8c83b4e7a2c4f6294bbea74c99ae05d70c2dd4a7
[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 join
471 Join multiple input streams into one multi-channel stream.
472
473 The filter accepts the following named parameters:
474 @table @option
475
476 @item inputs
477 Number of input streams. Defaults to 2.
478
479 @item channel_layout
480 Desired output channel layout. Defaults to stereo.
481
482 @item map
483 Map channels from inputs to output. The argument is a '|'-separated list of
484 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
485 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
486 can be either the name of the input channel (e.g. FL for front left) or its
487 index in the specified input stream. @var{out_channel} is the name of the output
488 channel.
489 @end table
490
491 The filter will attempt to guess the mappings when those are not specified
492 explicitly. It does so by first trying to find an unused matching input channel
493 and if that fails it picks the first unused input channel.
494
495 E.g. to join 3 inputs (with properly set channel layouts)
496 @example
497 avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
498 @end example
499
500 To build a 5.1 output from 6 single-channel streams:
501 @example
502 avconv -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
503 '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'
504 out
505 @end example
506
507 @section resample
508 Convert the audio sample format, sample rate and channel layout. This filter is
509 not meant to be used directly, it is inserted automatically by libavfilter
510 whenever conversion is needed. Use the @var{aformat} filter to force a specific
511 conversion.
512
513 @section volume
514
515 Adjust the input audio volume.
516
517 The filter accepts the following named parameters:
518 @table @option
519
520 @item volume
521 Expresses how the audio volume will be increased or decreased.
522
523 Output values are clipped to the maximum value.
524
525 The output audio volume is given by the relation:
526 @example
527 @var{output_volume} = @var{volume} * @var{input_volume}
528 @end example
529
530 Default value for @var{volume} is 1.0.
531
532 @item precision
533 Mathematical precision.
534
535 This determines which input sample formats will be allowed, which affects the
536 precision of the volume scaling.
537
538 @table @option
539 @item fixed
540 8-bit fixed-point; limits input sample format to U8, S16, and S32.
541 @item float
542 32-bit floating-point; limits input sample format to FLT. (default)
543 @item double
544 64-bit floating-point; limits input sample format to DBL.
545 @end table
546 @end table
547
548 @subsection Examples
549
550 @itemize
551 @item
552 Halve the input audio volume:
553 @example
554 volume=volume=0.5
555 volume=volume=1/2
556 volume=volume=-6.0206dB
557 @end example
558
559 @item
560 Increase input audio power by 6 decibels using fixed-point precision:
561 @example
562 volume=volume=6dB:precision=fixed
563 @end example
564 @end itemize
565
566 @c man end AUDIO FILTERS
567
568 @chapter Audio Sources
569 @c man begin AUDIO SOURCES
570
571 Below is a description of the currently available audio sources.
572
573 @section anullsrc
574
575 Null audio source, never return audio frames. It is mainly useful as a
576 template and to be employed in analysis / debugging tools.
577
578 It accepts as optional parameter a string of the form
579 @var{sample_rate}:@var{channel_layout}.
580
581 @var{sample_rate} specify the sample rate, and defaults to 44100.
582
583 @var{channel_layout} specify the channel layout, and can be either an
584 integer or a string representing a channel layout. The default value
585 of @var{channel_layout} is 3, which corresponds to CH_LAYOUT_STEREO.
586
587 Check the channel_layout_map definition in
588 @file{libavutil/channel_layout.c} for the mapping between strings and
589 channel layout values.
590
591 Follow some examples:
592 @example
593 # set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.
594 anullsrc=48000:4
595
596 # same as
597 anullsrc=48000:mono
598 @end example
599
600 @section abuffer
601 Buffer audio frames, and make them available to the filter chain.
602
603 This source is not intended to be part of user-supplied graph descriptions but
604 for insertion by calling programs through the interface defined in
605 @file{libavfilter/buffersrc.h}.
606
607 It accepts the following named parameters:
608 @table @option
609
610 @item time_base
611 Timebase which will be used for timestamps of submitted frames. It must be
612 either a floating-point number or in @var{numerator}/@var{denominator} form.
613
614 @item sample_rate
615 Audio sample rate.
616
617 @item sample_fmt
618 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
619
620 @item channel_layout
621 Channel layout of the audio data, in the form that can be accepted by
622 @code{av_get_channel_layout()}.
623 @end table
624
625 All the parameters need to be explicitly defined.
626
627 @c man end AUDIO SOURCES
628
629 @chapter Audio Sinks
630 @c man begin AUDIO SINKS
631
632 Below is a description of the currently available audio sinks.
633
634 @section anullsink
635
636 Null audio sink, do absolutely nothing with the input audio. It is
637 mainly useful as a template and to be employed in analysis / debugging
638 tools.
639
640 @section abuffersink
641 This sink is intended for programmatic use. Frames that arrive on this sink can
642 be retrieved by the calling program using the interface defined in
643 @file{libavfilter/buffersink.h}.
644
645 This filter accepts no parameters.
646
647 @c man end AUDIO SINKS
648
649 @chapter Video Filters
650 @c man begin VIDEO FILTERS
651
652 When you configure your Libav build, you can disable any of the
653 existing filters using --disable-filters.
654 The configure output will show the video filters included in your
655 build.
656
657 Below is a description of the currently available video filters.
658
659 @section blackframe
660
661 Detect frames that are (almost) completely black. Can be useful to
662 detect chapter transitions or commercials. Output lines consist of
663 the frame number of the detected frame, the percentage of blackness,
664 the position in the file if known or -1 and the timestamp in seconds.
665
666 In order to display the output lines, you need to set the loglevel at
667 least to the AV_LOG_INFO value.
668
669 The filter accepts the following options:
670
671 @table @option
672
673 @item amount
674 The percentage of the pixels that have to be below the threshold, defaults to
675 98.
676
677 @item threshold
678 Threshold below which a pixel value is considered black, defaults to 32.
679
680 @end table
681
682 @section boxblur
683
684 Apply boxblur algorithm to the input video.
685
686 This filter accepts the following options:
687
688 @table @option
689
690 @item luma_radius
691 @item luma_power
692 @item chroma_radius
693 @item chroma_power
694 @item alpha_radius
695 @item alpha_power
696
697 @end table
698
699 Chroma and alpha parameters are optional, if not specified they default
700 to the corresponding values set for @var{luma_radius} and
701 @var{luma_power}.
702
703 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
704 the radius in pixels of the box used for blurring the corresponding
705 input plane. They are expressions, and can contain the following
706 constants:
707 @table @option
708 @item w, h
709 the input width and height in pixels
710
711 @item cw, ch
712 the input chroma image width and height in pixels
713
714 @item hsub, vsub
715 horizontal and vertical chroma subsample values. For example for the
716 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
717 @end table
718
719 The radius must be a non-negative number, and must not be greater than
720 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
721 and of @code{min(cw,ch)/2} for the chroma planes.
722
723 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
724 how many times the boxblur filter is applied to the corresponding
725 plane.
726
727 Some examples follow:
728
729 @itemize
730
731 @item
732 Apply a boxblur filter with luma, chroma, and alpha radius
733 set to 2:
734 @example
735 boxblur=luma_radius=2:luma_power=1
736 @end example
737
738 @item
739 Set luma radius to 2, alpha and chroma radius to 0
740 @example
741 boxblur=2:1:0:0:0:0
742 @end example
743
744 @item
745 Set luma and chroma radius to a fraction of the video dimension
746 @example
747 boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1
748 @end example
749
750 @end itemize
751
752 @section copy
753
754 Copy the input source unchanged to the output. Mainly useful for
755 testing purposes.
756
757 @section crop
758
759 Crop the input video to given dimensions.
760
761 This filter accepts the following options:
762
763 @table @option
764
765 @item out_w
766 Width of the output video.
767
768 @item out_h
769 Height of the output video.
770
771 @item x
772 Horizontal position, in the input video, of the left edge of the output video.
773
774 @item y
775 Vertical position, in the input video, of the top edge of the output video.
776
777 @end table
778
779 The parameters are expressions containing the following constants:
780
781 @table @option
782 @item E, PI, PHI
783 the corresponding mathematical approximated values for e
784 (euler number), pi (greek PI), PHI (golden ratio)
785
786 @item x, y
787 the computed values for @var{x} and @var{y}. They are evaluated for
788 each new frame.
