1 /*
2 * This file is part of FFmpeg.
3 *
4 * FFmpeg is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * FFmpeg is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with FFmpeg; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18
19 #ifndef AVFILTER_FORMATS_H
20 #define AVFILTER_FORMATS_H
21
23
24 /**
25 * A list of supported formats for one end of a filter link. This is used
26 * during the format negotiation process to try to pick the best format to
27 * use to minimize the number of necessary conversions. Each filter gives a
28 * list of the formats supported by each input and output pad. The list
29 * given for each pad need not be distinct - they may be references to the
30 * same list of formats, as is often the case when a filter supports multiple
31 * formats, but will always output the same format as it is given in input.
32 *
33 * In this way, a list of possible input formats and a list of possible
34 * output formats are associated with each link. When a set of formats is
35 * negotiated over a link, the input and output lists are merged to form a
36 * new list containing only the common elements of each list. In the case
37 * that there were no common elements, a format conversion is necessary.
38 * Otherwise, the lists are merged, and all other links which reference
39 * either of the format lists involved in the merge are also affected.
40 *
41 * For example, consider the filter chain:
42 * filter (a) --> (b) filter (b) --> (c) filter
43 *
44 * where the letters in parenthesis indicate a list of formats supported on
45 * the input or output of the link. Suppose the lists are as follows:
46 * (a) = {A, B}
47 * (b) = {A, B, C}
48 * (c) = {B, C}
49 *
50 * First, the first link's lists are merged, yielding:
51 * filter (a) --> (a) filter (a) --> (c) filter
52 *
53 * Notice that format list (b) now refers to the same list as filter list (a).
54 * Next, the lists for the second link are merged, yielding:
55 * filter (a) --> (a) filter (a) --> (a) filter
56 *
57 * where (a) = {B}.
58 *
59 * Unfortunately, when the format lists at the two ends of a link are merged,
60 * we must ensure that all links which reference either pre-merge format list
61 * get updated as well. Therefore, we have the format list structure store a
62 * pointer to each of the pointers to itself.
63 */
67
68 unsigned refcount;
///< number of references to this list
70 };
71
72 /**
73 * A list of supported channel layouts.
74 *
75 * The list works the same as AVFilterFormats, except for the following
76 * differences:
77 * - A list with all_layouts = 1 means all channel layouts with a known
78 * disposition; nb_channel_layouts must then be 0.
79 * - A list with all_counts = 1 means all channel counts, with a known or
80 * unknown disposition; nb_channel_layouts must then be 0 and all_layouts 1.
81 * - The list must not contain a layout with a known disposition and a
82 * channel count with unknown disposition with the same number of channels
83 * (e.g. AV_CH_LAYOUT_STEREO and FF_COUNT2LAYOUT(2).
84 */
90
91 unsigned refcount;
///< number of references to this list
93 };
94
95 /**
96 * Encode a channel count as a channel layout.
97 * FF_COUNT2LAYOUT(c) means any channel layout with c channels, with a known
98 * or unknown disposition.
99 * The result is only valid inside AVFilterChannelLayouts and immediately
100 * related functions.
101 */
102 #define FF_COUNT2LAYOUT(c) ((AVChannelLayout) { .order = AV_CHANNEL_ORDER_UNSPEC, .nb_channels = c })
103
104 /**
105 * Decode a channel count encoded as a channel layout.
106 * Return 0 if the channel layout was a real one.
107 */
108 #define FF_LAYOUT2COUNT(l) (((l)->order == AV_CHANNEL_ORDER_UNSPEC) ? \
109 (l)->nb_channels : 0)
110
111 #define KNOWN(l) (!FF_LAYOUT2COUNT(l)) /* for readability */
112
113 /**
114 * Construct an empty AVFilterChannelLayouts/AVFilterFormats struct --
115 * representing any channel layout (with known disposition)/sample rate.
116 */
119
122
123 /**
124 * Construct an AVFilterChannelLayouts coding for any channel layout, with
125 * known or unknown disposition.
126 */
129
132
133 /**
134 * Construct an AVFilterFormats representing all possible color spaces.
135 *
136 * Note: This list does not include AVCOL_SPC_RESERVED.
137 */
140
141 /**
142 * Construct an AVFilterFormats representing all possible color ranges.
143 */
146
147 /**
148 * Construct an AVFilterFormats representing all possible alpha modes.
149 */
152
153 /**
154 * Helpers for query_formats() which set all free audio links to the same list
155 * of channel layouts/sample rates. If there are no links hooked to this list,
156 * the list is freed.
