@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".
 
 @section Filtergraph syntax
 
 A filtergraph can be represented using a textual representation, which

 is recognized by the @code{-vf} option of the ff*

 tools, and by the @code{avfilter_graph_parse()} 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.
 
 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{LINKLABELS}] @var{NAME} ["=" @var{FILTER_ARGUMENTS}] [@var{LINKLABELS}]

 @var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]
 @var{FILTERGRAPH}      ::= @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{packing_format}".
 
 @var{sample_format} specifies the sample format, and can be a string or
 the corresponding numeric value defined in @file{libavutil/samplefmt.h}.
 
 @var{channel_layout} specifies the channel layout, and can be a string

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

 
 @var{packing_format} specifies the type of packing in output, can be one
 of "planar" or "packed", or the corresponding numeric values "0" or "1".
 
 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 unsigned 8-bit, stereo, packed:
 @example
 aconvert=u8:stereo:packed
 @end example
 
 @item
 Convert input to unsigned 8-bit, automatically select out channel layout
 and packing format:
 @example
 aconvert=u8:auto: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 three lists of formats, separated by ":", in the form:
 "@var{sample_formats}:@var{channel_layouts}:@var{packing_formats}".
 
 Elements in each list are separated by "," which has to be escaped in the
 filtergraph specification.
 
 The special parameter "all", in place of a list of elements, signifies all
 supported formats.
 
 Some examples follow:
 @example
 aformat=u8\\,s16:mono:packed
 
 aformat=s16:mono\\,stereo:all
 @end example
 

 @section amerge
 
 Merge two audio streams into a single multi-channel stream.
 
 This filter does not need any argument.
 
 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.
 
 Both inputs must have the same sample rate, format and packing.
 
 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
 

 @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 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 planar
 if the packing format is planar, 0 if packed
 
 @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
 
 Pass on the input audio to two outputs. Both outputs are identical to
 the input audio.
 
 For example:
 @example
 [in] asplit[out0], showaudio[out1]
 @end example
 
 will create two separate outputs from the same input, one cropped and
 one padded.
 

 @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 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,
 @item the number of output channels is supported by libswresample (16 at the
       moment)
 @c if SWR_CH_MAX changes, fix the line above.
 @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
 

 @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}:@var{packing}
 
 @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}
 
 @item packing
 Either "packed" or "planar", or their integer representation: 0 or 1
 respectively.
 
 @end table
 
 For example:
 @example
 abuffer=44100:s16:stereo:planar
 @end example
 
 will instruct the source to accept planar 16bit signed stereo at 44100Hz.
 Since the sample format with name "s16" corresponds to the number
 1 and the "stereo" channel layout corresponds to the value 3, this is
 equivalent to:
 @example
 abuffer=44100:1:3:1
 @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. The output channel layout depends on the number of
 provided expressions, up to 8 channels are supported.
 
 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
 separated by ":".
 
 The description of the accepted options follows.
 
 @table @option
 

 @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 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 amovie
 
 Read an audio stream 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
 Specify 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
 Specify 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 stream_index, si
 Specify the index of the audio stream to read. If the value is -1,
 the best suited audio stream will be automatically selected. Default
 value is "-1".
 
 @end table
 

 @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
 
 @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.
 
 @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 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 in input the name of the ass file to render.
 
 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 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 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}.

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

 
 @item fontsize
 The font size to be used for drawing text.

 The default value of @var{fontsize} is 16.

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

 The parameters for @var{x} and @var{y} are expressions containing the
 following constants:
 
 @table @option

 @item W, H

 the input width and height

 
 @item tw, text_w
 the width of the rendered text
 
 @item th, text_h
 the height of the rendered text
 
 @item lh, line_h
 the height of each text line
 
 @item sar
 input sample aspect ratio
 
 @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 max_glyph_w
 maximum glyph width, that is the maximum width for all the glyphs
 contained in the rendered text
 
 @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_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 n
 the number of input frame, starting from 0
 
 @item t
 timestamp expressed in seconds, NAN if the input timestamp is unknown

 
 @item timecode
 initial timecode representation in "hh:mm:ss[:;.]ff" format. It can be used

 with or without text parameter. @var{rate} option must be specified.
 Note that timecode options are @emph{not} effective if FFmpeg is build with
 @code{--disable-avcodec}.

