{filter_params} specifies the parameters to pass to the libopencv
 filter. If not specified the default values are assumed.
 
 Refer to the official libopencv documentation for more precise

 information:

 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
 
 Follows the list of supported libopencv filters.
 

 @anchor{dilate}

 @subsection dilate
 
 Dilate an image by using a specific structuring element.
 This filter corresponds to the libopencv function @code{cvDilate}.
 
 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
 
 @var{struct_el} represents a structuring element, and has the syntax:
 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
 

 @var{cols} and @var{rows} represent the number of columns and rows of

 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
 point, and @var{shape} the shape for the structuring element, and
 can be one of the values "rect", "cross", "ellipse", "custom".
 
 If the value for @var{shape} is "custom", it must be followed by a
 string of the form "=@var{filename}". The file with name
 @var{filename} is assumed to represent a binary image, with each
 printable character corresponding to a bright pixel. When a custom
 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
 or columns and rows of the read file are assumed instead.
 
 The default value for @var{struct_el} is "3x3+0x0/rect".
 
 @var{nb_iterations} specifies the number of times the transform is
 applied to the image, and defaults to 1.
 
 Follow some example:
 @example
 # use the default values
 ocv=dilate
 
 # dilate using a structuring element with a 5x5 cross, iterate two times
 ocv=dilate=5x5+2x2/cross:2
 
 # read the shape from the file diamond.shape, iterate two times
 # the file diamond.shape may contain a pattern of characters like this:
 #   *
 #  ***
 # *****
 #  ***
 #   *
 # the specified cols and rows are ignored (but not the anchor point coordinates)
 ocv=0x0+2x2/custom=diamond.shape:2
 @end example
 

 @subsection erode
 
 Erode an image by using a specific structuring element.
 This filter corresponds to the libopencv function @code{cvErode}.
 
 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},

 with the same syntax and semantics as the @ref{dilate} filter.

 @subsection smooth
 
 Smooth the input video.
 
 The filter takes the following parameters:

 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
 
 @var{type} is the type of smooth filter to apply, and can be one of

 the following values: "blur", "blur_no_scale", "median", "gaussian",

 "bilateral". The default value is "gaussian".
 
 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
 parameters whose meanings depend on smooth type. @var{param1} and
 @var{param2} accept integer positive values or 0, @var{param3} and
 @var{param4} accept float values.
 
 The default value for @var{param1} is 3, the default value for the
 other parameters is 0.
 

 These parameters correspond to the parameters assigned to the

 libopencv function @code{cvSmooth}.

 @anchor{overlay}

 @section overlay
 
 Overlay one video on top of another.
 
 It takes two inputs and one output, the first input is the "main"
 video on which the second input is overlayed.
 

 It accepts the parameters: @var{x}:@var{y}[:@var{options}].

 
 @var{x} is the x coordinate of the overlayed video on the main video,

 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing

 the following parameters:
 
 @table @option
 @item main_w, main_h
 main input width and height
 
 @item W, H
 same as @var{main_w} and @var{main_h}
 
 @item overlay_w, overlay_h
 overlay input width and height
 
 @item w, h
 same as @var{overlay_w} and @var{overlay_h}
 @end table
 

 @var{options} is an optional list of @var{key}=@var{value} pairs,
 separated by ":".
 
 The description of the accepted options follows.
 
 @table @option
 @item rgb
 If set to 1, force the filter to accept inputs in the RGB

 color space. Default value is 0.

 @end table
 

 Be aware that frames are taken from each input video in timestamp
 order, hence, if their initial timestamps differ, it is a a good idea
 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
 have them begin in the same zero timestamp, as it does the example for
 the @var{movie} filter.
 
 Follow some examples:
 @example
 # draw the overlay at 10 pixels from the bottom right
 # corner of the main video.
 overlay=main_w-overlay_w-10:main_h-overlay_h-10
 
 # insert a transparent PNG logo in the bottom left corner of the input

 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output

 
 # insert 2 different transparent PNG logos (second logo on bottom
 # right corner):

 ffmpeg -i input -i logo1 -i logo2 -filter_complex

 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output

 
 # add a transparent color layer on top of the main video,
 # WxH specifies the size of the main input to the overlay filter
 color=red@.3:WxH [over]; [in][over] overlay [out]

 
 # play an original video and a filtered version (here with the deshake filter)
 # side by side
 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
 
 # the previous example is the same as:
 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'

 @end example
 

 You can chain together more overlays but the efficiency of such

 approach is yet to be tested.
 

 @section pad
 
 Add paddings to the input image, and places the original input at the
 given coordinates @var{x}, @var{y}.
 
 It accepts the following parameters:
 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
 

 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
 expressions containing the following constants:
 
 @table @option
 @item in_w, in_h

 the input video width and height

 
 @item iw, ih
 same as @var{in_w} and @var{in_h}
 
 @item out_w, out_h

 the output width and height, that is the size of the padded area as

 specified by the @var{width} and @var{height} expressions
 
 @item ow, oh
 same as @var{out_w} and @var{out_h}
 
 @item x, y
 x and y offsets as specified by the @var{x} and @var{y}
 expressions, or NAN if not yet specified
 

 @item a
 same as @var{iw} / @var{ih}

 @item sar
 input sample aspect ratio
 

 @item dar
 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
 

 @item hsub, vsub
 horizontal and vertical chroma subsample values. For example for the
 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
 @end table
 

 Follows the description of the accepted parameters.
 
 @table @option
 @item width, height
 
 Specify the size of the output image with the paddings added. If the
 value for @var{width} or @var{height} is 0, the corresponding input size
 is used for the output.
 

 The @var{width} expression can reference the value set by the

 @var{height} expression, and vice versa.

 The default value of @var{width} and @var{height} is 0.
 
 @item x, y
 
 Specify the offsets where to place the input image in the padded area
 with respect to the top/left border of the output image.
 

 The @var{x} expression can reference the value set by the @var{y}

 expression, and vice versa.

 The default value of @var{x} and @var{y} is 0.
 
 @item color
 
 Specify the color of the padded area, it can be the name of a color
 (case insensitive match) or a 0xRRGGBB[AA] sequence.
 

 The default value of @var{color} is "black".

