lavfi: add compand audio filter
[libav.git] / doc / filters.texi
1 @chapter Filtergraph description
2 @c man begin FILTERGRAPH DESCRIPTION
3
4 A filtergraph is a directed graph of connected filters. It can contain
5 cycles, and there can be multiple links between a pair of
6 filters. Each link has one input pad on one side connecting it to one
7 filter from which it takes its input, and one output pad on the other
8 side connecting it to the one filter accepting its output.
9
10 Each filter in a filtergraph is an instance of a filter class
11 registered in the application, which defines the features and the
12 number of input and output pads of the filter.
13
14 A filter with no input pads is called a "source", a filter with no
15 output pads is called a "sink".
16
17 @anchor{Filtergraph syntax}
18 @section Filtergraph syntax
19
20 A filtergraph can be represented using a textual representation, which is
21 recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}
22 options in @command{avconv} and @option{-vf} in @command{avplay}, and by the
23 @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in
24 @file{libavfilter/avfilter.h}.
25
26 A filterchain consists of a sequence of connected filters, each one
27 connected to the previous one in the sequence. A filterchain is
28 represented by a list of ","-separated filter descriptions.
29
30 A filtergraph consists of a sequence of filterchains. A sequence of
31 filterchains is represented by a list of ";"-separated filterchain
32 descriptions.
33
34 A filter is represented by a string of the form:
35 [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
36
37 @var{filter_name} is the name of the filter class of which the
38 described filter is an instance of, and has to be the name of one of
39 the filter classes registered in the program.
40 The name of the filter class is optionally followed by a string
41 "=@var{arguments}".
42
43 @var{arguments} is a string which contains the parameters used to
44 initialize the filter instance. It may have one of the two allowed forms:
45 @itemize
46
47 @item
48 A ':'-separated list of @var{key=value} pairs.
49
50 @item
51 A ':'-separated list of @var{value}. In this case, the keys are assumed to be
52 the option names in the order they are declared. E.g. the @code{fade} filter
53 declares three options in this order -- @option{type}, @option{start_frame} and
54 @option{nb_frames}. Then the parameter list @var{in:0:30} means that the value
55 @var{in} is assigned to the option @option{type}, @var{0} to
56 @option{start_frame} and @var{30} to @option{nb_frames}.
57
58 @end itemize
59
60 If the option value itself is a list of items (e.g. the @code{format} filter
61 takes a list of pixel formats), the items in the list are usually separated by
62 '|'.
63
64 The list of arguments can be quoted using the character "'" as initial
65 and ending mark, and the character '\' for escaping the characters
66 within the quoted text; otherwise the argument string is considered
67 terminated when the next special character (belonging to the set
68 "[]=;,") is encountered.
69
70 The name and arguments of the filter are optionally preceded and
71 followed by a list of link labels.
72 A link label allows to name a link and associate it to a filter output
73 or input pad. The preceding labels @var{in_link_1}
74 ... @var{in_link_N}, are associated to the filter input pads,
75 the following labels @var{out_link_1} ... @var{out_link_M}, are
76 associated to the output pads.
77
78 When two link labels with the same name are found in the
79 filtergraph, a link between the corresponding input and output pad is
80 created.
81
82 If an output pad is not labelled, it is linked by default to the first
83 unlabelled input pad of the next filter in the filterchain.
84 For example in the filterchain:
85 @example
86 nullsrc, split[L1], [L2]overlay, nullsink
87 @end example
88 the split filter instance has two output pads, and the overlay filter
89 instance two input pads. The first output pad of split is labelled
90 "L1", the first input pad of overlay is labelled "L2", and the second
91 output pad of split is linked to the second input pad of overlay,
92 which are both unlabelled.
93
94 In a complete filterchain all the unlabelled filter input and output
95 pads must be connected. A filtergraph is considered valid if all the
96 filter input and output pads of all the filterchains are connected.
97
98 Libavfilter will automatically insert @ref{scale} filters where format
99 conversion is required. It is possible to specify swscale flags
100 for those automatically inserted scalers by prepending
101 @code{sws_flags=@var{flags};}
102 to the filtergraph description.
103
104 Follows a BNF description for the filtergraph syntax:
105 @example
106 @var{NAME} ::= sequence of alphanumeric characters and '_'
107 @var{LINKLABEL} ::= "[" @var{NAME} "]"
108 @var{LINKLABELS} ::= @var{LINKLABEL} [@var{LINKLABELS}]
109 @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
110 @var{FILTER} ::= [@var{LINKLABELS}] @var{NAME} ["=" @var{FILTER_ARGUMENTS}] [@var{LINKLABELS}]
111 @var{FILTERCHAIN} ::= @var{FILTER} [,@var{FILTERCHAIN}]
112 @var{FILTERGRAPH} ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
113 @end example
114
115 @c man end FILTERGRAPH DESCRIPTION
116
117 @chapter Audio Filters
118 @c man begin AUDIO FILTERS
119
120 When you configure your Libav build, you can disable any of the
121 existing filters using --disable-filters.
122 The configure output will show the audio filters included in your
123 build.
124
125 Below is a description of the currently available audio filters.
126
127 @section aformat
128
129 Convert the input audio to one of the specified formats. The framework will
130 negotiate the most appropriate format to minimize conversions.
131
132 The filter accepts the following named parameters:
133 @table @option
134
135 @item sample_fmts
136 A '|'-separated list of requested sample formats.
137
138 @item sample_rates
139 A '|'-separated list of requested sample rates.
140
141 @item channel_layouts
142 A '|'-separated list of requested channel layouts.
143
144 @end table
145
146 If a parameter is omitted, all values are allowed.
147
148 For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
149 @example
150 aformat=sample_fmts=u8|s16:channel_layouts=stereo
151 @end example
152
153 @section amix
154
155 Mixes multiple audio inputs into a single output.
156
157 For example
158 @example
159 avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
160 @end example
161 will mix 3 input audio streams to a single output with the same duration as the
162 first input and a dropout transition time of 3 seconds.
163
164 The filter accepts the following named parameters:
165 @table @option
166
167 @item inputs
168 Number of inputs. If unspecified, it defaults to 2.
169
170 @item duration
171 How to determine the end-of-stream.
172 @table @option
173
174 @item longest
175 Duration of longest input. (default)
176
177 @item shortest
178 Duration of shortest input.
179
180 @item first
181 Duration of first input.
182
183 @end table
184
185 @item dropout_transition
186 Transition time, in seconds, for volume renormalization when an input
187 stream ends. The default value is 2 seconds.
188
189 @end table
190
191 @section anull
192
193 Pass the audio source unchanged to the output.
194
195 @section asetpts
196
197 Change the PTS (presentation timestamp) of the input audio frames.
198
199 This filter accepts the following options:
200
201 @table @option
202
203 @item expr
204 The expression which is evaluated for each frame to construct its timestamp.
205
206 @end table
207
208 The expression is evaluated through the eval API and can contain the following
209 constants:
210
211 @table @option
212 @item PTS
213 the presentation timestamp in input
214
215 @item PI
216 Greek PI
217
218 @item PHI
219 golden ratio
220
221 @item E
222 Euler number
223
224 @item N
225 Number of the audio samples pass through the filter so far, starting at 0.
226
227 @item S
228 Number of the audio samples in the current frame.
229
230 @item SR
231 Audio sample rate.
232
233 @item STARTPTS
234 the PTS of the first frame
235
236 @item PREV_INPTS
237 previous input PTS
238
239 @item PREV_OUTPTS
240 previous output PTS
241
242 @item RTCTIME
243 wallclock (RTC) time in microseconds
244
245 @item RTCSTART
246 wallclock (RTC) time at the start of the movie in microseconds
247
248 @end table
249
250 Some examples follow:
251
252 @example
253 # start counting PTS from zero
254 asetpts=expr=PTS-STARTPTS
255
256 #generate timestamps by counting samples
257 asetpts=expr=N/SR/TB
258
259 # generate timestamps from a "live source" and rebase onto the current timebase
260 asetpts='(RTCTIME - RTCSTART) / (TB * 1000000)"
261 @end example
262
263
264 @section ashowinfo
265
266 Show a line containing various information for each input audio frame.
267 The input audio is not modified.
268
269 The shown line contains a sequence of key/value pairs of the form
270 @var{key}:@var{value}.
271
272 A description of each shown parameter follows:
273
274 @table @option
275 @item n
276 sequential number of the input frame, starting from 0
277
278 @item pts
279 Presentation timestamp of the input frame, in time base units; the time base
280 depends on the filter input pad, and is usually 1/@var{sample_rate}.
281
282 @item pts_time
283 presentation timestamp of the input frame in seconds
284
285 @item fmt
286 sample format
287
288 @item chlayout
289 channel layout
290
291 @item rate
292 sample rate for the audio frame
293
294 @item nb_samples
295 number of samples (per channel) in the frame
296
297 @item checksum
298 Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
299 the data is treated as if all the planes were concatenated.
300
301 @item plane_checksums
302 A list of Adler-32 checksums for each data plane.
303 @end table
304
305 @section asplit
306
307 Split input audio into several identical outputs.
308
309 The filter accepts a single parameter which specifies the number of outputs. If
310 unspecified, it defaults to 2.
311
312 For example
313 @example
314 avconv -i INPUT -filter_complex asplit=5 OUTPUT
315 @end example
316 will create 5 copies of the input audio.
317
318 @section asyncts
319 Synchronize audio data with timestamps by squeezing/stretching it and/or
320 dropping samples/adding silence when needed.
321
322 The filter accepts the following named parameters:
323 @table @option
324
325 @item compensate
326 Enable stretching/squeezing the data to make it match the timestamps. Disabled
327 by default. When disabled, time gaps are covered with silence.
328
329 @item min_delta
330 Minimum difference between timestamps and audio data (in seconds) to trigger
331 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
332 this filter, try setting this parameter to 0.
333
334 @item max_comp
335 Maximum compensation in samples per second. Relevant only with compensate=1.
336 Default value 500.
337
338 @item first_pts
339 Assume the first pts should be this value. The time base is 1 / sample rate.
340 This allows for padding/trimming at the start of stream. By default, no
341 assumption is made about the first frame's expected pts, so no padding or
342 trimming is done. For example, this could be set to 0 to pad the beginning with
343 silence if an audio stream starts after the video stream or to trim any samples
344 with a negative pts due to encoder delay.
345
346 @end table
347
348 @section atrim
349 Trim the input so that the output contains one continuous subpart of the input.
350
351 This filter accepts the following options:
352 @table @option
353 @item start
354 Timestamp (in seconds) of the start of the kept section. I.e. the audio sample
355 with the timestamp @var{start} will be the first sample in the output.
