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 AVCODEC_CBS_H
20 #define AVCODEC_CBS_H
21
22 #include <stddef.h>
23 #include <stdint.h>
24
26
31
32
33 /*
34 * This defines a framework for converting between a coded bitstream
35 * and structures defining all individual syntax elements found in
36 * such a stream.
37 *
38 * Conversion in both directions is possible. Given a coded bitstream
39 * (any meaningful fragment), it can be parsed and decomposed into
40 * syntax elements stored in a set of codec-specific structures.
41 * Similarly, given a set of those same codec-specific structures the
42 * syntax elements can be serialised and combined to create a coded
43 * bitstream.
44 */
45
48
49 /**
50 * The codec-specific type of a bitstream unit.
51 *
52 * AV1: obu_type
53 * H.264 / AVC: nal_unit_type
54 * H.265 / HEVC: nal_unit_type
55 * JPEG: marker value (without 0xff prefix)
56 * MPEG-2: start code value (without prefix)
57 * VP9: unused, set to zero (every unit is a frame)
58 */
60
61 /**
62 * Coded bitstream unit structure.
63 *
64 * A bitstream unit the smallest element of a bitstream which
65 * is meaningful on its own. For example, an H.264 NAL unit.
66 *
67 * See the codec-specific header for the meaning of this for any
68 * particular codec.
69 */
71 /**
72 * Codec-specific type of this unit.
73 */
75
76 /**
77 * Pointer to the directly-parsable bitstream form of this unit.
78 *
79 * May be NULL if the unit currently only exists in decomposed form.
80 */
82 /**
83 * The number of bytes in the bitstream (including any padding bits
84 * in the final byte).
85 */
87 /**
88 * The number of bits which should be ignored in the final byte.
89 *
90 * This supports non-byte-aligned bitstreams.
91 */
93 /**
94 * A reference to the buffer containing data.
95 *
96 * Must be set if data is not NULL.
97 */
99
100 /**
101 * Pointer to the decomposed form of this unit.
102 *
103 * The type of this structure depends on both the codec and the
104 * type of this unit. May be NULL if the unit only exists in
105 * bitstream form.
106 */
108 /**
109 * If content is reference counted, a RefStruct reference backing content.
110 * NULL if content is not reference counted.
111 */
114
115 /**
116 * Coded bitstream fragment structure, combining one or more units.
117 *
118 * This is any sequence of units. It need not form some greater whole,
119 * though in many cases it will. For example, an H.264 access unit,
120 * which is composed of a sequence of H.264 NAL units.
121 */
123 /**
124 * Pointer to the bitstream form of this fragment.
125 *
126 * May be NULL if the fragment only exists as component units.
127 */
129 /**
130 * The number of bytes in the bitstream.
131 *
132 * The number of bytes in the bitstream (including any padding bits
133 * in the final byte).
134 */
136 /**
137 * The number of bits which should be ignored in the final byte.
138 */
140 /**
141 * A reference to the buffer containing data.
142 *
143 * Must be set if data is not NULL.
144 */
146
147 /**
148 * Number of units in this fragment.
149 *
150 * This may be zero if the fragment only exists in bitstream form
151 * and has not been decomposed.
152 */
154
155 /**
156 * Number of allocated units.
157 *
158 * Must always be >= nb_units; designed for internal use by cbs.
159 */
161
162 /**
163 * Pointer to an array of units of length nb_units_allocated.
164 * Only the first nb_units are valid.
165 *
166 * Must be NULL if nb_units_allocated is zero.
167 */
170
171
175
176 /**
177 * Callback type for read tracing.
178 *
179 * @param ctx User-set trace context.
180 * @param gbc A GetBitContext set at the start of the syntax
181 * element. This is a copy, the callee does not
182 * need to preserve it.
183 * @param length Length in bits of the syntax element.
184 * @param name String name of the syntax elements.
185 * @param subscripts If the syntax element is an array, a pointer to
186 * an array of subscripts into the array.
187 * @param value Parsed value of the syntax element.
188 */
191 int start_position,
193 const int *subscripts,
195
196 /**
197 * Callback type for write tracing.
198 *
199 * @param ctx User-set trace context.
200 * @param pbc A PutBitContext set at the end of the syntax
201 * element. The user must not modify this, but may
202 * inspect it to determine state.
203 * @param length Length in bits of the syntax element.
204 * @param name String name of the syntax elements.
205 * @param subscripts If the syntax element is an array, a pointer to
206 * an array of subscripts into the array.
207 * @param value Written value of the syntax element.
208 */
211 int start_position,
213 const int *subscripts,
215
216 /**
217 * Context structure for coded bitstream operations.
218 */
220 /**
221 * Logging context to be passed to all av_log() calls associated
222 * with this context.
223 */
225
226 /**
227 * Internal codec-specific hooks.