 
 @item r, rate
 frame rate (timecode only)

 @end table
 

 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
 

 @end itemize
 

 For more information about libfreetype, check:

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

 @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

 @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:
 @example
 # apply the distort0r effect, set the first two double parameters
 frei0r=distort0r:0.5:0.01
 
 # apply the colordistance effect, takes a color as first parameter
 frei0r=colordistance:0.2/0.3/0.4
 frei0r=colordistance:violet
 frei0r=colordistance:0x112233
 
 # apply the perspective effect, specify the top left and top right
 # image positions
 frei0r=perspective:0.2/0.2:0.8/0.2
 @end example
 
 For more information see:
 @url{http://piksel.org/frei0r}
 

 @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 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 2xsai
 @item decimate
 @item denoise3d
 @item detc
 @item dint
 @item divtc
 @item down3dright
 @item dsize
 @item eq2
 @item eq
 @item field
 @item fil
 @item fixpts
 @item framestep
 @item fspp
 @item geq
 @item harddup
 @item hqdn3d
 @item hue
 @item il
 @item ilpack
 @item ivtc
 @item kerndeint
 @item mcdeint
 @item mirror
 @item noise
 @item ow
 @item palette
 @item perspective
 @item phase
 @item pp7
 @item pullup
 @item qp
 @item rectangle

 @item remove-logo

 @item rotate
 @item sab
 @item screenshot
 @item smartblur
 @item softpulldown
 @item softskip
 @item spp
 @item swapuv
 @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:
 @example
 # remove a logo by interpolating the surrounding pixels
 mp=delogo=200:200:80:20:1
 
 # adjust gamma, brightness, contrast
 mp=eq2=1.0:2:0.5
 
 # tweak hue and saturation
 mp=hue=100:-10
 @end example
 
 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

 movie=logo.png [logo];

 [in][logo] overlay=10:main_h-overlay_h-10 [out]
 
 # insert 2 different transparent PNG logos (second logo on bottom
 # right corner):

 movie=logo1.png [logo1];
 movie=logo2.png [logo2];

 [in][logo1]       overlay=10:H-h-10 [in+logo1];
 [in+logo1][logo2] overlay=W-w-10:H-h-10 [out]
 
 # 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]
 @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
 

 Some examples follow:

 
 @example
 # 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.

 pad=640:480:0:40:violet

 
 # pad the input to get an output with dimensions increased bt 3/2,
 # and put the input video at the center of the padded area
 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
 
 # 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
 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
 
 # pad the input to get a final w/h ratio of 16:9
 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
 

 # for anamorphic video, in order to set the output display aspect ratio,
 # it is necessary to use sar in the expression, according to the relation:
 # (ih * X / ih) * sar = output_dar
 # X = output_dar / sar
 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
 

 # double output size and put the input video in the bottom-right
 # corner of the output padded area
 pad="2*iw:2*ih:ow-iw:oh-ih"

 @end example
 

 @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 scale
 

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

 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
 

 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 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)
 @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
 

 @anchor{setdar}
 @section setdar
 
 Set 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:
 @math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
 
 Keep in mind that this 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 filter accepts a parameter string which represents the wanted
 display aspect ratio.
 The parameter can be a floating point number string, or an expression
 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
 # the above is equivalent to
 setdar=1.77777
 @end example
 

 See also the @ref{setsar} filter documentation.

 @section setpts
 
 Change the PTS (presentation timestamp) of the input video frames.
 
 Accept in input an expression evaluated through the eval API, which
 can contain the following constants:
 
 @table @option
 @item PTS
 the presentation timestamp in input
 
 @item N
 the count of the input frame, starting from 0.
 
 @item STARTPTS
 the PTS of the first video frame
 
 @item INTERLACED
 tell if the current frame is interlaced
 
 @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_OUTPTS
 previous output PTS
 
 @end table
 
 Some examples follow:
 
 @example
 # start counting PTS from zero
 setpts=PTS-STARTPTS
 
 # fast motion
 setpts=0.5*PTS
 
 # slow motion
 setpts=2.0*PTS
 
 # fixed rate 25 fps
 setpts=N/(25*TB)
 
 # fixed rate 25 fps with some jitter
 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
 @end example
 

 @anchor{setsar}
 @section setsar
 
 Set 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 following
 equation:
 @math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
 
 Keep in mind that the sample aspect ratio set by this filter may be
 changed by later filters in the filterchain, e.g. if another "setsar"
 or a "setdar" filter is applied.
 