789
790 @item in_w, in_h
791 the input width and height
792
793 @item iw, ih
794 same as @var{in_w} and @var{in_h}
795
796 @item out_w, out_h
797 the output (cropped) width and height
798
799 @item ow, oh
800 same as @var{out_w} and @var{out_h}
801
802 @item n
803 the number of input frame, starting from 0
804
805 @item t
806 timestamp expressed in seconds, NAN if the input timestamp is unknown
807
808 @end table
809
810 The @var{out_w} and @var{out_h} parameters specify the expressions for
811 the width and height of the output (cropped) video. They are
812 evaluated just at the configuration of the filter.
813
814 The default value of @var{out_w} is "in_w", and the default value of
815 @var{out_h} is "in_h".
816
817 The expression for @var{out_w} may depend on the value of @var{out_h},
818 and the expression for @var{out_h} may depend on @var{out_w}, but they
819 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
820 evaluated after @var{out_w} and @var{out_h}.
821
822 The @var{x} and @var{y} parameters specify the expressions for the
823 position of the top-left corner of the output (non-cropped) area. They
824 are evaluated for each frame. If the evaluated value is not valid, it
825 is approximated to the nearest valid value.
826
827 The default value of @var{x} is "(in_w-out_w)/2", and the default
828 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
829 the center of the input image.
830
831 The expression for @var{x} may depend on @var{y}, and the expression
832 for @var{y} may depend on @var{x}.
833
834 Follow some examples:
835 @example
836 # crop the central input area with size 100x100
837 crop=out_w=100:out_h=100
838
839 # crop the central input area with size 2/3 of the input video
840 "crop=out_w=2/3*in_w:out_h=2/3*in_h"
841
842 # crop the input video central square
843 crop=out_w=in_h
844
845 # delimit the rectangle with the top-left corner placed at position
846 # 100:100 and the right-bottom corner corresponding to the right-bottom
847 # corner of the input image.
848 crop=out_w=in_w-100:out_h=in_h-100:x=100:y=100
849
850 # crop 10 pixels from the left and right borders, and 20 pixels from
851 # the top and bottom borders
852 "crop=out_w=in_w-2*10:out_h=in_h-2*20"
853
854 # keep only the bottom right quarter of the input image
855 "crop=out_w=in_w/2:out_h=in_h/2:x=in_w/2:y=in_h/2"
856
857 # crop height for getting Greek harmony
858 "crop=out_w=in_w:out_h=1/PHI*in_w"
859
860 # trembling effect
861 "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)"
862
863 # erratic camera effect depending on timestamp
864 "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)"
865
866 # set x depending on the value of y
867 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
868 @end example
869
870 @section cropdetect
871
872 Auto-detect crop size.
873
874 Calculate necessary cropping parameters and prints the recommended
875 parameters through the logging system. The detected dimensions
876 correspond to the non-black area of the input video.
877
878 This filter accepts the following options:
879
880 @table @option
881
882 @item limit
883 Threshold, which can be optionally specified from nothing (0) to
884 everything (255), defaults to 24.
885
886 @item round
887 Value which the width/height should be divisible by, defaults to
888 16. The offset is automatically adjusted to center the video. Use 2 to
889 get only even dimensions (needed for 4:2:2 video). 16 is best when
890 encoding to most video codecs.
891
892 @item reset
893 Counter that determines after how many frames cropdetect will reset
894 the previously detected largest video area and start over to detect
895 the current optimal crop area. Defaults to 0.
896
897 This can be useful when channel logos distort the video area. 0
898 indicates never reset and return the largest area encountered during
899 playback.
900 @end table
901
902 @section delogo
903
904 Suppress a TV station logo by a simple interpolation of the surrounding
905 pixels. Just set a rectangle covering the logo and watch it disappear
906 (and sometimes something even uglier appear - your mileage may vary).
907
908 This filter accepts the following options:
909 @table @option
910
911 @item x, y
912 Specify the top left corner coordinates of the logo. They must be
913 specified.
914
915 @item w, h
916 Specify the width and height of the logo to clear. They must be
917 specified.
918
919 @item band, t
920 Specify the thickness of the fuzzy edge of the rectangle (added to
921 @var{w} and @var{h}). The default value is 4.
922
923 @item show
924 When set to 1, a green rectangle is drawn on the screen to simplify
925 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
926 @var{band} is set to 4. The default value is 0.
927
928 @end table
929
930 Some examples follow.
931
932 @itemize
933
934 @item
935 Set a rectangle covering the area with top left corner coordinates 0,0
936 and size 100x77, setting a band of size 10:
937 @example
938 delogo=x=0:y=0:w=100:h=77:band=10
939 @end example
940
941 @end itemize
942
943 @section drawbox
944
945 Draw a colored box on the input image.
946
947 This filter accepts the following options:
948
949 @table @option
950
951 @item x, y
952 Specify the top left corner coordinates of the box. Default to 0.
953
954 @item width, height
955 Specify the width and height of the box, if 0 they are interpreted as
956 the input width and height. Default to 0.
957
958 @item color
959 Specify the color of the box to write, it can be the name of a color
960 (case insensitive match) or a 0xRRGGBB[AA] sequence.
961 @end table
962
963 Follow some examples:
964 @example
965 # draw a black box around the edge of the input image
966 drawbox
967
968 # draw a box with color red and an opacity of 50%
969 drawbox=x=10:y=20:width=200:height=60:color=red@@0.5"
970 @end example
971
972 @section drawtext
973
974 Draw text string or text from specified file on top of video using the
975 libfreetype library.
976
977 To enable compilation of this filter you need to configure Libav with
978 @code{--enable-libfreetype}.
979
980 The filter also recognizes strftime() sequences in the provided text
981 and expands them accordingly. Check the documentation of strftime().
982
983 The description of the accepted parameters follows.
984
985 @table @option
986
987 @item fontfile
988 The font file to be used for drawing text. Path must be included.
989 This parameter is mandatory.
990
991 @item text
992 The text string to be drawn. The text must be a sequence of UTF-8
993 encoded characters.
994 This parameter is mandatory if no file is specified with the parameter
995 @var{textfile}.
996
997 @item textfile
998 A text file containing text to be drawn. The text must be a sequence
999 of UTF-8 encoded characters.
1000
1001 This parameter is mandatory if no text string is specified with the
1002 parameter @var{text}.
1003
1004 If both text and textfile are specified, an error is thrown.
1005
1006 @item x, y
1007 The offsets where text will be drawn within the video frame.
1008 Relative to the top/left border of the output image.
1009 They accept expressions similar to the @ref{overlay} filter:
1010 @table @option
1011
1012 @item x, y
1013 the computed values for @var{x} and @var{y}. They are evaluated for
1014 each new frame.
1015
1016 @item main_w, main_h
1017 main input width and height
1018
1019 @item W, H
1020 same as @var{main_w} and @var{main_h}
1021
1022 @item text_w, text_h
1023 rendered text width and height
1024
1025 @item w, h
1026 same as @var{text_w} and @var{text_h}
1027
1028 @item n
1029 the number of frames processed, starting from 0
1030
1031 @item t
1032 timestamp expressed in seconds, NAN if the input timestamp is unknown
1033
1034 @end table
1035
1036 The default value of @var{x} and @var{y} is 0.
1037
1038 @item fontsize
1039 The font size to be used for drawing text.
1040 The default value of @var{fontsize} is 16.
1041
1042 @item fontcolor
1043 The color to be used for drawing fonts.
1044 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1045 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1046 The default value of @var{fontcolor} is "black".
1047
1048 @item boxcolor
1049 The color to be used for drawing box around text.
1050 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1051 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1052 The default value of @var{boxcolor} is "white".
1053
1054 @item box
1055 Used to draw a box around text using background color.
1056 Value should be either 1 (enable) or 0 (disable).
1057 The default value of @var{box} is 0.
1058
1059 @item shadowx, shadowy
1060 The x and y offsets for the text shadow position with respect to the
1061 position of the text. They can be either positive or negative
1062 values. Default value for both is "0".
1063
1064 @item shadowcolor
1065 The color to be used for drawing a shadow behind the drawn text. It
1066 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1067 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1068 The default value of @var{shadowcolor} is "black".
1069
1070 @item ft_load_flags
1071 Flags to be used for loading the fonts.
1072
1073 The flags map the corresponding flags supported by libfreetype, and are
1074 a combination of the following values:
1075 @table @var
1076 @item default
1077 @item no_scale
1078 @item no_hinting
1079 @item render
1080 @item no_bitmap
1081 @item vertical_layout
1082 @item force_autohint
1083 @item crop_bitmap
1084 @item pedantic
1085 @item ignore_global_advance_width
1086 @item no_recurse
1087 @item ignore_transform
1088 @item monochrome
1089 @item linear_design
1090 @item no_autohint
1091 @item end table
1092 @end table
1093
1094 Default value is "render".
1095
1096 For more information consult the documentation for the FT_LOAD_*
1097 libfreetype flags.