356
357 @item end
358 Timestamp (in seconds) of the first audio sample that will be dropped. I.e. the
359 audio sample immediately preceding the one with the timestamp @var{end} will be
360 the last sample in the output.
361
362 @item start_pts
363 Same as @var{start}, except this option sets the start timestamp in samples
364 instead of seconds.
365
366 @item end_pts
367 Same as @var{end}, except this option sets the end timestamp in samples instead
368 of seconds.
369
370 @item duration
371 Maximum duration of the output in seconds.
372
373 @item start_sample
374 Number of the first sample that should be passed to output.
375
376 @item end_sample
377 Number of the first sample that should be dropped.
378 @end table
379
380 Note that the first two sets of the start/end options and the @option{duration}
381 option look at the frame timestamp, while the _sample options simply count the
382 samples that pass through the filter. So start/end_pts and start/end_sample will
383 give different results when the timestamps are wrong, inexact or do not start at
384 zero. Also note that this filter does not modify the timestamps. If you wish
385 that the output timestamps start at zero, insert the asetpts filter after the
386 atrim filter.
387
388 If multiple start or end options are set, this filter tries to be greedy and
389 keep all samples that match at least one of the specified constraints. To keep
390 only the part that matches all the constraints at once, chain multiple atrim
391 filters.
392
393 The defaults are such that all the input is kept. So it is possible to set e.g.
394 just the end values to keep everything before the specified time.
395
396 Examples:
397 @itemize
398 @item
399 drop everything except the second minute of input
400 @example
401 avconv -i INPUT -af atrim=60:120
402 @end example
403
404 @item
405 keep only the first 1000 samples
406 @example
407 avconv -i INPUT -af atrim=end_sample=1000
408 @end example
409
410 @end itemize
411
412 @section channelsplit
413 Split each channel in input audio stream into a separate output stream.
414
415 This filter accepts the following named parameters:
416 @table @option
417 @item channel_layout
418 Channel layout of the input stream. Default is "stereo".
419 @end table
420
421 For example, assuming a stereo input MP3 file
422 @example
423 avconv -i in.mp3 -filter_complex channelsplit out.mkv
424 @end example
425 will create an output Matroska file with two audio streams, one containing only
426 the left channel and the other the right channel.
427
428 To split a 5.1 WAV file into per-channel files
429 @example
430 avconv -i in.wav -filter_complex
431 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
432 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
433 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
434 side_right.wav
435 @end example
436
437 @section channelmap
438 Remap input channels to new locations.
439
440 This filter accepts the following named parameters:
441 @table @option
442 @item channel_layout
443 Channel layout of the output stream.
444
445 @item map
446 Map channels from input to output. The argument is a '|'-separated list of
447 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
448 @var{in_channel} form. @var{in_channel} can be either the name of the input
449 channel (e.g. FL for front left) or its index in the input channel layout.
450 @var{out_channel} is the name of the output channel or its index in the output
451 channel layout. If @var{out_channel} is not given then it is implicitly an
452 index, starting with zero and increasing by one for each mapping.
453 @end table
454
455 If no mapping is present, the filter will implicitly map input channels to
456 output channels preserving index.
457
458 For example, assuming a 5.1+downmix input MOV file
459 @example
460 avconv -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav
461 @end example
462 will create an output WAV file tagged as stereo from the downmix channels of
463 the input.
464
465 To fix a 5.1 WAV improperly encoded in AAC's native channel order
466 @example
467 avconv -i in.wav -filter 'channelmap=1|2|0|5|3|4:channel_layout=5.1' out.wav
468 @end example
469
470 @section compand
471 Compress or expand audio dynamic range.
472
473 A description of the accepted options follows.
474
475 @table @option
476
477 @item attacks
478 @item decays
479 Set list of times in seconds for each channel over which the instantaneous level
480 of the input signal is averaged to determine its volume. @var{attacks} refers to
481 increase of volume and @var{decays} refers to decrease of volume. For most
482 situations, the attack time (response to the audio getting louder) should be
483 shorter than the decay time because the human ear is more sensitive to sudden
484 loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and
485 a typical value for decay is 0.8 seconds.
486
487 @item points
488 Set list of points for the transfer function, specified in dB relative to the
489 maximum possible signal amplitude. Each key points list must be defined using
490 the following syntax: @code{x0/y0|x1/y1|x2/y2|....}
491
492 The input values must be in strictly increasing order but the transfer function
493 does not have to be monotonically rising. The point @code{0/0} is assumed but
494 may be overridden (by @code{0/out-dBn}). Typical values for the transfer
495 function are @code{-70/-70|-60/-20}.
496
497 @item soft-knee
498 Set the curve radius in dB for all joints. Defaults to 0.01.
499
500 @item gain
501 Set additional gain in dB to be applied at all points on the transfer function.
502 This allows easy adjustment of the overall gain. Defaults to 0.
503
504 @item volume
505 Set initial volume in dB to be assumed for each channel when filtering starts.
506 This permits the user to supply a nominal level initially, so that, for
507 example, a very large gain is not applied to initial signal levels before the
508 companding has begun to operate. A typical value for audio which is initially
509 quiet is -90 dB. Defaults to 0.
510
511 @item delay
512 Set delay in seconds. The input audio is analyzed immediately, but audio is
513 delayed before being fed to the volume adjuster. Specifying a delay
514 approximately equal to the attack/decay times allows the filter to effectively
515 operate in predictive rather than reactive mode. Defaults to 0.
516
517 @end table
518
519 @subsection Examples
520
521 @itemize
522 @item
523 Make music with both quiet and loud passages suitable for listening in a noisy
524 environment:
525 @example
526 compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2
527 @end example
528
529 @item
530 Noise gate for when the noise is at a lower level than the signal:
531 @example
532 compand=.1|.1:.2|.2:-900/-900|-50.1/-900|-50/-50:.01:0:-90:.1
533 @end example
534
535 @item
536 Here is another noise gate, this time for when the noise is at a higher level
537 than the signal (making it, in some ways, similar to squelch):
538 @example
539 compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
540 @end example
541 @end itemize
542
543 @section join
544 Join multiple input streams into one multi-channel stream.
545
546 The filter accepts the following named parameters:
547 @table @option
548
549 @item inputs
550 Number of input streams. Defaults to 2.
551
552 @item channel_layout
553 Desired output channel layout. Defaults to stereo.
554
555 @item map
556 Map channels from inputs to output. The argument is a '|'-separated list of
557 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
558 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
559 can be either the name of the input channel (e.g. FL for front left) or its
560 index in the specified input stream. @var{out_channel} is the name of the output
561 channel.
562 @end table
563
564 The filter will attempt to guess the mappings when those are not specified
565 explicitly. It does so by first trying to find an unused matching input channel
566 and if that fails it picks the first unused input channel.
567
568 E.g. to join 3 inputs (with properly set channel layouts)
569 @example
570 avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
571 @end example
572
573 To build a 5.1 output from 6 single-channel streams:
574 @example
575 avconv -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
576 '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'
577 out
578 @end example
579
580 @section resample
581 Convert the audio sample format, sample rate and channel layout. This filter is
582 not meant to be used directly, it is inserted automatically by libavfilter
583 whenever conversion is needed. Use the @var{aformat} filter to force a specific
584 conversion.
585
586 @section volume
587
588 Adjust the input audio volume.
589
590 The filter accepts the following named parameters:
591 @table @option
592
593 @item volume
594 Expresses how the audio volume will be increased or decreased.
595
596 Output values are clipped to the maximum value.
597
598 The output audio volume is given by the relation:
599 @example
600 @var{output_volume} = @var{volume} * @var{input_volume}
601 @end example
602
603 Default value for @var{volume} is 1.0.
604
605 @item precision
606 Mathematical precision.
607
608 This determines which input sample formats will be allowed, which affects the
609 precision of the volume scaling.
610
611 @table @option
612 @item fixed
613 8-bit fixed-point; limits input sample format to U8, S16, and S32.
614 @item float
615 32-bit floating-point; limits input sample format to FLT. (default)
616 @item double
617 64-bit floating-point; limits input sample format to DBL.
618 @end table
619 @end table
620
621 @subsection Examples
622
623 @itemize
624 @item
625 Halve the input audio volume:
626 @example
627 volume=volume=0.5
628 volume=volume=1/2
629 volume=volume=-6.0206dB
630 @end example
631
632 @item
633 Increase input audio power by 6 decibels using fixed-point precision:
634 @example
635 volume=volume=6dB:precision=fixed
636 @end example
637 @end itemize
638
639 @c man end AUDIO FILTERS
640
641 @chapter Audio Sources
642 @c man begin AUDIO SOURCES
643
644 Below is a description of the currently available audio sources.
645
646 @section anullsrc
647
648 Null audio source, never return audio frames. It is mainly useful as a
649 template and to be employed in analysis / debugging tools.
650
651 It accepts as optional parameter a string of the form
652 @var{sample_rate}:@var{channel_layout}.
653
654 @var{sample_rate} specify the sample rate, and defaults to 44100.
655
656 @var{channel_layout} specify the channel layout, and can be either an
657 integer or a string representing a channel layout. The default value
658 of @var{channel_layout} is 3, which corresponds to CH_LAYOUT_STEREO.
659
660 Check the channel_layout_map definition in
661 @file{libavutil/channel_layout.c} for the mapping between strings and
662 channel layout values.
663
664 Follow some examples:
665 @example
666 # set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.
667 anullsrc=48000:4
668
669 # same as
670 anullsrc=48000:mono
671 @end example
672
673 @section abuffer
674 Buffer audio frames, and make them available to the filter chain.
675
676 This source is not intended to be part of user-supplied graph descriptions but
677 for insertion by calling programs through the interface defined in
678 @file{libavfilter/buffersrc.h}.
679
680 It accepts the following named parameters:
681 @table @option
682
683 @item time_base
684 Timebase which will be used for timestamps of submitted frames. It must be
685 either a floating-point number or in @var{numerator}/@var{denominator} form.
686
687 @item sample_rate
688 Audio sample rate.
689
690 @item sample_fmt
691 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
692
693 @item channel_layout
694 Channel layout of the audio data, in the form that can be accepted by
695 @code{av_get_channel_layout()}.
696 @end table
697
698 All the parameters need to be explicitly defined.
699
700 @c man end AUDIO SOURCES
701
702 @chapter Audio Sinks
703 @c man begin AUDIO SINKS
704
705 Below is a description of the currently available audio sinks.
706
707 @section anullsink
708
709 Null audio sink, do absolutely nothing with the input audio. It is
710 mainly useful as a template and to be employed in analysis / debugging
711 tools.
712
713 @section abuffersink
714 This sink is intended for programmatic use. Frames that arrive on this sink can
715 be retrieved by the calling program using the interface defined in
716 @file{libavfilter/buffersink.h}.
