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 -vf "[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{-vf} 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 @var{x}:@var{y}:@var{width}:@var{height}.
116 ./ffmpeg -i in.avi -vf "crop=0:0:0:240" out.avi
119 @var{x} and @var{y} specify the position of the top-left corner of the
120 output (non-cropped) area.
122 The default value of @var{x} and @var{y} is 0.
124 The @var{width} and @var{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 @var{width} and @var{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 -vf "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 -vf "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 Add paddings to the input image, and places the original input at the
183 given coordinates @var{x}, @var{y}.
185 It accepts the following parameters:
186 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
188 Follows the description of the accepted parameters.
193 Specify the size of the output image with the paddings added. If the
194 value for @var{width} or @var{height} is 0, the corresponding input size
195 is used for the output.
197 The default value of @var{width} and @var{height} is 0.
201 Specify the offsets where to place the input image in the padded area
202 with respect to the top/left border of the output image.
204 The default value of @var{x} and @var{y} is 0.
208 Specify the color of the padded area, it can be the name of a color
209 (case insensitive match) or a 0xRRGGBB[AA] sequence.
211 The default value of @var{color} is ``black''.
217 Scale the input video to @var{width}:@var{height} and/or convert the image format.
219 For example the command:
222 ./ffmpeg -i in.avi -vf "scale=200:100" out.avi
225 will scale the input video to a size of 200x100.
227 If the input image format is different from the format requested by
228 the next filter, the scale filter will convert the input to the
231 If the value for @var{width} or @var{height} is 0, the respective input
232 size is used for the output.
234 If the value for @var{width} or @var{height} is -1, the scale filter will
235 use, for the respective output size, a value that maintains the aspect
236 ratio of the input image.
238 The default value of @var{width} and @var{height} is 0.
242 Pass the images of input video on to next video filter as multiple
246 ./ffmpeg -i in.avi -vf "slicify=32" out.avi
249 The filter accepts the slice height as parameter. If the parameter is
250 not specified it will use the default value of 16.
252 Adding this in the beginning of filter chains should make filtering
253 faster due to better use of the memory cache.
257 Sharpen or blur the input video. It accepts the following parameters:
259 @multitable @columnfractions .2 .5 .1 .1 .1
260 @headitem Name @tab Description @tab Min @tab Max @tab Default
261 @item @var{luma_msize_x}
262 @tab Luma matrix horizontal size
266 @item @var{luma_msize_y}
267 @tab Luma matrix vertical size
271 @item @var{luma_amount}
272 @tab Luma effect strength
276 @item @var{chroma_msize_x}
277 @tab Chroma matrix horizontal size
281 @item @var{chroma_msize_y}
282 @tab Chroma matrix vertical size
286 @item @var{chroma_amount}
287 @tab Chroma effect strength
293 Negative values for the amount will blur the input video, while positive
294 values will sharpen. All parameters are optional and default to the
295 equivalent of the string '5:5:1.0:0:0:0.0'.
298 # Strong luma sharpen effect parameters
301 # Strong blur of both luma and chroma parameters
302 unsharp=7:7:-2:7:7:-2
304 # Use the default values with @command{ffmpeg}
305 ./ffmpeg -i in.avi -vf "unsharp" out.mp4
310 Flip the input video vertically.
313 ./ffmpeg -i in.avi -vf "vflip" out.avi
316 @chapter Available video sources
318 Below is a description of the currently available video sources.
322 Null video source, never return images. It is mainly useful as a
323 template and to be employed in analysis / debugging tools.
325 It accepts as optional parameter a string of the form
326 @var{width}:@var{height}, where @var{width} and @var{height} specify the size of
327 the configured source.
329 The default values of @var{width} and @var{height} are respectively 352
330 and 288 (corresponding to the CIF size format).
332 @chapter Available video sinks
334 Below is a description of the currently available video sinks.
338 Null video sink, do absolutely nothing with the input video. It is
339 mainly useful as a template and to be employed in analysis / debugging