1098
1099 @item tabsize
1100 The size in number of spaces to use for rendering the tab.
1101 Default value is 4.
1102
1103 @item fix_bounds
1104 If true, check and fix text coords to avoid clipping.
1105 @end table
1106
1107 For example the command:
1108 @example
1109 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
1110 @end example
1111
1112 will draw "Test Text" with font FreeSerif, using the default values
1113 for the optional parameters.
1114
1115 The command:
1116 @example
1117 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
1118 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
1119 @end example
1120
1121 will draw 'Test Text' with font FreeSerif of size 24 at position x=100
1122 and y=50 (counting from the top-left corner of the screen), text is
1123 yellow with a red box around it. Both the text and the box have an
1124 opacity of 20%.
1125
1126 Note that the double quotes are not necessary if spaces are not used
1127 within the parameter list.
1128
1129 For more information about libfreetype, check:
1130 @url{http://www.freetype.org/}.
1131
1132 @section fade
1133
1134 Apply fade-in/out effect to input video.
1135
1136 This filter accepts the following options:
1137
1138 @table @option
1139
1140 @item type
1141 The effect type -- can be either "in" for fade-in, or "out" for a fade-out
1142 effect.
1143
1144 @item start_frame
1145 The number of the start frame for starting to apply the fade effect.
1146
1147 @item nb_frames
1148 The number of frames for which the fade effect has to last. At the end of the
1149 fade-in effect the output video will have the same intensity as the input video,
1150 at the end of the fade-out transition the output video will be completely black.
1151
1152 @end table
1153
1154 A few usage examples follow, usable too as test scenarios.
1155 @example
1156 # fade in first 30 frames of video
1157 fade=type=in:nb_frames=30
1158
1159 # fade out last 45 frames of a 200-frame video
1160 fade=type=out:start_frame=155:nb_frames=45
1161
1162 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
1163 fade=type=in:start_frame=0:nb_frames=25, fade=type=out:start_frame=975:nb_frames=25
1164
1165 # make first 5 frames black, then fade in from frame 5-24
1166 fade=type=in:start_frame=5:nb_frames=20
1167 @end example
1168
1169 @section fieldorder
1170
1171 Transform the field order of the input video.
1172
1173 This filter accepts the following options:
1174
1175 @table @option
1176
1177 @item order
1178 Output field order. Valid values are @var{tff} for top field first or @var{bff}
1179 for bottom field first.
1180 @end table
1181
1182 Default value is "tff".
1183
1184 Transformation is achieved by shifting the picture content up or down
1185 by one line, and filling the remaining line with appropriate picture content.
1186 This method is consistent with most broadcast field order converters.
1187
1188 If the input video is not flagged as being interlaced, or it is already
1189 flagged as being of the required output field order then this filter does
1190 not alter the incoming video.
1191
1192 This filter is very useful when converting to or from PAL DV material,
1193 which is bottom field first.
1194
1195 For example:
1196 @example
1197 ./avconv -i in.vob -vf "fieldorder=order=bff" out.dv
1198 @end example
1199
1200 @section fifo
1201
1202 Buffer input images and send them when they are requested.
1203
1204 This filter is mainly useful when auto-inserted by the libavfilter
1205 framework.
1206
1207 The filter does not take parameters.
1208
1209 @section format
1210
1211 Convert the input video to one of the specified pixel formats.
1212 Libavfilter will try to pick one that is supported for the input to
1213 the next filter.
1214
1215 This filter accepts the following parameters:
1216 @table @option
1217
1218 @item pix_fmts
1219 A '|'-separated list of pixel format names, for example
1220 "pix_fmts=yuv420p|monow|rgb24".
1221
1222 @end table
1223
1224 Some examples follow:
1225 @example
1226 # convert the input video to the format "yuv420p"
1227 format=pix_fmts=yuv420p
1228
1229 # convert the input video to any of the formats in the list
1230 format=pix_fmts=yuv420p|yuv444p|yuv410p
1231 @end example
1232
1233 @anchor{fps}
1234 @section fps
1235
1236 Convert the video to specified constant framerate by duplicating or dropping
1237 frames as necessary.
1238
1239 This filter accepts the following named parameters:
1240 @table @option
1241
1242 @item fps
1243 Desired output framerate.
1244
1245 @item start_time
1246 Assume the first PTS should be the given value, in seconds. This allows for
1247 padding/trimming at the start of stream. By default, no assumption is made
1248 about the first frame's expected PTS, so no padding or trimming is done.
1249 For example, this could be set to 0 to pad the beginning with duplicates of
1250 the first frame if a video stream starts after the audio stream or to trim any
1251 frames with a negative PTS.
1252
1253 @end table
1254
1255 @section framepack
1256
1257 Pack two different video streams into a stereoscopic video, setting proper
1258 metadata on supported codecs. The two views should have the same size and
1259 framerate and processing will stop when the shorter video ends. Please note
1260 that you may conveniently adjust view properties with the @ref{scale} and
1261 @ref{fps} filters.
1262
1263 This filter accepts the following named parameters:
1264 @table @option
1265
1266 @item format
1267 Desired packing format. Supported values are:
1268
1269 @table @option
1270
1271 @item sbs
1272 Views are next to each other (default).
1273
1274 @item tab
1275 Views are on top of each other.
1276
1277 @item lines
1278 Views are packed by line.
1279
1280 @item columns
1281 Views are eacked by column.
1282
1283 @item frameseq
1284 Views are temporally interleaved.
1285
1286 @end table
1287
1288 @end table
1289
1290 Some examples follow:
1291
1292 @example
1293 # Convert left and right views into a frame sequential video.
1294 avconv -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT
1295
1296 # Convert views into a side-by-side video with the same output resolution as the input.
1297 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
1298 @end example
1299
1300 @anchor{frei0r}
1301 @section frei0r
1302
1303 Apply a frei0r effect to the input video.
1304
1305 To enable compilation of this filter you need to install the frei0r
1306 header and configure Libav with --enable-frei0r.
1307
1308 This filter accepts the following options:
1309
1310 @table @option
1311
1312 @item filter_name
1313 The name to the frei0r effect to load. If the environment variable
1314 @env{FREI0R_PATH} is defined, the frei0r effect is searched in each one of the
1315 directories specified by the colon separated list in @env{FREIOR_PATH},
1316 otherwise in the standard frei0r paths, which are in this order:
1317 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
1318 @file{/usr/lib/frei0r-1/}.
1319
1320 @item filter_params
1321 A '|'-separated list of parameters to pass to the frei0r effect.
1322
1323 @end table
1324
1325 A frei0r effect parameter can be a boolean (whose values are specified
1326 with "y" and "n"), a double, a color (specified by the syntax
1327 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
1328 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
1329 description), a position (specified by the syntax @var{X}/@var{Y},
1330 @var{X} and @var{Y} being float numbers) and a string.
1331
1332 The number and kind of parameters depend on the loaded effect. If an
1333 effect parameter is not specified the default value is set.
1334
1335 Some examples follow:
1336 @example
1337 # apply the distort0r effect, set the first two double parameters
1338 frei0r=filter_name=distort0r:filter_params=0.5|0.01
1339
1340 # apply the colordistance effect, takes a color as first parameter
1341 frei0r=colordistance:0.2/0.3/0.4
1342 frei0r=colordistance:violet
1343 frei0r=colordistance:0x112233
1344
1345 # apply the perspective effect, specify the top left and top right
1346 # image positions
1347 frei0r=perspective:0.2/0.2|0.8/0.2
1348 @end example
1349
1350 For more information see:
1351 @url{http://piksel.org/frei0r}
1352
1353 @section gradfun
1354
1355 Fix the banding artifacts that are sometimes introduced into nearly flat
1356 regions by truncation to 8bit colordepth.
1357 Interpolate the gradients that should go where the bands are, and
1358 dither them.
1359
1360 This filter is designed for playback only. Do not use it prior to
1361 lossy compression, because compression tends to lose the dither and
1362 bring back the bands.
1363
1364 This filter accepts the following options:
1365
1366 @table @option
1367
1368 @item strength
1369 The maximum amount by which the filter will change any one pixel. Also the
1370 threshold for detecting nearly flat regions. Acceptable values range from .51 to
1371 64, default value is 1.2, out-of-range values will be clipped to the valid
1372 range.
1373
1374 @item radius
1375 The neighborhood to fit the gradient to. A larger radius makes for smoother
1376 gradients, but also prevents the filter from modifying the pixels near detailed
1377 regions. Acceptable values are 8-32, default value is 16, out-of-range values
1378 will be clipped to the valid range.