717
718 This filter accepts no parameters.
719
720 @c man end AUDIO SINKS
721
722 @chapter Video Filters
723 @c man begin VIDEO FILTERS
724
725 When you configure your Libav build, you can disable any of the
726 existing filters using --disable-filters.
727 The configure output will show the video filters included in your
728 build.
729
730 Below is a description of the currently available video filters.
731
732 @section blackframe
733
734 Detect frames that are (almost) completely black. Can be useful to
735 detect chapter transitions or commercials. Output lines consist of
736 the frame number of the detected frame, the percentage of blackness,
737 the position in the file if known or -1 and the timestamp in seconds.
738
739 In order to display the output lines, you need to set the loglevel at
740 least to the AV_LOG_INFO value.
741
742 The filter accepts the following options:
743
744 @table @option
745
746 @item amount
747 The percentage of the pixels that have to be below the threshold, defaults to
748 98.
749
750 @item threshold
751 Threshold below which a pixel value is considered black, defaults to 32.
752
753 @end table
754
755 @section boxblur
756
757 Apply boxblur algorithm to the input video.
758
759 This filter accepts the following options:
760
761 @table @option
762
763 @item luma_radius
764 @item luma_power
765 @item chroma_radius
766 @item chroma_power
767 @item alpha_radius
768 @item alpha_power
769
770 @end table
771
772 Chroma and alpha parameters are optional, if not specified they default
773 to the corresponding values set for @var{luma_radius} and
774 @var{luma_power}.
775
776 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
777 the radius in pixels of the box used for blurring the corresponding
778 input plane. They are expressions, and can contain the following
779 constants:
780 @table @option
781 @item w, h
782 the input width and height in pixels
783
784 @item cw, ch
785 the input chroma image width and height in pixels
786
787 @item hsub, vsub
788 horizontal and vertical chroma subsample values. For example for the
789 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
790 @end table
791
792 The radius must be a non-negative number, and must not be greater than
793 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
794 and of @code{min(cw,ch)/2} for the chroma planes.
795
796 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
797 how many times the boxblur filter is applied to the corresponding
798 plane.
799
800 Some examples follow:
801
802 @itemize
803
804 @item
805 Apply a boxblur filter with luma, chroma, and alpha radius
806 set to 2:
807 @example
808 boxblur=luma_radius=2:luma_power=1
809 @end example
810
811 @item
812 Set luma radius to 2, alpha and chroma radius to 0
813 @example
814 boxblur=2:1:0:0:0:0
815 @end example
816
817 @item
818 Set luma and chroma radius to a fraction of the video dimension
819 @example
820 boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1
821 @end example
822
823 @end itemize
824
825 @section copy
826
827 Copy the input source unchanged to the output. Mainly useful for
828 testing purposes.
829
830 @section crop
831
832 Crop the input video to given dimensions.
833
834 This filter accepts the following options:
835
836 @table @option
837
838 @item out_w
839 Width of the output video.
840
841 @item out_h
842 Height of the output video.
843
844 @item x
845 Horizontal position, in the input video, of the left edge of the output video.
846
847 @item y
848 Vertical position, in the input video, of the top edge of the output video.
849
850 @end table
851
852 The parameters are expressions containing the following constants:
853
854 @table @option
855 @item E, PI, PHI
856 the corresponding mathematical approximated values for e
857 (euler number), pi (greek PI), PHI (golden ratio)
858
859 @item x, y
860 the computed values for @var{x} and @var{y}. They are evaluated for
861 each new frame.
862
863 @item in_w, in_h
864 the input width and height
865
866 @item iw, ih
867 same as @var{in_w} and @var{in_h}
868
869 @item out_w, out_h
870 the output (cropped) width and height
871
872 @item ow, oh
873 same as @var{out_w} and @var{out_h}
874
875 @item n
876 the number of input frame, starting from 0
877
878 @item t
879 timestamp expressed in seconds, NAN if the input timestamp is unknown
880
881 @end table
882
883 The @var{out_w} and @var{out_h} parameters specify the expressions for
884 the width and height of the output (cropped) video. They are
885 evaluated just at the configuration of the filter.
886
887 The default value of @var{out_w} is "in_w", and the default value of
888 @var{out_h} is "in_h".
889
890 The expression for @var{out_w} may depend on the value of @var{out_h},
891 and the expression for @var{out_h} may depend on @var{out_w}, but they
892 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
893 evaluated after @var{out_w} and @var{out_h}.
894
895 The @var{x} and @var{y} parameters specify the expressions for the
896 position of the top-left corner of the output (non-cropped) area. They
897 are evaluated for each frame. If the evaluated value is not valid, it
898 is approximated to the nearest valid value.
899
900 The default value of @var{x} is "(in_w-out_w)/2", and the default
901 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
902 the center of the input image.
903
904 The expression for @var{x} may depend on @var{y}, and the expression
905 for @var{y} may depend on @var{x}.
906
907 Follow some examples:
908 @example
909 # crop the central input area with size 100x100
910 crop=out_w=100:out_h=100
911
912 # crop the central input area with size 2/3 of the input video
913 "crop=out_w=2/3*in_w:out_h=2/3*in_h"
914
915 # crop the input video central square
916 crop=out_w=in_h
917
918 # delimit the rectangle with the top-left corner placed at position
919 # 100:100 and the right-bottom corner corresponding to the right-bottom
920 # corner of the input image.
921 crop=out_w=in_w-100:out_h=in_h-100:x=100:y=100
922
923 # crop 10 pixels from the left and right borders, and 20 pixels from
924 # the top and bottom borders
925 "crop=out_w=in_w-2*10:out_h=in_h-2*20"
926
927 # keep only the bottom right quarter of the input image
928 "crop=out_w=in_w/2:out_h=in_h/2:x=in_w/2:y=in_h/2"
929
930 # crop height for getting Greek harmony
931 "crop=out_w=in_w:out_h=1/PHI*in_w"
932
933 # trembling effect
934 "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)"
935
936 # erratic camera effect depending on timestamp
937 "crop=out_w=in_w/2:out_h=in_h/2:x=(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):y=(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
938
939 # set x depending on the value of y
940 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
941 @end example
942
943 @section cropdetect
944
945 Auto-detect crop size.
946
947 Calculate necessary cropping parameters and prints the recommended
948 parameters through the logging system. The detected dimensions
949 correspond to the non-black area of the input video.
950
951 This filter accepts the following options:
952
953 @table @option
954
955 @item limit
956 Threshold, which can be optionally specified from nothing (0) to
957 everything (255), defaults to 24.
958
959 @item round
960 Value which the width/height should be divisible by, defaults to
961 16. The offset is automatically adjusted to center the video. Use 2 to
962 get only even dimensions (needed for 4:2:2 video). 16 is best when
963 encoding to most video codecs.
964
965 @item reset
966 Counter that determines after how many frames cropdetect will reset
967 the previously detected largest video area and start over to detect
968 the current optimal crop area. Defaults to 0.
969
970 This can be useful when channel logos distort the video area. 0
971 indicates never reset and return the largest area encountered during
972 playback.
973 @end table
974
975 @section delogo
976
977 Suppress a TV station logo by a simple interpolation of the surrounding
978 pixels. Just set a rectangle covering the logo and watch it disappear
979 (and sometimes something even uglier appear - your mileage may vary).
980
981 This filter accepts the following options:
982 @table @option
983
984 @item x, y
985 Specify the top left corner coordinates of the logo. They must be
986 specified.
987
988 @item w, h
989 Specify the width and height of the logo to clear. They must be
990 specified.
991
992 @item band, t
993 Specify the thickness of the fuzzy edge of the rectangle (added to
994 @var{w} and @var{h}). The default value is 4.
995
996 @item show
997 When set to 1, a green rectangle is drawn on the screen to simplify
998 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
999 @var{band} is set to 4. The default value is 0.
1000
1001 @end table
1002
1003 Some examples follow.
1004
1005 @itemize
1006
1007 @item
1008 Set a rectangle covering the area with top left corner coordinates 0,0
1009 and size 100x77, setting a band of size 10:
1010 @example
1011 delogo=x=0:y=0:w=100:h=77:band=10
1012 @end example
1013
1014 @end itemize
1015
1016 @section drawbox
1017
1018 Draw a colored box on the input image.
1019
1020 This filter accepts the following options:
1021
1022 @table @option
1023
1024 @item x, y
1025 Specify the top left corner coordinates of the box. Default to 0.
1026
1027 @item width, height
1028 Specify the width and height of the box, if 0 they are interpreted as
1029 the input width and height. Default to 0.
1030
1031 @item color
1032 Specify the color of the box to write, it can be the name of a color
1033 (case insensitive match) or a 0xRRGGBB[AA] sequence.
1034 @end table
1035
1036 Follow some examples:
1037 @example
1038 # draw a black box around the edge of the input image
1039 drawbox
1040
1041 # draw a box with color red and an opacity of 50%
1042 drawbox=x=10:y=20:width=200:height=60:color=red@@0.5"
1043 @end example
1044
1045 @section drawtext
1046
1047 Draw text string or text from specified file on top of video using the
1048 libfreetype library.
1049
1050 To enable compilation of this filter you need to configure Libav with
1051 @code{--enable-libfreetype}.
1052
1053 The filter also recognizes strftime() sequences in the provided text
1054 and expands them accordingly. Check the documentation of strftime().
1055
1056 The description of the accepted parameters follows.
1057
1058 @table @option
1059
1060 @item fontfile
1061 The font file to be used for drawing text. Path must be included.
1062 This parameter is mandatory.
1063
1064 @item text
1065 The text string to be drawn. The text must be a sequence of UTF-8
1066 encoded characters.
1067 This parameter is mandatory if no file is specified with the parameter
1068 @var{textfile}.
1069
1070 @item textfile
1071 A text file containing text to be drawn. The text must be a sequence
1072 of UTF-8 encoded characters.
1073
1074 This parameter is mandatory if no text string is specified with the
1075 parameter @var{text}.
1076
1077 If both text and textfile are specified, an error is thrown.
1078
1079 @item x, y
1080 The offsets where text will be drawn within the video frame.
1081 Relative to the top/left border of the output image.
1082 They accept expressions similar to the @ref{overlay} filter:
1083 @table @option
1084
1085 @item x, y
1086 the computed values for @var{x} and @var{y}. They are evaluated for
1087 each new frame.
