1 @chapter Filtering Introduction
2 @c man begin FILTERING INTRODUCTION
4 Filtering in FFmpeg is enabled through the libavfilter library.
6 Libavfilter is the filtering API of FFmpeg. It is the substitute of
7 the now deprecated 'vhooks' and started as a Google Summer of Code
10 Audio filtering integration into the main FFmpeg repository is a work in
11 progress, so audio API and ABI should not be considered stable yet.
13 In libavfilter, it is possible for filters to have multiple inputs and
15 To illustrate the sorts of things that are possible, we can
16 use a complex filter graph. For example, the following one:
19 input --> split --> fifo -----------------------> overlay --> output
22 +------> fifo --> crop --> vflip --------+
25 splits the stream in two streams, sends one stream through the crop filter
26 and the vflip filter before merging it back with the other stream by
27 overlaying it on top. You can use the following command to achieve this:
30 ffmpeg -i input -vf "[in] split [T1], fifo, [T2] overlay=0:H/2 [out]; [T1] fifo, crop=iw:ih/2:0:ih/2, vflip [T2]" output
33 The result will be that in output the top half of the video is mirrored
36 Filters are loaded using the @var{-vf} or @var{-af} option passed to
37 @command{ffmpeg} or to @command{ffplay}. Filters in the same linear
38 chain are separated by commas. In our example, @var{split, fifo,
39 overlay} are in one linear chain, and @var{fifo, crop, vflip} are in
40 another. The points where the linear chains join are labeled by names
41 enclosed in square brackets. In our example, that is @var{[T1]} and
42 @var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points
43 where video is input and output.
45 Some filters take in input a list of parameters: they are specified
46 after the filter name and an equal sign, and are separated from each other
49 There exist so-called @var{source filters} that do not have an
50 audio/video input, and @var{sink filters} that will not have audio/video
53 @c man end FILTERING INTRODUCTION
56 @c man begin GRAPH2DOT
58 The @file{graph2dot} program included in the FFmpeg @file{tools}
59 directory can be used to parse a filter graph description and issue a
60 corresponding textual representation in the dot language.
67 to see how to use @file{graph2dot}.
69 You can then pass the dot description to the @file{dot} program (from
70 the graphviz suite of programs) and obtain a graphical representation
73 For example the sequence of commands:
75 echo @var{GRAPH_DESCRIPTION} | \
76 tools/graph2dot -o graph.tmp && \
77 dot -Tpng graph.tmp -o graph.png && \
81 can be used to create and display an image representing the graph
82 described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be
83 a complete self-contained graph, with its inputs and outputs explicitly defined.
84 For example if your command line is of the form:
86 ffmpeg -i infile -vf scale=640:360 outfile
88 your @var{GRAPH_DESCRIPTION} string will need to be of the form:
90 nullsrc,scale=640:360,nullsink
92 you may also need to set the @var{nullsrc} parameters and add a @var{format}
93 filter in order to simulate a specific input file.
97 @chapter Filtergraph description
98 @c man begin FILTERGRAPH DESCRIPTION
100 A filtergraph is a directed graph of connected filters. It can contain
101 cycles, and there can be multiple links between a pair of
102 filters. Each link has one input pad on one side connecting it to one
103 filter from which it takes its input, and one output pad on the other
104 side connecting it to the one filter accepting its output.
106 Each filter in a filtergraph is an instance of a filter class
107 registered in the application, which defines the features and the
108 number of input and output pads of the filter.
110 A filter with no input pads is called a "source", a filter with no
111 output pads is called a "sink".
113 @anchor{Filtergraph syntax}
114 @section Filtergraph syntax
116 A filtergraph can be represented using a textual representation, which is
117 recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}
118 options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the
119 @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in
120 @file{libavfilter/avfiltergraph.h}.
122 A filterchain consists of a sequence of connected filters, each one
123 connected to the previous one in the sequence. A filterchain is
124 represented by a list of ","-separated filter descriptions.
126 A filtergraph consists of a sequence of filterchains. A sequence of
127 filterchains is represented by a list of ";"-separated filterchain
130 A filter is represented by a string of the form:
131 [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
133 @var{filter_name} is the name of the filter class of which the
134 described filter is an instance of, and has to be the name of one of
135 the filter classes registered in the program.
136 The name of the filter class is optionally followed by a string
139 @var{arguments} is a string which contains the parameters used to
140 initialize the filter instance, and are described in the filter
143 The list of arguments can be quoted using the character "'" as initial
144 and ending mark, and the character '\' for escaping the characters
145 within the quoted text; otherwise the argument string is considered
146 terminated when the next special character (belonging to the set
147 "[]=;,") is encountered.
149 The name and arguments of the filter are optionally preceded and
150 followed by a list of link labels.
151 A link label allows to name a link and associate it to a filter output
152 or input pad. The preceding labels @var{in_link_1}
153 ... @var{in_link_N}, are associated to the filter input pads,
154 the following labels @var{out_link_1} ... @var{out_link_M}, are
155 associated to the output pads.
157 When two link labels with the same name are found in the
158 filtergraph, a link between the corresponding input and output pad is
161 If an output pad is not labelled, it is linked by default to the first
162 unlabelled input pad of the next filter in the filterchain.
163 For example in the filterchain:
165 nullsrc, split[L1], [L2]overlay, nullsink
167 the split filter instance has two output pads, and the overlay filter
168 instance two input pads. The first output pad of split is labelled
169 "L1", the first input pad of overlay is labelled "L2", and the second
170 output pad of split is linked to the second input pad of overlay,
171 which are both unlabelled.
173 In a complete filterchain all the unlabelled filter input and output
174 pads must be connected. A filtergraph is considered valid if all the
175 filter input and output pads of all the filterchains are connected.
177 Libavfilter will automatically insert scale filters where format
178 conversion is required. It is possible to specify swscale flags
179 for those automatically inserted scalers by prepending
180 @code{sws_flags=@var{flags};}
181 to the filtergraph description.
183 Follows a BNF description for the filtergraph syntax:
185 @var{NAME} ::= sequence of alphanumeric characters and '_'
186 @var{LINKLABEL} ::= "[" @var{NAME} "]"
187 @var{LINKLABELS} ::= @var{LINKLABEL} [@var{LINKLABELS}]
188 @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
189 @var{FILTER} ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]
190 @var{FILTERCHAIN} ::= @var{FILTER} [,@var{FILTERCHAIN}]
191 @var{FILTERGRAPH} ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
194 @section Notes on filtergraph escaping
196 Some filter arguments require the use of special characters, typically
197 @code{:} to separate key=value pairs in a named options list. In this
198 case the user should perform a first level escaping when specifying
199 the filter arguments. For example, consider the following literal
200 string to be embedded in the @ref{drawtext} filter arguments:
202 this is a 'string': may contain one, or more, special characters
205 Since @code{:} is special for the filter arguments syntax, it needs to
206 be escaped, so you get:
208 text=this is a \'string\'\: may contain one, or more, special characters
211 A second level of escaping is required when embedding the filter
212 arguments in a filtergraph description, in order to escape all the
213 filtergraph special characters. Thus the example above becomes:
215 drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
218 Finally an additional level of escaping may be needed when writing the
219 filtergraph description in a shell command, which depends on the
220 escaping rules of the adopted shell. For example, assuming that
221 @code{\} is special and needs to be escaped with another @code{\}, the
222 previous string will finally result in:
224 -vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
227 Sometimes, it might be more convenient to employ quoting in place of
228 escaping. For example the string:
230 Caesar: tu quoque, Brute, fili mi
233 Can be quoted in the filter arguments as:
235 text='Caesar: tu quoque, Brute, fili mi'
238 And finally inserted in a filtergraph like:
240 drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
243 See the @ref{quoting_and_escaping, Quoting and escaping} section for
244 more information about the escaping and quoting rules adopted by
247 @c man end FILTERGRAPH DESCRIPTION
249 @chapter Audio Filters
250 @c man begin AUDIO FILTERS
252 When you configure your FFmpeg build, you can disable any of the
253 existing filters using @code{--disable-filters}.
254 The configure output will show the audio filters included in your
257 Below is a description of the currently available audio filters.
261 Convert the input audio format to the specified formats.
263 The filter accepts a string of the form:
264 "@var{sample_format}:@var{channel_layout}".
266 @var{sample_format} specifies the sample format, and can be a string or the
267 corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p'
268 suffix for a planar sample format.
270 @var{channel_layout} specifies the channel layout, and can be a string
271 or the corresponding number value defined in @file{libavutil/channel_layout.h}.
273 The special parameter "auto", signifies that the filter will
274 automatically select the output format depending on the output filter.
276 Some examples follow.
280 Convert input to float, planar, stereo:
286 Convert input to unsigned 8-bit, automatically select out channel layout:
294 Convert the input audio to one of the specified formats. The framework will
295 negotiate the most appropriate format to minimize conversions.
297 The filter accepts the following named parameters:
301 A comma-separated list of requested sample formats.
304 A comma-separated list of requested sample rates.
306 @item channel_layouts
307 A comma-separated list of requested channel layouts.
311 If a parameter is omitted, all values are allowed.
313 For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
315 aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo
320 Merge two or more audio streams into a single multi-channel stream.
322 The filter accepts the following named options:
327 Set the number of inputs. Default is 2.
331 If the channel layouts of the inputs are disjoint, and therefore compatible,
332 the channel layout of the output will be set accordingly and the channels
333 will be reordered as necessary. If the channel layouts of the inputs are not
334 disjoint, the output will have all the channels of the first input then all
335 the channels of the second input, in that order, and the channel layout of
336 the output will be the default value corresponding to the total number of
339 For example, if the first input is in 2.1 (FL+FR+LF) and the second input
340 is FC+BL+BR, then the output will be in 5.1, with the channels in the
341 following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
342 first input, b1 is the first channel of the second input).
344 On the other hand, if both input are in stereo, the output channels will be
345 in the default order: a1, a2, b1, b2, and the channel layout will be
346 arbitrarily set to 4.0, which may or may not be the expected value.
348 All inputs must have the same sample rate, and format.
350 If inputs do not have the same duration, the output will stop with the
353 Example: merge two mono files into a stereo stream:
355 amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
358 Example: multiple merges:
361 amovie=input.mkv:si=0 [a0];
362 amovie=input.mkv:si=1 [a1];
363 amovie=input.mkv:si=2 [a2];
364 amovie=input.mkv:si=3 [a3];
365 amovie=input.mkv:si=4 [a4];
366 amovie=input.mkv:si=5 [a5];
367 [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
372 Mixes multiple audio inputs into a single output.
376 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
378 will mix 3 input audio streams to a single output with the same duration as the
379 first input and a dropout transition time of 3 seconds.
381 The filter accepts the following named parameters:
385 Number of inputs. If unspecified, it defaults to 2.
388 How to determine the end-of-stream.
392 Duration of longest input. (default)
395 Duration of shortest input.
398 Duration of first input.
402 @item dropout_transition
403 Transition time, in seconds, for volume renormalization when an input
404 stream ends. The default value is 2 seconds.
410 Pass the audio source unchanged to the output.
414 Resample the input audio to the specified sample rate.
416 The filter accepts exactly one parameter, the output sample rate. If not
417 specified then the filter will automatically convert between its input
418 and output sample rates.
420 For example, to resample the input audio to 44100Hz:
425 @section asetnsamples
427 Set the number of samples per each output audio frame.
429 The last output packet may contain a different number of samples, as
430 the filter will flush all the remaining samples when the input audio
433 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
438 @item nb_out_samples, n
439 Set the number of frames per each output audio frame. The number is
440 intended as the number of samples @emph{per each channel}.
441 Default value is 1024.
444 If set to 1, the filter will pad the last audio frame with zeroes, so
445 that the last frame will contain the same number of samples as the
446 previous ones. Default value is 1.
449 For example, to set the number of per-frame samples to 1234 and
450 disable padding for the last frame, use:
452 asetnsamples=n=1234:p=0
457 Show a line containing various information for each input audio frame.
458 The input audio is not modified.
460 The shown line contains a sequence of key/value pairs of the form
461 @var{key}:@var{value}.
463 A description of each shown parameter follows:
467 sequential number of the input frame, starting from 0
470 Presentation timestamp of the input frame, in time base units; the time base
471 depends on the filter input pad, and is usually 1/@var{sample_rate}.
474 presentation timestamp of the input frame in seconds
477 position of the frame in the input stream, -1 if this information in
478 unavailable and/or meaningless (for example in case of synthetic audio)
487 sample rate for the audio frame
490 number of samples (per channel) in the frame
493 Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
494 the data is treated as if all the planes were concatenated.
496 @item plane_checksums
497 A list of Adler-32 checksums for each data plane.
502 Split input audio into several identical outputs.
504 The filter accepts a single parameter which specifies the number of outputs. If
505 unspecified, it defaults to 2.
509 [in] asplit [out0][out1]
512 will create two separate outputs from the same input.
514 To create 3 or more outputs, you need to specify the number of
517 [in] asplit=3 [out0][out1][out2]
521 ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
523 will create 5 copies of the input audio.
528 Forward two audio streams and control the order the buffers are forwarded.
530 The argument to the filter is an expression deciding which stream should be
531 forwarded next: if the result is negative, the first stream is forwarded; if
532 the result is positive or zero, the second stream is forwarded. It can use
533 the following variables:
537 number of buffers forwarded so far on each stream
539 number of samples forwarded so far on each stream
541 current timestamp of each stream
544 The default value is @code{t1-t2}, which means to always forward the stream
545 that has a smaller timestamp.
547 Example: stress-test @code{amerge} by randomly sending buffers on the wrong
548 input, while avoiding too much of a desynchronization:
550 amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
551 [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
559 The filter accepts exactly one parameter, the audio tempo. If not
560 specified then the filter will assume nominal 1.0 tempo. Tempo must
561 be in the [0.5, 2.0] range.
