\input texinfo @c -*- texinfo -*-
 

 @settitle Libavfilter Documentation

 @titlepage
 @sp 7

 @center @titlefont{Libavfilter Documentation}

 @sp 3
 @end titlepage
 
 
 @chapter Introduction
 
 Libavfilter is the filtering API of FFmpeg. It is the substitute of the
 now deprecated 'vhooks' and started as a Google Summer of Code project.
 
 Integrating libavfilter into the main FFmpeg repository is a work in
 progress. If you wish to try the unfinished development code of
 libavfilter then check it out from the libavfilter repository into
 some directory of your choice by:
 
 @example
    svn checkout svn://svn.ffmpeg.org/soc/libavfilter
 @end example
 
 And then read the README file in the top directory to learn how to
 integrate it into ffmpeg and ffplay.
 
 But note that there may still be serious bugs in the code and its API
 and ABI should not be considered stable yet!
 

 @chapter Tutorial
 

 In libavfilter, it is possible for filters to have multiple inputs and
 multiple outputs.
 To illustrate the sorts of things that are possible, we can
 use a complex filter graph. For example, the following one:
 
 @example
 input --> split --> fifo -----------------------> overlay --> output
             |                                        ^
             |                                        |
             +------> fifo --> crop --> vflip --------+
 @end example
 
 splits the stream in two streams, sends one stream through the crop filter
 and the vflip filter before merging it back with the other stream by
 overlaying it on top. You can use the following command to achieve this:
 
 @example
 ./ffmpeg -i in.avi -s 240x320 -vfilters "[in] split [T1], fifo, [T2] overlay= 0:240 [out]; [T1] fifo, crop=0:0:-1:240, vflip [T2]
 @end example
 
 where input_video.avi has a vertical resolution of 480 pixels. The
 result will be that in output the top half of the video is mirrored
 onto the bottom half.
 
 Video filters are loaded using the @var{-vfilters} option passed to
 ffmpeg or to ffplay. Filters in the same linear chain are separated by
 commas. In our example, @var{split, fifo, overlay} are in one linear
 chain, and @var{fifo, crop, vflip} are in another. The points where
 the linear chains join are labeled by names enclosed in square
 brackets. In our example, that is @var{[T1]} and @var{[T2]}. The magic
 labels @var{[in]} and @var{[out]} are the points where video is input
 and output.
 
 Some filters take in input a list of parameters: they are specified
 after the filter name and an equal sign, and are separated each other
 by a semicolon.
 
 There exist so-called @var{source filters} that do not have a video
 input, and we expect in the future some @var{sink filters} that will
 not have video output.
 

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

 @chapter Available video filters
 
 When you configure your FFmpeg build, you can disable any of the
 existing video filters.
 The configure output will show the video filters included in your
 build.
 
 Below is a description of the currently available video filters.
 

 @section crop
 

 Crop the input video to @var{x}:@var{y}:@var{width}:@var{height}.

 
 @example
 ./ffmpeg -i in.avi -vfilters "crop=0:0:0:240" out.avi
 @end example
 

 @var{x} and @var{y} specify the position of the top-left corner of the

 output (non-cropped) area.
 

 The default value of @var{x} and @var{y} is 0.

 The @var{width} and @var{height} parameters specify the width and height

 of the output (non-cropped) area.

 
 A value of 0 is interpreted as the maximum possible size contained in
 the area delimited by the top-left corner at position x:y.
 
 For example the parameters:
 
 @example
 "crop=100:100:0:0"
 @end example
 
 will 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.
 

 The default value of @var{width} and @var{height} is 0.

 @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''.

 
 The following command:
 
 @example
 ./ffmpeg -i in.avi -vfilters "format=yuv420p" out.avi
 @end example
 
 will convert the input video to the format ``yuv420p''.
 
 @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''.

 
 The following command:
 
 @example
 ./ffmpeg -i in.avi -vfilters "noformat=yuv420p, vflip" out.avi
 @end example
 

 will make libavfilter use a format different from ``yuv420p'' for the

 input to the vflip filter.
 

 @section null
 
 Pass the source unchanged to the output.
 

 @section scale
 

 Scale the input video to @var{width}:@var{height} and/or convert the image format.

 
 For example the command:
 
 @example
 ./ffmpeg -i in.avi -vfilters "scale=200:100" out.avi
 @end example
 
 will scale the input video to a size of 200x100.
 
 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.

 @section slicify
 
 Pass the images of input video on to next video filter as multiple
 slices.
 
 @example
 ./ffmpeg -i in.avi -vfilters "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 unsharp
 
 Sharpen or blur the input video. It accepts the following parameters:
 
 @multitable @columnfractions .2 .5 .1 .1 .1
 @headitem Name @tab Description @tab Min @tab Max @tab Default
 @item @var{luma_msize_x}
 @tab Luma matrix horizontal size
 @tab 3
 @tab 13
 @tab 5
 @item @var{luma_msize_y}
 @tab Luma matrix vertical size
 @tab 3
 @tab 13
 @tab 5
 @item @var{luma_amount}
 @tab Luma effect strength
 @tab -2.0
 @tab 5.0
 @tab 1.0
 @item @var{chroma_msize_x}
 @tab Chroma matrix horizontal size
 @tab 3
 @tab 13
 @tab 0
 @item @var{chroma_msize_y}
 @tab Chroma matrix vertical size
 @tab 3
 @tab 13
 @tab 0
 @item @var{chroma_amount}
 @tab Chroma effect strength
 @tab -2.0
 @tab 5.0
 @tab 0.0
 @end multitable
 
 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 '5:5:1.0:0:0:0.0'.
 
 @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 -vfilters "unsharp" out.mp4
 @end example
 

 @section vflip
 
 Flip the input video vertically.
 
 @example
 ./ffmpeg -i in.avi -vfilters "vflip" out.avi
 @end example
 

 @chapter Available video sources
 
 Below is a description of the currently available video sources.
 
 @section nullsrc
 
 Null video source, never return images. It is mainly useful as a
 template and to be employed in analysis / debugging tools.
 
 It accepts as optional parameter a string of the form

 @var{width}:@var{height}, where @var{width} and @var{height} specify the size of

 the configured source.
 

 The default values of @var{width} and @var{height} are respectively 352

 and 288 (corresponding to the CIF size format).
 

 @chapter Available video sinks
 
 Below is a description of the currently available video sinks.
 
 @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.
 

 @bye