1088
1089 @item main_w, main_h
1090 main input width and height
1091
1092 @item W, H
1093 same as @var{main_w} and @var{main_h}
1094
1095 @item text_w, text_h
1096 rendered text width and height
1097
1098 @item w, h
1099 same as @var{text_w} and @var{text_h}
1100
1101 @item n
1102 the number of frames processed, starting from 0
1103
1104 @item t
1105 timestamp expressed in seconds, NAN if the input timestamp is unknown
1106
1107 @end table
1108
1109 The default value of @var{x} and @var{y} is 0.
1110
1111 @item fontsize
1112 The font size to be used for drawing text.
1113 The default value of @var{fontsize} is 16.
1114
1115 @item fontcolor
1116 The color to be used for drawing fonts.
1117 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1118 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1119 The default value of @var{fontcolor} is "black".
1120
1121 @item boxcolor
1122 The color to be used for drawing box around text.
1123 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1124 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1125 The default value of @var{boxcolor} is "white".
1126
1127 @item box
1128 Used to draw a box around text using background color.
1129 Value should be either 1 (enable) or 0 (disable).
1130 The default value of @var{box} is 0.
1131
1132 @item shadowx, shadowy
1133 The x and y offsets for the text shadow position with respect to the
1134 position of the text. They can be either positive or negative
1135 values. Default value for both is "0".
1136
1137 @item shadowcolor
1138 The color to be used for drawing a shadow behind the drawn text. It
1139 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1140 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1141 The default value of @var{shadowcolor} is "black".
1142
1143 @item ft_load_flags
1144 Flags to be used for loading the fonts.
1145
1146 The flags map the corresponding flags supported by libfreetype, and are
1147 a combination of the following values:
1148 @table @var
1149 @item default
1150 @item no_scale
1151 @item no_hinting
1152 @item render
1153 @item no_bitmap
1154 @item vertical_layout
1155 @item force_autohint
1156 @item crop_bitmap
1157 @item pedantic
1158 @item ignore_global_advance_width
1159 @item no_recurse
1160 @item ignore_transform
1161 @item monochrome
1162 @item linear_design
1163 @item no_autohint
1164 @item end table
1165 @end table
1166
1167 Default value is "render".
1168
1169 For more information consult the documentation for the FT_LOAD_*
1170 libfreetype flags.
1171
1172 @item tabsize
1173 The size in number of spaces to use for rendering the tab.
1174 Default value is 4.
1175
1176 @item fix_bounds
1177 If true, check and fix text coords to avoid clipping.
1178 @end table
1179
1180 For example the command:
1181 @example
1182 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
1183 @end example
1184
1185 will draw "Test Text" with font FreeSerif, using the default values
1186 for the optional parameters.
1187
1188 The command:
1189 @example
1190 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
1191 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
1192 @end example
1193
1194 will draw 'Test Text' with font FreeSerif of size 24 at position x=100
1195 and y=50 (counting from the top-left corner of the screen), text is
1196 yellow with a red box around it. Both the text and the box have an
1197 opacity of 20%.
1198
1199 Note that the double quotes are not necessary if spaces are not used
1200 within the parameter list.
1201
1202 For more information about libfreetype, check:
1203 @url{http://www.freetype.org/}.
1204
1205 @section fade
1206
1207 Apply fade-in/out effect to input video.
1208
1209 This filter accepts the following options:
1210
1211 @table @option
1212
1213 @item type
1214 The effect type -- can be either "in" for fade-in, or "out" for a fade-out
1215 effect.
1216
1217 @item start_frame
1218 The number of the start frame for starting to apply the fade effect.
1219
1220 @item nb_frames
1221 The number of frames for which the fade effect has to last. At the end of the
1222 fade-in effect the output video will have the same intensity as the input video,
1223 at the end of the fade-out transition the output video will be completely black.
1224
1225 @end table
1226
1227 A few usage examples follow, usable too as test scenarios.
1228 @example
1229 # fade in first 30 frames of video
1230 fade=type=in:nb_frames=30
1231
1232 # fade out last 45 frames of a 200-frame video
1233 fade=type=out:start_frame=155:nb_frames=45
1234
1235 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
1236 fade=type=in:start_frame=0:nb_frames=25, fade=type=out:start_frame=975:nb_frames=25
1237
1238 # make first 5 frames black, then fade in from frame 5-24
1239 fade=type=in:start_frame=5:nb_frames=20
1240 @end example
1241
1242 @section fieldorder
1243
1244 Transform the field order of the input video.
1245
1246 This filter accepts the following options:
1247
1248 @table @option
1249
1250 @item order
1251 Output field order. Valid values are @var{tff} for top field first or @var{bff}
1252 for bottom field first.
1253 @end table
1254
1255 Default value is "tff".
1256
1257 Transformation is achieved by shifting the picture content up or down
1258 by one line, and filling the remaining line with appropriate picture content.
1259 This method is consistent with most broadcast field order converters.
1260
1261 If the input video is not flagged as being interlaced, or it is already
1262 flagged as being of the required output field order then this filter does
1263 not alter the incoming video.
1264
1265 This filter is very useful when converting to or from PAL DV material,
1266 which is bottom field first.
1267
1268 For example:
1269 @example
1270 ./avconv -i in.vob -vf "fieldorder=order=bff" out.dv
1271 @end example
1272
1273 @section fifo
1274
1275 Buffer input images and send them when they are requested.
1276
1277 This filter is mainly useful when auto-inserted by the libavfilter
1278 framework.
1279
1280 The filter does not take parameters.
1281
1282 @section format
1283
1284 Convert the input video to one of the specified pixel formats.
1285 Libavfilter will try to pick one that is supported for the input to
1286 the next filter.
1287
1288 This filter accepts the following parameters:
1289 @table @option
1290
1291 @item pix_fmts
1292 A '|'-separated list of pixel format names, for example
1293 "pix_fmts=yuv420p|monow|rgb24".
1294
1295 @end table
1296
1297 Some examples follow:
1298 @example
1299 # convert the input video to the format "yuv420p"
1300 format=pix_fmts=yuv420p
1301
1302 # convert the input video to any of the formats in the list
1303 format=pix_fmts=yuv420p|yuv444p|yuv410p
1304 @end example
1305
1306 @anchor{fps}
1307 @section fps
1308
1309 Convert the video to specified constant framerate by duplicating or dropping
1310 frames as necessary.
1311
1312 This filter accepts the following named parameters:
1313 @table @option
1314
1315 @item fps
1316 Desired output framerate.
1317
1318 @item start_time
1319 Assume the first PTS should be the given value, in seconds. This allows for
1320 padding/trimming at the start of stream. By default, no assumption is made
1321 about the first frame's expected PTS, so no padding or trimming is done.
1322 For example, this could be set to 0 to pad the beginning with duplicates of
1323 the first frame if a video stream starts after the audio stream or to trim any
1324 frames with a negative PTS.
1325
1326 @end table
1327
1328 @section framepack
1329
1330 Pack two different video streams into a stereoscopic video, setting proper
1331 metadata on supported codecs. The two views should have the same size and
1332 framerate and processing will stop when the shorter video ends. Please note
1333 that you may conveniently adjust view properties with the @ref{scale} and
1334 @ref{fps} filters.
1335
1336 This filter accepts the following named parameters:
1337 @table @option
1338
1339 @item format
1340 Desired packing format. Supported values are:
1341
1342 @table @option
1343
1344 @item sbs
1345 Views are next to each other (default).
1346
1347 @item tab
1348 Views are on top of each other.
1349
1350 @item lines
1351 Views are packed by line.
1352
1353 @item columns
1354 Views are eacked by column.
1355
1356 @item frameseq
1357 Views are temporally interleaved.
1358
1359 @end table
1360
1361 @end table
1362
1363 Some examples follow:
1364
1365 @example
1366 # Convert left and right views into a frame sequential video.
1367 avconv -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT
1368
1369 # Convert views into a side-by-side video with the same output resolution as the input.
1370 avconv -i LEFT -i RIGHT -filter_complex [0:v]scale=w=iw/2[left],[1:v]scale=w=iw/2[right],[left][right]framepack=sbs OUTPUT
1371 @end example
1372
1373 @anchor{frei0r}
1374 @section frei0r
1375
1376 Apply a frei0r effect to the input video.
1377
1378 To enable compilation of this filter you need to install the frei0r
1379 header and configure Libav with --enable-frei0r.
1380
1381 This filter accepts the following options:
1382
1383 @table @option
1384
1385 @item filter_name
1386 The name to the frei0r effect to load. If the environment variable
1387 @env{FREI0R_PATH} is defined, the frei0r effect is searched in each one of the
1388 directories specified by the colon separated list in @env{FREIOR_PATH},
1389 otherwise in the standard frei0r paths, which are in this order:
1390 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
1391 @file{/usr/lib/frei0r-1/}.
1392
1393 @item filter_params
1394 A '|'-separated list of parameters to pass to the frei0r effect.
1395
1396 @end table
1397
1398 A frei0r effect parameter can be a boolean (whose values are specified
1399 with "y" and "n"), a double, a color (specified by the syntax
1400 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
1401 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
1402 description), a position (specified by the syntax @var{X}/@var{Y},
1403 @var{X} and @var{Y} being float numbers) and a string.
1404
1405 The number and kind of parameters depend on the loaded effect. If an
1406 effect parameter is not specified the default value is set.
1407
1408 Some examples follow:
1409 @example
1410 # apply the distort0r effect, set the first two double parameters
1411 frei0r=filter_name=distort0r:filter_params=0.5|0.01
1412
1413 # apply the colordistance effect, takes a color as first parameter
1414 frei0r=colordistance:0.2/0.3/0.4
1415 frei0r=colordistance:violet
1416 frei0r=colordistance:0x112233
1417
1418 # apply the perspective effect, specify the top left and top right
1419 # image positions
1420 frei0r=perspective:0.2/0.2|0.8/0.2
1421 @end example
1422
1423 For more information see:
1424 @url{http://piksel.org/frei0r}
1425
1426 @section gradfun
1427
1428 Fix the banding artifacts that are sometimes introduced into nearly flat
1429 regions by truncation to 8bit colordepth.
1430 Interpolate the gradients that should go where the bands are, and
1431 dither them.
1432
1433 This filter is designed for playback only. Do not use it prior to
1434 lossy compression, because compression tends to lose the dither and
1435 bring back the bands.
1436
1437 This filter accepts the following options:
1438
1439 @table @option
1440
1441 @item strength
1442 The maximum amount by which the filter will change any one pixel. Also the
1443 threshold for detecting nearly flat regions. Acceptable values range from .51 to
1444 64, default value is 1.2, out-of-range values will be clipped to the valid
1445 range.
1446
1447 @item radius
1448 The neighborhood to fit the gradient to. A larger radius makes for smoother
1449 gradients, but also prevents the filter from modifying the pixels near detailed
1450 regions. Acceptable values are 8-32, default value is 16, out-of-range values
1451 will be clipped to the valid range.