1379
1380 @end table
1381
1382 @example
1383 # default parameters
1384 gradfun=strength=1.2:radius=16
1385
1386 # omitting radius
1387 gradfun=1.2
1388 @end example
1389
1390 @section hflip
1391
1392 Flip the input video horizontally.
1393
1394 For example to horizontally flip the input video with @command{avconv}:
1395 @example
1396 avconv -i in.avi -vf "hflip" out.avi
1397 @end example
1398
1399 @section hqdn3d
1400
1401 High precision/quality 3d denoise filter. This filter aims to reduce
1402 image noise producing smooth images and making still images really
1403 still. It should enhance compressibility.
1404
1405 It accepts the following optional parameters:
1406
1407 @table @option
1408 @item luma_spatial
1409 a non-negative float number which specifies spatial luma strength,
1410 defaults to 4.0
1411
1412 @item chroma_spatial
1413 a non-negative float number which specifies spatial chroma strength,
1414 defaults to 3.0*@var{luma_spatial}/4.0
1415
1416 @item luma_tmp
1417 a float number which specifies luma temporal strength, defaults to
1418 6.0*@var{luma_spatial}/4.0
1419
1420 @item chroma_tmp
1421 a float number which specifies chroma temporal strength, defaults to
1422 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
1423 @end table
1424
1425 @section interlace
1426
1427 Simple interlacing filter from progressive contents. This interleaves upper (or
1428 lower) lines from odd frames with lower (or upper) lines from even frames,
1429 halving the frame rate and preserving image height.
1430
1431 @example
1432 Original Original New Frame
1433 Frame 'j' Frame 'j+1' (tff)
1434 ========== =========== ==================
1435 Line 0 --------------------> Frame 'j' Line 0
1436 Line 1 Line 1 ----> Frame 'j+1' Line 1
1437 Line 2 ---------------------> Frame 'j' Line 2
1438 Line 3 Line 3 ----> Frame 'j+1' Line 3
1439 ... ... ...
1440 New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on
1441 @end example
1442
1443 It accepts the following optional parameters:
1444
1445 @table @option
1446 @item scan
1447 determines whether the interlaced frame is taken from the even (tff - default)
1448 or odd (bff) lines of the progressive frame.
1449
1450 @item lowpass
1451 Enable (default) or disable the vertical lowpass filter to avoid twitter
1452 interlacing and reduce moire patterns.
1453 @end table
1454
1455 @section lut, lutrgb, lutyuv
1456
1457 Compute a look-up table for binding each pixel component input value
1458 to an output value, and apply it to input video.
1459
1460 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
1461 to an RGB input video.
1462
1463 These filters accept the following options:
1464 @table @option
1465 @item @var{c0} (first pixel component)
1466 @item @var{c1} (second pixel component)
1467 @item @var{c2} (third pixel component)
1468 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
1469
1470 @item @var{r} (red component)
1471 @item @var{g} (green component)
1472 @item @var{b} (blue component)
1473 @item @var{a} (alpha component)
1474
1475 @item @var{y} (Y/luminance component)
1476 @item @var{u} (U/Cb component)
1477 @item @var{v} (V/Cr component)
1478 @end table
1479
1480 Each of them specifies the expression to use for computing the lookup table for
1481 the corresponding pixel component values.
1482
1483 The exact component associated to each of the @var{c*} options depends on the
1484 format in input.
1485
1486 The @var{lut} filter requires either YUV or RGB pixel formats in input,
1487 @var{lutrgb} requires RGB pixel formats in input, and @var{lutyuv} requires YUV.
1488
1489 The expressions can contain the following constants and functions:
1490
1491 @table @option
1492 @item E, PI, PHI
1493 the corresponding mathematical approximated values for e
1494 (euler number), pi (greek PI), PHI (golden ratio)
1495
1496 @item w, h
1497 the input width and height
1498
1499 @item val
1500 input value for the pixel component
1501
1502 @item clipval
1503 the input value clipped in the @var{minval}-@var{maxval} range
1504
1505 @item maxval
1506 maximum value for the pixel component
1507
1508 @item minval
1509 minimum value for the pixel component
1510
1511 @item negval
1512 the negated value for the pixel component value clipped in the
1513 @var{minval}-@var{maxval} range , it corresponds to the expression
1514 "maxval-clipval+minval"
1515
1516 @item clip(val)
1517 the computed value in @var{val} clipped in the
1518 @var{minval}-@var{maxval} range
1519
1520 @item gammaval(gamma)
1521 the computed gamma correction value of the pixel component value
1522 clipped in the @var{minval}-@var{maxval} range, corresponds to the
1523 expression
1524 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
1525
1526 @end table
1527
1528 All expressions default to "val".
1529
1530 Some examples follow:
1531 @example
1532 # negate input video
1533 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
1534 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
1535
1536 # the above is the same as
1537 lutrgb="r=negval:g=negval:b=negval"
1538 lutyuv="y=negval:u=negval:v=negval"
1539
1540 # negate luminance
1541 lutyuv=negval
1542
1543 # remove chroma components, turns the video into a graytone image
1544 lutyuv="u=128:v=128"
1545
1546 # apply a luma burning effect
1547 lutyuv="y=2*val"
1548
1549 # remove green and blue components
1550 lutrgb="g=0:b=0"
1551
1552 # set a constant alpha channel value on input
1553 format=rgba,lutrgb=a="maxval-minval/2"
1554
1555 # correct luminance gamma by a 0.5 factor
1556 lutyuv=y=gammaval(0.5)
1557 @end example
1558
1559 @section negate
1560
1561 Negate input video.
1562
1563 This filter accepts an integer in input, if non-zero it negates the
1564 alpha component (if available). The default value in input is 0.
1565
1566 @section noformat
1567
1568 Force libavfilter not to use any of the specified pixel formats for the
1569 input to the next filter.
1570
1571 This filter accepts the following parameters:
1572 @table @option
1573
1574 @item pix_fmts
1575 A '|'-separated list of pixel format names, for example
1576 "pix_fmts=yuv420p|monow|rgb24".
1577
1578 @end table
1579
1580 Some examples follow:
1581 @example
1582 # force libavfilter to use a format different from "yuv420p" for the
1583 # input to the vflip filter
1584 noformat=pix_fmts=yuv420p,vflip
1585
1586 # convert the input video to any of the formats not contained in the list
1587 noformat=yuv420p|yuv444p|yuv410p
1588 @end example
1589
1590 @section null
1591
1592 Pass the video source unchanged to the output.
1593
1594 @section ocv
1595
1596 Apply video transform using libopencv.
1597
1598 To enable this filter install libopencv library and headers and
1599 configure Libav with --enable-libopencv.
1600
1601 This filter accepts the following parameters:
1602
1603 @table @option
1604
1605 @item filter_name
1606 The name of the libopencv filter to apply.
1607
1608 @item filter_params
1609 The parameters to pass to the libopencv filter. If not specified the default
1610 values are assumed.
1611
1612 @end table
1613
1614 Refer to the official libopencv documentation for more precise
1615 information:
1616 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
1617
1618 Follows the list of supported libopencv filters.
1619
1620 @anchor{dilate}
1621 @subsection dilate
1622
1623 Dilate an image by using a specific structuring element.
1624 This filter corresponds to the libopencv function @code{cvDilate}.
1625
1626 It accepts the parameters: @var{struct_el}|@var{nb_iterations}.
1627
1628 @var{struct_el} represents a structuring element, and has the syntax:
1629 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
1630
1631 @var{cols} and @var{rows} represent the number of columns and rows of
1632 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
1633 point, and @var{shape} the shape for the structuring element, and
1634 can be one of the values "rect", "cross", "ellipse", "custom".
1635
1636 If the value for @var{shape} is "custom", it must be followed by a
1637 string of the form "=@var{filename}". The file with name
1638 @var{filename} is assumed to represent a binary image, with each
1639 printable character corresponding to a bright pixel. When a custom
1640 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
1641 or columns and rows of the read file are assumed instead.
1642
1643 The default value for @var{struct_el} is "3x3+0x0/rect".
1644
1645 @var{nb_iterations} specifies the number of times the transform is
1646 applied to the image, and defaults to 1.
1647
1648 Follow some example:
1649 @example
1650 # use the default values
1651 ocv=dilate
1652
1653 # dilate using a structuring element with a 5x5 cross, iterate two times
1654 ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2
1655
1656 # read the shape from the file diamond.shape, iterate two times
1657 # the file diamond.shape may contain a pattern of characters like this:
1658 # *
1659 # ***
1660 # *****
1661 # ***
1662 # *
1663 # the specified cols and rows are ignored (but not the anchor point coordinates)
1664 ocv=dilate:0x0+2x2/custom=diamond.shape|2
1665 @end example
1666
1667 @subsection erode
1668
1669 Erode an image by using a specific structuring element.
1670 This filter corresponds to the libopencv function @code{cvErode}.
1671
1672 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
1673 with the same syntax and semantics as the @ref{dilate} filter.