157 */
161 /**
162 * Equivalent to ff_set_common_channel_layouts(ctx, ff_make_channel_layout_list(fmts))
163 */
167 /**
168 * Equivalent to ff_set_common_channel_layouts(ctx, ff_all_channel_counts())
169 */
172
176 /**
177 * Equivalent to ff_set_common_samplerates(ctx, ff_make_format_list(samplerates))
178 */
181 const int *samplerates);
182 /**
183 * Equivalent to ff_set_common_samplerates(ctx, ff_all_samplerates())
184 */
187
191 /**
192 * Equivalent to ff_set_common_color_spaces(ctx, ff_make_format_list(color_spaces))
193 */
196 const int *color_spaces);
197
198 /**
199 * Equivalent to ff_set_common_color_spaces(ctx, ff_all_color_spaces())
200 */
203
207 /**
208 * Equivalent to ff_set_common_color_ranges(ctx, ff_make_format_list(color_ranges))
209 */
212 const int *color_ranges);
213
214 /**
215 * Equivalent to ff_set_common_color_ranges(ctx, ff_all_color_ranges())
216 */
219
223 /**
224 * Equivalent to ff_set_common_alpha_modes(ctx, ff_make_format_list(alpha_modes))
225 */
228 const int *alpha_modes);
229
230 /**
231 * Equivalent to ff_set_common_alpha_modes(ctx, ff_all_alpha_modes())
232 */
235
236
237 /**
238 * A helper for query_formats() which sets all links to the same list of
239 * formats. If there are no links hooked to this filter, the list of formats is
240 * freed.
241 */
244
245 /**
246 * Equivalent to ff_set_common_formats(ctx, ff_make_format_list(fmts))
247 */
250
251 /**
252 * Helpers for query_formats2() which set all free audio links to the same list
253 * of channel layouts/sample rates. If there are no links hooked to this list,
254 * the list is freed.
255 */
261
271
277
282 const int *samplerates);
283
288
294
299 const int *color_spaces);
300
305
311
316 const int *color_ranges);
317
322
328
333 const int *alpha_modes);
334
339
345
350 const int *fmts);
351
355
356 /**
357 * Add *ref as a new reference to f.
358 */
362
363 /**
364 * Remove a reference to a channel layouts list.
365 */
367
370
371 /**
372 * Sets all remaining unset filter lists for all inputs/outputs to their
373 * corresponding `ff_all_*()` lists.
374 */
377
378 /**
379 * Create a list of supported formats. This is intended for use in
380 * AVFilter->query_formats().
381 *
382 * @param fmts list of media formats, terminated by -1
383 * @return the format list, with no existing references
384 */
387
388 /**
389 * Equivalent to ff_make_format_list({const int[]}{ fmt, -1 })
390 */
393
394 /**
395 * Add fmt to the list of media formats contained in *avff.
396 * If *avff is NULL the function allocates the filter formats struct
397 * and puts its pointer in *avff.
398 *
399 * @return a non negative value in case of success, or a negative
400 * value corresponding to an AVERROR code in case of error
401 */
404
405 /**
406 * Return a list of all formats supported by FFmpeg for the given media type.
407 */
410
411 /**
412 * Construct a formats list containing all pixel formats with certain
413 * properties
414 */
417
418 //* format is software, non-planar with sub-sampling
419 #define FF_PIX_FMT_FLAG_SW_FLAT_SUB (1 << 24)
420
421 /**
422 * Construct a formats list containing all planar sample formats.
423 */
426
427 /**
428 * Add *ref as a new reference to formats.
429 * That is the pointers will point like in the ascii art below:
430 * ________
431 * |formats |<--------.
432 * | ____ | ____|___________________
433 * | |refs| | | __|_
434 * | |* * | | | | | | AVFilterLink
435 * | |* *--------->|*ref|
436 * | |____| | | |____|
437 * |________| |________________________
438 */
441
442 /**
443 * If *ref is non-NULL, remove *ref as a reference to the format list
444 * it currently points to, deallocates that list if this was the last
445 * reference, and sets *ref to NULL.
446 *
447 * Before After
448 * ________ ________ NULL
449 * |formats |<--------. |formats | ^
450 * | ____ | ____|________________ | ____ | ____|________________
451 * | |refs| | | __|_ | |refs| | | __|_
452 * | |* * | | | | | | AVFilterLink | |* * | | | | | | AVFilterLink
453 * | |* *--------->|*ref| | |* | | | |*ref|
454 * | |____| | | |____| | |____| | | |____|
455 * |________| |_____________________ |________| |_____________________
456 */
458
459 /**
460 * Before After
461 * ________ ________
462 * |formats |<---------. |formats |<---------.