563 For example, to slow down audio to 80% tempo:
568 For example, to speed up audio to 125% tempo:
575 Make audio easier to listen to on headphones.
577 This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
578 so that when listened to on headphones the stereo image is moved from
579 inside your head (standard for headphones) to outside and in front of
580 the listener (standard for speakers).
586 Mix channels with specific gain levels. The filter accepts the output
587 channel layout followed by a set of channels definitions.
589 This filter is also designed to remap efficiently the channels of an audio
592 The filter accepts parameters of the form:
593 "@var{l}:@var{outdef}:@var{outdef}:..."
597 output channel layout or number of channels
600 output channel specification, of the form:
601 "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
604 output channel to define, either a channel name (FL, FR, etc.) or a channel
605 number (c0, c1, etc.)
608 multiplicative coefficient for the channel, 1 leaving the volume unchanged
611 input channel to use, see out_name for details; it is not possible to mix
612 named and numbered input channels
615 If the `=' in a channel specification is replaced by `<', then the gains for
616 that specification will be renormalized so that the total is 1, thus
617 avoiding clipping noise.
619 @subsection Mixing examples
621 For example, if you want to down-mix from stereo to mono, but with a bigger
622 factor for the left channel:
624 pan=1:c0=0.9*c0+0.1*c1
627 A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
630 pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
633 Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
634 that should be preferred (see "-ac" option) unless you have very specific
637 @subsection Remapping examples
639 The channel remapping will be effective if, and only if:
642 @item gain coefficients are zeroes or ones,
643 @item only one input per channel output,
646 If all these conditions are satisfied, the filter will notify the user ("Pure
647 channel mapping detected"), and use an optimized and lossless method to do the
650 For example, if you have a 5.1 source and want a stereo audio stream by
651 dropping the extra channels:
653 pan="stereo: c0=FL : c1=FR"
656 Given the same source, you can also switch front left and front right channels
657 and keep the input channel layout:
659 pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
662 If the input is a stereo audio stream, you can mute the front left channel (and
663 still keep the stereo channel layout) with:
668 Still with a stereo audio stream input, you can copy the right channel in both
669 front left and right:
671 pan="stereo: c0=FR : c1=FR"
674 @section silencedetect
676 Detect silence in an audio stream.
678 This filter logs a message when it detects that the input audio volume is less
679 or equal to a noise tolerance value for a duration greater or equal to the
680 minimum detected noise duration.
682 The printed times and duration are expressed in seconds.
686 Set silence duration until notification (default is 2 seconds).
689 Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
690 specified value) or amplitude ratio. Default is -60dB, or 0.001.
693 Detect 5 seconds of silence with -50dB noise tolerance:
695 silencedetect=n=-50dB:d=5
698 Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
699 tolerance in @file{silence.mp3}:
701 ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
705 Synchronize audio data with timestamps by squeezing/stretching it and/or
706 dropping samples/adding silence when needed.
708 The filter accepts the following named parameters:
712 Enable stretching/squeezing the data to make it match the timestamps. Disabled
713 by default. When disabled, time gaps are covered with silence.
716 Minimum difference between timestamps and audio data (in seconds) to trigger
717 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
718 this filter, try setting this parameter to 0.
721 Maximum compensation in samples per second. Relevant only with compensate=1.
725 Assume the first pts should be this value.
726 This allows for padding/trimming at the start of stream. By default, no
727 assumption is made about the first frame's expected pts, so no padding or
728 trimming is done. For example, this could be set to 0 to pad the beginning with
729 silence if an audio stream starts after the video stream.
733 @section channelsplit
734 Split each channel in input audio stream into a separate output stream.
736 This filter accepts the following named parameters:
739 Channel layout of the input stream. Default is "stereo".
742 For example, assuming a stereo input MP3 file
744 ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
746 will create an output Matroska file with two audio streams, one containing only
747 the left channel and the other the right channel.
749 To split a 5.1 WAV file into per-channel files
751 ffmpeg -i in.wav -filter_complex
752 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
753 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
754 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
759 Remap input channels to new locations.
761 This filter accepts the following named parameters:
764 Channel layout of the output stream.
767 Map channels from input to output. The argument is a comma-separated list of
768 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
769 @var{in_channel} form. @var{in_channel} can be either the name of the input
770 channel (e.g. FL for front left) or its index in the input channel layout.
771 @var{out_channel} is the name of the output channel or its index in the output
772 channel layout. If @var{out_channel} is not given then it is implicitly an
773 index, starting with zero and increasing by one for each mapping.
776 If no mapping is present, the filter will implicitly map input channels to
777 output channels preserving index.
779 For example, assuming a 5.1+downmix input MOV file
781 ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
783 will create an output WAV file tagged as stereo from the downmix channels of
786 To fix a 5.1 WAV improperly encoded in AAC's native channel order
788 ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
792 Join multiple input streams into one multi-channel stream.
794 The filter accepts the following named parameters:
798 Number of input streams. Defaults to 2.
801 Desired output channel layout. Defaults to stereo.
804 Map channels from inputs to output. The argument is a comma-separated list of
805 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
806 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
807 can be either the name of the input channel (e.g. FL for front left) or its
808 index in the specified input stream. @var{out_channel} is the name of the output
812 The filter will attempt to guess the mappings when those are not specified
813 explicitly. It does so by first trying to find an unused matching input channel
814 and if that fails it picks the first unused input channel.
816 E.g. to join 3 inputs (with properly set channel layouts)
818 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
821 To build a 5.1 output from 6 single-channel streams:
823 ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
824 'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE'
829 Convert the audio sample format, sample rate and channel layout. This filter is
830 not meant to be used directly.
834 Adjust the input audio volume.
836 The filter accepts the following named parameters. If the key of the
837 first options is omitted, the arguments are interpreted according to
838 the following syntax:
840 volume=@var{volume}:@var{precision}
846 Expresses how the audio volume will be increased or decreased.
848 Output values are clipped to the maximum value.
850 The output audio volume is given by the relation:
852 @var{output_volume} = @var{volume} * @var{input_volume}
855 Default value for @var{volume} is 1.0.
858 Set the mathematical precision.
860 This determines which input sample formats will be allowed, which affects the
861 precision of the volume scaling.
865 8-bit fixed-point; limits input sample format to U8, S16, and S32.
867 32-bit floating-point; limits input sample format to FLT. (default)
869 64-bit floating-point; limits input sample format to DBL.
877 Halve the input audio volume:
881 volume=volume=-6.0206dB
884 In all the above example the named key for @option{volume} can be
885 omitted, for example like in:
891 Increase input audio power by 6 decibels using fixed-point precision:
893 volume=volume=6dB:precision=fixed
897 @section volumedetect
899 Detect the volume of the input video.
901 The filter has no parameters. The input is not modified. Statistics about
902 the volume will be printed in the log when the input stream end is reached.
904 In particular it will show the mean volume (root mean square), maximum
905 volume (on a per-sample basis), and the beginning of an histogram of the
906 registered volume values (from the maximum value to a cumulated 1/1000 of
909 All volumes are in decibels relative to the maximum PCM value.
911 Here is an excerpt of the output:
913 [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
914 [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
915 [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
916 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
917 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
918 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
919 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
920 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
921 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
927 The mean square energy is approximately -27 dB, or 10^-2.7.
929 The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
931 There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
934 In other words, raising the volume by +4 dB does not cause any clipping,
935 raising it by +5 dB causes clipping for 6 samples, etc.
937 @c man end AUDIO FILTERS
939 @chapter Audio Sources
940 @c man begin AUDIO SOURCES
942 Below is a description of the currently available audio sources.
946 Buffer audio frames, and make them available to the filter chain.
948 This source is mainly intended for a programmatic use, in particular
949 through the interface defined in @file{libavfilter/asrc_abuffer.h}.
951 It accepts the following mandatory parameters:
952 @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}
957 The sample rate of the incoming audio buffers.
960 The sample format of the incoming audio buffers.
961 Either a sample format name or its corresponging integer representation from
962 the enum AVSampleFormat in @file{libavutil/samplefmt.h}
965 The channel layout of the incoming audio buffers.
966 Either a channel layout name from channel_layout_map in
967 @file{libavutil/channel_layout.c} or its corresponding integer representation
968 from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h}
974 abuffer=44100:s16p:stereo
977 will instruct the source to accept planar 16bit signed stereo at 44100Hz.
978 Since the sample format with name "s16p" corresponds to the number
979 6 and the "stereo" channel layout corresponds to the value 0x3, this is
987 Generate an audio signal specified by an expression.
989 This source accepts in input one or more expressions (one for each
990 channel), which are evaluated and used to generate a corresponding
993 It accepts the syntax: @var{exprs}[::@var{options}].
994 @var{exprs} is a list of expressions separated by ":", one for each
995 separate channel. In case the @var{channel_layout} is not
996 specified, the selected channel layout depends on the number of
997 provided expressions.
999 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
1002 The description of the accepted options follows.
1006 @item channel_layout, c
1007 Set the channel layout. The number of channels in the specified layout
1008 must be equal to the number of specified expressions.
1011 Set the minimum duration of the sourced audio. See the function
1012 @code{av_parse_time()} for the accepted format.
1013 Note that the resulting duration may be greater than the specified
1014 duration, as the generated audio is always cut at the end of a
1017 If not specified, or the expressed duration is negative, the audio is
1018 supposed to be generated forever.
1021 Set the number of samples per channel per each output frame,
1024 @item sample_rate, s
1025 Specify the sample rate, default to 44100.
1028 Each expression in @var{exprs} can contain the following constants:
1032 number of the evaluated sample, starting from 0
1035 time of the evaluated sample expressed in seconds, starting from 0
1042 @subsection Examples
1054 Generate a sin signal with frequency of 440 Hz, set sample rate to
1057 aevalsrc="sin(440*2*PI*t)::s=8000"
1061 Generate a two channels signal, specify the channel layout (Front
1062 Center + Back Center) explicitly:
1064 aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
1068 Generate white noise:
1070 aevalsrc="-2+random(0)"
1074 Generate an amplitude modulated signal:
1076 aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
1080 Generate 2.5 Hz binaural beats on a 360 Hz carrier:
1082 aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
1089 Null audio source, return unprocessed audio frames. It is mainly useful
1090 as a template and to be employed in analysis / debugging tools, or as
1091 the source for filters which ignore the input data (for example the sox
1094 It accepts an optional sequence of @var{key}=@var{value} pairs,
1097 The description of the accepted options follows.
1101 @item sample_rate, s
1102 Specify the sample rate, and defaults to 44100.
1104 @item channel_layout, cl
1106 Specify the channel layout, and can be either an integer or a string
1107 representing a channel layout. The default value of @var{channel_layout}
1110 Check the channel_layout_map definition in
1111 @file{libavutil/channel_layout.c} for the mapping between strings and
1112 channel layout values.
1115 Set the number of samples per requested frames.
1119 Follow some examples:
1121 # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
1122 anullsrc=r=48000:cl=4
1125 anullsrc=r=48000:cl=mono
1129 Buffer audio frames, and make them available to the filter chain.
1131 This source is not intended to be part of user-supplied graph descriptions but
1132 for insertion by calling programs through the interface defined in
1133 @file{libavfilter/buffersrc.h}.
1135 It accepts the following named parameters:
1139 Timebase which will be used for timestamps of submitted frames. It must be
1140 either a floating-point number or in @var{numerator}/@var{denominator} form.
1146 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
1148 @item channel_layout
1149 Channel layout of the audio data, in the form that can be accepted by
1150 @code{av_get_channel_layout()}.
1153 All the parameters need to be explicitly defined.
1157 Synthesize a voice utterance using the libflite library.
1159 To enable compilation of this filter you need to configure FFmpeg with
1160 @code{--enable-libflite}.
1162 Note that the flite library is not thread-safe.
1164 The source accepts parameters as a list of @var{key}=@var{value} pairs,
1167 The description of the accepted parameters follows.
1172 If set to 1, list the names of the available voices and exit
1173 immediately. Default value is 0.
1176 Set the maximum number of samples per frame. Default value is 512.
1179 Set the filename containing the text to speak.
1182 Set the text to speak.
1185 Set the voice to use for the speech synthesis. Default value is
1186 @code{kal}. See also the @var{list_voices} option.
1189 @subsection Examples
1193 Read from file @file{speech.txt}, and synthetize the text using the
1194 standard flite voice:
1196 flite=textfile=speech.txt
1200 Read the specified text selecting the @code{slt} voice:
1202 flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1206 Input text to ffmpeg:
1208 ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1212 Make @file{ffplay} speak the specified text, using @code{flite} and
1213 the @code{lavfi} device:
1215 ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
1219 For more information about libflite, check:
1220 @url{http://www.speech.cs.cmu.edu/flite/}
1222 @c man end AUDIO SOURCES
1224 @chapter Audio Sinks
1225 @c man begin AUDIO SINKS
1227 Below is a description of the currently available audio sinks.
1229 @section abuffersink
1231 Buffer audio frames, and make them available to the end of filter chain.
1233 This sink is mainly intended for programmatic use, in particular
1234 through the interface defined in @file{libavfilter/buffersink.h}.
1236 It requires a pointer to an AVABufferSinkContext structure, which
1237 defines the incoming buffers' formats, to be passed as the opaque
1238 parameter to @code{avfilter_init_filter} for initialization.
1242 Null audio sink, do absolutely nothing with the input audio. It is
1243 mainly useful as a template and to be employed in analysis / debugging
1246 @section abuffersink
1247 This sink is intended for programmatic use. Frames that arrive on this sink can
1248 be retrieved by the calling program using the interface defined in
1249 @file{libavfilter/buffersink.h}.
1251 This filter accepts no parameters.
1253 @c man end AUDIO SINKS
1255 @chapter Video Filters
1256 @c man begin VIDEO FILTERS
1258 When you configure your FFmpeg build, you can disable any of the
1259 existing filters using @code{--disable-filters}.
1260 The configure output will show the video filters included in your
1263 Below is a description of the currently available video filters.
1265 @section alphaextract
1267 Extract the alpha component from the input as a grayscale video. This
1268 is especially useful with the @var{alphamerge} filter.