1674
1675 @subsection smooth
1676
1677 Smooth the input video.
1678
1679 The filter takes the following parameters:
1680 @var{type}|@var{param1}|@var{param2}|@var{param3}|@var{param4}.
1681
1682 @var{type} is the type of smooth filter to apply, and can be one of
1683 the following values: "blur", "blur_no_scale", "median", "gaussian",
1684 "bilateral". The default value is "gaussian".
1685
1686 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
1687 parameters whose meanings depend on smooth type. @var{param1} and
1688 @var{param2} accept integer positive values or 0, @var{param3} and
1689 @var{param4} accept float values.
1690
1691 The default value for @var{param1} is 3, the default value for the
1692 other parameters is 0.
1693
1694 These parameters correspond to the parameters assigned to the
1695 libopencv function @code{cvSmooth}.
1696
1697 @anchor{overlay}
1698 @section overlay
1699
1700 Overlay one video on top of another.
1701
1702 It takes two inputs and one output, the first input is the "main"
1703 video on which the second input is overlayed.
1704
1705 This filter accepts the following parameters:
1706
1707 @table @option
1708
1709 @item x
1710 The horizontal position of the left edge of the overlaid video on the main video.
1711
1712 @item y
1713 The vertical position of the top edge of the overlaid video on the main video.
1714
1715 @end table
1716
1717 The parameters are expressions containing the following parameters:
1718
1719 @table @option
1720 @item main_w, main_h
1721 main input width and height
1722
1723 @item W, H
1724 same as @var{main_w} and @var{main_h}
1725
1726 @item overlay_w, overlay_h
1727 overlay input width and height
1728
1729 @item w, h
1730 same as @var{overlay_w} and @var{overlay_h}
1731
1732 @item eof_action
1733 The action to take when EOF is encountered on the secondary input, accepts one
1734 of the following values:
1735
1736 @table @option
1737 @item repeat
1738 repeat the last frame (the default)
1739 @item endall
1740 end both streams
1741 @item pass
1742 pass through the main input
1743 @end table
1744
1745 @end table
1746
1747 Be aware that frames are taken from each input video in timestamp
1748 order, hence, if their initial timestamps differ, it is a a good idea
1749 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
1750 have them begin in the same zero timestamp, as it does the example for
1751 the @var{movie} filter.
1752
1753 Follow some examples:
1754 @example
1755 # draw the overlay at 10 pixels from the bottom right
1756 # corner of the main video.
1757 overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10
1758
1759 # insert a transparent PNG logo in the bottom left corner of the input
1760 avconv -i input -i logo -filter_complex 'overlay=x=10:y=main_h-overlay_h-10' output
1761
1762 # insert 2 different transparent PNG logos (second logo on bottom
1763 # right corner):
1764 avconv -i input -i logo1 -i logo2 -filter_complex
1765 'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output
1766
1767 # add a transparent color layer on top of the main video,
1768 # WxH specifies the size of the main input to the overlay filter
1769 color=red@.3:WxH [over]; [in][over] overlay [out]
1770
1771 # mask 10-20 seconds of a video by applying the delogo filter to a section
1772 avconv -i test.avi -codec:v:0 wmv2 -ar 11025 -b:v 9000k
1773 -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]'
1774 masked.avi
1775 @end example
1776
1777 You can chain together more overlays but the efficiency of such
1778 approach is yet to be tested.
1779
1780 @section pad
1781
1782 Add paddings to the input image, and places the original input at the
1783 given coordinates @var{x}, @var{y}.
1784
1785 This filter accepts the following parameters:
1786
1787 @table @option
1788 @item width, height
1789
1790 Specify the size of the output image with the paddings added. If the
1791 value for @var{width} or @var{height} is 0, the corresponding input size
1792 is used for the output.
1793
1794 The @var{width} expression can reference the value set by the
1795 @var{height} expression, and vice versa.
1796
1797 The default value of @var{width} and @var{height} is 0.
1798
1799 @item x, y
1800
1801 Specify the offsets where to place the input image in the padded area
1802 with respect to the top/left border of the output image.
1803
1804 The @var{x} expression can reference the value set by the @var{y}
1805 expression, and vice versa.
1806
1807 The default value of @var{x} and @var{y} is 0.
1808
1809 @item color
1810
1811 Specify the color of the padded area, it can be the name of a color
1812 (case insensitive match) or a 0xRRGGBB[AA] sequence.
1813
1814 The default value of @var{color} is "black".
1815
1816 @end table
1817
1818 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
1819 expressions containing the following constants:
1820
1821 @table @option
1822 @item E, PI, PHI
1823 the corresponding mathematical approximated values for e
1824 (euler number), pi (greek PI), phi (golden ratio)
1825
1826 @item in_w, in_h
1827 the input video width and height
1828
1829 @item iw, ih
1830 same as @var{in_w} and @var{in_h}
1831
1832 @item out_w, out_h
1833 the output width and height, that is the size of the padded area as
1834 specified by the @var{width} and @var{height} expressions
1835
1836 @item ow, oh
1837 same as @var{out_w} and @var{out_h}
1838
1839 @item x, y
1840 x and y offsets as specified by the @var{x} and @var{y}
1841 expressions, or NAN if not yet specified
1842
1843 @item a
1844 input display aspect ratio, same as @var{iw} / @var{ih}
1845
1846 @item hsub, vsub
1847 horizontal and vertical chroma subsample values. For example for the
1848 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1849 @end table
1850
1851 Some examples follow:
1852
1853 @example
1854 # Add paddings with color "violet" to the input video. Output video
1855 # size is 640x480, the top-left corner of the input video is placed at
1856 # column 0, row 40.
1857 pad=width=640:height=480:x=0:y=40:color=violet
1858
1859 # pad the input to get an output with dimensions increased bt 3/2,
1860 # and put the input video at the center of the padded area
1861 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
1862
1863 # pad the input to get a squared output with size equal to the maximum
1864 # value between the input width and height, and put the input video at
1865 # the center of the padded area
1866 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
1867
1868 # pad the input to get a final w/h ratio of 16:9
1869 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
1870
1871 # double output size and put the input video in the bottom-right
1872 # corner of the output padded area
1873 pad="2*iw:2*ih:ow-iw:oh-ih"
1874 @end example
1875
1876 @section pixdesctest
1877
1878 Pixel format descriptor test filter, mainly useful for internal
1879 testing. The output video should be equal to the input video.
1880
1881 For example:
1882 @example
1883 format=monow, pixdesctest
1884 @end example
1885
1886 can be used to test the monowhite pixel format descriptor definition.
1887
1888 @anchor{scale}
1889 @section scale
1890
1891 Scale the input video and/or convert the image format.
1892
1893 This filter accepts the following options:
1894
1895 @table @option
1896
1897 @item w
1898 Output video width.
1899
1900 @item h
1901 Output video height.
1902
1903 @end table
1904
1905 The parameters @var{w} and @var{h} are expressions containing
1906 the following constants:
1907
1908 @table @option
1909 @item E, PI, PHI
1910 the corresponding mathematical approximated values for e
1911 (euler number), pi (greek PI), phi (golden ratio)
1912
1913 @item in_w, in_h
1914 the input width and height
1915
1916 @item iw, ih
1917 same as @var{in_w} and @var{in_h}
1918
1919 @item out_w, out_h
1920 the output (cropped) width and height
1921
1922 @item ow, oh
1923 same as @var{out_w} and @var{out_h}
1924
1925 @item a
1926 same as @var{iw} / @var{ih}
1927
1928 @item sar
1929 input sample aspect ratio
1930
1931 @item dar
1932 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1933
1934 @item hsub, vsub
1935 horizontal and vertical chroma subsample values. For example for the
1936 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1937 @end table
1938
1939 If the input image format is different from the format requested by
1940 the next filter, the scale filter will convert the input to the
1941 requested format.
1942
1943 If the value for @var{w} or @var{h} is 0, the respective input
1944 size is used for the output.
1945
1946 If the value for @var{w} or @var{h} is -1, the scale filter will use, for the
1947 respective output size, a value that maintains the aspect ratio of the input
1948 image.
1949
1950 The default value of @var{w} and @var{h} is 0.
1951
1952 Some examples follow:
1953 @example
1954 # scale the input video to a size of 200x100.