 The filter accepts a parameter string which represents the wanted
 sample aspect ratio.
 The parameter can be a floating point number string, or an expression
 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 sample aspect ratio to 10:11, specify:
 @example
 setsar=10:11
 @end example
 

 @section settb
 
 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), and "intb" (the input timebase).
 
 The default value for the input is "intb".
 
 Follow some examples.
 
 @example
 # set the timebase to 1/25
 settb=1/25
 
 # set the timebase to 1/10
 settb=0.1
 
 #set the timebase to 1001/1000
 settb=1+0.001
 
 #set the timebase to 2*intb
 settb=2*intb
 
 #set the default timebase value
 settb=AVTB
 @end example
 

 @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 split
 
 Pass on the input video to two outputs. Both outputs are identical to
 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 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 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 0
 Move odd frames into the upper field, even into the lower field,
 generating a double height frame at half framerate.
 
 @item 1
 Only output even frames, odd frames are dropped, generating a frame with
 unchanged height at half framerate.
 
 @item 2
 Only output odd frames, even frames are dropped, generating a frame with
 unchanged height at half framerate.
 
 @item 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 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 5
 Interleave the lower field from odd frames with the upper field from
 even frames, generating a frame with unchanged height at half framerate.

 @end table
 
 Default mode is 0.
 

 @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
 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
 @example
 L.R     L.l
 . . ->  . .
 l.r     R.r
 @end example
 
 @item 1
 Rotate by 90 degrees clockwise, that is:
 @example
 L.R     l.L
 . . ->  . .
 l.r     r.R
 @end example
 
 @item 2
 Rotate by 90 degrees counterclockwise, that is:
 @example
 L.R     R.r
 . . ->  . .
 l.r     L.l
 @end example
 
 @item 3
 Rotate by 90 degrees clockwise and vertically flip, that is:
 @example
 L.R     r.R
 . . ->  . .
 l.r     l.L
 @end example
 @end table
 

 @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 the following parameters:

 @var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}:@var{sample_aspect_ratio_num}:@var{sample_aspect_ratio.den}:@var{scale_params}

 All the parameters but @var{scale_params} need to be explicitly

 defined.

 
 Follows the list of the accepted parameters.
 
 @table @option
 
 @item width, height
 Specify the width and height of the buffered video frames.
 
 @item pix_fmt_string
 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 timebase_num, timebase_den
 Specify numerator and denomitor of the timebase assumed by the
 timestamps of the buffered frames.

 
 @item sample_aspect_ratio.num, sample_aspect_ratio.den
 Specify numerator and denominator of the sample aspect ratio assumed
 by the video frames.

 
 @item scale_params
 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=320:240:yuv410p:1:24:1:1

 @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=320:240:6:1:24:1:1

 @end example
 

 @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 color
 
 Provide an uniformly colored input.
 
 It accepts the following parameters:

 @var{color}:@var{frame_size}:@var{frame_rate}

 
 Follows the description of the accepted parameters.
 
 @table @option
 
 @item color
 Specify the color of the 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 frame_size
 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 frame_rate
 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".
 
 @end table
 
 For example 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, which will be overlayed over the source connected
 to the pad with identifier "in".
 
 @example
 "color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
 @end example
 

 @section movie
 
 Read a video stream 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 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".
 
 @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:
 @example
 # skip 3.2 seconds from the start of the avi file in.avi, and overlay it
 # on top of the input labelled as "in".
 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
 
 # read from a video4linux2 device, and overlay it on top of the input
 # labelled as "in"
 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
 
 @end example
 

 @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.

 
 Some examples follow:
 @example

 # generate a frei0r partik0l source with size 200x200 and frame rate 10

 # which is overlayed on the overlay filter main input
 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 nullsrc, rgbtestsrc, testsrc
 
 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{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 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.

 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