1272 Add or replace the alpha component of the primary input with the
1273 grayscale value of a second input. This is intended for use with
1274 @var{alphaextract} to allow the transmission or storage of frame
1275 sequences that have alpha in a format that doesn't support an alpha
1278 For example, to reconstruct full frames from a normal YUV-encoded video
1279 and a separate video created with @var{alphaextract}, you might use:
1281 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
1284 Since this filter is designed for reconstruction, it operates on frame
1285 sequences without considering timestamps, and terminates when either
1286 input reaches end of stream. This will cause problems if your encoding
1287 pipeline drops frames. If you're trying to apply an image as an
1288 overlay to a video stream, consider the @var{overlay} filter instead.
1292 Same as the @ref{subtitles} filter, except that it doesn't require libavcodec
1293 and libavformat to work. On the other hand, it is limited to ASS (Advanced
1294 Substation Alpha) subtitles files.
1298 Compute the bounding box for the non-black pixels in the input frame
1301 This filter computes the bounding box containing all the pixels with a
1302 luminance value greater than the minimum allowed value.
1303 The parameters describing the bounding box are printed on the filter
1306 @section blackdetect
1308 Detect video intervals that are (almost) completely black. Can be
1309 useful to detect chapter transitions, commercials, or invalid
1310 recordings. Output lines contains the time for the start, end and
1311 duration of the detected black interval expressed in seconds.
1313 In order to display the output lines, you need to set the loglevel at
1314 least to the AV_LOG_INFO value.
1316 This filter accepts a list of options in the form of
1317 @var{key}=@var{value} pairs separated by ":". A description of the
1318 accepted options follows.
1321 @item black_min_duration, d
1322 Set the minimum detected black duration expressed in seconds. It must
1323 be a non-negative floating point number.
1325 Default value is 2.0.
1327 @item picture_black_ratio_th, pic_th
1328 Set the threshold for considering a picture "black".
1329 Express the minimum value for the ratio:
1331 @var{nb_black_pixels} / @var{nb_pixels}
1334 for which a picture is considered black.
1335 Default value is 0.98.
1337 @item pixel_black_th, pix_th
1338 Set the threshold for considering a pixel "black".
1340 The threshold expresses the maximum pixel luminance value for which a
1341 pixel is considered "black". The provided value is scaled according to
1342 the following equation:
1344 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
1347 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
1348 the input video format, the range is [0-255] for YUV full-range
1349 formats and [16-235] for YUV non full-range formats.
1351 Default value is 0.10.
1354 The following example sets the maximum pixel threshold to the minimum
1355 value, and detects only black intervals of 2 or more seconds:
1357 blackdetect=d=2:pix_th=0.00
1362 Detect frames that are (almost) completely black. Can be useful to
1363 detect chapter transitions or commercials. Output lines consist of
1364 the frame number of the detected frame, the percentage of blackness,
1365 the position in the file if known or -1 and the timestamp in seconds.
1367 In order to display the output lines, you need to set the loglevel at
1368 least to the AV_LOG_INFO value.
1370 The filter accepts the syntax:
1372 blackframe[=@var{amount}:[@var{threshold}]]
1375 @var{amount} is the percentage of the pixels that have to be below the
1376 threshold, and defaults to 98.
1378 @var{threshold} is the threshold below which a pixel value is
1379 considered black, and defaults to 32.
1383 Apply boxblur algorithm to the input video.
1385 This filter accepts the parameters:
1386 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
1388 Chroma and alpha parameters are optional, if not specified they default
1389 to the corresponding values set for @var{luma_radius} and
1392 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
1393 the radius in pixels of the box used for blurring the corresponding
1394 input plane. They are expressions, and can contain the following
1398 the input width and height in pixels
1401 the input chroma image width and height in pixels
1404 horizontal and vertical chroma subsample values. For example for the
1405 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1408 The radius must be a non-negative number, and must not be greater than
1409 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
1410 and of @code{min(cw,ch)/2} for the chroma planes.
1412 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
1413 how many times the boxblur filter is applied to the corresponding
1416 Some examples follow:
1421 Apply a boxblur filter with luma, chroma, and alpha radius
1428 Set luma radius to 2, alpha and chroma radius to 0
1434 Set luma and chroma radius to a fraction of the video dimension
1436 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
1441 @section colormatrix
1443 The colormatrix filter allows conversion between any of the following color
1444 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
1445 and FCC (@var{fcc}).
1447 The syntax of the parameters is @var{source}:@var{destination}:
1450 colormatrix=bt601:smpte240m
1455 Copy the input source unchanged to the output. Mainly useful for
1460 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
1462 The @var{keep_aspect} parameter is optional, if specified and set to a
1463 non-zero value will force the output display aspect ratio to be the
1464 same of the input, by changing the output sample aspect ratio.
1466 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1467 expressions containing the following constants:
1471 the computed values for @var{x} and @var{y}. They are evaluated for
1475 the input width and height
1478 same as @var{in_w} and @var{in_h}
1481 the output (cropped) width and height
1484 same as @var{out_w} and @var{out_h}
1487 same as @var{iw} / @var{ih}
1490 input sample aspect ratio
1493 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1496 horizontal and vertical chroma subsample values. For example for the
1497 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1500 the number of input frame, starting from 0
1503 the position in the file of the input frame, NAN if unknown
1506 timestamp expressed in seconds, NAN if the input timestamp is unknown
1510 The @var{out_w} and @var{out_h} parameters specify the expressions for
1511 the width and height of the output (cropped) video. They are
1512 evaluated just at the configuration of the filter.
1514 The default value of @var{out_w} is "in_w", and the default value of
1515 @var{out_h} is "in_h".
1517 The expression for @var{out_w} may depend on the value of @var{out_h},
1518 and the expression for @var{out_h} may depend on @var{out_w}, but they
1519 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1520 evaluated after @var{out_w} and @var{out_h}.
1522 The @var{x} and @var{y} parameters specify the expressions for the
1523 position of the top-left corner of the output (non-cropped) area. They
1524 are evaluated for each frame. If the evaluated value is not valid, it
1525 is approximated to the nearest valid value.
1527 The default value of @var{x} is "(in_w-out_w)/2", and the default
1528 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
1529 the center of the input image.
1531 The expression for @var{x} may depend on @var{y}, and the expression
1532 for @var{y} may depend on @var{x}.
1534 Follow some examples:
1536 # crop the central input area with size 100x100
1539 # crop the central input area with size 2/3 of the input video
1540 "crop=2/3*in_w:2/3*in_h"
1542 # crop the input video central square
1545 # delimit the rectangle with the top-left corner placed at position
1546 # 100:100 and the right-bottom corner corresponding to the right-bottom
1547 # corner of the input image.
1548 crop=in_w-100:in_h-100:100:100
1550 # crop 10 pixels from the left and right borders, and 20 pixels from
1551 # the top and bottom borders
1552 "crop=in_w-2*10:in_h-2*20"
1554 # keep only the bottom right quarter of the input image
1555 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1557 # crop height for getting Greek harmony
1558 "crop=in_w:1/PHI*in_w"
1561 "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)"
1563 # erratic camera effect depending on timestamp
1564 "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)"
1566 # set x depending on the value of y
1567 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1572 Auto-detect crop size.
1574 Calculate necessary cropping parameters and prints the recommended
1575 parameters through the logging system. The detected dimensions
1576 correspond to the non-black area of the input video.
1578 It accepts the syntax:
1580 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1586 Threshold, which can be optionally specified from nothing (0) to
1587 everything (255), defaults to 24.
1590 Value which the width/height should be divisible by, defaults to
1591 16. The offset is automatically adjusted to center the video. Use 2 to
1592 get only even dimensions (needed for 4:2:2 video). 16 is best when
1593 encoding to most video codecs.
1596 Counter that determines after how many frames cropdetect will reset
1597 the previously detected largest video area and start over to detect
1598 the current optimal crop area. Defaults to 0.
1600 This can be useful when channel logos distort the video area. 0
1601 indicates never reset and return the largest area encountered during
1607 This filter drops frames that do not differ greatly from the previous
1608 frame in order to reduce framerate. The main use of this filter is
1609 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1610 it could in theory be used for fixing movies that were
1611 inverse-telecined incorrectly.
1613 It accepts the following parameters:
1614 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1619 Set the maximum number of consecutive frames which can be dropped (if
1620 positive), or the minimum interval between dropped frames (if
1621 negative). If the value is 0, the frame is dropped unregarding the
1622 number of previous sequentially dropped frames.
1627 Set the dropping threshold values.
1629 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1630 represent actual pixel value differences, so a threshold of 64
1631 corresponds to 1 unit of difference for each pixel, or the same spread
1632 out differently over the block.
1634 A frame is a candidate for dropping if no 8x8 blocks differ by more
1635 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1636 meaning the whole image) differ by more than a threshold of @var{lo}.
1638 Default value for @var{hi} is 64*12, default value for @var{lo} is
1639 64*5, and default value for @var{frac} is 0.33.
1644 Suppress a TV station logo by a simple interpolation of the surrounding
1645 pixels. Just set a rectangle covering the logo and watch it disappear
1646 (and sometimes something even uglier appear - your mileage may vary).
1648 The filter accepts parameters as a string of the form
1649 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1650 @var{key}=@var{value} pairs, separated by ":".
1652 The description of the accepted parameters follows.
1657 Specify the top left corner coordinates of the logo. They must be
1661 Specify the width and height of the logo to clear. They must be
1665 Specify the thickness of the fuzzy edge of the rectangle (added to
1666 @var{w} and @var{h}). The default value is 4.
1669 When set to 1, a green rectangle is drawn on the screen to simplify
1670 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1671 @var{band} is set to 4. The default value is 0.
1675 Some examples follow.
1680 Set a rectangle covering the area with top left corner coordinates 0,0
1681 and size 100x77, setting a band of size 10:
1683 delogo=0:0:100:77:10
1687 As the previous example, but use named options:
1689 delogo=x=0:y=0:w=100:h=77:band=10
1696 Attempt to fix small changes in horizontal and/or vertical shift. This
1697 filter helps remove camera shake from hand-holding a camera, bumping a
1698 tripod, moving on a vehicle, etc.
1700 The filter accepts parameters as a string of the form
1701 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1703 A description of the accepted parameters follows.
1708 Specify a rectangular area where to limit the search for motion
1710 If desired the search for motion vectors can be limited to a
1711 rectangular area of the frame defined by its top left corner, width
1712 and height. These parameters have the same meaning as the drawbox
1713 filter which can be used to visualise the position of the bounding
1716 This is useful when simultaneous movement of subjects within the frame
1717 might be confused for camera motion by the motion vector search.
1719 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1720 then the full frame is used. This allows later options to be set
1721 without specifying the bounding box for the motion vector search.
1723 Default - search the whole frame.
1726 Specify the maximum extent of movement in x and y directions in the
1727 range 0-64 pixels. Default 16.
1730 Specify how to generate pixels to fill blanks at the edge of the
1731 frame. An integer from 0 to 3 as follows:
1734 Fill zeroes at blank locations
1736 Original image at blank locations
1738 Extruded edge value at blank locations
1740 Mirrored edge at blank locations
1743 The default setting is mirror edge at blank locations.
1746 Specify the blocksize to use for motion search. Range 4-128 pixels,
1750 Specify the contrast threshold for blocks. Only blocks with more than
1751 the specified contrast (difference between darkest and lightest
1752 pixels) will be considered. Range 1-255, default 125.
1755 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1756 search. Default - exhaustive search.
1759 If set then a detailed log of the motion search is written to the
1766 Draw a colored box on the input image.
1768 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1771 The description of the accepted parameters follows.
1775 Specify the top left corner coordinates of the box. Default to 0.
1779 Specify the width and height of the box, if 0 they are interpreted as
1780 the input width and height. Default to 0.
1783 Specify the color of the box to write, it can be the name of a color
1784 (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
1785 value @code{invert} is used, the box edge color is the same as the
1786 video with inverted luma.
1789 Set the thickness of the box edge. Default value is @code{4}.
1792 If the key of the first options is omitted, the arguments are
1793 interpreted according to the following syntax:
1795 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness}
1798 Some examples follow:
1801 Draw a black box around the edge of the input image:
1807 Draw a box with color red and an opacity of 50%:
1809 drawbox=10:20:200:60:red@@0.5
1812 The previous example can be specified as:
1814 drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
1818 Fill the box with pink color:
1820 drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
1827 Draw text string or text from specified file on top of video using the
1828 libfreetype library.
1830 To enable compilation of this filter you need to configure FFmpeg with
1831 @code{--enable-libfreetype}.
1835 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1838 The description of the accepted parameters follows.
1843 Used to draw a box around text using background color.
1844 Value should be either 1 (enable) or 0 (disable).
1845 The default value of @var{box} is 0.
1848 The color to be used for drawing box around text.
1849 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1850 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1851 The default value of @var{boxcolor} is "white".
1854 Set an expression which specifies if the text should be drawn. If the
1855 expression evaluates to 0, the text is not drawn. This is useful for
1856 specifying that the text should be drawn only when specific conditions
1859 Default value is "1".
1861 See below for the list of accepted constants and functions.
1864 Select how the @var{text} is expanded. Can be either @code{none},
1865 @code{strftime} (default for compatibity reasons but deprecated) or
1866 @code{normal}. See the @ref{drawtext_expansion, Text expansion} section
1870 If true, check and fix text coords to avoid clipping.
1873 The color to be used for drawing fonts.
1874 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1875 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1876 The default value of @var{fontcolor} is "black".
1879 The font file to be used for drawing text. Path must be included.
1880 This parameter is mandatory.
1883 The font size to be used for drawing text.
1884 The default value of @var{fontsize} is 16.
1887 Flags to be used for loading the fonts.
1889 The flags map the corresponding flags supported by libfreetype, and are
1890 a combination of the following values:
1897 @item vertical_layout
1898 @item force_autohint
1901 @item ignore_global_advance_width
1903 @item ignore_transform
1910 Default value is "render".
1912 For more information consult the documentation for the FT_LOAD_*
1916 The color to be used for drawing a shadow behind the drawn text. It
1917 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1918 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1919 The default value of @var{shadowcolor} is "black".