1955 scale=w=200:h=100
1956
1957 # scale the input to 2x
1958 scale=w=2*iw:h=2*ih
1959 # the above is the same as
1960 scale=2*in_w:2*in_h
1961
1962 # scale the input to half size
1963 scale=w=iw/2:h=ih/2
1964
1965 # increase the width, and set the height to the same size
1966 scale=3/2*iw:ow
1967
1968 # seek for Greek harmony
1969 scale=iw:1/PHI*iw
1970 scale=ih*PHI:ih
1971
1972 # increase the height, and set the width to 3/2 of the height
1973 scale=w=3/2*oh:h=3/5*ih
1974
1975 # increase the size, but make the size a multiple of the chroma
1976 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
1977
1978 # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
1979 scale=w='min(500\, iw*3/2):h=-1'
1980 @end example
1981
1982 @section select
1983 Select frames to pass in output.
1984
1985 This filter accepts the following options:
1986
1987 @table @option
1988
1989 @item expr
1990 An expression, which is evaluated for each input frame. If the expression is
1991 evaluated to a non-zero value, the frame is selected and passed to the output,
1992 otherwise it is discarded.
1993
1994 @end table
1995
1996 The expression can contain the following constants:
1997
1998 @table @option
1999 @item PI
2000 Greek PI
2001
2002 @item PHI
2003 golden ratio
2004
2005 @item E
2006 Euler number
2007
2008 @item n
2009 the sequential number of the filtered frame, starting from 0
2010
2011 @item selected_n
2012 the sequential number of the selected frame, starting from 0
2013
2014 @item prev_selected_n
2015 the sequential number of the last selected frame, NAN if undefined
2016
2017 @item TB
2018 timebase of the input timestamps
2019
2020 @item pts
2021 the PTS (Presentation TimeStamp) of the filtered video frame,
2022 expressed in @var{TB} units, NAN if undefined
2023
2024 @item t
2025 the PTS (Presentation TimeStamp) of the filtered video frame,
2026 expressed in seconds, NAN if undefined
2027
2028 @item prev_pts
2029 the PTS of the previously filtered video frame, NAN if undefined
2030
2031 @item prev_selected_pts
2032 the PTS of the last previously filtered video frame, NAN if undefined
2033
2034 @item prev_selected_t
2035 the PTS of the last previously selected video frame, NAN if undefined
2036
2037 @item start_pts
2038 the PTS of the first video frame in the video, NAN if undefined
2039
2040 @item start_t
2041 the time of the first video frame in the video, NAN if undefined
2042
2043 @item pict_type
2044 the type of the filtered frame, can assume one of the following
2045 values:
2046 @table @option
2047 @item I
2048 @item P
2049 @item B
2050 @item S
2051 @item SI
2052 @item SP
2053 @item BI
2054 @end table
2055
2056 @item interlace_type
2057 the frame interlace type, can assume one of the following values:
2058 @table @option
2059 @item PROGRESSIVE
2060 the frame is progressive (not interlaced)
2061 @item TOPFIRST
2062 the frame is top-field-first
2063 @item BOTTOMFIRST
2064 the frame is bottom-field-first
2065 @end table
2066
2067 @item key
2068 1 if the filtered frame is a key-frame, 0 otherwise
2069
2070 @end table
2071
2072 The default value of the select expression is "1".
2073
2074 Some examples follow:
2075
2076 @example
2077 # select all frames in input
2078 select
2079
2080 # the above is the same as:
2081 select=expr=1
2082
2083 # skip all frames:
2084 select=expr=0
2085
2086 # select only I-frames
2087 select='expr=eq(pict_type\,I)'
2088
2089 # select one frame every 100
2090 select='not(mod(n\,100))'
2091
2092 # select only frames contained in the 10-20 time interval
2093 select='gte(t\,10)*lte(t\,20)'
2094
2095 # select only I frames contained in the 10-20 time interval
2096 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
2097
2098 # select frames with a minimum distance of 10 seconds
2099 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
2100 @end example
2101
2102 @anchor{setdar}
2103 @section setdar
2104
2105 Set the Display Aspect Ratio for the filter output video.
2106
2107 This is done by changing the specified Sample (aka Pixel) Aspect
2108 Ratio, according to the following equation:
2109 @math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
2110
2111 Keep in mind that this filter does not modify the pixel dimensions of
2112 the video frame. Also the display aspect ratio set by this filter may
2113 be changed by later filters in the filterchain, e.g. in case of
2114 scaling or if another "setdar" or a "setsar" filter is applied.
2115
2116 This filter accepts the following options:
2117
2118 @table @option
2119
2120 @item dar
2121 Output display aspect ratio.
2122
2123 @end table
2124
2125 The parameter @var{dar} is an expression containing
2126 the following constants:
2127
2128 @table @option
2129 @item E, PI, PHI
2130 the corresponding mathematical approximated values for e
2131 (euler number), pi (greek PI), phi (golden ratio)
2132
2133 @item w, h
2134 the input width and height
2135
2136 @item a
2137 same as @var{w} / @var{h}
2138
2139 @item sar
2140 input sample aspect ratio
2141
2142 @item dar
2143 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
2144
2145 @item hsub, vsub
2146 horizontal and vertical chroma subsample values. For example for the
2147 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2148 @end table
2149
2150 For example to change the display aspect ratio to 16:9, specify:
2151 @example
2152 setdar=dar=16/9
2153 # the above is equivalent to
2154 setdar=dar=1.77777
2155 @end example
2156
2157 See also the @ref{setsar} filter documentation.
2158
2159 @section setpts
2160
2161 Change the PTS (presentation timestamp) of the input video frames.
2162
2163 This filter accepts the following options:
2164
2165 @table @option
2166
2167 @item expr
2168 The expression which is evaluated for each frame to construct its timestamp.
2169
2170 @end table
2171
2172 The expression is evaluated through the eval API and can contain the following
2173 constants:
2174
2175 @table @option
2176 @item PTS
2177 the presentation timestamp in input
2178
2179 @item PI
2180 Greek PI
2181
2182 @item PHI
2183 golden ratio
2184
2185 @item E
2186 Euler number
2187
2188 @item N
2189 the count of the input frame, starting from 0.
2190
2191 @item STARTPTS
2192 the PTS of the first video frame
2193
2194 @item INTERLACED
2195 tell if the current frame is interlaced
2196
2197 @item PREV_INPTS
2198 previous input PTS
2199
2200 @item PREV_OUTPTS
2201 previous output PTS
2202
2203 @item RTCTIME
2204 wallclock (RTC) time in microseconds
2205
2206 @item RTCSTART
2207 wallclock (RTC) time at the start of the movie in microseconds
2208
2209 @item TB
2210 timebase of the input timestamps
2211
2212 @end table
2213
2214 Some examples follow:
2215
2216 @example
2217 # start counting PTS from zero
2218 setpts=expr=PTS-STARTPTS
2219
2220 # fast motion
2221 setpts=expr=0.5*PTS
2222
2223 # slow motion
2224 setpts=2.0*PTS
2225
2226 # fixed rate 25 fps
2227 setpts=N/(25*TB)
2228
2229 # fixed rate 25 fps with some jitter
2230 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
2231
2232 # generate timestamps from a "live source" and rebase onto the current timebase
2233 setpts='(RTCTIME - RTCSTART) / (TB * 1000000)"
2234 @end example
2235
2236 @anchor{setsar}
2237 @section setsar
2238
2239 Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
2240
2241 Note that as a consequence of the application of this filter, the
2242 output display aspect ratio will change according to the following
2243 equation:
2244 @math{DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR}
2245
2246 Keep in mind that the sample aspect ratio set by this filter may be
2247 changed by later filters in the filterchain, e.g. if another "setsar"
2248 or a "setdar" filter is applied.
2249
2250 This filter accepts the following options:
2251
2252 @table @option
2253
2254 @item sar
2255 Output sample aspect ratio.
2256
2257 @end table
2258
2259 The parameter @var{sar} is an expression containing
2260 the following constants:
2261
2262 @table @option
2263 @item E, PI, PHI
2264 the corresponding mathematical approximated values for e
2265 (euler number), pi (greek PI), phi (golden ratio)
2266
2267 @item w, h
2268 the input width and height
2269
2270 @item a
2271 same as @var{w} / @var{h}
2272
2273 @item sar
2274 input sample aspect ratio
2275
2276 @item dar
2277 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
2278
2279 @item hsub, vsub
2280 horizontal and vertical chroma subsample values. For example for the
2281 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2282 @end table
2283
2284 For example to change the sample aspect ratio to 10:11, specify:
2285 @example
2286 setsar=sar=10/11
2287 @end example
2288
2289 @section settb
2290
2291 Set the timebase to use for the output frames timestamps.
2292 It is mainly useful for testing timebase configuration.
2293
2294 This filter accepts the following options:
2295
2296 @table @option
2297
2298 @item expr
2299 The expression which is evaluated into the output timebase.
2300
2301 @end table
2302
2303 The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
2304 default timebase), and "intb" (the input timebase).