1452
1453 @end table
1454
1455 @example
1456 # default parameters
1457 gradfun=strength=1.2:radius=16
1458
1459 # omitting radius
1460 gradfun=1.2
1461 @end example
1462
1463 @section hflip
1464
1465 Flip the input video horizontally.
1466
1467 For example to horizontally flip the input video with @command{avconv}:
1468 @example
1469 avconv -i in.avi -vf "hflip" out.avi
1470 @end example
1471
1472 @section hqdn3d
1473
1474 High precision/quality 3d denoise filter. This filter aims to reduce
1475 image noise producing smooth images and making still images really
1476 still. It should enhance compressibility.
1477
1478 It accepts the following optional parameters:
1479
1480 @table @option
1481 @item luma_spatial
1482 a non-negative float number which specifies spatial luma strength,
1483 defaults to 4.0
1484
1485 @item chroma_spatial
1486 a non-negative float number which specifies spatial chroma strength,
1487 defaults to 3.0*@var{luma_spatial}/4.0
1488
1489 @item luma_tmp
1490 a float number which specifies luma temporal strength, defaults to
1491 6.0*@var{luma_spatial}/4.0
1492
1493 @item chroma_tmp
1494 a float number which specifies chroma temporal strength, defaults to
1495 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
1496 @end table
1497
1498 @section interlace
1499
1500 Simple interlacing filter from progressive contents. This interleaves upper (or
1501 lower) lines from odd frames with lower (or upper) lines from even frames,
1502 halving the frame rate and preserving image height.
1503
1504 @example
1505 Original Original New Frame
1506 Frame 'j' Frame 'j+1' (tff)
1507 ========== =========== ==================
1508 Line 0 --------------------> Frame 'j' Line 0
1509 Line 1 Line 1 ----> Frame 'j+1' Line 1
1510 Line 2 ---------------------> Frame 'j' Line 2
1511 Line 3 Line 3 ----> Frame 'j+1' Line 3
1512 ... ... ...
1513 New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on
1514 @end example
1515
1516 It accepts the following optional parameters:
1517
1518 @table @option
1519 @item scan
1520 determines whether the interlaced frame is taken from the even (tff - default)
1521 or odd (bff) lines of the progressive frame.
1522
1523 @item lowpass
1524 Enable (default) or disable the vertical lowpass filter to avoid twitter
1525 interlacing and reduce moire patterns.
1526 @end table
1527
1528 @section lut, lutrgb, lutyuv
1529
1530 Compute a look-up table for binding each pixel component input value
1531 to an output value, and apply it to input video.
1532
1533 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
1534 to an RGB input video.
1535
1536 These filters accept the following options:
1537 @table @option
1538 @item @var{c0} (first pixel component)
1539 @item @var{c1} (second pixel component)
1540 @item @var{c2} (third pixel component)
1541 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
1542
1543 @item @var{r} (red component)
1544 @item @var{g} (green component)
1545 @item @var{b} (blue component)
1546 @item @var{a} (alpha component)
1547
1548 @item @var{y} (Y/luminance component)
1549 @item @var{u} (U/Cb component)
1550 @item @var{v} (V/Cr component)
1551 @end table
1552
1553 Each of them specifies the expression to use for computing the lookup table for
1554 the corresponding pixel component values.
1555
1556 The exact component associated to each of the @var{c*} options depends on the
1557 format in input.
1558
1559 The @var{lut} filter requires either YUV or RGB pixel formats in input,
1560 @var{lutrgb} requires RGB pixel formats in input, and @var{lutyuv} requires YUV.
1561
1562 The expressions can contain the following constants and functions:
1563
1564 @table @option
1565 @item E, PI, PHI
1566 the corresponding mathematical approximated values for e
1567 (euler number), pi (greek PI), PHI (golden ratio)
1568
1569 @item w, h
1570 the input width and height
1571
1572 @item val
1573 input value for the pixel component
1574
1575 @item clipval
1576 the input value clipped in the @var{minval}-@var{maxval} range
1577
1578 @item maxval
1579 maximum value for the pixel component
1580
1581 @item minval
1582 minimum value for the pixel component
1583
1584 @item negval
1585 the negated value for the pixel component value clipped in the
1586 @var{minval}-@var{maxval} range , it corresponds to the expression
1587 "maxval-clipval+minval"
1588
1589 @item clip(val)
1590 the computed value in @var{val} clipped in the
1591 @var{minval}-@var{maxval} range
1592
1593 @item gammaval(gamma)
1594 the computed gamma correction value of the pixel component value
1595 clipped in the @var{minval}-@var{maxval} range, corresponds to the
1596 expression
1597 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
1598
1599 @end table
1600
1601 All expressions default to "val".
1602
1603 Some examples follow:
1604 @example
1605 # negate input video
1606 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
1607 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
1608
1609 # the above is the same as
1610 lutrgb="r=negval:g=negval:b=negval"
1611 lutyuv="y=negval:u=negval:v=negval"
1612
1613 # negate luminance
1614 lutyuv=negval
1615
1616 # remove chroma components, turns the video into a graytone image
1617 lutyuv="u=128:v=128"
1618
1619 # apply a luma burning effect
1620 lutyuv="y=2*val"
1621
1622 # remove green and blue components
1623 lutrgb="g=0:b=0"
1624
1625 # set a constant alpha channel value on input
1626 format=rgba,lutrgb=a="maxval-minval/2"
1627
1628 # correct luminance gamma by a 0.5 factor
1629 lutyuv=y=gammaval(0.5)
1630 @end example
1631
1632 @section negate
1633
1634 Negate input video.
1635
1636 This filter accepts an integer in input, if non-zero it negates the
1637 alpha component (if available). The default value in input is 0.
1638
1639 @section noformat
1640
1641 Force libavfilter not to use any of the specified pixel formats for the
1642 input to the next filter.
1643
1644 This filter accepts the following parameters:
1645 @table @option
1646
1647 @item pix_fmts
1648 A '|'-separated list of pixel format names, for example
1649 "pix_fmts=yuv420p|monow|rgb24".
1650
1651 @end table
1652
1653 Some examples follow:
1654 @example
1655 # force libavfilter to use a format different from "yuv420p" for the
1656 # input to the vflip filter
1657 noformat=pix_fmts=yuv420p,vflip
1658
1659 # convert the input video to any of the formats not contained in the list
1660 noformat=yuv420p|yuv444p|yuv410p
1661 @end example
1662
1663 @section null
1664
1665 Pass the video source unchanged to the output.
1666
1667 @section ocv
1668
1669 Apply video transform using libopencv.
1670
1671 To enable this filter install libopencv library and headers and
1672 configure Libav with --enable-libopencv.
1673
1674 This filter accepts the following parameters:
1675
1676 @table @option
1677
1678 @item filter_name
1679 The name of the libopencv filter to apply.
1680
1681 @item filter_params
1682 The parameters to pass to the libopencv filter. If not specified the default
1683 values are assumed.
1684
1685 @end table
1686
1687 Refer to the official libopencv documentation for more precise
1688 information:
1689 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
1690
1691 Follows the list of supported libopencv filters.
1692
1693 @anchor{dilate}
1694 @subsection dilate
1695
1696 Dilate an image by using a specific structuring element.
1697 This filter corresponds to the libopencv function @code{cvDilate}.
1698
1699 It accepts the parameters: @var{struct_el}|@var{nb_iterations}.
1700
1701 @var{struct_el} represents a structuring element, and has the syntax:
1702 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
1703
1704 @var{cols} and @var{rows} represent the number of columns and rows of
1705 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
1706 point, and @var{shape} the shape for the structuring element, and
1707 can be one of the values "rect", "cross", "ellipse", "custom".
1708
1709 If the value for @var{shape} is "custom", it must be followed by a
1710 string of the form "=@var{filename}". The file with name
1711 @var{filename} is assumed to represent a binary image, with each
1712 printable character corresponding to a bright pixel. When a custom
1713 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
1714 or columns and rows of the read file are assumed instead.
1715
1716 The default value for @var{struct_el} is "3x3+0x0/rect".
1717
1718 @var{nb_iterations} specifies the number of times the transform is
1719 applied to the image, and defaults to 1.
1720
1721 Follow some example:
1722 @example
1723 # use the default values
1724 ocv=dilate
1725
1726 # dilate using a structuring element with a 5x5 cross, iterate two times
1727 ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2
1728
1729 # read the shape from the file diamond.shape, iterate two times
1730 # the file diamond.shape may contain a pattern of characters like this:
1731 # *
1732 # ***
1733 # *****
1734 # ***
1735 # *
1736 # the specified cols and rows are ignored (but not the anchor point coordinates)
1737 ocv=dilate:0x0+2x2/custom=diamond.shape|2
1738 @end example
1739
1740 @subsection erode
1741
1742 Erode an image by using a specific structuring element.
1743 This filter corresponds to the libopencv function @code{cvErode}.
1744
1745 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
1746 with the same syntax and semantics as the @ref{dilate} filter.
1747
1748 @subsection smooth
1749
1750 Smooth the input video.
1751
1752 The filter takes the following parameters:
1753 @var{type}|@var{param1}|@var{param2}|@var{param3}|@var{param4}.
1754
1755 @var{type} is the type of smooth filter to apply, and can be one of
1756 the following values: "blur", "blur_no_scale", "median", "gaussian",
1757 "bilateral". The default value is "gaussian".
1758
1759 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
1760 parameters whose meanings depend on smooth type. @var{param1} and
1761 @var{param2} accept integer positive values or 0, @var{param3} and
1762 @var{param4} accept float values.
1763
1764 The default value for @var{param1} is 3, the default value for the
1765 other parameters is 0.
1766
1767 These parameters correspond to the parameters assigned to the
1768 libopencv function @code{cvSmooth}.
1769
1770 @anchor{overlay}
1771 @section overlay
1772
1773 Overlay one video on top of another.
1774
1775 It takes two inputs and one output, the first input is the "main"
1776 video on which the second input is overlayed.
1777
1778 This filter accepts the following parameters:
1779
1780 @table @option
1781
1782 @item x
1783 The horizontal position of the left edge of the overlaid video on the main video.
1784
1785 @item y
1786 The vertical position of the top edge of the overlaid video on the main video.
1787
1788 @end table
1789
1790 The parameters are expressions containing the following parameters:
1791
1792 @table @option
1793 @item main_w, main_h
1794 main input width and height
1795
1796 @item W, H
1797 same as @var{main_w} and @var{main_h}
1798
1799 @item overlay_w, overlay_h
1800 overlay input width and height
1801
1802 @item w, h
1803 same as @var{overlay_w} and @var{overlay_h}
1804
1805 @item eof_action
1806 The action to take when EOF is encountered on the secondary input, accepts one
1807 of the following values:
1808
1809 @table @option
1810 @item repeat
1811 repeat the last frame (the default)
1812 @item endall
1813 end both streams
1814 @item pass
1815 pass through the main input
1816 @end table
1817
1818 @end table
1819
1820 Be aware that frames are taken from each input video in timestamp
1821 order, hence, if their initial timestamps differ, it is a a good idea
1822 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
1823 have them begin in the same zero timestamp, as it does the example for
1824 the @var{movie} filter.