1921 @item shadowx, shadowy
1922 The x and y offsets for the text shadow position with respect to the
1923 position of the text. They can be either positive or negative
1924 values. Default value for both is "0".
1927 The size in number of spaces to use for rendering the tab.
1931 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
1932 format. It can be used with or without text parameter. @var{timecode_rate}
1933 option must be specified.
1935 @item timecode_rate, rate, r
1936 Set the timecode frame rate (timecode only).
1939 The text string to be drawn. The text must be a sequence of UTF-8
1941 This parameter is mandatory if no file is specified with the parameter
1945 A text file containing text to be drawn. The text must be a sequence
1946 of UTF-8 encoded characters.
1948 This parameter is mandatory if no text string is specified with the
1949 parameter @var{text}.
1951 If both @var{text} and @var{textfile} are specified, an error is thrown.
1954 If set to 1, the @var{textfile} will be reloaded before each frame.
1955 Be sure to update it atomically, or it may be read partially, or even fail.
1958 The expressions which specify the offsets where text will be drawn
1959 within the video frame. They are relative to the top/left border of the
1962 The default value of @var{x} and @var{y} is "0".
1964 See below for the list of accepted constants and functions.
1967 The parameters for @var{x} and @var{y} are expressions containing the
1968 following constants and functions:
1972 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
1975 horizontal and vertical chroma subsample values. For example for the
1976 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1979 the height of each text line
1987 @item max_glyph_a, ascent
1988 the maximum distance from the baseline to the highest/upper grid
1989 coordinate used to place a glyph outline point, for all the rendered
1991 It is a positive value, due to the grid's orientation with the Y axis
1994 @item max_glyph_d, descent
1995 the maximum distance from the baseline to the lowest grid coordinate
1996 used to place a glyph outline point, for all the rendered glyphs.
1997 This is a negative value, due to the grid's orientation, with the Y axis
2001 maximum glyph height, that is the maximum height for all the glyphs
2002 contained in the rendered text, it is equivalent to @var{ascent} -
2006 maximum glyph width, that is the maximum width for all the glyphs
2007 contained in the rendered text
2010 the number of input frame, starting from 0
2012 @item rand(min, max)
2013 return a random number included between @var{min} and @var{max}
2016 input sample aspect ratio
2019 timestamp expressed in seconds, NAN if the input timestamp is unknown
2022 the height of the rendered text
2025 the width of the rendered text
2028 the x and y offset coordinates where the text is drawn.
2030 These parameters allow the @var{x} and @var{y} expressions to refer
2031 each other, so you can for example specify @code{y=x/dar}.
2034 If libavfilter was built with @code{--enable-fontconfig}, then
2035 @option{fontfile} can be a fontconfig pattern or omitted.
2037 @anchor{drawtext_expansion}
2038 @subsection Text expansion
2040 If @option{expansion} is set to @code{strftime} (which is the default for
2041 now), the filter recognizes strftime() sequences in the provided text and
2042 expands them accordingly. Check the documentation of strftime(). This
2043 feature is deprecated.
2045 If @option{expansion} is set to @code{none}, the text is printed verbatim.
2047 If @option{expansion} is set to @code{normal} (which will be the default),
2048 the following expansion mechanism is used.
2050 The backslash character '\', followed by any character, always expands to
2051 the second character.
2053 Sequence of the form @code{%@{...@}} are expanded. The text between the
2054 braces is a function name, possibly followed by arguments separated by ':'.
2055 If the arguments contain special characters or delimiters (':' or '@}'),
2056 they should be escaped.
2058 Note that they probably must also be escaped as the value for the
2059 @option{text} option in the filter argument string and as the filter
2060 argument in the filter graph description, and possibly also for the shell,
2061 that makes up to four levels of escaping; using a text file avoids these
2064 The following functions are available:
2069 The expression evaluation result.
2071 It must take one argument specifying the expression to be evaluated,
2072 which accepts the same constants and functions as the @var{x} and
2073 @var{y} values. Note that not all constants should be used, for
2074 example the text size is not known when evaluating the expression, so
2075 the constants @var{text_w} and @var{text_h} will have an undefined
2079 The time at which the filter is running, expressed in UTC.
2080 It can accept an argument: a strftime() format string.
2083 The time at which the filter is running, expressed in the local time zone.
2084 It can accept an argument: a strftime() format string.
2087 The frame number, starting from 0.
2090 The timestamp of the current frame, in seconds, with microsecond accuracy.
2094 @subsection Examples
2096 Some examples follow.
2101 Draw "Test Text" with font FreeSerif, using the default values for the
2102 optional parameters.
2105 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
2109 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
2110 and y=50 (counting from the top-left corner of the screen), text is
2111 yellow with a red box around it. Both the text and the box have an
2115 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
2116 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
2119 Note that the double quotes are not necessary if spaces are not used
2120 within the parameter list.
2123 Show the text at the center of the video frame:
2125 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
2129 Show a text line sliding from right to left in the last row of the video
2130 frame. The file @file{LONG_LINE} is assumed to contain a single line
2133 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
2137 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
2139 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
2143 Draw a single green letter "g", at the center of the input video.
2144 The glyph baseline is placed at half screen height.
2146 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2150 Show text for 1 second every 3 seconds:
2152 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
2156 Use fontconfig to set the font. Note that the colons need to be escaped.
2158 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
2162 Print the date of a real-time encoding (see strftime(3)):
2164 drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%@{localtime:%a %b %d %Y@}'
2169 For more information about libfreetype, check:
2170 @url{http://www.freetype.org/}.
2172 For more information about fontconfig, check:
2173 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2177 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2179 This filter accepts the following optional named parameters:
2183 Set low and high threshold values used by the Canny thresholding
2186 The high threshold selects the "strong" edge pixels, which are then
2187 connected through 8-connectivity with the "weak" edge pixels selected
2188 by the low threshold.
2190 @var{low} and @var{high} threshold values must be choosen in the range
2191 [0,1], and @var{low} should be lesser or equal to @var{high}.
2193 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2199 edgedetect=low=0.1:high=0.4
2204 Apply fade-in/out effect to input video.
2206 It accepts the parameters:
2207 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2209 @var{type} specifies if the effect type, can be either "in" for
2210 fade-in, or "out" for a fade-out effect.
2212 @var{start_frame} specifies the number of the start frame for starting
2213 to apply the fade effect.
2215 @var{nb_frames} specifies the number of frames for which the fade
2216 effect has to last. At the end of the fade-in effect the output video
2217 will have the same intensity as the input video, at the end of the
2218 fade-out transition the output video will be completely black.
2220 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2221 separated by ":". The description of the accepted options follows.
2228 @item start_frame, s
2229 See @var{start_frame}.
2232 See @var{nb_frames}.
2235 If set to 1, fade only alpha channel, if one exists on the input.
2239 A few usage examples follow, usable too as test scenarios.
2241 # fade in first 30 frames of video
2244 # fade out last 45 frames of a 200-frame video
2247 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2248 fade=in:0:25, fade=out:975:25
2250 # make first 5 frames black, then fade in from frame 5-24
2253 # fade in alpha over first 25 frames of video
2254 fade=in:0:25:alpha=1
2259 Extract a single field from an interlaced image using stride
2260 arithmetic to avoid wasting CPU time. The output frames are marked as
2263 This filter accepts the following named options:
2266 Specify whether to extract the top (if the value is @code{0} or
2267 @code{top}) or the bottom field (if the value is @code{1} or
2271 If the option key is not specified, the first value sets the @var{type}
2272 option. For example:
2284 Transform the field order of the input video.
2286 It accepts one parameter which specifies the required field order that
2287 the input interlaced video will be transformed to. The parameter can
2288 assume one of the following values:
2292 output bottom field first
2294 output top field first
2297 Default value is "tff".
2299 Transformation is achieved by shifting the picture content up or down
2300 by one line, and filling the remaining line with appropriate picture content.
2301 This method is consistent with most broadcast field order converters.
2303 If the input video is not flagged as being interlaced, or it is already
2304 flagged as being of the required output field order then this filter does
2305 not alter the incoming video.
2307 This filter is very useful when converting to or from PAL DV material,
2308 which is bottom field first.
2312 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2317 Buffer input images and send them when they are requested.
2319 This filter is mainly useful when auto-inserted by the libavfilter
2322 The filter does not take parameters.
2326 Convert the input video to one of the specified pixel formats.
2327 Libavfilter will try to pick one that is supported for the input to
2330 The filter accepts a list of pixel format names, separated by ":",
2331 for example "yuv420p:monow:rgb24".
2333 Some examples follow:
2335 # convert the input video to the format "yuv420p"
2338 # convert the input video to any of the formats in the list
2339 format=yuv420p:yuv444p:yuv410p
2344 Convert the video to specified constant framerate by duplicating or dropping
2345 frames as necessary.
2347 This filter accepts the following named parameters:
2351 Desired output framerate.
2354 Rounding method. The default is @code{near}.
2360 Select one frame every N.
2362 This filter accepts in input a string representing a positive
2363 integer. Default argument is @code{1}.
2368 Apply a frei0r effect to the input video.
2370 To enable compilation of this filter you need to install the frei0r
2371 header and configure FFmpeg with @code{--enable-frei0r}.
2373 The filter supports the syntax:
2375 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2378 @var{filter_name} is the name of the frei0r effect to load. If the
2379 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2380 is searched in each one of the directories specified by the colon (or
2381 semicolon on Windows platforms) separated list in @env{FREIOR_PATH},
2382 otherwise in the standard frei0r paths, which are in this order:
2383 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
2384 @file{/usr/lib/frei0r-1/}.
2386 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2387 for the frei0r effect.
2389 A frei0r effect parameter can be a boolean (whose values are specified
2390 with "y" and "n"), a double, a color (specified by the syntax
2391 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2392 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2393 description), a position (specified by the syntax @var{X}/@var{Y},
2394 @var{X} and @var{Y} being float numbers) and a string.
2396 The number and kind of parameters depend on the loaded effect. If an
2397 effect parameter is not specified the default value is set.
2399 Some examples follow:
2403 Apply the distort0r effect, set the first two double parameters:
2405 frei0r=distort0r:0.5:0.01
2409 Apply the colordistance effect, take a color as first parameter:
2411 frei0r=colordistance:0.2/0.3/0.4
2412 frei0r=colordistance:violet
2413 frei0r=colordistance:0x112233
2417 Apply the perspective effect, specify the top left and top right image
2420 frei0r=perspective:0.2/0.2:0.8/0.2
2424 For more information see:
2425 @url{http://frei0r.dyne.org}
2429 The filter takes one, two or three equations as parameter, separated by ':'.
2430 The first equation is mandatory and applies to the luma plane. The two
2431 following are respectively for chroma blue and chroma red planes.
2433 The filter syntax allows named parameters:
2437 the luminance expression
2439 the chrominance blue expression
2441 the chrominance red expression
2444 If one of the chrominance expression is not defined, it falls back on the other
2445 one. If none of them are specified, they will evaluate the luminance
2448 The expressions can use the following variables and functions:
2452 The sequential number of the filtered frame, starting from @code{0}.
2455 The coordinates of the current sample.
2458 The width and height of the image.
2461 Width and height scale depending on the currently filtered plane. It is the
2462 ratio between the corresponding luma plane number of pixels and the current
2463 plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
2464 @code{0.5,0.5} for chroma planes.
2467 Time of the current frame, expressed in seconds.
2470 Return the value of the pixel at location (@var{x},@var{y}) of the current
2474 Return the value of the pixel at location (@var{x},@var{y}) of the luminance
2478 Return the value of the pixel at location (@var{x},@var{y}) of the
2479 blue-difference chroma plane.
2482 Return the value of the pixel at location (@var{x},@var{y}) of the
2483 red-difference chroma plane.
2486 For functions, if @var{x} and @var{y} are outside the area, the value will be
2487 automatically clipped to the closer edge.
2489 Some examples follow:
2493 Flip the image horizontally:
2499 Generate a bidimensional sine wave, with angle @code{PI/3} and a
2500 wavelength of 100 pixels:
2502 geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
2506 Generate a fancy enigmatic moving light:
2508 nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128
2514 Fix the banding artifacts that are sometimes introduced into nearly flat
2515 regions by truncation to 8bit color depth.
2516 Interpolate the gradients that should go where the bands are, and
2519 This filter is designed for playback only. Do not use it prior to
2520 lossy compression, because compression tends to lose the dither and
2521 bring back the bands.
2523 The filter takes two optional parameters, separated by ':':
2524 @var{strength}:@var{radius}
2526 @var{strength} is the maximum amount by which the filter will change
2527 any one pixel. Also the threshold for detecting nearly flat
2528 regions. Acceptable values range from .51 to 255, default value is
2529 1.2, out-of-range values will be clipped to the valid range.
2531 @var{radius} is the neighborhood to fit the gradient to. A larger
2532 radius makes for smoother gradients, but also prevents the filter from
2533 modifying the pixels near detailed regions. Acceptable values are
2534 8-32, default value is 16, out-of-range values will be clipped to the
2538 # default parameters
2547 Flip the input video horizontally.
2549 For example to horizontally flip the input video with @command{ffmpeg}:
2551 ffmpeg -i in.avi -vf "hflip" out.avi
2556 High precision/quality 3d denoise filter. This filter aims to reduce
2557 image noise producing smooth images and making still images really
2558 still. It should enhance compressibility.
2560 It accepts the following optional parameters:
2561 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2565 a non-negative float number which specifies spatial luma strength,
2568 @item chroma_spatial
2569 a non-negative float number which specifies spatial chroma strength,
2570 defaults to 3.0*@var{luma_spatial}/4.0
2573 a float number which specifies luma temporal strength, defaults to
2574 6.0*@var{luma_spatial}/4.0
2577 a float number which specifies chroma temporal strength, defaults to
2578 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2583 Modify the hue and/or the saturation of the input.