 
 @end table
 

 @section Examples

 @itemize
 @item
 Add paddings with color "violet" to the input video. Output video
 size is 640x480, the top-left corner of the input video is placed at
 column 0, row 40:

 @example
 pad=640:480:0:40:violet

 @end example

 @item
 Pad the input to get an output with dimensions increased by 3/2,
 and put the input video at the center of the padded area:
 @example

 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"

 @end example

 @item
 Pad the input to get a squared output with size equal to the maximum
 value between the input width and height, and put the input video at
 the center of the padded area:
 @example

 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"

 @end example

 @item
 Pad the input to get a final w/h ratio of 16:9:
 @example

 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"

 @end example
 
 @item
 In case of anamorphic video, in order to set the output display aspect
 correctly, it is necessary to use @var{sar} in the expression,
 according to the relation:
 @example
 (ih * X / ih) * sar = output_dar
 X = output_dar / sar
 @end example

 Thus the previous example needs to be modified to:
 @example

 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"

 @end example

 @item
 Double output size and put the input video in the bottom-right
 corner of the output padded area:
 @example

 pad="2*iw:2*ih:ow-iw:oh-ih"

 @end example

 @end itemize

 @section pixdesctest
 
 Pixel format descriptor test filter, mainly useful for internal
 testing. The output video should be equal to the input video.
 
 For example:
 @example
 format=monow, pixdesctest
 @end example
 
 can be used to test the monowhite pixel format descriptor definition.
 

 @section removelogo
 
 Suppress a TV station logo, using an image file to determine which
 pixels comprise the logo. It works by filling in the pixels that
 comprise the logo with neighboring pixels.
 
 This filter requires one argument which specifies the filter bitmap
 file, which can be any image format supported by libavformat. The
 width and height of the image file must match those of the video
 stream being processed.
 
 Pixels in the provided bitmap image with a value of zero are not
 considered part of the logo, non-zero pixels are considered part of
 the logo. If you use white (255) for the logo and black (0) for the
 rest, you will be safe. For making the filter bitmap, it is
 recommended to take a screen capture of a black frame with the logo
 visible, and then using a threshold filter followed by the erode
 filter once or twice.
 
 If needed, little splotches can be fixed manually. Remember that if
 logo pixels are not covered, the filter quality will be much
 reduced. Marking too many pixels as part of the logo does not hurt as
 much, but it will increase the amount of blurring needed to cover over
 the image and will destroy more information than necessary, and extra
 pixels will slow things down on a large logo.
 

 @section scale
 

 Scale the input video to @var{width}:@var{height}[:@var{interl}=@{1|-1@}] and/or convert the image format.

 The scale filter forces the output display aspect ratio to be the same
 of the input, by changing the output sample aspect ratio.
 

 The parameters @var{width} and @var{height} are expressions containing
 the following constants:

 @table @option
 @item in_w, in_h

 the input width and height

 
 @item iw, ih
 same as @var{in_w} and @var{in_h}

 @item out_w, out_h

 the output (cropped) width and height

 
 @item ow, oh
 same as @var{out_w} and @var{out_h}
 

 @item a
 same as @var{iw} / @var{ih}

 @item sar
 input sample aspect ratio
 

 @item dar
 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
 

 @item hsub, vsub
 horizontal and vertical chroma subsample values. For example for the
 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
 @end table

 
 If the input image format is different from the format requested by
 the next filter, the scale filter will convert the input to the
 requested format.
 
 If the value for @var{width} or @var{height} is 0, the respective input
 size is used for the output.
 
 If the value for @var{width} or @var{height} is -1, the scale filter will
 use, for the respective output size, a value that maintains the aspect
 ratio of the input image.
 
 The default value of @var{width} and @var{height} is 0.
 

 Valid values for the optional parameter @var{interl} are:
 
 @table @option
 @item 1
 force interlaced aware scaling
 
 @item -1
 select interlaced aware scaling depending on whether the source frames
 are flagged as interlaced or not
 @end table
 

 Unless @var{interl} is set to one of the above options, interlaced scaling will not be used.
 

 Some examples follow:
 @example
 # scale the input video to a size of 200x100.
 scale=200:100
 
 # scale the input to 2x
 scale=2*iw:2*ih
 # the above is the same as
 scale=2*in_w:2*in_h
 

 # scale the input to 2x with forced interlaced scaling
 scale=2*iw:2*ih:interl=1
 

 # scale the input to half size
 scale=iw/2:ih/2
 
 # increase the width, and set the height to the same size
 scale=3/2*iw:ow
 
 # seek for Greek harmony
 scale=iw:1/PHI*iw
 scale=ih*PHI:ih
 
 # increase the height, and set the width to 3/2 of the height
 scale=3/2*oh:3/5*ih
 
 # increase the size, but make the size a multiple of the chroma
 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
 
 # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
 scale='min(500\, iw*3/2):-1'
 @end example
 

 @section select
 Select frames to pass in output.
 
 It accepts in input an expression, which is evaluated for each input
 frame. If the expression is evaluated to a non-zero value, the frame
 is selected and passed to the output, otherwise it is discarded.
 
 The expression can contain the following constants:
 
 @table @option
 @item n
 the sequential number of the filtered frame, starting from 0
 
 @item selected_n
 the sequential number of the selected frame, starting from 0
 
 @item prev_selected_n
 the sequential number of the last selected frame, NAN if undefined
 
 @item TB
 timebase of the input timestamps
 
 @item pts
 the PTS (Presentation TimeStamp) of the filtered video frame,
 expressed in @var{TB} units, NAN if undefined
 
 @item t
 the PTS (Presentation TimeStamp) of the filtered video frame,
 expressed in seconds, NAN if undefined
 
 @item prev_pts
 the PTS of the previously filtered video frame, NAN if undefined
 
 @item prev_selected_pts
 the PTS of the last previously filtered video frame, NAN if undefined
 
 @item prev_selected_t
 the PTS of the last previously selected video frame, NAN if undefined
 
 @item start_pts
 the PTS of the first video frame in the video, NAN if undefined
 
 @item start_t
 the time of the first video frame in the video, NAN if undefined
 
 @item pict_type

 the type of the filtered frame, can assume one of the following

 values:
 @table @option

 @item I
 @item P
 @item B
 @item S
 @item SI
 @item SP
 @item BI

 @end table
 
 @item interlace_type
 the frame interlace type, can assume one of the following values:
 @table @option

 @item PROGRESSIVE

 the frame is progressive (not interlaced)

 @item TOPFIRST

 the frame is top-field-first

 @item BOTTOMFIRST

 the frame is bottom-field-first
 @end table
 
 @item key
 1 if the filtered frame is a key-frame, 0 otherwise
 
 @item pos
 the position in the file of the filtered frame, -1 if the information
 is not available (e.g. for synthetic video)

 
 @item scene
 value between 0 and 1 to indicate a new scene; a low value reflects a low
 probability for the current frame to introduce a new scene, while a higher
 value means the current frame is more likely to be one (see the example below)
 

 @end table
 
 The default value of the select expression is "1".
 
 Some examples follow:
 
 @example
 # select all frames in input
 select
 
 # the above is the same as:
 select=1
 
 # skip all frames:
 select=0
 
 # select only I-frames

 select='eq(pict_type\,I)'

 
 # select one frame every 100
 select='not(mod(n\,100))'
 
 # select only frames contained in the 10-20 time interval
 select='gte(t\,10)*lte(t\,20)'
 
 # select only I frames contained in the 10-20 time interval

 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'

 
 # select frames with a minimum distance of 10 seconds
 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
 @end example
 

 Complete example to create a mosaic of the first scenes:
 
 @example
 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
 @end example
 
 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
 choice.
 