1825
1826 Follow some examples:
1827 @example
1828 # draw the overlay at 10 pixels from the bottom right
1829 # corner of the main video.
1830 overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10
1831
1832 # insert a transparent PNG logo in the bottom left corner of the input
1833 avconv -i input -i logo -filter_complex 'overlay=x=10:y=main_h-overlay_h-10' output
1834
1835 # insert 2 different transparent PNG logos (second logo on bottom
1836 # right corner):
1837 avconv -i input -i logo1 -i logo2 -filter_complex
1838 'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output
1839
1840 # add a transparent color layer on top of the main video,
1841 # WxH specifies the size of the main input to the overlay filter
1842 color=red@.3:WxH [over]; [in][over] overlay [out]
1843
1844 # mask 10-20 seconds of a video by applying the delogo filter to a section
1845 avconv -i test.avi -codec:v:0 wmv2 -ar 11025 -b:v 9000k
1846 -vf '[in]split[split_main][split_delogo];[split_delogo]trim=start=360:end=371,delogo=0:0:640:480[delogoed];[split_main][delogoed]overlay=eof_action=pass[out]'
1847 masked.avi
1848 @end example
1849
1850 You can chain together more overlays but the efficiency of such
1851 approach is yet to be tested.
1852
1853 @section pad
1854
1855 Add paddings to the input image, and places the original input at the
1856 given coordinates @var{x}, @var{y}.
1857
1858 This filter accepts the following parameters:
1859
1860 @table @option
1861 @item width, height
1862
1863 Specify the size of the output image with the paddings added. If the
1864 value for @var{width} or @var{height} is 0, the corresponding input size
1865 is used for the output.
1866
1867 The @var{width} expression can reference the value set by the
1868 @var{height} expression, and vice versa.
1869
1870 The default value of @var{width} and @var{height} is 0.
1871
1872 @item x, y
1873
1874 Specify the offsets where to place the input image in the padded area
1875 with respect to the top/left border of the output image.
1876
1877 The @var{x} expression can reference the value set by the @var{y}
1878 expression, and vice versa.
1879
1880 The default value of @var{x} and @var{y} is 0.
1881
1882 @item color
1883
1884 Specify the color of the padded area, it can be the name of a color
1885 (case insensitive match) or a 0xRRGGBB[AA] sequence.
1886
1887 The default value of @var{color} is "black".
1888
1889 @end table
1890
1891 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
1892 expressions containing the following constants:
1893
1894 @table @option
1895 @item E, PI, PHI
1896 the corresponding mathematical approximated values for e
1897 (euler number), pi (greek PI), phi (golden ratio)
1898
1899 @item in_w, in_h
1900 the input video width and height
1901
1902 @item iw, ih
1903 same as @var{in_w} and @var{in_h}
1904
1905 @item out_w, out_h
1906 the output width and height, that is the size of the padded area as
1907 specified by the @var{width} and @var{height} expressions
1908
1909 @item ow, oh
1910 same as @var{out_w} and @var{out_h}
1911
1912 @item x, y
1913 x and y offsets as specified by the @var{x} and @var{y}
1914 expressions, or NAN if not yet specified
1915
1916 @item a
1917 input display aspect ratio, same as @var{iw} / @var{ih}
1918
1919 @item hsub, vsub
1920 horizontal and vertical chroma subsample values. For example for the
1921 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1922 @end table
1923
1924 Some examples follow:
1925
1926 @example
1927 # Add paddings with color "violet" to the input video. Output video
1928 # size is 640x480, the top-left corner of the input video is placed at
1929 # column 0, row 40.
1930 pad=width=640:height=480:x=0:y=40:color=violet
1931
1932 # pad the input to get an output with dimensions increased bt 3/2,
1933 # and put the input video at the center of the padded area
1934 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
1935
1936 # pad the input to get a squared output with size equal to the maximum
1937 # value between the input width and height, and put the input video at
1938 # the center of the padded area
1939 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
1940
1941 # pad the input to get a final w/h ratio of 16:9
1942 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
1943
1944 # double output size and put the input video in the bottom-right
1945 # corner of the output padded area
1946 pad="2*iw:2*ih:ow-iw:oh-ih"
1947 @end example
1948
1949 @section pixdesctest
1950
1951 Pixel format descriptor test filter, mainly useful for internal
1952 testing. The output video should be equal to the input video.
1953
1954 For example:
1955 @example
1956 format=monow, pixdesctest
1957 @end example
1958
1959 can be used to test the monowhite pixel format descriptor definition.
1960
1961 @anchor{scale}
1962 @section scale
1963
1964 Scale the input video and/or convert the image format.
1965
1966 This filter accepts the following options:
1967
1968 @table @option
1969
1970 @item w
1971 Output video width.
1972
1973 @item h
1974 Output video height.
1975
1976 @end table
1977
1978 The parameters @var{w} and @var{h} are expressions containing
1979 the following constants:
1980
1981 @table @option
1982 @item E, PI, PHI
1983 the corresponding mathematical approximated values for e
1984 (euler number), pi (greek PI), phi (golden ratio)
1985
1986 @item in_w, in_h
1987 the input width and height
1988
1989 @item iw, ih
1990 same as @var{in_w} and @var{in_h}
1991
1992 @item out_w, out_h
1993 the output (cropped) width and height
1994
1995 @item ow, oh
1996 same as @var{out_w} and @var{out_h}
1997
1998 @item a
1999 same as @var{iw} / @var{ih}
2000
2001 @item sar
2002 input sample aspect ratio
2003
2004 @item dar
2005 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
2006
2007 @item hsub, vsub
2008 horizontal and vertical chroma subsample values. For example for the
2009 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2010 @end table
2011
2012 If the input image format is different from the format requested by
2013 the next filter, the scale filter will convert the input to the
2014 requested format.
2015
2016 If the value for @var{w} or @var{h} is 0, the respective input
2017 size is used for the output.
2018
2019 If the value for @var{w} or @var{h} is -1, the scale filter will use, for the
2020 respective output size, a value that maintains the aspect ratio of the input
2021 image.
2022
2023 The default value of @var{w} and @var{h} is 0.
2024
2025 Some examples follow:
2026 @example
2027 # scale the input video to a size of 200x100.
2028 scale=w=200:h=100
2029
2030 # scale the input to 2x
2031 scale=w=2*iw:h=2*ih
2032 # the above is the same as
2033 scale=2*in_w:2*in_h
2034
2035 # scale the input to half size
2036 scale=w=iw/2:h=ih/2
2037
2038 # increase the width, and set the height to the same size
2039 scale=3/2*iw:ow
2040
2041 # seek for Greek harmony
2042 scale=iw:1/PHI*iw
2043 scale=ih*PHI:ih
2044
2045 # increase the height, and set the width to 3/2 of the height
2046 scale=w=3/2*oh:h=3/5*ih
2047
2048 # increase the size, but make the size a multiple of the chroma
2049 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
2050
2051 # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
2052 scale=w='min(500\, iw*3/2):h=-1'
2053 @end example
2054
2055 @section select
2056 Select frames to pass in output.
2057
2058 This filter accepts the following options:
2059
2060 @table @option
2061
2062 @item expr
2063 An expression, which is evaluated for each input frame. If the expression is
2064 evaluated to a non-zero value, the frame is selected and passed to the output,
2065 otherwise it is discarded.
2066
2067 @end table
2068
2069 The expression can contain the following constants:
2070
2071 @table @option
2072 @item PI
2073 Greek PI
2074
2075 @item PHI
2076 golden ratio
2077
2078 @item E
2079 Euler number
2080
2081 @item n
2082 the sequential number of the filtered frame, starting from 0
2083
2084 @item selected_n
2085 the sequential number of the selected frame, starting from 0
2086
2087 @item prev_selected_n
2088 the sequential number of the last selected frame, NAN if undefined
2089
2090 @item TB
2091 timebase of the input timestamps
2092
2093 @item pts
2094 the PTS (Presentation TimeStamp) of the filtered video frame,
2095 expressed in @var{TB} units, NAN if undefined
2096
2097 @item t
2098 the PTS (Presentation TimeStamp) of the filtered video frame,
2099 expressed in seconds, NAN if undefined
2100
2101 @item prev_pts
2102 the PTS of the previously filtered video frame, NAN if undefined
2103
2104 @item prev_selected_pts
2105 the PTS of the last previously filtered video frame, NAN if undefined
2106
2107 @item prev_selected_t
2108 the PTS of the last previously selected video frame, NAN if undefined
2109
2110 @item start_pts
2111 the PTS of the first video frame in the video, NAN if undefined
2112
2113 @item start_t
2114 the time of the first video frame in the video, NAN if undefined
2115
2116 @item pict_type
2117 the type of the filtered frame, can assume one of the following
2118 values:
2119 @table @option
2120 @item I
2121 @item P
2122 @item B
2123 @item S
2124 @item SI
2125 @item SP
2126 @item BI
2127 @end table
2128
2129 @item interlace_type
2130 the frame interlace type, can assume one of the following values:
2131 @table @option
2132 @item PROGRESSIVE
2133 the frame is progressive (not interlaced)
2134 @item TOPFIRST
2135 the frame is top-field-first
2136 @item BOTTOMFIRST
2137 the frame is bottom-field-first
2138 @end table
2139
2140 @item key
2141 1 if the filtered frame is a key-frame, 0 otherwise
2142
2143 @end table
2144
2145 The default value of the select expression is "1".
2146
2147 Some examples follow:
2148
2149 @example
2150 # select all frames in input
2151 select
2152
2153 # the above is the same as:
2154 select=expr=1
2155
2156 # skip all frames:
2157 select=expr=0
2158
2159 # select only I-frames
2160 select='expr=eq(pict_type\,I)'
2161
2162 # select one frame every 100
2163 select='not(mod(n\,100))'
2164
2165 # select only frames contained in the 10-20 time interval
2166 select='gte(t\,10)*lte(t\,20)'
2167
2168 # select only I frames contained in the 10-20 time interval
2169 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
2170
2171 # select frames with a minimum distance of 10 seconds
2172 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
2173 @end example
2174
2175 @anchor{setdar}
2176 @section setdar
2177
2178 Set the Display Aspect Ratio for the filter output video.
2179
2180 This is done by changing the specified Sample (aka Pixel) Aspect
2181 Ratio, according to the following equation:
2182 @math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
2183
2184 Keep in mind that this filter does not modify the pixel dimensions of
2185 the video frame. Also the display aspect ratio set by this filter may
2186 be changed by later filters in the filterchain, e.g. in case of
2187 scaling or if another "setdar" or a "setsar" filter is applied.