2585 This filter accepts the following optional named options:
2589 Specify the hue angle as a number of degrees. It accepts a float
2590 number or an expression, and defaults to 0.0.
2593 Specify the hue angle as a number of degrees. It accepts a float
2594 number or an expression, and defaults to 0.0.
2597 Specify the saturation in the [-10,10] range. It accepts a float number and
2601 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2602 following constants:
2606 frame count of the input frame starting from 0
2609 presentation timestamp of the input frame expressed in time base units
2612 frame rate of the input video, NAN if the input frame rate is unknown
2615 timestamp expressed in seconds, NAN if the input timestamp is unknown
2618 time base of the input video
2621 The options can also be set using the syntax: @var{hue}:@var{saturation}
2623 In this case @var{hue} is expressed in degrees.
2625 Some examples follow:
2628 Set the hue to 90 degrees and the saturation to 1.0:
2634 Same command but expressing the hue in radians:
2640 Same command without named options, hue must be expressed in degrees:
2646 Note that "h:s" syntax does not support expressions for the values of
2647 h and s, so the following example will issue an error:
2653 Rotate hue and make the saturation swing between 0
2654 and 2 over a period of 1 second:
2656 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2660 Apply a 3 seconds saturation fade-in effect starting at 0:
2665 The general fade-in expression can be written as:
2667 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2671 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2673 hue="s=max(0\, min(1\, (8-t)/3))"
2676 The general fade-out expression can be written as:
2678 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2683 @subsection Commands
2685 This filter supports the following command:
2688 Modify the hue and/or the saturation of the input video.
2689 The command accepts the same named options and syntax than when calling the
2690 filter from the command-line.
2692 If a parameter is omitted, it is kept at its current value.
2697 Interlaceing detect filter. This filter tries to detect if the input is
2698 interlaced or progressive. Top or bottom field first.
2700 @section lut, lutrgb, lutyuv
2702 Compute a look-up table for binding each pixel component input value
2703 to an output value, and apply it to input video.
2705 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2706 to an RGB input video.
2708 These filters accept in input a ":"-separated list of options, which
2709 specify the expressions used for computing the lookup table for the
2710 corresponding pixel component values.
2712 The @var{lut} filter requires either YUV or RGB pixel formats in
2713 input, and accepts the options:
2715 @item @var{c0} (first pixel component)
2716 @item @var{c1} (second pixel component)
2717 @item @var{c2} (third pixel component)
2718 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
2721 The exact component associated to each option depends on the format in
2724 The @var{lutrgb} filter requires RGB pixel formats in input, and
2725 accepts the options:
2727 @item @var{r} (red component)
2728 @item @var{g} (green component)
2729 @item @var{b} (blue component)
2730 @item @var{a} (alpha component)
2733 The @var{lutyuv} filter requires YUV pixel formats in input, and
2734 accepts the options:
2736 @item @var{y} (Y/luminance component)
2737 @item @var{u} (U/Cb component)
2738 @item @var{v} (V/Cr component)
2739 @item @var{a} (alpha component)
2742 The expressions can contain the following constants and functions:
2746 the input width and height
2749 input value for the pixel component
2752 the input value clipped in the @var{minval}-@var{maxval} range
2755 maximum value for the pixel component
2758 minimum value for the pixel component
2761 the negated value for the pixel component value clipped in the
2762 @var{minval}-@var{maxval} range , it corresponds to the expression
2763 "maxval-clipval+minval"
2766 the computed value in @var{val} clipped in the
2767 @var{minval}-@var{maxval} range
2769 @item gammaval(gamma)
2770 the computed gamma correction value of the pixel component value
2771 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2773 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2777 All expressions default to "val".
2779 Some examples follow:
2781 # negate input video
2782 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2783 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2785 # the above is the same as
2786 lutrgb="r=negval:g=negval:b=negval"
2787 lutyuv="y=negval:u=negval:v=negval"
2792 # remove chroma components, turns the video into a graytone image
2793 lutyuv="u=128:v=128"
2795 # apply a luma burning effect
2798 # remove green and blue components
2801 # set a constant alpha channel value on input
2802 format=rgba,lutrgb=a="maxval-minval/2"
2804 # correct luminance gamma by a 0.5 factor
2805 lutyuv=y=gammaval(0.5)
2810 Apply an MPlayer filter to the input video.
2812 This filter provides a wrapper around most of the filters of
2815 This wrapper is considered experimental. Some of the wrapped filters
2816 may not work properly and we may drop support for them, as they will
2817 be implemented natively into FFmpeg. Thus you should avoid
2818 depending on them when writing portable scripts.
2820 The filters accepts the parameters:
2821 @var{filter_name}[:=]@var{filter_params}
2823 @var{filter_name} is the name of a supported MPlayer filter,
2824 @var{filter_params} is a string containing the parameters accepted by
2827 The list of the currently supported filters follows:
2862 The parameter syntax and behavior for the listed filters are the same
2863 of the corresponding MPlayer filters. For detailed instructions check
2864 the "VIDEO FILTERS" section in the MPlayer manual.
2866 Some examples follow:
2869 Adjust gamma, brightness, contrast:
2875 Add temporal noise to input video:
2881 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2887 This filter accepts an integer in input, if non-zero it negates the
2888 alpha component (if available). The default value in input is 0.
2892 Force libavfilter not to use any of the specified pixel formats for the
2893 input to the next filter.
2895 The filter accepts a list of pixel format names, separated by ":",
2896 for example "yuv420p:monow:rgb24".
2898 Some examples follow:
2900 # force libavfilter to use a format different from "yuv420p" for the
2901 # input to the vflip filter
2902 noformat=yuv420p,vflip
2904 # convert the input video to any of the formats not contained in the list
2905 noformat=yuv420p:yuv444p:yuv410p
2910 Pass the video source unchanged to the output.
2914 Apply video transform using libopencv.
2916 To enable this filter install libopencv library and headers and
2917 configure FFmpeg with @code{--enable-libopencv}.
2919 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
2921 @var{filter_name} is the name of the libopencv filter to apply.
2923 @var{filter_params} specifies the parameters to pass to the libopencv
2924 filter. If not specified the default values are assumed.
2926 Refer to the official libopencv documentation for more precise
2928 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
2930 Follows the list of supported libopencv filters.
2935 Dilate an image by using a specific structuring element.
2936 This filter corresponds to the libopencv function @code{cvDilate}.
2938 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
2940 @var{struct_el} represents a structuring element, and has the syntax:
2941 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
2943 @var{cols} and @var{rows} represent the number of columns and rows of
2944 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
2945 point, and @var{shape} the shape for the structuring element, and
2946 can be one of the values "rect", "cross", "ellipse", "custom".
2948 If the value for @var{shape} is "custom", it must be followed by a
2949 string of the form "=@var{filename}". The file with name
2950 @var{filename} is assumed to represent a binary image, with each
2951 printable character corresponding to a bright pixel. When a custom
2952 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
2953 or columns and rows of the read file are assumed instead.
2955 The default value for @var{struct_el} is "3x3+0x0/rect".
2957 @var{nb_iterations} specifies the number of times the transform is
2958 applied to the image, and defaults to 1.
2960 Follow some example:
2962 # use the default values
2965 # dilate using a structuring element with a 5x5 cross, iterate two times
2966 ocv=dilate=5x5+2x2/cross:2
2968 # read the shape from the file diamond.shape, iterate two times
2969 # the file diamond.shape may contain a pattern of characters like this:
2975 # the specified cols and rows are ignored (but not the anchor point coordinates)
2976 ocv=0x0+2x2/custom=diamond.shape:2
2981 Erode an image by using a specific structuring element.
2982 This filter corresponds to the libopencv function @code{cvErode}.
2984 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
2985 with the same syntax and semantics as the @ref{dilate} filter.
2989 Smooth the input video.
2991 The filter takes the following parameters:
2992 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
2994 @var{type} is the type of smooth filter to apply, and can be one of
2995 the following values: "blur", "blur_no_scale", "median", "gaussian",
2996 "bilateral". The default value is "gaussian".
2998 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
2999 parameters whose meanings depend on smooth type. @var{param1} and
3000 @var{param2} accept integer positive values or 0, @var{param3} and
3001 @var{param4} accept float values.
3003 The default value for @var{param1} is 3, the default value for the
3004 other parameters is 0.
3006 These parameters correspond to the parameters assigned to the
3007 libopencv function @code{cvSmooth}.
3012 Overlay one video on top of another.
3014 It takes two inputs and one output, the first input is the "main"
3015 video on which the second input is overlayed.
3017 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
3019 @var{x} is the x coordinate of the overlayed video on the main video,
3020 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
3021 the following parameters:
3024 @item main_w, main_h
3025 main input width and height
3028 same as @var{main_w} and @var{main_h}
3030 @item overlay_w, overlay_h
3031 overlay input width and height
3034 same as @var{overlay_w} and @var{overlay_h}
3037 @var{options} is an optional list of @var{key}=@var{value} pairs,
3040 The description of the accepted options follows.
3044 If set to 1, force the filter to accept inputs in the RGB
3045 color space. Default value is 0.
3048 Be aware that frames are taken from each input video in timestamp
3049 order, hence, if their initial timestamps differ, it is a a good idea
3050 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
3051 have them begin in the same zero timestamp, as it does the example for
3052 the @var{movie} filter.
3054 Follow some examples:
3056 # draw the overlay at 10 pixels from the bottom right
3057 # corner of the main video.
3058 overlay=main_w-overlay_w-10:main_h-overlay_h-10
3060 # insert a transparent PNG logo in the bottom left corner of the input
3061 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
3063 # insert 2 different transparent PNG logos (second logo on bottom
3065 ffmpeg -i input -i logo1 -i logo2 -filter_complex
3066 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
3068 # add a transparent color layer on top of the main video,
3069 # WxH specifies the size of the main input to the overlay filter
3070 color=red@@.3:WxH [over]; [in][over] overlay [out]
3072 # play an original video and a filtered version (here with the deshake filter)
3074 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
3076 # the previous example is the same as:
3077 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
3080 You can chain together more overlays but the efficiency of such
3081 approach is yet to be tested.
3085 Add paddings to the input image, and places the original input at the
3086 given coordinates @var{x}, @var{y}.
3088 It accepts the following parameters:
3089 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
3091 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
3092 expressions containing the following constants:
3096 the input video width and height
3099 same as @var{in_w} and @var{in_h}
3102 the output width and height, that is the size of the padded area as
3103 specified by the @var{width} and @var{height} expressions
3106 same as @var{out_w} and @var{out_h}
3109 x and y offsets as specified by the @var{x} and @var{y}
3110 expressions, or NAN if not yet specified
3113 same as @var{iw} / @var{ih}
3116 input sample aspect ratio
3119 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3122 horizontal and vertical chroma subsample values. For example for the
3123 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3126 Follows the description of the accepted parameters.
3131 Specify the size of the output image with the paddings added. If the
3132 value for @var{width} or @var{height} is 0, the corresponding input size
3133 is used for the output.
3135 The @var{width} expression can reference the value set by the
3136 @var{height} expression, and vice versa.
3138 The default value of @var{width} and @var{height} is 0.
3142 Specify the offsets where to place the input image in the padded area
3143 with respect to the top/left border of the output image.
3145 The @var{x} expression can reference the value set by the @var{y}
3146 expression, and vice versa.
3148 The default value of @var{x} and @var{y} is 0.
3152 Specify the color of the padded area, it can be the name of a color
3153 (case insensitive match) or a 0xRRGGBB[AA] sequence.
3155 The default value of @var{color} is "black".
3159 @subsection Examples
3163 Add paddings with color "violet" to the input video. Output video
3164 size is 640x480, the top-left corner of the input video is placed at
3167 pad=640:480:0:40:violet
3171 Pad the input to get an output with dimensions increased by 3/2,
3172 and put the input video at the center of the padded area:
3174 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
3178 Pad the input to get a squared output with size equal to the maximum
3179 value between the input width and height, and put the input video at
3180 the center of the padded area:
3182 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
3186 Pad the input to get a final w/h ratio of 16:9:
3188 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
3192 In case of anamorphic video, in order to set the output display aspect
3193 correctly, it is necessary to use @var{sar} in the expression,
3194 according to the relation:
3196 (ih * X / ih) * sar = output_dar
3197 X = output_dar / sar
3200 Thus the previous example needs to be modified to:
3202 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
3206 Double output size and put the input video in the bottom-right
3207 corner of the output padded area:
3209 pad="2*iw:2*ih:ow-iw:oh-ih"
3213 @section pixdesctest
3215 Pixel format descriptor test filter, mainly useful for internal
3216 testing. The output video should be equal to the input video.
3220 format=monow, pixdesctest
3223 can be used to test the monowhite pixel format descriptor definition.
3227 Suppress a TV station logo, using an image file to determine which
3228 pixels comprise the logo. It works by filling in the pixels that
3229 comprise the logo with neighboring pixels.
3231 This filter requires one argument which specifies the filter bitmap
3232 file, which can be any image format supported by libavformat. The
3233 width and height of the image file must match those of the video
3234 stream being processed.
3236 Pixels in the provided bitmap image with a value of zero are not
3237 considered part of the logo, non-zero pixels are considered part of
3238 the logo. If you use white (255) for the logo and black (0) for the
3239 rest, you will be safe. For making the filter bitmap, it is
3240 recommended to take a screen capture of a black frame with the logo
3241 visible, and then using a threshold filter followed by the erode
3242 filter once or twice.
3244 If needed, little splotches can be fixed manually. Remember that if
3245 logo pixels are not covered, the filter quality will be much
3246 reduced. Marking too many pixels as part of the logo does not hurt as
3247 much, but it will increase the amount of blurring needed to cover over
3248 the image and will destroy more information than necessary, and extra
3249 pixels will slow things down on a large logo.