 @section setdar, setsar

 The @code{setdar} filter sets the Display Aspect Ratio for the filter
 output video.

 
 This is done by changing the specified Sample (aka Pixel) Aspect
 Ratio, according to the following equation:

 @example
 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
 @end example

 Keep in mind that the @code{setdar} filter does not modify the pixel
 dimensions of the video frame. Also the display aspect ratio set by
 this filter may be changed by later filters in the filterchain,
 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
 applied.

 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
 the filter output video.
 
 Note that as a consequence of the application of this filter, the
 output display aspect ratio will change according to the equation
 above.
 
 Keep in mind that the sample aspect ratio set by the @code{setsar}
 filter may be changed by later filters in the filterchain, e.g. if
 another "setsar" or a "setdar" filter is applied.
 
 The @code{setdar} and @code{setsar} filters accept a parameter string
 which represents the wanted aspect ratio.  The parameter can
 be a floating point number string, an expression, or a string of the form
 @var{num}:@var{den}, where @var{num} and @var{den} are the numerator
 and denominator of the aspect ratio. If the parameter is not
 specified, it is assumed the value "0:1".

 
 For example to change the display aspect ratio to 16:9, specify:
 @example
 setdar=16:9

 @end example
 
 The example above is equivalent to:
 @example

 setdar=1.77777
 @end example
 

 To change the sample aspect ratio to 10:11, specify:
 @example
 setsar=10:11
 @end example

 @section setfield
 
 Force field for the output video frame.
 
 The @code{setfield} filter marks the interlace type field for the
 output frames. It does not change the input frame, but only sets the
 corresponding property, which affects how the frame is treated by

 following filters (e.g. @code{fieldorder} or @code{yadif}).

 It accepts a string parameter, which can assume the following values:

 @table @samp

 @item auto

 Keep the same field property.
 

 @item bff

 Mark the frame as bottom-field-first.
 

 @item tff

 Mark the frame as top-field-first.

 
 @item prog
 Mark the frame as progressive.

 @end table
 

 @section showinfo
 
 Show a line containing various information for each input video frame.
 The input video is not modified.
 
 The shown line contains a sequence of key/value pairs of the form
 @var{key}:@var{value}.
 
 A description of each shown parameter follows:
 
 @table @option
 @item n
 sequential number of the input frame, starting from 0
 
 @item pts
 Presentation TimeStamp of the input frame, expressed as a number of
 time base units. The time base unit depends on the filter input pad.
 
 @item pts_time
 Presentation TimeStamp of the input frame, expressed as a number of
 seconds
 
 @item pos
 position of the frame in the input stream, -1 if this information in

 unavailable and/or meaningless (for example in case of synthetic video)

 
 @item fmt
 pixel format name
 
 @item sar
 sample aspect ratio of the input frame, expressed in the form
 @var{num}/@var{den}
 
 @item s
 size of the input frame, expressed in the form
 @var{width}x@var{height}
 
 @item i
 interlaced mode ("P" for "progressive", "T" for top field first, "B"
 for bottom field first)
 
 @item iskey
 1 if the frame is a key frame, 0 otherwise
 
 @item type
 picture type of the input frame ("I" for an I-frame, "P" for a
 P-frame, "B" for a B-frame, "?" for unknown type).
 Check also the documentation of the @code{AVPictureType} enum and of
 the @code{av_get_picture_type_char} function defined in
 @file{libavutil/avutil.h}.
 

 @item checksum

 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame

 @item plane_checksum

 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"

 @end table
 

 @section slicify
 
 Pass the images of input video on to next video filter as multiple
 slices.
 
 @example

 ffmpeg -i in.avi -vf "slicify=32" out.avi

 @end example
 
 The filter accepts the slice height as parameter. If the parameter is
 not specified it will use the default value of 16.
 
 Adding this in the beginning of filter chains should make filtering
 faster due to better use of the memory cache.
 

 @section smartblur
 
 Blur the input video without impacting the outlines.
 
 The filter accepts the following parameters:
 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
 
 Parameters prefixed by @var{luma} indicate that they work on the
 luminance of the pixels whereas parameters prefixed by @var{chroma}
 refer to the chrominance of the pixels.
 
 If the chroma parameters are not set, the luma parameters are used for
 either the luminance and the chrominance of the pixels.
 
 @var{luma_radius} or @var{chroma_radius} must be a float number in the
 range [0.1,5.0] that specifies the variance of the gaussian filter
 used to blur the image (slower if larger).
 
 @var{luma_strength} or @var{chroma_strength} must be a float number in
 the range [-1.0,1.0] that configures the blurring. A value included in
 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
 will sharpen the image.
 
 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
 the range [-30,30] that is used as a coefficient to determine whether
 a pixel should be blurred or not. A value of 0 will filter all the
 image, a value included in [0,30] will filter flat areas and a value
 included in [-30,0] will filter edges.
 

 @section split
 

 Split input video into several identical outputs.
 
 The filter accepts a single parameter which specifies the number of outputs. If
 unspecified, it defaults to 2.
 
 For example
 @example

 ffmpeg -i INPUT -filter_complex split=5 OUTPUT

 @end example
 will create 5 copies of the input video.

 
 For example:
 @example
 [in] split [splitout1][splitout2];
 [splitout1] crop=100:100:0:0    [cropout];
 [splitout2] pad=200:200:100:100 [padout];
 @end example
 
 will create two separate outputs from the same input, one cropped and
 one padded.
 

 @section super2xsai
 
 Scale the input by 2x and smooth using the Super2xSaI (Scale and
 Interpolate) pixel art scaling algorithm.
 
 Useful for enlarging pixel art images without reducing sharpness.
 

 @section swapuv
 Swap U & V plane.
 

 @section thumbnail
 Select the most representative frame in a given sequence of consecutive frames.
 
 It accepts as argument the frames batch size to analyze (default @var{N}=100);
 in a set of @var{N} frames, the filter will pick one of them, and then handle
 the next batch of @var{N} frames until the end.
 
 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
 value will result in a higher memory usage, so a high value is not recommended.
 
 The following example extract one picture each 50 frames:
 @example
 thumbnail=50
 @end example
 
 Complete example of a thumbnail creation with @command{ffmpeg}:
 @example
 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
 @end example
 

 @section tile
 
 Tile several successive frames together.
 
 It accepts as argument the tile size (i.e. the number of lines and columns)
 in the form "@var{w}x@var{h}".
 
 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
 nokey}) in a movie:
 @example
 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
 @end example
 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
 duplicating each output frame to accomodate the originally detected frame
 rate.
 

