1 \input texinfo @c -*- texinfo -*-
3 @settitle Libavfilter Documentation
6 @center @titlefont{Libavfilter Documentation}
13 Libavfilter is the filtering API of FFmpeg. It is the substitute of the
14 now deprecated 'vhooks' and started as a Google Summer of Code project.
16 Integrating libavfilter into the main FFmpeg repository is a work in
17 progress. If you wish to try the unfinished development code of
18 libavfilter then check it out from the libavfilter repository into
19 some directory of your choice by:
22 svn checkout svn://svn.ffmpeg.org/soc/libavfilter
25 And then read the README file in the top directory to learn how to
26 integrate it into ffmpeg and ffplay.
28 But note that there may still be serious bugs in the code and its API
29 and ABI should not be considered stable yet!
33 In libavfilter, it is possible for filters to have multiple inputs and
35 To illustrate the sorts of things that are possible, we can
36 use a complex filter graph. For example, the following one:
39 input --> split --> fifo -----------------------> overlay --> output
42 +------> fifo --> crop --> vflip --------+
45 splits the stream in two streams, sends one stream through the crop filter
46 and the vflip filter before merging it back with the other stream by
47 overlaying it on top. You can use the following command to achieve this:
50 ./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]
53 where input_video.avi has a vertical resolution of 480 pixels. The
54 result will be that in output the top half of the video is mirrored
57 Video filters are loaded using the @var{-vfilters} option passed to
58 ffmpeg or to ffplay. Filters in the same linear chain are separated by
59 commas. In our example, @var{split, fifo, overlay} are in one linear
60 chain, and @var{fifo, crop, vflip} are in another. The points where
61 the linear chains join are labeled by names enclosed in square
62 brackets. In our example, that is @var{[T1]} and @var{[T2]}. The magic
63 labels @var{[in]} and @var{[out]} are the points where video is input
66 Some filters take in input a list of parameters: they are specified
67 after the filter name and an equal sign, and are separated each other
70 There exist so-called @var{source filters} that do not have a video
71 input, and we expect in the future some @var{sink filters} that will
72 not have video output.
76 The @file{graph2dot} program included in the FFmpeg @file{tools}
77 directory can be used to parse a filter graph description and issue a
78 corresponding textual representation in the dot language.
85 to see how to use @file{graph2dot}.
87 You can then pass the dot description to the @file{dot} program (from
88 the graphviz suite of programs) and obtain a graphical representation
91 For example the sequence of commands:
93 echo @var{GRAPH_DESCRIPTION} | \
94 tools/graph2dot -o graph.tmp && \
95 dot -Tpng graph.tmp -o graph.png && \
99 can be used to create and display an image representing the graph
100 described by the @var{GRAPH_DESCRIPTION} string.
102 @chapter Available video filters
104 When you configure your FFmpeg build, you can disable any of the
105 existing video filters.
106 The configure output will show the video filters included in your
109 Below is a description of the currently available video filters.
113 Crop the input video to x:y:width:height.
116 ./ffmpeg -i in.avi -vfilters "crop=0:0:0:240" out.avi
119 ``x'' and ``y'' specify the position of the top-left corner of the
120 output (non-cropped) area.
122 The default value of ``x'' and ``y'' is 0.
124 The ``width'' and ``height'' parameters specify the width and height
125 of the output (non-cropped) area.
127 A value of 0 is interpreted as the maximum possible size contained in
128 the area delimited by the top-left corner at position x:y.
130 For example the parameters:
136 will delimit the rectangle with the top-left corner placed at position
137 100:100 and the right-bottom corner corresponding to the right-bottom
138 corner of the input image.
140 The default value of ``width'' and ``height'' is 0.
144 Convert the input video to one of the specified pixel formats.
145 Libavfilter will try to pick one that is supported for the input to
148 The filter accepts a list of pixel format names, separated by ``:'',
149 for example ``yuv420p:monow:rgb24''.
151 The following command:
154 ./ffmpeg -i in.avi -vfilters "format=yuv420p" out.avi
157 will convert the input video to the format ``yuv420p''.
161 Force libavfilter not to use any of the specified pixel formats for the
162 input to the next filter.
164 The filter accepts a list of pixel format names, separated by ``:'',
165 for example ``yuv420p:monow:rgb24''.
167 The following command:
170 ./ffmpeg -i in.avi -vfilters "noformat=yuv420p, vflip" out.avi
173 will make libavfilter use a format different from ``yuv420p'' for the
174 input to the vflip filter.
178 Pass the source unchanged to the output.
182 Scale the input video to width:height and/or convert the image format.
184 For example the command:
187 ./ffmpeg -i in.avi -vfilters "scale=200:100" out.avi
190 will scale the input video to a size of 200x100.
192 If the input image format is different from the format requested by
193 the next filter, the scale filter will convert the input to the
196 If the value for ``width'' or ``height'' is 0, the respective input
197 size is used for the output.
199 If the value for ``width'' or ``height'' is -1, the scale filter will
200 use, for the respective output size, a value that maintains the aspect
201 ratio of the input image.
203 The default value of ``width'' and ``height'' is 0.
207 Pass the images of input video on to next video filter as multiple
211 ./ffmpeg -i in.avi -vfilters "slicify=32" out.avi
214 The filter accepts the slice height as parameter. If the parameter is
215 not specified it will use the default value of 16.
217 Adding this in the beginning of filter chains should make filtering
218 faster due to better use of the memory cache.
222 Flip the input video vertically.
225 ./ffmpeg -i in.avi -vfilters "vflip" out.avi
228 @chapter Available video sources
230 Below is a description of the currently available video sources.
234 Null video source, never return images. It is mainly useful as a
235 template and to be employed in analysis / debugging tools.
237 It accepts as optional parameter a string of the form
238 ``width:height'', where ``width'' and ``height'' specify the size of
239 the configured source.
241 The default values of ``width'' and ``height'' are respectively 352
242 and 288 (corresponding to the CIF size format).
244 @chapter Available video sinks
246 Below is a description of the currently available video sinks.
250 Null video sink, do absolutely nothing with the input video. It is
251 mainly useful as a template and to be employed in analysis / debugging