2305
2306 The default value for the input is "intb".
2307
2308 Follow some examples.
2309
2310 @example
2311 # set the timebase to 1/25
2312 settb=expr=1/25
2313
2314 # set the timebase to 1/10
2315 settb=expr=0.1
2316
2317 #set the timebase to 1001/1000
2318 settb=1+0.001
2319
2320 #set the timebase to 2*intb
2321 settb=2*intb
2322
2323 #set the default timebase value
2324 settb=AVTB
2325 @end example
2326
2327 @section showinfo
2328
2329 Show a line containing various information for each input video frame.
2330 The input video is not modified.
2331
2332 The shown line contains a sequence of key/value pairs of the form
2333 @var{key}:@var{value}.
2334
2335 A description of each shown parameter follows:
2336
2337 @table @option
2338 @item n
2339 sequential number of the input frame, starting from 0
2340
2341 @item pts
2342 Presentation TimeStamp of the input frame, expressed as a number of
2343 time base units. The time base unit depends on the filter input pad.
2344
2345 @item pts_time
2346 Presentation TimeStamp of the input frame, expressed as a number of
2347 seconds
2348
2349 @item pos
2350 position of the frame in the input stream, -1 if this information in
2351 unavailable and/or meaningless (for example in case of synthetic video)
2352
2353 @item fmt
2354 pixel format name
2355
2356 @item sar
2357 sample aspect ratio of the input frame, expressed in the form
2358 @var{num}/@var{den}
2359
2360 @item s
2361 size of the input frame, expressed in the form
2362 @var{width}x@var{height}
2363
2364 @item i
2365 interlaced mode ("P" for "progressive", "T" for top field first, "B"
2366 for bottom field first)
2367
2368 @item iskey
2369 1 if the frame is a key frame, 0 otherwise
2370
2371 @item type
2372 picture type of the input frame ("I" for an I-frame, "P" for a
2373 P-frame, "B" for a B-frame, "?" for unknown type).
2374 Check also the documentation of the @code{AVPictureType} enum and of
2375 the @code{av_get_picture_type_char} function defined in
2376 @file{libavutil/avutil.h}.
2377
2378 @item checksum
2379 Adler-32 checksum of all the planes of the input frame
2380
2381 @item plane_checksum
2382 Adler-32 checksum of each plane of the input frame, expressed in the form
2383 "[@var{c0} @var{c1} @var{c2} @var{c3}]"
2384 @end table
2385
2386 @section split
2387
2388 Split input video into several identical outputs.
2389
2390 The filter accepts a single parameter which specifies the number of outputs. If
2391 unspecified, it defaults to 2.
2392
2393 For example
2394 @example
2395 avconv -i INPUT -filter_complex split=5 OUTPUT
2396 @end example
2397 will create 5 copies of the input video.
2398
2399 @section transpose
2400
2401 Transpose rows with columns in the input video and optionally flip it.
2402
2403 This filter accepts the following options:
2404
2405 @table @option
2406
2407 @item dir
2408 The direction of the transpose.
2409
2410 @end table
2411
2412 The direction can assume the following values:
2413
2414 @table @samp
2415 @item cclock_flip
2416 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
2417 @example
2418 L.R L.l
2419 . . -> . .
2420 l.r R.r
2421 @end example
2422
2423 @item clock
2424 Rotate by 90 degrees clockwise, that is:
2425 @example
2426 L.R l.L
2427 . . -> . .
2428 l.r r.R
2429 @end example
2430
2431 @item cclock
2432 Rotate by 90 degrees counterclockwise, that is:
2433 @example
2434 L.R R.r
2435 . . -> . .
2436 l.r L.l
2437 @end example
2438
2439 @item clock_flip
2440 Rotate by 90 degrees clockwise and vertically flip, that is:
2441 @example
2442 L.R r.R
2443 . . -> . .
2444 l.r l.L
2445 @end example
2446 @end table
2447
2448 @section trim
2449 Trim the input so that the output contains one continuous subpart of the input.
2450
2451 This filter accepts the following options:
2452 @table @option
2453 @item start
2454 Timestamp (in seconds) of the start of the kept section. I.e. the frame with the
2455 timestamp @var{start} will be the first frame in the output.
2456
2457 @item end
2458 Timestamp (in seconds) of the first frame that will be dropped. I.e. the frame
2459 immediately preceding the one with the timestamp @var{end} will be the last
2460 frame in the output.
2461
2462 @item start_pts
2463 Same as @var{start}, except this option sets the start timestamp in timebase
2464 units instead of seconds.
2465
2466 @item end_pts
2467 Same as @var{end}, except this option sets the end timestamp in timebase units
2468 instead of seconds.
2469
2470 @item duration
2471 Maximum duration of the output in seconds.
2472
2473 @item start_frame
2474 Number of the first frame that should be passed to output.
2475
2476 @item end_frame
2477 Number of the first frame that should be dropped.
2478 @end table
2479
2480 Note that the first two sets of the start/end options and the @option{duration}
2481 option look at the frame timestamp, while the _frame variants simply count the
2482 frames that pass through the filter. Also note that this filter does not modify
2483 the timestamps. If you wish that the output timestamps start at zero, insert a
2484 setpts filter after the trim filter.
2485
2486 If multiple start or end options are set, this filter tries to be greedy and
2487 keep all the frames that match at least one of the specified constraints. To keep
2488 only the part that matches all the constraints at once, chain multiple trim
2489 filters.
2490
2491 The defaults are such that all the input is kept. So it is possible to set e.g.
2492 just the end values to keep everything before the specified time.
2493
2494 Examples:
2495 @itemize
2496 @item
2497 drop everything except the second minute of input
2498 @example
2499 avconv -i INPUT -vf trim=60:120
2500 @end example
2501
2502 @item
2503 keep only the first second
2504 @example
2505 avconv -i INPUT -vf trim=duration=1
2506 @end example
2507
2508 @end itemize
2509 @section unsharp
2510
2511 Sharpen or blur the input video.
2512
2513 It accepts the following parameters:
2514
2515 @table @option
2516
2517 @item luma_msize_x
2518 Set the luma matrix horizontal size. It can be an integer between 3
2519 and 13, default value is 5.
2520
2521 @item luma_msize_y
2522 Set the luma matrix vertical size. It can be an integer between 3
2523 and 13, default value is 5.
2524
2525 @item luma_amount
2526 Set the luma effect strength. It can be a float number between -2.0
2527 and 5.0, default value is 1.0.
2528
2529 @item chroma_msize_x
2530 Set the chroma matrix horizontal size. It can be an integer between 3
2531 and 13, default value is 5.
2532
2533 @item chroma_msize_y
2534 Set the chroma matrix vertical size. It can be an integer between 3
2535 and 13, default value is 5.
2536
2537 @item chroma_amount
2538 Set the chroma effect strength. It can be a float number between -2.0
2539 and 5.0, default value is 0.0.
2540
2541 @end table
2542
2543 Negative values for the amount will blur the input video, while positive
2544 values will sharpen. All parameters are optional and default to the
2545 equivalent of the string '5:5:1.0:5:5:0.0'.
2546
2547 @example
2548 # Strong luma sharpen effect parameters
2549 unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5
2550
2551 # Strong blur of both luma and chroma parameters
2552 unsharp=7:7:-2:7:7:-2
2553
2554 # Use the default values with @command{avconv}
2555 ./avconv -i in.avi -vf "unsharp" out.mp4
2556 @end example
2557
2558 @section vflip
2559
2560 Flip the input video vertically.
2561
2562 @example
2563 ./avconv -i in.avi -vf "vflip" out.avi
2564 @end example
2565
2566 @section yadif
2567
2568 Deinterlace the input video ("yadif" means "yet another deinterlacing
2569 filter").
2570
2571 This filter accepts the following options:
2572
2573 @table @option
2574
2575 @item mode
2576 The interlacing mode to adopt, accepts one of the following values:
2577
2578 @table @option
2579 @item 0
2580 output 1 frame for each frame
2581 @item 1
2582 output 1 frame for each field
2583 @item 2
2584 like 0 but skips spatial interlacing check
2585 @item 3
2586 like 1 but skips spatial interlacing check
2587 @end table
2588
2589 Default value is 0.
2590
2591 @item parity
2592 The picture field parity assumed for the input interlaced video, accepts one of
2593 the following values:
2594
2595 @table @option
2596 @item 0
2597 assume top field first
2598 @item 1
2599 assume bottom field first
2600 @item -1
2601 enable automatic detection
2602 @end table
2603
2604 Default value is -1.
2605 If interlacing is unknown or decoder does not export this information,
2606 top field first will be assumed.