463 * | ____ | ___|___ | ____ | ___|___
464 * | |refs| | | | | | |refs| | | | | NULL
465 * | |* *--------->|*oldref| | |* *--------->|*newref| ^
466 * | |* * | | |_______| | |* * | | |_______| ___|___
467 * | |____| | | |____| | | | |
468 * |________| |________| |*oldref|
469 * |_______|
470 */
472
473 /**
474 * Check that fmts is a valid pixel formats list.
475 *
476 * In particular, check for duplicates.
477 */
479
480 /**
481 * Check that fmts is a valid sample formats list.
482 *
483 * In particular, check for duplicates.
484 */
486
487 /**
488 * Check that fmts is a valid sample rates list.
489 *
490 * In particular, check for duplicates.
491 */
493
494 /**
495 * Check that fmts is a valid channel layouts list.
496 *
497 * In particular, check for duplicates.
498 */
500
501 /**
502 * Check that fmts is a valid formats list for YUV colorspace metadata.
503 *
504 * In particular, check for duplicates.
505 */
508
509 /**
510 * Check that fmts is a valid formats list for alpha modes.
511 *
512 * In particular, check for duplicates.
513 */
515
522 } AVFilterFormatsMerger;
523
524 /**
525 * Callbacks and properties to describe the steps of a format negotiation.
526 *
527 * The steps are:
528 *
529 * 1. query_formats(): call the callbacks on all filter to set lists of
530 * supported formats.
531 * When links on a filter must eventually have the same
532 * format, the lists of supported formats are the same
533 * object in memory.
534 * See:
535 * http://www.normalesup.org/~george/articles/format_negotiation_in_libavfilter/#12
536 *
537 *
538 * 2. query_formats(): merge lists of supported formats or insert automatic
539 * conversion filters.
540 * Compute the intersection of the lists of supported
541 * formats on the ends of links. If it succeeds, replace
542 * both objects with the intersection everywhere they
543 * are referenced.
544 * If the intersection is empty, insert an automatic
545 * conversion filter.
546 * If several formats are negotiated at once (format,
547 * rate, layout), only merge if all three can be, since
548 * the conversion filter can convert all three at once.
549 * This process goes on as long as progress is made.
550 * See:
551 * http://www.normalesup.org/~george/articles/format_negotiation_in_libavfilter/#14
552 * http://www.normalesup.org/~george/articles/format_negotiation_in_libavfilter/#29
553 *
554 * 3. reduce_formats(): try to reduce format conversion within filters.
555 * For each link where there is only one supported
556 * formats on output, for each output of the connected
557 * filter, if the media type is the same and said
558 * format is supported, keep only this one.
559 * This process goes on as long as progress is made.
560 * Rationale: conversion filters will set a large list
561 * of supported formats on outputs but users will
562 * expect the output to be as close as possible as the
563 * input (examples: scale without changing the pixel
564 * format, resample without changint the layout).
565 * FIXME: this can probably be done by merging the
566 * input and output lists instead of re-implementing
567 * the logic.
568 *
569 * 4. swap_sample_fmts():
570 * swap_samplerates():
571 * swap_channel_layouts(): For each filter with an input with only one
572 * supported format, when outputs have several
573 * supported formats, put the best one with
574 * reference to the input at the beginning of the
575 * list, to prepare it for being picked up by
576 * pick_formats().
577 * The best format is the one that is most
578 * similar to the input while not losing too much
579 * information.
580 * This process need to run only once.
581 * FIXME: reduce_formats() operates on all inputs
582 * with a single format, swap_*() operates on the
583 * first one only: check if the difference makes
584 * sense.
585 * TODO: the swapping done for one filter can
586 * override the swapping done for another filter
587 * connected to the same list of formats, maybe
588 * it would be better to compute a total score
589 * for all connected filters and use the score to
590 * pick the format instead of just swapping.
591 * TODO: make the similarity logic available as
592 * public functions in libavutil.
593 *
594 * 5. pick_formats(): Choose one format from the lists of supported formats,
595 * use it for the link and reduce the list to a single
596 * element to force other filters connected to the same
597 * list to use it.
598 * First process all links where there is a single format
599 * and the output links of all filters with an input,
600 * trying to preserve similarity between input and
601 * outputs.
602 * Repeat as long as process is made.
603 * Then do a final run for the remaining filters.
604 * FIXME: the similarity logic (the ref argument to
605 * pick_format()) added in FFmpeg duplicates and
606 * overrides the swapping logic added in libav. Better
607 * merge them into a score system.
608 */
613
615
616 #endif /* AVFILTER_FORMATS_H */