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