2188
2189 This filter accepts the following options:
2190
2191 @table @option
2192
2193 @item dar
2194 Output display aspect ratio.
2195
2196 @end table
2197
2198 The parameter @var{dar} is an expression containing
2199 the following constants:
2200
2201 @table @option
2202 @item E, PI, PHI
2203 the corresponding mathematical approximated values for e
2204 (euler number), pi (greek PI), phi (golden ratio)
2205
2206 @item w, h
2207 the input width and height
2208
2209 @item a
2210 same as @var{w} / @var{h}
2211
2212 @item sar
2213 input sample aspect ratio
2214
2215 @item dar
2216 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
2217
2218 @item hsub, vsub
2219 horizontal and vertical chroma subsample values. For example for the
2220 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2221 @end table
2222
2223 For example to change the display aspect ratio to 16:9, specify:
2224 @example
2225 setdar=dar=16/9
2226 # the above is equivalent to
2227 setdar=dar=1.77777
2228 @end example
2229
2230 See also the @ref{setsar} filter documentation.
2231
2232 @section setpts
2233
2234 Change the PTS (presentation timestamp) of the input video frames.
2235
2236 This filter accepts the following options:
2237
2238 @table @option
2239
2240 @item expr
2241 The expression which is evaluated for each frame to construct its timestamp.
2242
2243 @end table
2244
2245 The expression is evaluated through the eval API and can contain the following
2246 constants:
2247
2248 @table @option
2249 @item PTS
2250 the presentation timestamp in input
2251
2252 @item PI
2253 Greek PI
2254
2255 @item PHI
2256 golden ratio
2257
2258 @item E
2259 Euler number
2260
2261 @item N
2262 the count of the input frame, starting from 0.
2263
2264 @item STARTPTS
2265 the PTS of the first video frame
2266
2267 @item INTERLACED
2268 tell if the current frame is interlaced
2269
2270 @item PREV_INPTS
2271 previous input PTS
2272
2273 @item PREV_OUTPTS
2274 previous output PTS
2275
2276 @item RTCTIME
2277 wallclock (RTC) time in microseconds
2278
2279 @item RTCSTART
2280 wallclock (RTC) time at the start of the movie in microseconds
2281
2282 @item TB
2283 timebase of the input timestamps
2284
2285 @end table
2286
2287 Some examples follow:
2288
2289 @example
2290 # start counting PTS from zero
2291 setpts=expr=PTS-STARTPTS
2292
2293 # fast motion
2294 setpts=expr=0.5*PTS
2295
2296 # slow motion
2297 setpts=2.0*PTS
2298
2299 # fixed rate 25 fps
2300 setpts=N/(25*TB)
2301
2302 # fixed rate 25 fps with some jitter
2303 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
2304
2305 # generate timestamps from a "live source" and rebase onto the current timebase
2306 setpts='(RTCTIME - RTCSTART) / (TB * 1000000)"
2307 @end example
2308
2309 @anchor{setsar}
2310 @section setsar
2311
2312 Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
2313
2314 Note that as a consequence of the application of this filter, the
2315 output display aspect ratio will change according to the following
2316 equation:
2317 @math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
2318
2319 Keep in mind that the sample aspect ratio set by this filter may be
2320 changed by later filters in the filterchain, e.g. if another "setsar"
2321 or a "setdar" filter is applied.
2322
2323 This filter accepts the following options:
2324
2325 @table @option
2326
2327 @item sar
2328 Output sample aspect ratio.
2329
2330 @end table
2331
2332 The parameter @var{sar} is an expression containing
2333 the following constants:
2334
2335 @table @option
2336 @item E, PI, PHI
2337 the corresponding mathematical approximated values for e
2338 (euler number), pi (greek PI), phi (golden ratio)
2339
2340 @item w, h
2341 the input width and height
2342
2343 @item a
2344 same as @var{w} / @var{h}
2345
2346 @item sar
2347 input sample aspect ratio
2348
2349 @item dar
2350 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
2351
2352 @item hsub, vsub
2353 horizontal and vertical chroma subsample values. For example for the
2354 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2355 @end table
2356
2357 For example to change the sample aspect ratio to 10:11, specify:
2358 @example
2359 setsar=sar=10/11
2360 @end example
2361
2362 @section settb
2363
2364 Set the timebase to use for the output frames timestamps.
2365 It is mainly useful for testing timebase configuration.
2366
2367 This filter accepts the following options:
2368
2369 @table @option
2370
2371 @item expr
2372 The expression which is evaluated into the output timebase.
2373
2374 @end table
2375
2376 The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
2377 default timebase), and "intb" (the input timebase).
2378
2379 The default value for the input is "intb".
2380
2381 Follow some examples.
2382
2383 @example
2384 # set the timebase to 1/25
2385 settb=expr=1/25
2386
2387 # set the timebase to 1/10
2388 settb=expr=0.1
2389
2390 #set the timebase to 1001/1000
2391 settb=1+0.001
2392
2393 #set the timebase to 2*intb
2394 settb=2*intb
2395
2396 #set the default timebase value
2397 settb=AVTB
2398 @end example
2399
2400 @section showinfo
2401
2402 Show a line containing various information for each input video frame.
2403 The input video is not modified.
2404
2405 The shown line contains a sequence of key/value pairs of the form
2406 @var{key}:@var{value}.
2407
2408 A description of each shown parameter follows:
2409
2410 @table @option
2411 @item n
2412 sequential number of the input frame, starting from 0
2413
2414 @item pts
2415 Presentation TimeStamp of the input frame, expressed as a number of
2416 time base units. The time base unit depends on the filter input pad.
2417
2418 @item pts_time
2419 Presentation TimeStamp of the input frame, expressed as a number of
2420 seconds
2421
2422 @item pos
2423 position of the frame in the input stream, -1 if this information in
2424 unavailable and/or meaningless (for example in case of synthetic video)
2425
2426 @item fmt
2427 pixel format name
2428
2429 @item sar
2430 sample aspect ratio of the input frame, expressed in the form
2431 @var{num}/@var{den}
2432
2433 @item s
2434 size of the input frame, expressed in the form
2435 @var{width}x@var{height}
2436
2437 @item i
2438 interlaced mode ("P" for "progressive", "T" for top field first, "B"
2439 for bottom field first)
2440
2441 @item iskey
2442 1 if the frame is a key frame, 0 otherwise
2443
2444 @item type
2445 picture type of the input frame ("I" for an I-frame, "P" for a
2446 P-frame, "B" for a B-frame, "?" for unknown type).
2447 Check also the documentation of the @code{AVPictureType} enum and of
2448 the @code{av_get_picture_type_char} function defined in
2449 @file{libavutil/avutil.h}.
2450
2451 @item checksum
2452 Adler-32 checksum of all the planes of the input frame
2453
2454 @item plane_checksum
2455 Adler-32 checksum of each plane of the input frame, expressed in the form
2456 "[@var{c0} @var{c1} @var{c2} @var{c3}]"
2457 @end table
2458
2459 @section split
2460
2461 Split input video into several identical outputs.
2462
2463 The filter accepts a single parameter which specifies the number of outputs. If
2464 unspecified, it defaults to 2.
2465
2466 For example
2467 @example
2468 avconv -i INPUT -filter_complex split=5 OUTPUT
2469 @end example
2470 will create 5 copies of the input video.
2471
2472 @section transpose
2473
2474 Transpose rows with columns in the input video and optionally flip it.
2475
2476 This filter accepts the following options:
2477
2478 @table @option
2479
2480 @item dir
2481 The direction of the transpose.
2482
2483 @end table
2484
2485 The direction can assume the following values:
2486
2487 @table @samp
2488 @item cclock_flip
2489 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
2490 @example
2491 L.R L.l
2492 . . -> . .
2493 l.r R.r
2494 @end example
2495
2496 @item clock
2497 Rotate by 90 degrees clockwise, that is:
2498 @example
2499 L.R l.L
2500 . . -> . .
2501 l.r r.R
2502 @end example
2503
2504 @item cclock
2505 Rotate by 90 degrees counterclockwise, that is:
2506 @example
2507 L.R R.r
2508 . . -> . .
2509 l.r L.l
2510 @end example
2511
2512 @item clock_flip
2513 Rotate by 90 degrees clockwise and vertically flip, that is:
2514 @example
2515 L.R r.R
2516 . . -> . .
2517 l.r l.L
2518 @end example
2519 @end table
2520
2521 @section trim
2522 Trim the input so that the output contains one continuous subpart of the input.
2523
2524 This filter accepts the following options:
2525 @table @option
2526 @item start
2527 Timestamp (in seconds) of the start of the kept section. I.e. the frame with the
2528 timestamp @var{start} will be the first frame in the output.
2529
2530 @item end
2531 Timestamp (in seconds) of the first frame that will be dropped. I.e. the frame
2532 immediately preceding the one with the timestamp @var{end} will be the last
2533 frame in the output.
2534
2535 @item start_pts
2536 Same as @var{start}, except this option sets the start timestamp in timebase
2537 units instead of seconds.
2538
2539 @item end_pts
2540 Same as @var{end}, except this option sets the end timestamp in timebase units
2541 instead of seconds.
2542
2543 @item duration
2544 Maximum duration of the output in seconds.
2545
2546 @item start_frame
2547 Number of the first frame that should be passed to output.
2548
2549 @item end_frame
2550 Number of the first frame that should be dropped.
2551 @end table
2552
2553 Note that the first two sets of the start/end options and the @option{duration}
2554 option look at the frame timestamp, while the _frame variants simply count the
2555 frames that pass through the filter. Also note that this filter does not modify
2556 the timestamps. If you wish that the output timestamps start at zero, insert a
2557 setpts filter after the trim filter.
2558
2559 If multiple start or end options are set, this filter tries to be greedy and
2560 keep all the frames that match at least one of the specified constraints. To keep
2561 only the part that matches all the constraints at once, chain multiple trim
2562 filters.
2563
2564 The defaults are such that all the input is kept. So it is possible to set e.g.
2565 just the end values to keep everything before the specified time.
2566
2567 Examples:
2568 @itemize
2569 @item
2570 drop everything except the second minute of input
2571 @example
2572 avconv -i INPUT -vf trim=60:120
2573 @end example
2574
2575 @item
2576 keep only the first second
2577 @example
2578 avconv -i INPUT -vf trim=duration=1
2579 @end example
2580
2581 @end itemize
2582 @section unsharp
2583
2584 Sharpen or blur the input video.
2585
2586 It accepts the following parameters:
2587
2588 @table @option
2589
2590 @item luma_msize_x
2591 Set the luma matrix horizontal size. It can be an integer between 3
2592 and 13, default value is 5.