3253 Scale (resize) the input video, using the libswscale library.
3255 The scale filter forces the output display aspect ratio to be the same
3256 of the input, by changing the output sample aspect ratio.
3258 This filter accepts a list of named options in the form of
3259 @var{key}=@var{value} pairs separated by ":". If the key for the first
3260 two options is not specified, the assumed keys for the first two
3261 values are @code{w} and @code{h}. If the first option has no key and
3262 can be interpreted like a video size specification, it will be used
3263 to set the video size.
3265 A description of the accepted options follows.
3269 Set the video width expression, default value is @code{iw}. See below
3270 for the list of accepted constants.
3273 Set the video heiht expression, default value is @code{ih}.
3274 See below for the list of accepted constants.
3277 Set the interlacing. It accepts the following values:
3281 force interlaced aware scaling
3284 do not apply interlaced scaling
3287 select interlaced aware scaling depending on whether the source frames
3288 are flagged as interlaced or not
3291 Default value is @code{0}.
3294 Set libswscale scaling flags. If not explictly specified the filter
3295 applies a bilinear scaling algorithm.
3298 Set the video size, the value must be a valid abbreviation or in the
3299 form @var{width}x@var{height}.
3302 The values of the @var{w} and @var{h} options are expressions
3303 containing the following constants:
3307 the input width and height
3310 same as @var{in_w} and @var{in_h}
3313 the output (cropped) width and height
3316 same as @var{out_w} and @var{out_h}
3319 same as @var{iw} / @var{ih}
3322 input sample aspect ratio
3325 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3328 horizontal and vertical chroma subsample values. For example for the
3329 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3332 If the input image format is different from the format requested by
3333 the next filter, the scale filter will convert the input to the
3336 If the value for @var{width} or @var{height} is 0, the respective input
3337 size is used for the output.
3339 If the value for @var{width} or @var{height} is -1, the scale filter will
3340 use, for the respective output size, a value that maintains the aspect
3341 ratio of the input image.
3343 @subsection Examples
3347 Scale the input video to a size of 200x100:
3352 This is equivalent to:
3363 Specify a size abbreviation for the output size:
3368 which can also be written as:
3374 Scale the input to 2x:
3380 The above is the same as:
3386 Scale the input to 2x with forced interlaced scaling:
3388 scale=2*iw:2*ih:interl=1
3392 Scale the input to half size:
3398 Increase the width, and set the height to the same size:
3404 Seek for Greek harmony:
3411 Increase the height, and set the width to 3/2 of the height:
3417 Increase the size, but make the size a multiple of the chroma:
3419 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3423 Increase the width to a maximum of 500 pixels, keep the same input
3426 scale='min(500\, iw*3/2):-1'
3431 Select frames to pass in output.
3433 It accepts in input an expression, which is evaluated for each input
3434 frame. If the expression is evaluated to a non-zero value, the frame
3435 is selected and passed to the output, otherwise it is discarded.
3437 The expression can contain the following constants:
3441 the sequential number of the filtered frame, starting from 0
3444 the sequential number of the selected frame, starting from 0
3446 @item prev_selected_n
3447 the sequential number of the last selected frame, NAN if undefined
3450 timebase of the input timestamps
3453 the PTS (Presentation TimeStamp) of the filtered video frame,
3454 expressed in @var{TB} units, NAN if undefined
3457 the PTS (Presentation TimeStamp) of the filtered video frame,
3458 expressed in seconds, NAN if undefined
3461 the PTS of the previously filtered video frame, NAN if undefined
3463 @item prev_selected_pts
3464 the PTS of the last previously filtered video frame, NAN if undefined
3466 @item prev_selected_t
3467 the PTS of the last previously selected video frame, NAN if undefined
3470 the PTS of the first video frame in the video, NAN if undefined
3473 the time of the first video frame in the video, NAN if undefined
3476 the type of the filtered frame, can assume one of the following
3488 @item interlace_type
3489 the frame interlace type, can assume one of the following values:
3492 the frame is progressive (not interlaced)
3494 the frame is top-field-first
3496 the frame is bottom-field-first
3500 1 if the filtered frame is a key-frame, 0 otherwise
3503 the position in the file of the filtered frame, -1 if the information
3504 is not available (e.g. for synthetic video)
3507 value between 0 and 1 to indicate a new scene; a low value reflects a low
3508 probability for the current frame to introduce a new scene, while a higher
3509 value means the current frame is more likely to be one (see the example below)
3513 The default value of the select expression is "1".
3515 Some examples follow:
3518 # select all frames in input
3521 # the above is the same as:
3527 # select only I-frames
3528 select='eq(pict_type\,I)'
3530 # select one frame every 100
3531 select='not(mod(n\,100))'
3533 # select only frames contained in the 10-20 time interval
3534 select='gte(t\,10)*lte(t\,20)'
3536 # select only I frames contained in the 10-20 time interval
3537 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
3539 # select frames with a minimum distance of 10 seconds
3540 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
3543 Complete example to create a mosaic of the first scenes:
3546 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
3549 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
3552 @section setdar, setsar
3554 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3557 This is done by changing the specified Sample (aka Pixel) Aspect
3558 Ratio, according to the following equation:
3560 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3563 Keep in mind that the @code{setdar} filter does not modify the pixel
3564 dimensions of the video frame. Also the display aspect ratio set by
3565 this filter may be changed by later filters in the filterchain,
3566 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3569 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3570 the filter output video.
3572 Note that as a consequence of the application of this filter, the
3573 output display aspect ratio will change according to the equation
3576 Keep in mind that the sample aspect ratio set by the @code{setsar}
3577 filter may be changed by later filters in the filterchain, e.g. if
3578 another "setsar" or a "setdar" filter is applied.
3580 The @code{setdar} and @code{setsar} filters accept a string in the
3581 form @var{num}:@var{den} expressing an aspect ratio, or the following
3582 named options, expressed as a sequence of @var{key}=@var{value} pairs,
3587 Set the maximum integer value to use for expressing numerator and
3588 denominator when reducing the expressed aspect ratio to a rational.
3589 Default value is @code{100}.
3592 Set the aspect ratio used by the filter.
3594 The parameter can be a floating point number string, an expression, or
3595 a string of the form @var{num}:@var{den}, where @var{num} and
3596 @var{den} are the numerator and denominator of the aspect ratio. If
3597 the parameter is not specified, it is assumed the value "0".
3598 In case the form "@var{num}:@var{den}" the @code{:} character should
3602 If the keys are omitted in the named options list, the specifed values
3603 are assumed to be @var{ratio} and @var{max} in that order.
3605 For example to change the display aspect ratio to 16:9, specify:
3610 The example above is equivalent to:
3615 To change the sample aspect ratio to 10:11, specify:
3620 To set a display aspect ratio of 16:9, and specify a maximum integer value of
3621 1000 in the aspect ratio reduction, use the command:
3623 setdar=ratio='16:9':max=1000
3628 Force field for the output video frame.
3630 The @code{setfield} filter marks the interlace type field for the
3631 output frames. It does not change the input frame, but only sets the
3632 corresponding property, which affects how the frame is treated by
3633 following filters (e.g. @code{fieldorder} or @code{yadif}).
3635 It accepts a string parameter, which can assume the following values:
3638 Keep the same field property.
3641 Mark the frame as bottom-field-first.
3644 Mark the frame as top-field-first.
3647 Mark the frame as progressive.
3652 Show a line containing various information for each input video frame.
3653 The input video is not modified.
3655 The shown line contains a sequence of key/value pairs of the form
3656 @var{key}:@var{value}.
3658 A description of each shown parameter follows:
3662 sequential number of the input frame, starting from 0
3665 Presentation TimeStamp of the input frame, expressed as a number of
3666 time base units. The time base unit depends on the filter input pad.
3669 Presentation TimeStamp of the input frame, expressed as a number of
3673 position of the frame in the input stream, -1 if this information in
3674 unavailable and/or meaningless (for example in case of synthetic video)
3680 sample aspect ratio of the input frame, expressed in the form
3684 size of the input frame, expressed in the form
3685 @var{width}x@var{height}
3688 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3689 for bottom field first)
3692 1 if the frame is a key frame, 0 otherwise
3695 picture type of the input frame ("I" for an I-frame, "P" for a
3696 P-frame, "B" for a B-frame, "?" for unknown type).
3697 Check also the documentation of the @code{AVPictureType} enum and of
3698 the @code{av_get_picture_type_char} function defined in
3699 @file{libavutil/avutil.h}.
3702 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3704 @item plane_checksum
3705 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3706 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3711 Blur the input video without impacting the outlines.
3713 The filter accepts the following parameters:
3714 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3716 Parameters prefixed by @var{luma} indicate that they work on the
3717 luminance of the pixels whereas parameters prefixed by @var{chroma}
3718 refer to the chrominance of the pixels.
3720 If the chroma parameters are not set, the luma parameters are used for
3721 either the luminance and the chrominance of the pixels.
3723 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3724 range [0.1,5.0] that specifies the variance of the gaussian filter
3725 used to blur the image (slower if larger).
3727 @var{luma_strength} or @var{chroma_strength} must be a float number in
3728 the range [-1.0,1.0] that configures the blurring. A value included in
3729 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3730 will sharpen the image.
3732 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3733 the range [-30,30] that is used as a coefficient to determine whether
3734 a pixel should be blurred or not. A value of 0 will filter all the
3735 image, a value included in [0,30] will filter flat areas and a value
3736 included in [-30,0] will filter edges.
3741 Draw subtitles on top of input video using the libass library.
3743 To enable compilation of this filter you need to configure FFmpeg with
3744 @code{--enable-libass}. This filter also requires a build with libavcodec and
3745 libavformat to convert the passed subtitles file to ASS (Advanced Substation
3746 Alpha) subtitles format.
3748 This filter accepts the following named options, expressed as a
3749 sequence of @var{key}=@var{value} pairs, separated by ":".
3753 Set the filename of the subtitle file to read. It must be specified.
3756 Specify the size of the original video, the video for which the ASS file
3757 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
3758 necessary to correctly scale the fonts if the aspect ratio has been changed.
3761 If the first key is not specified, it is assumed that the first value
3762 specifies the @option{filename}.
3764 For example, to render the file @file{sub.srt} on top of the input
3765 video, use the command:
3770 which is equivalent to:
3772 subtitles=filename=sub.srt
3777 Split input video into several identical outputs.
3779 The filter accepts a single parameter which specifies the number of outputs. If
3780 unspecified, it defaults to 2.
3784 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3786 will create 5 copies of the input video.
3790 [in] split [splitout1][splitout2];
3791 [splitout1] crop=100:100:0:0 [cropout];
3792 [splitout2] pad=200:200:100:100 [padout];
3795 will create two separate outputs from the same input, one cropped and
3800 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3801 Interpolate) pixel art scaling algorithm.
3803 Useful for enlarging pixel art images without reducing sharpness.
3809 Select the most representative frame in a given sequence of consecutive frames.
3811 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3812 in a set of @var{N} frames, the filter will pick one of them, and then handle
3813 the next batch of @var{N} frames until the end.
3815 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3816 value will result in a higher memory usage, so a high value is not recommended.
3818 The following example extract one picture each 50 frames:
3823 Complete example of a thumbnail creation with @command{ffmpeg}:
3825 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3830 Tile several successive frames together.
3832 It accepts a list of options in the form of @var{key}=@var{value} pairs
3833 separated by ":". A description of the accepted options follows.
3838 Set the grid size (i.e. the number of lines and columns) in the form
3842 Set the outer border margin in pixels.
3845 Set the inner border thickness (i.e. the number of pixels between frames). For
3846 more advanced padding options (such as having different values for the edges),
3847 refer to the pad video filter.
3850 Set the maximum number of frames to render in the given area. It must be less
3851 than or equal to @var{w}x@var{h}. The default value is @code{0}, meaning all
3852 the area will be used.
3856 Alternatively, the options can be specified as a flat string:
3858 @var{layout}[:@var{nb_frames}[:@var{margin}[:@var{padding}]]]
3860 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3863 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3865 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3866 duplicating each output frame to accomodate the originally detected frame
3869 Another example to display @code{5} pictures in an area of @code{3x2} frames,
3870 with @code{7} pixels between them, and @code{2} pixels of initial margin, using
3871 mixed flat and named options:
3873 tile=3x2:nb_frames=5:padding=7:margin=2
3878 Perform various types of temporal field interlacing.
3880 Frames are counted starting from 1, so the first input frame is
3883 This filter accepts a single option @option{mode} specifying the mode,
3884 which can be specified either by specyfing @code{mode=VALUE} either
3885 specifying the value alone. Available values are:
3889 Move odd frames into the upper field, even into the lower field,
3890 generating a double height frame at half framerate.
3893 Only output even frames, odd frames are dropped, generating a frame with
3894 unchanged height at half framerate.
3897 Only output odd frames, even frames are dropped, generating a frame with
3898 unchanged height at half framerate.
3901 Expand each frame to full height, but pad alternate lines with black,
3902 generating a frame with double height at the same input framerate.
3904 @item interleave_top, 4
3905 Interleave the upper field from odd frames with the lower field from
3906 even frames, generating a frame with unchanged height at half framerate.
3908 @item interleave_bottom, 5
3909 Interleave the lower field from odd frames with the upper field from
3910 even frames, generating a frame with unchanged height at half framerate.
3912 @item interlacex2, 6
3913 Double frame rate with unchanged height. Frames are inserted each
3914 containing the second temporal field from the previous input frame and
3915 the first temporal field from the next input frame. This mode relies on
3916 the top_field_first flag. Useful for interlaced video displays with no
3917 field synchronisation.
3920 Numeric values are deprecated but are accepted for backward
3921 compatibility reasons.