 @section tinterlace
 
 Perform various types of temporal field interlacing.
 
 Frames are counted starting from 1, so the first input frame is
 considered odd.
 
 This filter accepts a single parameter specifying the mode. Available
 modes are:
 
 @table @samp

 @item merge, 0

 Move odd frames into the upper field, even into the lower field,
 generating a double height frame at half framerate.
 

 @item drop_odd, 1

 Only output even frames, odd frames are dropped, generating a frame with
 unchanged height at half framerate.
 

 @item drop_even, 2

 Only output odd frames, even frames are dropped, generating a frame with
 unchanged height at half framerate.
 

 @item pad, 3

 Expand each frame to full height, but pad alternate lines with black,
 generating a frame with double height at the same input framerate.
 

 @item interleave_top, 4

 Interleave the upper field from odd frames with the lower field from
 even frames, generating a frame with unchanged height at half framerate.

 @item interleave_bottom, 5

 Interleave the lower field from odd frames with the upper field from
 even frames, generating a frame with unchanged height at half framerate.

 @item interlacex2, 6

 Double frame rate with unchanged height. Frames are inserted each
 containing the second temporal field from the previous input frame and
 the first temporal field from the next input frame. This mode relies on
 the top_field_first flag. Useful for interlaced video displays with no
 field synchronisation.

 @end table
 

 Numeric values are deprecated but are accepted for backward
 compatibility reasons.
 
 Default mode is @code{merge}.

 @section transpose
 
 Transpose rows with columns in the input video and optionally flip it.
 
 It accepts a parameter representing an integer, which can assume the
 values:
 
 @table @samp

 @item 0, 4

 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
 @example
 L.R     L.l
 . . ->  . .
 l.r     R.r
 @end example
 

 @item 1, 5

 Rotate by 90 degrees clockwise, that is:
 @example
 L.R     l.L
 . . ->  . .
 l.r     r.R
 @end example
 

 @item 2, 6

 Rotate by 90 degrees counterclockwise, that is:
 @example
 L.R     R.r
 . . ->  . .
 l.r     L.l
 @end example
 

 @item 3, 7

 Rotate by 90 degrees clockwise and vertically flip, that is:
 @example
 L.R     r.R
 . . ->  . .
 l.r     l.L
 @end example
 @end table
 

 For values between 4-7 transposition is only done if the input video
 geometry is portrait and not landscape.
 

 @section unsharp
 

 Sharpen or blur the input video.
 
 It accepts the following parameters:
 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}

 
 Negative values for the amount will blur the input video, while positive
 values will sharpen. All parameters are optional and default to the

 equivalent of the string '5:5:1.0:5:5:0.0'.

 
 @table @option
 
 @item luma_msize_x
 Set the luma matrix horizontal size. It can be an integer between 3
 and 13, default value is 5.
 
 @item luma_msize_y
 Set the luma matrix vertical size. It can be an integer between 3
 and 13, default value is 5.
 
 @item luma_amount
 Set the luma effect strength. It can be a float number between -2.0
 and 5.0, default value is 1.0.
 
 @item chroma_msize_x
 Set the chroma matrix horizontal size. It can be an integer between 3

 and 13, default value is 5.

 
 @item chroma_msize_y
 Set the chroma matrix vertical size. It can be an integer between 3

 and 13, default value is 5.

 @item chroma_amount

 Set the chroma effect strength. It can be a float number between -2.0
 and 5.0, default value is 0.0.
 
 @end table
 
 @example
 # Strong luma sharpen effect parameters
 unsharp=7:7:2.5
 
 # Strong blur of both luma and chroma parameters
 unsharp=7:7:-2:7:7:-2
 
 # Use the default values with @command{ffmpeg}

 ffmpeg -i in.avi -vf "unsharp" out.mp4

 @end example
 
 @section vflip
 
 Flip the input video vertically.
 
 @example

 ffmpeg -i in.avi -vf "vflip" out.avi

 @end example
 

 @section yadif
 

 Deinterlace the input video ("yadif" means "yet another deinterlacing
 filter").

 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.

 @var{mode} specifies the interlacing mode to adopt, accepts one of the
 following values:

 @table @option
 @item 0
 output 1 frame for each frame
 @item 1
 output 1 frame for each field
 @item 2
 like 0 but skips spatial interlacing check
 @item 3
 like 1 but skips spatial interlacing check
 @end table

 
 Default value is 0.
 

 @var{parity} specifies the picture field parity assumed for the input
 interlaced video, accepts one of the following values:

 @table @option
 @item 0
 assume top field first

 @item 1
 assume bottom field first

 @item -1
 enable automatic detection

 @end table
 

 Default value is -1.

 If interlacing is unknown or decoder does not export this information,
 top field first will be assumed.

 @var{auto} specifies if deinterlacer should trust the interlaced flag

 and only deinterlace frames marked as interlaced
 
 @table @option
 @item 0
 deinterlace all frames
 @item 1
 only deinterlace frames marked as interlaced
 @end table
 
 Default value is 0.
 

 @c man end VIDEO FILTERS
 
 @chapter Video Sources
 @c man begin VIDEO SOURCES
 
 Below is a description of the currently available video sources.
 

 @section buffer
 
 Buffer video frames, and make them available to the filter chain.
 
 This source is mainly intended for a programmatic use, in particular

 through the interface defined in @file{libavfilter/vsrc_buffer.h}.

 It accepts a list of options in the form of @var{key}=@var{value} pairs
 separated by ":". A descroption of the accepted options follows.

 
 @table @option
 

 @item video_size
 Specify the size (width and height) of the buffered video frames.

 @item pix_fmt

 A string representing the pixel format of the buffered video frames.
 It may be a number corresponding to a pixel format, or a pixel format
 name.
 

 @item time_base
 Specify the timebase assumed by the timestamps of the buffered frames.

 @item time_base
 Specify the frame rate expected for the video stream.
 

 @item pixel_aspect
 Specify the sample aspect ratio assumed by the video frames.

 @item sws_param

 Specify the optional parameters to be used for the scale filter which
 is automatically inserted when an input change is detected in the
 input size or format.

 @end table
 
 For example:
 @example

 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1

 @end example
 
 will instruct the source to accept video frames with size 320x240 and

 with format "yuv410p", assuming 1/24 as the timestamps timebase and
 square pixels (1:1 sample aspect ratio).

 Since the pixel format with name "yuv410p" corresponds to the number 6
 (check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
 this example corresponds to:

 @example

 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1

 @end example
 

 Alternatively, the options can be specified as a flat string, but this
 syntax is deprecated:
 
 @var{width}:@var{height}:@var{pix_fmt}:@var{time_base.num}:@var{time_base.den}:@var{pixel_aspect.num}:@var{pixel_aspect.den}[:@var{sws_param}]
 

 @section cellauto
 
 Create a pattern generated by an elementary cellular automaton.
 