2593
2594 @item luma_msize_y
2595 Set the luma matrix vertical size. It can be an integer between 3
2596 and 13, default value is 5.
2597
2598 @item luma_amount
2599 Set the luma effect strength. It can be a float number between -2.0
2600 and 5.0, default value is 1.0.
2601
2602 @item chroma_msize_x
2603 Set the chroma matrix horizontal size. It can be an integer between 3
2604 and 13, default value is 5.
2605
2606 @item chroma_msize_y
2607 Set the chroma matrix vertical size. It can be an integer between 3
2608 and 13, default value is 5.
2609
2610 @item chroma_amount
2611 Set the chroma effect strength. It can be a float number between -2.0
2612 and 5.0, default value is 0.0.
2613
2614 @end table
2615
2616 Negative values for the amount will blur the input video, while positive
2617 values will sharpen. All parameters are optional and default to the
2618 equivalent of the string '5:5:1.0:5:5:0.0'.
2619
2620 @example
2621 # Strong luma sharpen effect parameters
2622 unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5
2623
2624 # Strong blur of both luma and chroma parameters
2625 unsharp=7:7:-2:7:7:-2
2626
2627 # Use the default values with @command{avconv}
2628 ./avconv -i in.avi -vf "unsharp" out.mp4
2629 @end example
2630
2631 @section vflip
2632
2633 Flip the input video vertically.
2634
2635 @example
2636 ./avconv -i in.avi -vf "vflip" out.avi
2637 @end example
2638
2639 @section yadif
2640
2641 Deinterlace the input video ("yadif" means "yet another deinterlacing
2642 filter").
2643
2644 This filter accepts the following options:
2645
2646 @table @option
2647
2648 @item mode
2649 The interlacing mode to adopt, accepts one of the following values:
2650
2651 @table @option
2652 @item 0
2653 output 1 frame for each frame
2654 @item 1
2655 output 1 frame for each field
2656 @item 2
2657 like 0 but skips spatial interlacing check
2658 @item 3
2659 like 1 but skips spatial interlacing check
2660 @end table
2661
2662 Default value is 0.
2663
2664 @item parity
2665 The picture field parity assumed for the input interlaced video, accepts one of
2666 the following values:
2667
2668 @table @option
2669 @item 0
2670 assume top field first
2671 @item 1
2672 assume bottom field first
2673 @item -1
2674 enable automatic detection
2675 @end table
2676
2677 Default value is -1.
2678 If interlacing is unknown or decoder does not export this information,
2679 top field first will be assumed.
2680
2681 @item auto
2682 Whether deinterlacer should trust the interlaced flag and only deinterlace
2683 frames marked as interlaced
2684
2685 @table @option
2686 @item 0
2687 deinterlace all frames
2688 @item 1
2689 only deinterlace frames marked as interlaced
2690 @end table
2691
2692 Default value is 0.
2693
2694 @end table
2695
2696 @c man end VIDEO FILTERS
2697
2698 @chapter Video Sources
2699 @c man begin VIDEO SOURCES
2700
2701 Below is a description of the currently available video sources.
2702
2703 @section buffer
2704
2705 Buffer video frames, and make them available to the filter chain.
2706
2707 This source is mainly intended for a programmatic use, in particular
2708 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
2709
2710 This filter accepts the following parameters:
2711
2712 @table @option
2713
2714 @item width
2715 Input video width.
2716
2717 @item height
2718 Input video height.
2719
2720 @item pix_fmt
2721 Name of the input video pixel format.
2722
2723 @item time_base
2724 The time base used for input timestamps.
2725
2726 @item sar
2727 Sample (pixel) aspect ratio of the input video.
2728
2729 @end table
2730
2731 For example:
2732 @example
2733 buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1
2734 @end example
2735
2736 will instruct the source to accept video frames with size 320x240 and
2737 with format "yuv410p", assuming 1/24 as the timestamps timebase and
2738 square pixels (1:1 sample aspect ratio).
2739
2740 @section color
2741
2742 Provide an uniformly colored input.
2743
2744 It accepts the following parameters:
2745
2746 @table @option
2747
2748 @item color
2749 Specify the color of the source. It can be the name of a color (case
2750 insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
2751 alpha specifier. The default value is "black".
2752
2753 @item size
2754 Specify the size of the sourced video, it may be a string of the form
2755 @var{width}x@var{height}, or the name of a size abbreviation. The
2756 default value is "320x240".
2757
2758 @item framerate
2759 Specify the frame rate of the sourced video, as the number of frames
2760 generated per second. It has to be a string in the format
2761 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
2762 number or a valid video frame rate abbreviation. The default value is
2763 "25".
2764
2765 @end table
2766
2767 For example the following graph description will generate a red source
2768 with an opacity of 0.2, with size "qcif" and a frame rate of 10
2769 frames per second, which will be overlayed over the source connected
2770 to the pad with identifier "in".
2771
2772 @example
2773 "color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
2774 @end example
2775
2776 @section movie
2777
2778 Read a video stream from a movie container.
2779
2780 Note that this source is a hack that bypasses the standard input path. It can be
2781 useful in applications that do not support arbitrary filter graphs, but its use
2782 is discouraged in those that do. Specifically in @command{avconv} this filter
2783 should never be used, the @option{-filter_complex} option fully replaces it.
2784
2785 This filter accepts the following options:
2786
2787 @table @option
2788
2789 @item filename
2790 The name of the resource to read (not necessarily a file but also a device or a
2791 stream accessed through some protocol).
2792
2793 @item format_name, f
2794 Specifies the format assumed for the movie to read, and can be either
2795 the name of a container or an input device. If not specified the
2796 format is guessed from @var{movie_name} or by probing.
2797
2798 @item seek_point, sp
2799 Specifies the seek point in seconds, the frames will be output
2800 starting from this seek point, the parameter is evaluated with
2801 @code{av_strtod} so the numerical value may be suffixed by an IS
2802 postfix. Default value is "0".
2803
2804 @item stream_index, si
2805 Specifies the index of the video stream to read. If the value is -1,
2806 the best suited video stream will be automatically selected. Default
2807 value is "-1".
2808
2809 @end table
2810
2811 This filter allows to overlay a second video on top of main input of
2812 a filtergraph as shown in this graph:
2813 @example
2814 input -----------> deltapts0 --> overlay --> output
2815 ^
2816 |
2817 movie --> scale--> deltapts1 -------+
2818 @end example
2819
2820 Some examples follow:
2821 @example
2822 # skip 3.2 seconds from the start of the avi file in.avi, and overlay it
2823 # on top of the input labelled as "in".
2824 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
2825 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
2826
2827 # read from a video4linux2 device, and overlay it on top of the input
2828 # labelled as "in"
2829 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
2830 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
2831
2832 @end example
2833
2834 @section nullsrc
2835
2836 Null video source, never return images. It is mainly useful as a
2837 template and to be employed in analysis / debugging tools.
2838
2839 It accepts as optional parameter a string of the form
2840 @var{width}:@var{height}:@var{timebase}.
2841
2842 @var{width} and @var{height} specify the size of the configured
2843 source. The default values of @var{width} and @var{height} are
2844 respectively 352 and 288 (corresponding to the CIF size format).
2845
2846 @var{timebase} specifies an arithmetic expression representing a
2847 timebase. The expression can contain the constants "PI", "E", "PHI",
2848 "AVTB" (the default timebase), and defaults to the value "AVTB".
2849
2850 @section frei0r_src
2851
2852 Provide a frei0r source.
2853
2854 To enable compilation of this filter you need to install the frei0r
2855 header and configure Libav with --enable-frei0r.
2856
2857 This source accepts the following options:
2858
2859 @table @option
2860
2861 @item size
2862 The size of the video to generate, may be a string of the form
2863 @var{width}x@var{height} or a frame size abbreviation.
2864
2865 @item framerate
2866 Framerate of the generated video, may be a string of the form
2867 @var{num}/@var{den} or a frame rate abbreviation.
2868
2869 @item filter_name
2870 The name to the frei0r source to load. For more information regarding frei0r and
2871 how to set the parameters read the section @ref{frei0r} in the description of
2872 the video filters.
2873
2874 @item filter_params
2875 A '|'-separated list of parameters to pass to the frei0r source.
2876
2877 @end table
2878
2879 Some examples follow:
2880 @example
2881 # generate a frei0r partik0l source with size 200x200 and framerate 10
2882 # which is overlayed on the overlay filter main input
2883 frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay
2884 @end example
2885
2886 @section rgbtestsrc, testsrc
2887
2888 The @code{rgbtestsrc} source generates an RGB test pattern useful for
2889 detecting RGB vs BGR issues. You should see a red, green and blue
2890 stripe from top to bottom.
2891
2892 The @code{testsrc} source generates a test video pattern, showing a
2893 color pattern, a scrolling gradient and a timestamp. This is mainly
2894 intended for testing purposes.
2895
2896 The sources accept the following options:
2897
2898 @table @option
2899
2900 @item size, s
2901 Specify the size of the sourced video, it may be a string of the form
2902 @var{width}x@var{height}, or the name of a size abbreviation. The
2903 default value is "320x240".
2904
2905 @item rate, r
2906 Specify the frame rate of the sourced video, as the number of frames
2907 generated per second. It has to be a string in the format
2908 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
2909 number or a valid video frame rate abbreviation. The default value is
2910 "25".
2911
2912 @item sar
2913 Set the sample aspect ratio of the sourced video.
2914
2915 @item duration
2916 Set the video duration of the sourced video. The accepted syntax is:
2917 @example
2918 [-]HH[:MM[:SS[.m...]]]
2919 [-]S+[.m...]
2920 @end example
2921 See also the function @code{av_parse_time()}.
2922
2923 If not specified, or the expressed duration is negative, the video is
2924 supposed to be generated forever.
2925 @end table
2926
2927 For example the following:
2928 @example
2929 testsrc=duration=5.3:size=qcif:rate=10
2930 @end example
2931
2932 will generate a video with a duration of 5.3 seconds, with size
2933 176x144 and a framerate of 10 frames per second.
2934
2935 @c man end VIDEO SOURCES
2936
2937 @chapter Video Sinks
2938 @c man begin VIDEO SINKS
2939
2940 Below is a description of the currently available video sinks.
2941
2942 @section buffersink
2943
2944 Buffer video frames, and make them available to the end of the filter
2945 graph.
2946
2947 This sink is intended for a programmatic use through the interface defined in
2948 @file{libavfilter/buffersink.h}.
2949
2950 @section nullsink
2951
2952 Null video sink, do absolutely nothing with the input video. It is
2953 mainly useful as a template and to be employed in analysis / debugging
2954 tools.
2955
2956 @c man end VIDEO SINKS