3923 Default mode is @code{merge}.
3927 Transpose rows with columns in the input video and optionally flip it.
3929 This filter accepts the following named parameters:
3933 Specify the transposition direction. Can assume the following values:
3937 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3945 Rotate by 90 degrees clockwise, that is:
3953 Rotate by 90 degrees counterclockwise, that is:
3961 Rotate by 90 degrees clockwise and vertically flip, that is:
3969 For values between 4-7, the transposition is only done if the input
3970 video geometry is portrait and not landscape. These values are
3971 deprecated, the @code{passthrough} option should be used instead.
3974 Do not apply the transposition if the input geometry matches the one
3975 specified by the specified value. It accepts the following values:
3978 Always apply transposition.
3980 Preserve portrait geometry (when @var{height} >= @var{width}).
3982 Preserve landscape geometry (when @var{width} >= @var{height}).
3985 Default value is @code{none}.
3990 Sharpen or blur the input video.
3992 It accepts the following parameters:
3993 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3995 Negative values for the amount will blur the input video, while positive
3996 values will sharpen. All parameters are optional and default to the
3997 equivalent of the string '5:5:1.0:5:5:0.0'.
4002 Set the luma matrix horizontal size. It can be an integer between 3
4003 and 13, default value is 5.
4006 Set the luma matrix vertical size. It can be an integer between 3
4007 and 13, default value is 5.
4010 Set the luma effect strength. It can be a float number between -2.0
4011 and 5.0, default value is 1.0.
4013 @item chroma_msize_x
4014 Set the chroma matrix horizontal size. It can be an integer between 3
4015 and 13, default value is 5.
4017 @item chroma_msize_y
4018 Set the chroma matrix vertical size. It can be an integer between 3
4019 and 13, default value is 5.
4022 Set the chroma effect strength. It can be a float number between -2.0
4023 and 5.0, default value is 0.0.
4028 # Strong luma sharpen effect parameters
4031 # Strong blur of both luma and chroma parameters
4032 unsharp=7:7:-2:7:7:-2
4034 # Use the default values with @command{ffmpeg}
4035 ffmpeg -i in.avi -vf "unsharp" out.mp4
4040 Flip the input video vertically.
4043 ffmpeg -i in.avi -vf "vflip" out.avi
4048 Deinterlace the input video ("yadif" means "yet another deinterlacing
4051 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
4053 @var{mode} specifies the interlacing mode to adopt, accepts one of the
4058 output 1 frame for each frame
4060 output 1 frame for each field
4062 like 0 but skips spatial interlacing check
4064 like 1 but skips spatial interlacing check
4069 @var{parity} specifies the picture field parity assumed for the input
4070 interlaced video, accepts one of the following values:
4074 assume top field first
4076 assume bottom field first
4078 enable automatic detection
4081 Default value is -1.
4082 If interlacing is unknown or decoder does not export this information,
4083 top field first will be assumed.
4085 @var{auto} specifies if deinterlacer should trust the interlaced flag
4086 and only deinterlace frames marked as interlaced
4090 deinterlace all frames
4092 only deinterlace frames marked as interlaced
4097 @c man end VIDEO FILTERS
4099 @chapter Video Sources
4100 @c man begin VIDEO SOURCES
4102 Below is a description of the currently available video sources.
4106 Buffer video frames, and make them available to the filter chain.
4108 This source is mainly intended for a programmatic use, in particular
4109 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
4111 It accepts a list of options in the form of @var{key}=@var{value} pairs
4112 separated by ":". A description of the accepted options follows.
4117 Specify the size (width and height) of the buffered video frames.
4120 A string representing the pixel format of the buffered video frames.
4121 It may be a number corresponding to a pixel format, or a pixel format
4125 Specify the timebase assumed by the timestamps of the buffered frames.
4128 Specify the frame rate expected for the video stream.
4131 Specify the sample aspect ratio assumed by the video frames.
4134 Specify the optional parameters to be used for the scale filter which
4135 is automatically inserted when an input change is detected in the
4136 input size or format.
4141 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
4144 will instruct the source to accept video frames with size 320x240 and
4145 with format "yuv410p", assuming 1/24 as the timestamps timebase and
4146 square pixels (1:1 sample aspect ratio).
4147 Since the pixel format with name "yuv410p" corresponds to the number 6
4148 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
4149 this example corresponds to:
4151 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
4154 Alternatively, the options can be specified as a flat string, but this
4155 syntax is deprecated:
4157 @var{width}:@var{height}:@var{pix_fmt}:@var{time_base.num}:@var{time_base.den}:@var{pixel_aspect.num}:@var{pixel_aspect.den}[:@var{sws_param}]
4161 Create a pattern generated by an elementary cellular automaton.
4163 The initial state of the cellular automaton can be defined through the
4164 @option{filename}, and @option{pattern} options. If such options are
4165 not specified an initial state is created randomly.
4167 At each new frame a new row in the video is filled with the result of
4168 the cellular automaton next generation. The behavior when the whole
4169 frame is filled is defined by the @option{scroll} option.
4171 This source accepts a list of options in the form of
4172 @var{key}=@var{value} pairs separated by ":". A description of the
4173 accepted options follows.
4177 Read the initial cellular automaton state, i.e. the starting row, from
4179 In the file, each non-whitespace character is considered an alive
4180 cell, a newline will terminate the row, and further characters in the
4181 file will be ignored.
4184 Read the initial cellular automaton state, i.e. the starting row, from
4185 the specified string.
4187 Each non-whitespace character in the string is considered an alive
4188 cell, a newline will terminate the row, and further characters in the
4189 string will be ignored.
4192 Set the video rate, that is the number of frames generated per second.
4195 @item random_fill_ratio, ratio
4196 Set the random fill ratio for the initial cellular automaton row. It
4197 is a floating point number value ranging from 0 to 1, defaults to
4200 This option is ignored when a file or a pattern is specified.
4202 @item random_seed, seed
4203 Set the seed for filling randomly the initial row, must be an integer
4204 included between 0 and UINT32_MAX. If not specified, or if explicitly
4205 set to -1, the filter will try to use a good random seed on a best
4209 Set the cellular automaton rule, it is a number ranging from 0 to 255.
4210 Default value is 110.
4213 Set the size of the output video.
4215 If @option{filename} or @option{pattern} is specified, the size is set
4216 by default to the width of the specified initial state row, and the
4217 height is set to @var{width} * PHI.
4219 If @option{size} is set, it must contain the width of the specified
4220 pattern string, and the specified pattern will be centered in the
4223 If a filename or a pattern string is not specified, the size value
4224 defaults to "320x518" (used for a randomly generated initial state).
4227 If set to 1, scroll the output upward when all the rows in the output
4228 have been already filled. If set to 0, the new generated row will be
4229 written over the top row just after the bottom row is filled.
4232 @item start_full, full
4233 If set to 1, completely fill the output with generated rows before
4234 outputting the first frame.
4235 This is the default behavior, for disabling set the value to 0.
4238 If set to 1, stitch the left and right row edges together.
4239 This is the default behavior, for disabling set the value to 0.
4242 @subsection Examples
4246 Read the initial state from @file{pattern}, and specify an output of
4249 cellauto=f=pattern:s=200x400
4253 Generate a random initial row with a width of 200 cells, with a fill
4256 cellauto=ratio=2/3:s=200x200
4260 Create a pattern generated by rule 18 starting by a single alive cell
4261 centered on an initial row with width 100:
4263 cellauto=p=@@:s=100x400:full=0:rule=18
4267 Specify a more elaborated initial pattern:
4269 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
4276 Generate a Mandelbrot set fractal, and progressively zoom towards the
4277 point specified with @var{start_x} and @var{start_y}.
4279 This source accepts a list of options in the form of
4280 @var{key}=@var{value} pairs separated by ":". A description of the
4281 accepted options follows.
4286 Set the terminal pts value. Default value is 400.
4289 Set the terminal scale value.
4290 Must be a floating point value. Default value is 0.3.
4293 Set the inner coloring mode, that is the algorithm used to draw the
4294 Mandelbrot fractal internal region.
4296 It shall assume one of the following values:
4301 Show time until convergence.
4303 Set color based on point closest to the origin of the iterations.
4308 Default value is @var{mincol}.
4311 Set the bailout value. Default value is 10.0.
4314 Set the maximum of iterations performed by the rendering
4315 algorithm. Default value is 7189.
4318 Set outer coloring mode.
4319 It shall assume one of following values:
4321 @item iteration_count
4322 Set iteration cound mode.
4323 @item normalized_iteration_count
4324 set normalized iteration count mode.
4326 Default value is @var{normalized_iteration_count}.
4329 Set frame rate, expressed as number of frames per second. Default
4333 Set frame size. Default value is "640x480".
4336 Set the initial scale value. Default value is 3.0.
4339 Set the initial x position. Must be a floating point value between
4340 -100 and 100. Default value is -0.743643887037158704752191506114774.
4343 Set the initial y position. Must be a floating point value between
4344 -100 and 100. Default value is -0.131825904205311970493132056385139.
4349 Generate various test patterns, as generated by the MPlayer test filter.
4351 The size of the generated video is fixed, and is 256x256.
4352 This source is useful in particular for testing encoding features.
4354 This source accepts an optional sequence of @var{key}=@var{value} pairs,
4355 separated by ":". The description of the accepted options follows.
4360 Specify the frame rate of the sourced video, as the number of frames
4361 generated per second. It has to be a string in the format
4362 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4363 number or a valid video frame rate abbreviation. The default value is
4367 Set the video duration of the sourced video. The accepted syntax is:
4372 See also the function @code{av_parse_time()}.
4374 If not specified, or the expressed duration is negative, the video is
4375 supposed to be generated forever.
4379 Set the number or the name of the test to perform. Supported tests are:
4394 Default value is "all", which will cycle through the list of all tests.
4397 For example the following:
4402 will generate a "dc_luma" test pattern.
4406 Provide a frei0r source.
4408 To enable compilation of this filter you need to install the frei0r
4409 header and configure FFmpeg with @code{--enable-frei0r}.
4411 The source supports the syntax:
4413 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
4416 @var{size} is the size of the video to generate, may be a string of the
4417 form @var{width}x@var{height} or a frame size abbreviation.
4418 @var{rate} is the rate of the video to generate, may be a string of
4419 the form @var{num}/@var{den} or a frame rate abbreviation.
4420 @var{src_name} is the name to the frei0r source to load. For more
4421 information regarding frei0r and how to set the parameters read the
4422 section @ref{frei0r} in the description of the video filters.
4424 For example, to generate a frei0r partik0l source with size 200x200
4425 and frame rate 10 which is overlayed on the overlay filter main input:
4427 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4432 Generate a life pattern.
4434 This source is based on a generalization of John Conway's life game.
4436 The sourced input represents a life grid, each pixel represents a cell
4437 which can be in one of two possible states, alive or dead. Every cell
4438 interacts with its eight neighbours, which are the cells that are
4439 horizontally, vertically, or diagonally adjacent.
4441 At each interaction the grid evolves according to the adopted rule,
4442 which specifies the number of neighbor alive cells which will make a
4443 cell stay alive or born. The @option{rule} option allows to specify
4446 This source accepts a list of options in the form of
4447 @var{key}=@var{value} pairs separated by ":". A description of the
4448 accepted options follows.
4452 Set the file from which to read the initial grid state. In the file,
4453 each non-whitespace character is considered an alive cell, and newline
4454 is used to delimit the end of each row.
4456 If this option is not specified, the initial grid is generated
4460 Set the video rate, that is the number of frames generated per second.
4463 @item random_fill_ratio, ratio
4464 Set the random fill ratio for the initial random grid. It is a
4465 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4466 It is ignored when a file is specified.
4468 @item random_seed, seed
4469 Set the seed for filling the initial random grid, must be an integer
4470 included between 0 and UINT32_MAX. If not specified, or if explicitly
4471 set to -1, the filter will try to use a good random seed on a best
4477 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4478 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4479 @var{NS} specifies the number of alive neighbor cells which make a
4480 live cell stay alive, and @var{NB} the number of alive neighbor cells
4481 which make a dead cell to become alive (i.e. to "born").
4482 "s" and "b" can be used in place of "S" and "B", respectively.
4484 Alternatively a rule can be specified by an 18-bits integer. The 9
4485 high order bits are used to encode the next cell state if it is alive
4486 for each number of neighbor alive cells, the low order bits specify
4487 the rule for "borning" new cells. Higher order bits encode for an
4488 higher number of neighbor cells.
4489 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4490 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4492 Default value is "S23/B3", which is the original Conway's game of life
4493 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4494 cells, and will born a new cell if there are three alive cells around
4498 Set the size of the output video.
4500 If @option{filename} is specified, the size is set by default to the
4501 same size of the input file. If @option{size} is set, it must contain
4502 the size specified in the input file, and the initial grid defined in
4503 that file is centered in the larger resulting area.
4505 If a filename is not specified, the size value defaults to "320x240"
4506 (used for a randomly generated initial grid).
4509 If set to 1, stitch the left and right grid edges together, and the
4510 top and bottom edges also. Defaults to 1.
4513 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4514 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4515 value from 0 to 255.
4518 Set the color of living (or new born) cells.
4521 Set the color of dead cells. If @option{mold} is set, this is the first color
4522 used to represent a dead cell.
4525 Set mold color, for definitely dead and moldy cells.
4528 @subsection Examples
4532 Read a grid from @file{pattern}, and center it on a grid of size
4535 life=f=pattern:s=300x300
4539 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4541 life=ratio=2/3:s=200x200
4545 Specify a custom rule for evolving a randomly generated grid:
4551 Full example with slow death effect (mold) using @command{ffplay}:
4553 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4557 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4559 The @code{color} source provides an uniformly colored input.
4561 The @code{nullsrc} source returns unprocessed video frames. It is
4562 mainly useful to be employed in analysis / debugging tools, or as the
4563 source for filters which ignore the input data.
4565 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4566 detecting RGB vs BGR issues. You should see a red, green and blue
4567 stripe from top to bottom.
4569 The @code{smptebars} source generates a color bars pattern, based on
4570 the SMPTE Engineering Guideline EG 1-1990.