 The initial state of the cellular automaton can be defined through the
 @option{filename}, and @option{pattern} options. If such options are
 not specified an initial state is created randomly.
 
 At each new frame a new row in the video is filled with the result of
 the cellular automaton next generation. The behavior when the whole
 frame is filled is defined by the @option{scroll} option.
 
 This source accepts a list of options in the form of
 @var{key}=@var{value} pairs separated by ":". A description of the
 accepted options follows.
 
 @table @option
 @item filename, f
 Read the initial cellular automaton state, i.e. the starting row, from
 the specified file.
 In the file, each non-whitespace character is considered an alive
 cell, a newline will terminate the row, and further characters in the
 file will be ignored.
 
 @item pattern, p
 Read the initial cellular automaton state, i.e. the starting row, from
 the specified string.
 
 Each non-whitespace character in the string is considered an alive
 cell, a newline will terminate the row, and further characters in the
 string will be ignored.
 
 @item rate, r
 Set the video rate, that is the number of frames generated per second.
 Default is 25.
 
 @item random_fill_ratio, ratio
 Set the random fill ratio for the initial cellular automaton row. It
 is a floating point number value ranging from 0 to 1, defaults to
 1/PHI.
 
 This option is ignored when a file or a pattern is specified.
 
 @item random_seed, seed
 Set the seed for filling randomly the initial row, must be an integer
 included between 0 and UINT32_MAX. If not specified, or if explicitly
 set to -1, the filter will try to use a good random seed on a best
 effort basis.
 
 @item rule
 Set the cellular automaton rule, it is a number ranging from 0 to 255.
 Default value is 110.
 
 @item size, s
 Set the size of the output video.
 
 If @option{filename} or @option{pattern} is specified, the size is set
 by default to the width of the specified initial state row, and the
 height is set to @var{width} * PHI.
 
 If @option{size} is set, it must contain the width of the specified
 pattern string, and the specified pattern will be centered in the
 larger row.
 
 If a filename or a pattern string is not specified, the size value
 defaults to "320x518" (used for a randomly generated initial state).
 
 @item scroll
 If set to 1, scroll the output upward when all the rows in the output
 have been already filled. If set to 0, the new generated row will be
 written over the top row just after the bottom row is filled.
 Defaults to 1.
 
 @item start_full, full
 If set to 1, completely fill the output with generated rows before
 outputting the first frame.
 This is the default behavior, for disabling set the value to 0.
 
 @item stitch
 If set to 1, stitch the left and right row edges together.
 This is the default behavior, for disabling set the value to 0.
 @end table
 
 @subsection Examples
 
 @itemize
 @item
 Read the initial state from @file{pattern}, and specify an output of
 size 200x400.
 @example
 cellauto=f=pattern:s=200x400
 @end example
 
 @item
 Generate a random initial row with a width of 200 cells, with a fill
 ratio of 2/3:
 @example
 cellauto=ratio=2/3:s=200x200
 @end example
 
 @item
 Create a pattern generated by rule 18 starting by a single alive cell
 centered on an initial row with width 100:
 @example
 cellauto=p=@@:s=100x400:full=0:rule=18
 @end example
 
 @item
 Specify a more elaborated initial pattern:
 @example
 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
 @end example
 
 @end itemize
 

 @section mandelbrot
 
 Generate a Mandelbrot set fractal, and progressively zoom towards the
 point specified with @var{start_x} and @var{start_y}.
 
 This source accepts a list of options in the form of
 @var{key}=@var{value} pairs separated by ":". A description of the
 accepted options follows.
 
 @table @option
 
 @item end_pts
 Set the terminal pts value. Default value is 400.
 
 @item end_scale
 Set the terminal scale value.
 Must be a floating point value. Default value is 0.3.
 
 @item inner
 Set the inner coloring mode, that is the algorithm used to draw the
 Mandelbrot fractal internal region.
 
 It shall assume one of the following values:
 @table @option
 @item black
 Set black mode.

 @item convergence

 Show time until convergence.
 @item mincol
 Set color based on point closest to the origin of the iterations.
 @item period
 Set period mode.
 @end table
 
 Default value is @var{mincol}.
 
 @item bailout
 Set the bailout value. Default value is 10.0.
 
 @item maxiter
 Set the maximum of iterations performed by the rendering
 algorithm. Default value is 7189.
 
 @item outer
 Set outer coloring mode.
 It shall assume one of following values:
 @table @option
 @item iteration_count
 Set iteration cound mode.
 @item normalized_iteration_count
 set normalized iteration count mode.

 @end table

 Default value is @var{normalized_iteration_count}.
 
 @item rate, r
 Set frame rate, expressed as number of frames per second. Default
 value is "25".
 
 @item size, s
 Set frame size. Default value is "640x480".
 
 @item start_scale
 Set the initial scale value. Default value is 3.0.
 
 @item start_x
 Set the initial x position. Must be a floating point value between
 -100 and 100. Default value is -0.743643887037158704752191506114774.
 
 @item start_y
 Set the initial y position. Must be a floating point value between
 -100 and 100. Default value is -0.131825904205311970493132056385139.
 @end table
 

 @section mptestsrc
 
 Generate various test patterns, as generated by the MPlayer test filter.
 
 The size of the generated video is fixed, and is 256x256.
 This source is useful in particular for testing encoding features.
 
 This source accepts an optional sequence of @var{key}=@var{value} pairs,
 separated by ":". The description of the accepted options follows.
 
 @table @option
 
 @item rate, r
 Specify the frame rate of the sourced video, as the number of frames
 generated per second. It has to be a string in the format
 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
 number or a valid video frame rate abbreviation. The default value is
 "25".
 
 @item duration, d
 Set the video duration of the sourced video. The accepted syntax is:
 @example

 [-]HH:MM:SS[.m...]

 [-]S+[.m...]
 @end example
 See also the function @code{av_parse_time()}.
 
 If not specified, or the expressed duration is negative, the video is
 supposed to be generated forever.
 
 @item test, t
 
 Set the number or the name of the test to perform. Supported tests are:
 @table @option
 @item dc_luma
 @item dc_chroma
 @item freq_luma
 @item freq_chroma
 @item amp_luma
 @item amp_chroma
 @item cbp
 @item mv
 @item ring1
 @item ring2
 @item all
 @end table
 
 Default value is "all", which will cycle through the list of all tests.
 @end table
 
 For example the following:
 @example
 testsrc=t=dc_luma
 @end example
 
 will generate a "dc_luma" test pattern.
 

 @section frei0r_src
 
 Provide a frei0r source.
 
 To enable compilation of this filter you need to install the frei0r

 header and configure FFmpeg with @code{--enable-frei0r}.