2607
2608 @item auto
2609 Whether deinterlacer should trust the interlaced flag and only deinterlace
2610 frames marked as interlaced
2611
2612 @table @option
2613 @item 0
2614 deinterlace all frames
2615 @item 1
2616 only deinterlace frames marked as interlaced
2617 @end table
2618
2619 Default value is 0.
2620
2621 @end table
2622
2623 @c man end VIDEO FILTERS
2624
2625 @chapter Video Sources
2626 @c man begin VIDEO SOURCES
2627
2628 Below is a description of the currently available video sources.
2629
2630 @section buffer
2631
2632 Buffer video frames, and make them available to the filter chain.
2633
2634 This source is mainly intended for a programmatic use, in particular
2635 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
2636
2637 This filter accepts the following parameters:
2638
2639 @table @option
2640
2641 @item width
2642 Input video width.
2643
2644 @item height
2645 Input video height.
2646
2647 @item pix_fmt
2648 Name of the input video pixel format.
2649
2650 @item time_base
2651 The time base used for input timestamps.
2652
2653 @item sar
2654 Sample (pixel) aspect ratio of the input video.
2655
2656 @end table
2657
2658 For example:
2659 @example
2660 buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1
2661 @end example
2662
2663 will instruct the source to accept video frames with size 320x240 and
2664 with format "yuv410p", assuming 1/24 as the timestamps timebase and
2665 square pixels (1:1 sample aspect ratio).
2666
2667 @section color
2668
2669 Provide an uniformly colored input.
2670
2671 It accepts the following parameters:
2672
2673 @table @option
2674
2675 @item color
2676 Specify the color of the source. It can be the name of a color (case
2677 insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
2678 alpha specifier. The default value is "black".
2679
2680 @item size
2681 Specify the size of the sourced video, it may be a string of the form
2682 @var{width}x@var{height}, or the name of a size abbreviation. The
2683 default value is "320x240".
2684
2685 @item framerate
2686 Specify the frame rate of the sourced video, as the number of frames
2687 generated per second. It has to be a string in the format
2688 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
2689 number or a valid video frame rate abbreviation. The default value is
2690 "25".
2691
2692 @end table
2693
2694 For example the following graph description will generate a red source
2695 with an opacity of 0.2, with size "qcif" and a frame rate of 10
2696 frames per second, which will be overlayed over the source connected
2697 to the pad with identifier "in".
2698
2699 @example
2700 "color=red@@0.2:qcif:10 [color]; [in][color] overlay [out]"
2701 @end example
2702
2703 @section movie
2704
2705 Read a video stream from a movie container.
2706
2707 Note that this source is a hack that bypasses the standard input path. It can be
2708 useful in applications that do not support arbitrary filter graphs, but its use
2709 is discouraged in those that do. Specifically in @command{avconv} this filter
2710 should never be used, the @option{-filter_complex} option fully replaces it.
2711
2712 This filter accepts the following options:
2713
2714 @table @option
2715
2716 @item filename
2717 The name of the resource to read (not necessarily a file but also a device or a
2718 stream accessed through some protocol).
2719
2720 @item format_name, f
2721 Specifies the format assumed for the movie to read, and can be either
2722 the name of a container or an input device. If not specified the
2723 format is guessed from @var{movie_name} or by probing.
2724
2725 @item seek_point, sp
2726 Specifies the seek point in seconds, the frames will be output
2727 starting from this seek point, the parameter is evaluated with
2728 @code{av_strtod} so the numerical value may be suffixed by an IS
2729 postfix. Default value is "0".
2730
2731 @item stream_index, si
2732 Specifies the index of the video stream to read. If the value is -1,
2733 the best suited video stream will be automatically selected. Default
2734 value is "-1".
2735
2736 @end table
2737
2738 This filter allows to overlay a second video on top of main input of
2739 a filtergraph as shown in this graph:
2740 @example
2741 input -----------> deltapts0 --> overlay --> output
2742 ^
2743 |
2744 movie --> scale--> deltapts1 -------+
2745 @end example
2746
2747 Some examples follow:
2748 @example
2749 # skip 3.2 seconds from the start of the avi file in.avi, and overlay it
2750 # on top of the input labelled as "in".
2751 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
2752 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
2753
2754 # read from a video4linux2 device, and overlay it on top of the input
2755 # labelled as "in"
2756 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
2757 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
2758
2759 @end example
2760
2761 @section nullsrc
2762
2763 Null video source, never return images. It is mainly useful as a
2764 template and to be employed in analysis / debugging tools.
2765
2766 It accepts as optional parameter a string of the form
2767 @var{width}:@var{height}:@var{timebase}.
2768
2769 @var{width} and @var{height} specify the size of the configured
2770 source. The default values of @var{width} and @var{height} are
2771 respectively 352 and 288 (corresponding to the CIF size format).
2772
2773 @var{timebase} specifies an arithmetic expression representing a
2774 timebase. The expression can contain the constants "PI", "E", "PHI",
2775 "AVTB" (the default timebase), and defaults to the value "AVTB".
2776
2777 @section frei0r_src
2778
2779 Provide a frei0r source.
2780
2781 To enable compilation of this filter you need to install the frei0r
2782 header and configure Libav with --enable-frei0r.
2783
2784 This source accepts the following options:
2785
2786 @table @option
2787
2788 @item size
2789 The size of the video to generate, may be a string of the form
2790 @var{width}x@var{height} or a frame size abbreviation.
2791
2792 @item framerate
2793 Framerate of the generated video, may be a string of the form
2794 @var{num}/@var{den} or a frame rate abbreviation.
2795
2796 @item filter_name
2797 The name to the frei0r source to load. For more information regarding frei0r and
2798 how to set the parameters read the section @ref{frei0r} in the description of
2799 the video filters.
2800
2801 @item filter_params
2802 A '|'-separated list of parameters to pass to the frei0r source.
2803
2804 @end table
2805
2806 Some examples follow:
2807 @example
2808 # generate a frei0r partik0l source with size 200x200 and framerate 10
2809 # which is overlayed on the overlay filter main input
2810 frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay
2811 @end example
2812
2813 @section rgbtestsrc, testsrc
2814
2815 The @code{rgbtestsrc} source generates an RGB test pattern useful for
2816 detecting RGB vs BGR issues. You should see a red, green and blue
2817 stripe from top to bottom.
2818
2819 The @code{testsrc} source generates a test video pattern, showing a
2820 color pattern, a scrolling gradient and a timestamp. This is mainly
2821 intended for testing purposes.
2822
2823 The sources accept the following options:
2824
2825 @table @option
2826
2827 @item size, s
2828 Specify the size of the sourced video, it may be a string of the form
2829 @var{width}x@var{height}, or the name of a size abbreviation. The
2830 default value is "320x240".
2831
2832 @item rate, r
2833 Specify the frame rate of the sourced video, as the number of frames
2834 generated per second. It has to be a string in the format
2835 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
2836 number or a valid video frame rate abbreviation. The default value is
2837 "25".
2838
2839 @item sar
2840 Set the sample aspect ratio of the sourced video.
2841
2842 @item duration
2843 Set the video duration of the sourced video. The accepted syntax is:
2844 @example
2845 [-]HH[:MM[:SS[.m...]]]
2846 [-]S+[.m...]
2847 @end example
2848 See also the function @code{av_parse_time()}.
2849
2850 If not specified, or the expressed duration is negative, the video is
2851 supposed to be generated forever.
2852 @end table
2853
2854 For example the following:
2855 @example
2856 testsrc=duration=5.3:size=qcif:rate=10
2857 @end example
2858
2859 will generate a video with a duration of 5.3 seconds, with size
2860 176x144 and a framerate of 10 frames per second.
2861
2862 @c man end VIDEO SOURCES
2863
2864 @chapter Video Sinks
2865 @c man begin VIDEO SINKS
2866
2867 Below is a description of the currently available video sinks.
2868
2869 @section buffersink
2870
2871 Buffer video frames, and make them available to the end of the filter
2872 graph.
2873
2874 This sink is intended for a programmatic use through the interface defined in
2875 @file{libavfilter/buffersink.h}.
2876
2877 @section nullsink
2878
2879 Null video sink, do absolutely nothing with the input video. It is
2880 mainly useful as a template and to be employed in analysis / debugging
2881 tools.
2882
2883 @c man end VIDEO SINKS