4572 The @code{testsrc} source generates a test video pattern, showing a
4573 color pattern, a scrolling gradient and a timestamp. This is mainly
4574 intended for testing purposes.
4576 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4577 separated by ":". The description of the accepted options follows.
4582 Specify the color of the source, only used in the @code{color}
4583 source. It can be the name of a color (case insensitive match) or a
4584 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4585 default value is "black".
4588 Specify the size of the sourced video, it may be a string of the form
4589 @var{width}x@var{height}, or the name of a size abbreviation. The
4590 default value is "320x240".
4593 Specify the frame rate of the sourced video, as the number of frames
4594 generated per second. It has to be a string in the format
4595 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4596 number or a valid video frame rate abbreviation. The default value is
4600 Set the sample aspect ratio of the sourced video.
4603 Set the video duration of the sourced video. The accepted syntax is:
4605 [-]HH[:MM[:SS[.m...]]]
4608 See also the function @code{av_parse_time()}.
4610 If not specified, or the expressed duration is negative, the video is
4611 supposed to be generated forever.
4614 Set the number of decimals to show in the timestamp, only used in the
4615 @code{testsrc} source.
4617 The displayed timestamp value will correspond to the original
4618 timestamp value multiplied by the power of 10 of the specified
4619 value. Default value is 0.
4622 For example the following:
4624 testsrc=duration=5.3:size=qcif:rate=10
4627 will generate a video with a duration of 5.3 seconds, with size
4628 176x144 and a frame rate of 10 frames per second.
4630 The following graph description will generate a red source
4631 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4634 color=c=red@@0.2:s=qcif:r=10
4637 If the input content is to be ignored, @code{nullsrc} can be used. The
4638 following command generates noise in the luminance plane by employing
4639 the @code{geq} filter:
4641 nullsrc=s=256x256, geq=random(1)*255:128:128
4644 @c man end VIDEO SOURCES
4646 @chapter Video Sinks
4647 @c man begin VIDEO SINKS
4649 Below is a description of the currently available video sinks.
4653 Buffer video frames, and make them available to the end of the filter
4656 This sink is mainly intended for a programmatic use, in particular
4657 through the interface defined in @file{libavfilter/buffersink.h}.
4659 It does not require a string parameter in input, but you need to
4660 specify a pointer to a list of supported pixel formats terminated by
4661 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4662 when initializing this sink.
4666 Null video sink, do absolutely nothing with the input video. It is
4667 mainly useful as a template and to be employed in analysis / debugging
4670 @c man end VIDEO SINKS
4672 @chapter Multimedia Filters
4673 @c man begin MULTIMEDIA FILTERS
4675 Below is a description of the currently available multimedia filters.
4677 @section asendcmd, sendcmd
4679 Send commands to filters in the filtergraph.
4681 These filters read commands to be sent to other filters in the
4684 @code{asendcmd} must be inserted between two audio filters,
4685 @code{sendcmd} must be inserted between two video filters, but apart
4686 from that they act the same way.
4688 The specification of commands can be provided in the filter arguments
4689 with the @var{commands} option, or in a file specified by the
4690 @var{filename} option.
4692 These filters accept the following options:
4695 Set the commands to be read and sent to the other filters.
4697 Set the filename of the commands to be read and sent to the other
4701 @subsection Commands syntax
4703 A commands description consists of a sequence of interval
4704 specifications, comprising a list of commands to be executed when a
4705 particular event related to that interval occurs. The occurring event
4706 is typically the current frame time entering or leaving a given time
4709 An interval is specified by the following syntax:
4711 @var{START}[-@var{END}] @var{COMMANDS};
4714 The time interval is specified by the @var{START} and @var{END} times.
4715 @var{END} is optional and defaults to the maximum time.
4717 The current frame time is considered within the specified interval if
4718 it is included in the interval [@var{START}, @var{END}), that is when
4719 the time is greater or equal to @var{START} and is lesser than
4722 @var{COMMANDS} consists of a sequence of one or more command
4723 specifications, separated by ",", relating to that interval. The
4724 syntax of a command specification is given by:
4726 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4729 @var{FLAGS} is optional and specifies the type of events relating to
4730 the time interval which enable sending the specified command, and must
4731 be a non-null sequence of identifier flags separated by "+" or "|" and
4732 enclosed between "[" and "]".
4734 The following flags are recognized:
4737 The command is sent when the current frame timestamp enters the
4738 specified interval. In other words, the command is sent when the
4739 previous frame timestamp was not in the given interval, and the
4743 The command is sent when the current frame timestamp leaves the
4744 specified interval. In other words, the command is sent when the
4745 previous frame timestamp was in the given interval, and the
4749 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4752 @var{TARGET} specifies the target of the command, usually the name of
4753 the filter class or a specific filter instance name.
4755 @var{COMMAND} specifies the name of the command for the target filter.
4757 @var{ARG} is optional and specifies the optional list of argument for
4758 the given @var{COMMAND}.
4760 Between one interval specification and another, whitespaces, or
4761 sequences of characters starting with @code{#} until the end of line,
4762 are ignored and can be used to annotate comments.
4764 A simplified BNF description of the commands specification syntax
4767 @var{COMMAND_FLAG} ::= "enter" | "leave"
4768 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4769 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4770 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4771 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4772 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4775 @subsection Examples
4779 Specify audio tempo change at second 4:
4781 asendcmd=c='4.0 atempo tempo 1.5',atempo
4785 Specify a list of drawtext and hue commands in a file.
4787 # show text in the interval 5-10
4788 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4789 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4791 # desaturate the image in the interval 15-20
4792 15.0-20.0 [enter] hue reinit s=0,
4793 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4794 [leave] hue reinit s=1,
4795 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4797 # apply an exponential saturation fade-out effect, starting from time 25
4798 25 [enter] hue s=exp(t-25)
4801 A filtergraph allowing to read and process the above command list
4802 stored in a file @file{test.cmd}, can be specified with:
4804 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4808 @section asetpts, setpts
4810 Change the PTS (presentation timestamp) of the input frames.
4812 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4814 Accept in input an expression evaluated through the eval API, which
4815 can contain the following constants:
4819 frame rate, only defined for constant frame-rate video
4822 the presentation timestamp in input
4825 the count of the input frame, starting from 0.
4827 @item NB_CONSUMED_SAMPLES
4828 the number of consumed samples, not including the current frame (only
4832 the number of samples in the current frame (only audio)
4838 the PTS of the first frame
4841 the time in seconds of the first frame
4844 tell if the current frame is interlaced
4847 the time in seconds of the current frame
4853 original position in the file of the frame, or undefined if undefined
4854 for the current frame
4860 previous input time in seconds
4866 previous output time in seconds
4869 @subsection Examples
4873 Start counting PTS from zero
4879 Apply fast motion effect:
4885 Apply slow motion effect:
4891 Set fixed rate of 25 frames per second:
4897 Set fixed rate 25 fps with some jitter:
4899 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
4903 Apply an offset of 10 seconds to the input PTS:
4911 EBU R128 scanner filter. This filter takes an audio stream as input and outputs
4912 it unchanged. By default, it logs a message at a frequency of 10Hz with the
4913 Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
4914 Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
4916 The filter also has a video output (see the @var{video} option) with a real
4917 time graph to observe the loudness evolution. The graphic contains the logged
4918 message mentioned above, so it is not printed anymore when this option is set,
4919 unless the verbose logging is set. The main graphing area contains the
4920 short-term loudness (3 seconds of analysis), and the gauge on the right is for
4921 the momentary loudness (400 milliseconds).
4923 More information about the Loudness Recommendation EBU R128 on
4924 @url{http://tech.ebu.ch/loudness}.
4926 The filter accepts the following named parameters:
4931 Activate the video output. The audio stream is passed unchanged whether this
4932 option is set or no. The video stream will be the first output stream if
4933 activated. Default is @code{0}.
4936 Set the video size. This option is for video only. Default and minimum
4937 resolution is @code{640x480}.
4940 Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
4941 @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
4942 other integer value between this range is allowed.
4946 Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
4948 ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
4951 Run an analysis with @command{ffmpeg}:
4953 ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
4956 @section settb, asettb
4958 Set the timebase to use for the output frames timestamps.
4959 It is mainly useful for testing timebase configuration.
4961 It accepts in input an arithmetic expression representing a rational.
4962 The expression can contain the constants "AVTB" (the
4963 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
4966 The default value for the input is "intb".
4968 @subsection Examples
4972 Set the timebase to 1/25:
4978 Set the timebase to 1/10:
4984 Set the timebase to 1001/1000:
4990 Set the timebase to 2*intb:
4996 Set the default timebase value:
5004 Concatenate audio and video streams, joining them together one after the
5007 The filter works on segments of synchronized video and audio streams. All
5008 segments must have the same number of streams of each type, and that will
5009 also be the number of streams at output.
5011 The filter accepts the following named parameters:
5015 Set the number of segments. Default is 2.
5018 Set the number of output video streams, that is also the number of video
5019 streams in each segment. Default is 1.
5022 Set the number of output audio streams, that is also the number of video
5023 streams in each segment. Default is 0.
5026 Activate unsafe mode: do not fail if segments have a different format.
5030 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
5031 @var{a} audio outputs.
5033 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
5034 segment, in the same order as the outputs, then the inputs for the second
5037 Related streams do not always have exactly the same duration, for various
5038 reasons including codec frame size or sloppy authoring. For that reason,
5039 related synchronized streams (e.g. a video and its audio track) should be
5040 concatenated at once. The concat filter will use the duration of the longest
5041 stream in each segment (except the last one), and if necessary pad shorter
5042 audio streams with silence.
5044 For this filter to work correctly, all segments must start at timestamp 0.
5046 All corresponding streams must have the same parameters in all segments; the
5047 filtering system will automatically select a common pixel format for video
5048 streams, and a common sample format, sample rate and channel layout for
5049 audio streams, but other settings, such as resolution, must be converted
5050 explicitly by the user.
5052 Different frame rates are acceptable but will result in variable frame rate
5053 at output; be sure to configure the output file to handle it.
5058 Concatenate an opening, an episode and an ending, all in bilingual version
5059 (video in stream 0, audio in streams 1 and 2):
5061 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
5062 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
5063 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
5064 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
5068 Concatenate two parts, handling audio and video separately, using the
5069 (a)movie sources, and adjusting the resolution:
5071 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
5072 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
5073 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
5075 Note that a desync will happen at the stitch if the audio and video streams
5076 do not have exactly the same duration in the first file.
5080 @section showspectrum
5082 Convert input audio to a video output, representing the audio frequency
5085 The filter accepts the following named parameters:
5088 Specify the video size for the output. Default value is @code{640x480}.
5090 Specify if the spectrum should slide along the window. Default value is
5094 The usage is very similar to the showwaves filter; see the examples in that
5099 Convert input audio to a video output, representing the samples waves.
5101 The filter accepts the following named parameters:
5105 Set the number of samples which are printed on the same column. A
5106 larger value will decrease the frame rate. Must be a positive
5107 integer. This option can be set only if the value for @var{rate}
5108 is not explicitly specified.
5111 Set the (approximate) output frame rate. This is done by setting the
5112 option @var{n}. Default value is "25".
5115 Specify the video size for the output. Default value is "600x240".
5118 Some examples follow.
5121 Output the input file audio and the corresponding video representation
5124 amovie=a.mp3,asplit[out0],showwaves[out1]
5128 Create a synthetic signal and show it with showwaves, forcing a
5129 framerate of 30 frames per second:
5131 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
5135 @c man end MULTIMEDIA FILTERS
5137 @chapter Multimedia Sources
5138 @c man begin MULTIMEDIA SOURCES
5140 Below is a description of the currently available multimedia sources.
5144 This is the same as @ref{src_movie} source, except it selects an audio
5150 Read audio and/or video stream(s) from a movie container.
5152 It accepts the syntax: @var{movie_name}[:@var{options}] where
5153 @var{movie_name} is the name of the resource to read (not necessarily
5154 a file but also a device or a stream accessed through some protocol),
5155 and @var{options} is an optional sequence of @var{key}=@var{value}
5156 pairs, separated by ":".
5158 The description of the accepted options follows.
5162 @item format_name, f
5163 Specifies the format assumed for the movie to read, and can be either
5164 the name of a container or an input device. If not specified the
5165 format is guessed from @var{movie_name} or by probing.
5167 @item seek_point, sp
5168 Specifies the seek point in seconds, the frames will be output
5169 starting from this seek point, the parameter is evaluated with
5170 @code{av_strtod} so the numerical value may be suffixed by an IS
5171 postfix. Default value is "0".
5174 Specifies the streams to read. Several streams can be specified, separated
5175 by "+". The source will then have as many outputs, in the same order. The
5176 syntax is explained in the @ref{Stream specifiers} chapter. Two special
5177 names, "dv" and "da" specify respectively the default (best suited) video
5178 and audio stream. Default is "dv", or "da" if the filter is called as
5181 @item stream_index, si
5182 Specifies the index of the video stream to read. If the value is -1,
5183 the best suited video stream will be automatically selected. Default
5184 value is "-1". Deprecated. If the filter is called "amovie", it will select
5185 audio instead of video.
5188 Specifies how many times to read the stream in sequence.
5189 If the value is less than 1, the stream will be read again and again.
5190 Default value is "1".
5192 Note that when the movie is looped the source timestamps are not
5193 changed, so it will generate non monotonically increasing timestamps.
5196 This filter allows to overlay a second video on top of main input of
5197 a filtergraph as shown in this graph:
5199 input -----------> deltapts0 --> overlay --> output
5202 movie --> scale--> deltapts1 -------+
5205 Some examples follow.
5209 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
5210 on top of the input labelled as "in":
5212 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5213 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5217 Read from a video4linux2 device, and overlay it on top of the input
5220 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5221 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5225 Read the first video stream and the audio stream with id 0x81 from
5226 dvd.vob; the video is connected to the pad named "video" and the audio is
5227 connected to the pad named "audio":
5229 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
5233 @c man end MULTIMEDIA SOURCES