 
 The source supports the syntax:
 @example
 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
 @end example
 
 @var{size} is the size of the video to generate, may be a string of the
 form @var{width}x@var{height} or a frame size abbreviation.
 @var{rate} is the rate of the video to generate, may be a string of
 the form @var{num}/@var{den} or a frame rate abbreviation.
 @var{src_name} is the name to the frei0r source to load. For more
 information regarding frei0r and how to set the parameters read the

 section @ref{frei0r} in the description of the video filters.

 For example, to generate a frei0r partik0l source with size 200x200
 and frame rate 10 which is overlayed on the overlay filter main input:

 @example
 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
 @end example
 

 @section life
 
 Generate a life pattern.
 
 This source is based on a generalization of John Conway's life game.
 
 The sourced input represents a life grid, each pixel represents a cell
 which can be in one of two possible states, alive or dead. Every cell
 interacts with its eight neighbours, which are the cells that are
 horizontally, vertically, or diagonally adjacent.
 
 At each interaction the grid evolves according to the adopted rule,
 which specifies the number of neighbor alive cells which will make a
 cell stay alive or born. The @option{rule} option allows to specify
 the rule to adopt.
 
 This source accepts a list of options in the form of
 @var{key}=@var{value} pairs separated by ":". A description of the
 accepted options follows.
 
 @table @option
 @item filename, f
 Set the file from which to read the initial grid state. In the file,
 each non-whitespace character is considered an alive cell, and newline
 is used to delimit the end of each row.
 
 If this option is not specified, the initial grid is generated
 randomly.
 
 @item rate, r
 Set the video rate, that is the number of frames generated per second.
 Default is 25.
 
 @item random_fill_ratio, ratio
 Set the random fill ratio for the initial random grid. It is a
 floating point number value ranging from 0 to 1, defaults to 1/PHI.
 It is ignored when a file is specified.
 
 @item random_seed, seed
 Set the seed for filling the initial random grid, must be an integer
 included between 0 and UINT32_MAX. If not specified, or if explicitly
 set to -1, the filter will try to use a good random seed on a best
 effort basis.
 
 @item rule
 Set the life rule.
 
 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
 @var{NS} specifies the number of alive neighbor cells which make a
 live cell stay alive, and @var{NB} the number of alive neighbor cells
 which make a dead cell to become alive (i.e. to "born").
 "s" and "b" can be used in place of "S" and "B", respectively.
 
 Alternatively a rule can be specified by an 18-bits integer. The 9
 high order bits are used to encode the next cell state if it is alive
 for each number of neighbor alive cells, the low order bits specify
 the rule for "borning" new cells. Higher order bits encode for an
 higher number of neighbor cells.
 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
 
 Default value is "S23/B3", which is the original Conway's game of life
 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
 cells, and will born a new cell if there are three alive cells around
 a dead cell.
 
 @item size, s
 Set the size of the output video.
 
 If @option{filename} is specified, the size is set by default to the
 same size of the input file. If @option{size} is set, it must contain
 the size specified in the input file, and the initial grid defined in
 that file is centered in the larger resulting area.
 
 If a filename is not specified, the size value defaults to "320x240"
 (used for a randomly generated initial grid).
 
 @item stitch
 If set to 1, stitch the left and right grid edges together, and the
 top and bottom edges also. Defaults to 1.

 
 @item mold
 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
 value from 0 to 255.
 
 @item life_color
 Set the color of living (or new born) cells.
 
 @item death_color
 Set the color of dead cells. If @option{mold} is set, this is the first color
 used to represent a dead cell.
 
 @item mold_color
 Set mold color, for definitely dead and moldy cells.

 @end table
 
 @subsection Examples
 
 @itemize
 @item
 Read a grid from @file{pattern}, and center it on a grid of size
 300x300 pixels:
 @example
 life=f=pattern:s=300x300
 @end example
 
 @item
 Generate a random grid of size 200x200, with a fill ratio of 2/3:
 @example
 life=ratio=2/3:s=200x200
 @end example
 
 @item
 Specify a custom rule for evolving a randomly generated grid:
 @example
 life=rule=S14/B34
 @end example
 

 @item
 Full example with slow death effect (mold) using @command{ffplay}:
 @example
 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
 @end example

 @end itemize
 

 @section color, nullsrc, rgbtestsrc, smptebars, testsrc

 
 The @code{color} source provides an uniformly colored input.

 
 The @code{nullsrc} source returns unprocessed video frames. It is
 mainly useful to be employed in analysis / debugging tools, or as the
 source for filters which ignore the input data.

 The @code{rgbtestsrc} source generates an RGB test pattern useful for
 detecting RGB vs BGR issues. You should see a red, green and blue
 stripe from top to bottom.

 The @code{smptebars} source generates a color bars pattern, based on
 the SMPTE Engineering Guideline EG 1-1990.
 

 The @code{testsrc} source generates a test video pattern, showing a
 color pattern, a scrolling gradient and a timestamp. This is mainly
 intended for testing purposes.
 

 These sources accept an optional sequence of @var{key}=@var{value} pairs,

 separated by ":". The description of the accepted options follows.
 
 @table @option
 

 @item color, c
 Specify the color of the source, only used in the @code{color}
 source. It can be the name of a color (case insensitive match) or a
 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
 default value is "black".
 

 @item size, s
 Specify the size of the sourced video, it may be a string of the form

 @var{width}x@var{height}, or the name of a size abbreviation. The

 default value is "320x240".
 
 @item rate, r
 Specify the frame rate of the sourced video, as the number of frames
 generated per second. It has to be a string in the format
 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
 number or a valid video frame rate abbreviation. The default value is
 "25".
 

 @item sar
 Set the sample aspect ratio of the sourced video.
 

 @item duration, d

 Set the video duration of the sourced video. The accepted syntax is:
 @example
 [-]HH[:MM[:SS[.m...]]]
 [-]S+[.m...]
 @end example
 See also the function @code{av_parse_time()}.
 
 If not specified, or the expressed duration is negative, the video is
 supposed to be generated forever.

 
 @item decimals, n
 Set the number of decimals to show in the timestamp, only used in the
 @code{testsrc} source.
 
 The displayed timestamp value will correspond to the original
 timestamp value multiplied by the power of 10 of the specified
 value. Default value is 0.

 @end table
 
 For example the following:
 @example
 testsrc=duration=5.3:size=qcif:rate=10
 @end example
 
 will generate a video with a duration of 5.3 seconds, with size

 176x144 and a frame rate of 10 frames per second.

 The following graph description will generate a red source
 with an opacity of 0.2, with size "qcif" and a frame rate of 10
 frames per second.
 @example
 color=c=red@@0.2:s=qcif:r=10
 @end example
 

 If the input content is to be ignored, @code{nullsrc} can be used. The
 following command generates noise in the luminance plane by employing
 the @code{mp=geq} filter:
 @example
 nullsrc=s=256x256, mp=geq=random(1)*255:128:128
 @end example
 

 @c man end VIDEO SOURCES
 
 @chapter Video Sinks
 @c man begin VIDEO SINKS
 
 Below is a description of the currently available video sinks.
 

 @section buffersink
 
 Buffer video frames, and make them available to the end of the filter
 graph.
 
 This sink is mainly intended for a programmatic use, in particular

 through the interface defined in @file{libavfilter/buffersink.h}.

 
 It does not require a string parameter in input, but you need to
 specify a pointer to a list of supported pixel formats terminated by
 -1 in the opaque parameter provided to @code{avfilter_init_filter}
 when initializing this sink.
 

 @section nullsink
 
 Null video sink, do absolutely nothing with the input video. It is
 mainly useful as a template and to be employed in analysis / debugging
 tools.
 
 @c man end VIDEO SINKS

 @chapter Multimedia Filters
 @c man begin MULTIMEDIA FILTERS

 Below is a description of the currently available multimedia filters.

 @section asendcmd, sendcmd
 
 Send commands to filters in the filtergraph.
 
 These filters read commands to be sent to other filters in the
 filtergraph.
 
 @code{asendcmd} must be inserted between two audio filters,
 @code{sendcmd} must be inserted between two video filters, but apart
 from that they act the same way.
 
 The specification of commands can be provided in the filter arguments
 with the @var{commands} option, or in a file specified by the
 @var{filename} option.
 
 These filters accept the following options:
 @table @option
 @item commands, c
 Set the commands to be read and sent to the other filters.
 @item filename, f
 Set the filename of the commands to be read and sent to the other
 filters.
 @end table
 
 @subsection Commands syntax
 
 A commands description consists of a sequence of interval
 specifications, comprising a list of commands to be executed when a
 particular event related to that interval occurs. The occurring event
 is typically the current frame time entering or leaving a given time
 interval.
 
 An interval is specified by the following syntax:
 @example
 @var{START}[-@var{END}] @var{COMMANDS};
 @end example
 
 The time interval is specified by the @var{START} and @var{END} times.
 @var{END} is optional and defaults to the maximum time.
 
 The current frame time is considered within the specified interval if
 it is included in the interval [@var{START}, @var{END}), that is when
 the time is greater or equal to @var{START} and is lesser than
 @var{END}.
 
 @var{COMMANDS} consists of a sequence of one or more command
 specifications, separated by ",", relating to that interval.  The
 syntax of a command specification is given by:
 @example
 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
 @end example
 
 @var{FLAGS} is optional and specifies the type of events relating to
 the time interval which enable sending the specified command, and must
 be a non-null sequence of identifier flags separated by "+" or "|" and
 enclosed between "[" and "]".
 
 The following flags are recognized:
 @table @option
 @item enter
 The command is sent when the current frame timestamp enters the
 specified interval. In other words, the command is sent when the
 previous frame timestamp was not in the given interval, and the
 current is.
 
 @item leave
 The command is sent when the current frame timestamp leaves the
 specified interval. In other words, the command is sent when the
 previous frame timestamp was in the given interval, and the
 current is not.
 @end table
 
 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
 assumed.
 
 @var{TARGET} specifies the target of the command, usually the name of
 the filter class or a specific filter instance name.
 
 @var{COMMAND} specifies the name of the command for the target filter.
 
 @var{ARG} is optional and specifies the optional list of argument for
 the given @var{COMMAND}.
 
 Between one interval specification and another, whitespaces, or
 sequences of characters starting with @code{#} until the end of line,
 are ignored and can be used to annotate comments.
 
 A simplified BNF description of the commands specification syntax
 follows:
 @example
 @var{COMMAND_FLAG}  ::= "enter" | "leave"
 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
 @var{COMMAND}       ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
 @var{COMMANDS}      ::= @var{COMMAND} [,@var{COMMANDS}]
 @var{INTERVAL}      ::= @var{START}[-@var{END}] @var{COMMANDS}
 @var{INTERVALS}     ::= @var{INTERVAL}[;@var{INTERVALS}]
 @end example
 
 @subsection Examples
 
 @itemize
 @item
 Specify audio tempo change at second 4:
 @example
 asendcmd=c='4.0 atempo tempo 1.5',atempo
 @end example
 
 @item
 Specify a list of drawtext and hue commands in a file.
 @example
 # show text in the interval 5-10
 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
          [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
 
 # desaturate the image in the interval 15-20
 15.0-20.0 [enter] hue reinit s=0,
           [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
           [leave] hue reinit s=1,
           [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
 
 # apply an exponential saturation fade-out effect, starting from time 25
 25 [enter] hue s=exp(t-25)
 @end example
 
 A filtergraph allowing to read and process the above command list
 stored in a file @file{test.cmd}, can be specified with:
 @example
 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
 @end example
 @end itemize
 

 @section asetpts, setpts
 
 Change the PTS (presentation timestamp) of the input frames.
 
 @code{asetpts} works on audio frames, @code{setpts} on video frames.
 
 Accept in input an expression evaluated through the eval API, which
 can contain the following constants:
 
 @table @option

 @item FRAME_RATE
 frame rate, only defined for constant frame-rate video
 

 @item PTS
 the presentation timestamp in input
 
 @item N
 the count of the input frame, starting from 0.
 
 @item NB_CONSUMED_SAMPLES
 the number of consumed samples, not including the current frame (only
 audio)
 
 @item NB_SAMPLES
 the number of samples in the current frame (only audio)
 
 @item SAMPLE_RATE
 audio sample rate
 
 @item STARTPTS
 the PTS of the first frame
 

 @item STARTT
 the time in seconds of the first frame
 

 @item INTERLACED
 tell if the current frame is interlaced
 

 @item T
 the time in seconds of the current frame
 

 @item TB
 the time base
 
 @item POS
 original position in the file of the frame, or undefined if undefined
 for the current frame
 
 @item PREV_INPTS
 previous input PTS
 

 @item PREV_INT
 previous input time in seconds
 

 @item PREV_OUTPTS
 previous output PTS
 

 @item PREV_OUTT
 previous output time in seconds

 @end table
 

 @subsection Examples

 @itemize
 @item
 Start counting PTS from zero

 @example
 setpts=PTS-STARTPTS

 @end example

 @item
 Apply fast motion effect:
 @example

 setpts=0.5*PTS

 @end example

 @item
 Apply slow motion effect:
 @example

 setpts=2.0*PTS

 @end example

 @item
 Set fixed rate of 25 frames per second:
 @example

 setpts=N/(25*TB)

 @end example

 @item
 Set fixed rate 25 fps with some jitter:
 @example

 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'

 @end example

 @item
 Apply an offset of 10 seconds to the input PTS:
 @example

 setpts=PTS+10/TB
 @end example

 @end itemize

 
 @section settb, asettb
 
 Set the timebase to use for the output frames timestamps.
 It is mainly useful for testing timebase configuration.
 
 It accepts in input an arithmetic expression representing a rational.
 The expression can contain the constants "AVTB" (the
 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
 audio only).
 
 The default value for the input is "intb".
 

 @subsection Examples

 @itemize
 @item
 Set the timebase to 1/25:

 @example
 settb=1/25

 @end example

 @item
 Set the timebase to 1/10:
 @example

 settb=0.1

 @end example

 @item
 Set the timebase to 1001/1000:
 @example

 settb=1+0.001

 @end example

 @item
 Set the timebase to 2*intb:
 @example

 settb=2*intb

 @end example

 @item
 Set the default timebase value:
 @example

 settb=AVTB
 @end example

 @end itemize

 @section concat
 
 Concatenate audio and video streams, joining them together one after the
 other.
 
 The filter works on segments of synchronized video and audio streams. All
 segments must have the same number of streams of each type, and that will
 also be the number of streams at output.
 
 The filter accepts the following named parameters:
 @table @option
 
 @item n
 Set the number of segments. Default is 2.
 
 @item v
 Set the number of output video streams, that is also the number of video
 streams in each segment. Default is 1.
 
 @item a
 Set the number of output audio streams, that is also the number of video
 streams in each segment. Default is 0.
 
 @end table
 
 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
 @var{a} audio outputs.
 
 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
 segment, in the same order as the outputs, then the inputs for the second
 segment, etc.
 
 Related streams do not always have exactly the same duration, for various
 reasons including codec frame size or sloppy authoring. For that reason,
 related synchronized streams (e.g. a video and its audio track) should be
 concatenated at once. The concat filter will use the duration of the longest
 stream in each segment (except the last one), and if necessary pad shorter
 audio streams with silence.
 
 For this filter to work correctly, all segments must start at timestamp 0.
 
 All corresponding streams must have the same parameters in all segments; the
 filtering system will automatically select a common pixel format for video
 streams, and a common sample format, sample rate and channel layout for
 audio streams, but other settings, such as resolution, must be converted
 explicitly by the user.
 
 Different frame rates are acceptable but will result in variable frame rate
 at output; be sure to configure the output file to handle it.
 
 Examples:
 @itemize
 @item
 Concatenate an opening, an episode and an ending, all in bilingual version
 (video in stream 0, audio in streams 1 and 2):
 @example
 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
   '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
    concat=n=3:v=1:a=2 [v] [a1] [a2]' \
   -map '[v]' -map '[a1]' -map '[a2]' output.mkv
 @end example
 
 @item
 Concatenate two parts, handling audio and video separately, using the
 (a)movie sources, and adjusting the resolution:
 @example
 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
 @end example
 Note that a desync will happen at the stitch if the audio and video streams
 do not have exactly the same duration in the first file.
 
 @end itemize
 

 @section showspectrum
 
 Convert input audio to a video output, representing the audio frequency
 spectrum.
 
 The filter accepts the following named parameters:
 @table @option
 @item size, s
 Specify the video size for the output. Default value is @code{640x480}.
 @end table
 
 The usage is very similar to the showwaves filter; see the examples in that
 section.
 

 @section showwaves
 
 Convert input audio to a video output, representing the samples waves.
 
 The filter accepts the following named parameters:
 @table @option
 
 @item n
 Set the number of samples which are printed on the same column. A
 larger value will decrease the frame rate. Must be a positive
 integer. This option can be set only if the value for @var{rate}
 is not explicitly specified.
 
 @item rate, r
 Set the (approximate) output frame rate. This is done by setting the
 option @var{n}. Default value is "25".
 
 @item size, s
 Specify the video size for the output. Default value is "600x240".
 @end table
 
 Some examples follow.
 @itemize
 @item
 Output the input file audio and the corresponding video representation
 at the same time:
 @example
 amovie=a.mp3,asplit[out0],showwaves[out1]
 @end example
 
 @item
 Create a synthetic signal and show it with showwaves, forcing a
 framerate of 30 frames per second:
 @example
 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
 @end example
 @end itemize
 

 @c man end MULTIMEDIA FILTERS

 
 @chapter Multimedia Sources
 @c man begin MULTIMEDIA SOURCES
 
 Below is a description of the currently available multimedia sources.
 
 @section amovie
 
 This is the same as @ref{src_movie} source, except it selects an audio
 stream by default.
 
 @anchor{src_movie}
 @section movie
 
 Read audio and/or video stream(s) from a movie container.
 
 It accepts the syntax: @var{movie_name}[:@var{options}] where
 @var{movie_name} is the name of the resource to read (not necessarily
 a file but also a device or a stream accessed through some protocol),
 and @var{options} is an optional sequence of @var{key}=@var{value}
 pairs, separated by ":".
 
 The description of the accepted options follows.
 
 @table @option
 
 @item format_name, f
 Specifies the format assumed for the movie to read, and can be either
 the name of a container or an input device. If not specified the
 format is guessed from @var{movie_name} or by probing.
 
 @item seek_point, sp
 Specifies the seek point in seconds, the frames will be output
 starting from this seek point, the parameter is evaluated with
 @code{av_strtod} so the numerical value may be suffixed by an IS
 postfix. Default value is "0".
 
 @item streams, s
 Specifies the streams to read. Several streams can be specified, separated
 by "+". The source will then have as many outputs, in the same order. The
 syntax is explained in the @ref{Stream specifiers} chapter. Two special
 names, "dv" and "da" specify respectively the default (best suited) video
 and audio stream. Default is "dv", or "da" if the filter is called as
 "amovie".
 
 @item stream_index, si
 Specifies the index of the video stream to read. If the value is -1,
 the best suited video stream will be automatically selected. Default
 value is "-1". Deprecated. If the filter is called "amovie", it will select
 audio instead of video.
 
 @item loop
 Specifies how many times to read the stream in sequence.
 If the value is less than 1, the stream will be read again and again.
 Default value is "1".
 
 Note that when the movie is looped the source timestamps are not
 changed, so it will generate non monotonically increasing timestamps.
 @end table
 
 This filter allows to overlay a second video on top of main input of
 a filtergraph as shown in this graph:
 @example
 input -----------> deltapts0 --> overlay --> output
                                     ^
                                     |
 movie --> scale--> deltapts1 -------+
 @end example
 

 Some examples follow.
 
 @itemize
 @item
 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
 on top of the input labelled as "in":

 @example
 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]

 @end example

 @item
 Read from a video4linux2 device, and overlay it on top of the input
 labelled as "in":
 @example

 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]

 @end example

 @item
 Read the first video stream and the audio stream with id 0x81 from
 dvd.vob; the video is connected to the pad named "video" and the audio is
 connected to the pad named "audio":
 @example

 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
 @end example

 @end itemize

 
 @c man end MULTIMEDIA SOURCES