228 */
230
231 /**
232 * Internal codec-specific data.
233 *
234 * This contains any information needed when reading/writing
235 * bitsteams which will not necessarily be present in a fragment.
236 * For example, for H.264 it contains all currently visible
237 * parameter sets - they are required to determine the bitstream
238 * syntax but need not be present in every access unit.
239 */
241
242 /**
243 * Array of unit types which should be decomposed when reading.
244 *
245 * Types not in this list will be available in bitstream form only.
246 * If NULL, all supported types will be decomposed.
247 */
249 /**
250 * Length of the decompose_unit_types array.
251 */
253
254 /**
255 * Enable trace output during read/write operations.
256 */
258 /**
259 * Log level to use for default trace output.
260 *
261 * From AV_LOG_*; defaults to AV_LOG_TRACE.
262 */
264 /**
265 * User context pointer to pass to trace callbacks.
266 */
268 /**
269 * Callback for read tracing.
270 *
271 * If tracing is enabled then this is called once for each syntax
272 * element parsed.
273 */
275 /**
276 * Callback for write tracing.
277 *
278 * If tracing is enabled then this is called once for each syntax
279 * element written.
280 */
282
283 /**
284 * Write buffer. Used as intermediate buffer when writing units.
285 * For internal use of cbs only.
286 */
290
291
292 /**
293 * Table of all supported codec IDs.
294 *
295 * Terminated by AV_CODEC_ID_NONE.
296 */
298
299
300 /**
301 * Create and initialise a new context for the given codec.
302 */
305
306 /**
307 * Reset all internal state in a context.
308 */
310
311 /**
312 * Close a context and free all internal state.
313 */
315
316
317 /**
318 * Read the extradata bitstream found in codec parameters into a
319 * fragment, then split into units and decompose.
320 *
321 * This also updates the internal state, so will need to be called for
322 * codecs with extradata to read parameter sets necessary for further
323 * parsing even if the fragment itself is not desired.
324 *
325 * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
326 * before use.
327 */
331
332 /**
333 * Read the extradata bitstream found in a codec context into a
334 * fragment, then split into units and decompose.
335 *
336 * This acts identical to ff_cbs_read_extradata() for the case where
337 * you already have a codec context.
338 */
342
346
347 /**
348 * Read the data bitstream from a packet into a fragment, then
349 * split into units and decompose.
350 *
351 * This also updates the internal state of the coded bitstream context
352 * with any persistent data from the fragment which may be required to
353 * read following fragments (e.g. parameter sets).
354 *
355 * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
356 * before use.
357 */
361
362 /**
363 * Read a bitstream from a memory region into a fragment, then
364 * split into units and decompose.
365 *
366 * This also updates the internal state of the coded bitstream context
367 * with any persistent data from the fragment which may be required to
368 * read following fragments (e.g. parameter sets).
369 *
370 * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
371 * before use.
372 */
376
377
378 /**
379 * Write the content of the fragment to its own internal buffer.
380 *
381 * Writes the content of all units and then assembles them into a new
382 * data buffer. When modifying the content of decomposed units, this
383 * can be used to regenerate the bitstream form of units or the whole
384 * fragment so that it can be extracted for other use.
385 *
386 * This also updates the internal state of the coded bitstream context
387 * with any persistent data from the fragment which may be required to
388 * write following fragments (e.g. parameter sets).
389 */
392
393 /**
394 * Write the bitstream of a fragment to the extradata in codec parameters.
395 *
396 * Modifies context and fragment as ff_cbs_write_fragment_data does and
397 * replaces any existing extradata in the structure.
398 */
402
403 /**
404 * Write the bitstream of a fragment to a packet.
405 *
406 * Modifies context and fragment as ff_cbs_write_fragment_data does.
407 *
408 * On success, the packet's buf is unreferenced and its buf, data and
409 * size fields are set to the corresponding values from the newly updated
410 * fragment; other fields are not touched. On failure, the packet is not
411 * touched at all.
412 */
416
417
418 /**
419 * Free the units contained in a fragment as well as the fragment's
420 * own data buffer, but not the units array itself.
421 */
423
424 /**
425 * Free the units array of a fragment in addition to what
426 * ff_cbs_fragment_reset does.
427 */
429
430 /**
431 * Allocate a new internal content buffer matching the type of the unit.
432 *
433 * The content will be zeroed.
434 */
437
438 /**
439 * Insert a new unit into a fragment with the given content.
440 *
441 * If content_ref is supplied, it has to be a RefStruct reference
442 * backing content; the user keeps ownership of the supplied reference.
443 * The content structure continues to be owned by the caller if
444 * content_ref is not supplied.
445 */
447 int position,
449 void *content,
450 void *content_ref);
451
452 /**
453 * Add a new unit to a fragment with the given data bitstream.
454 *
455 * If data_buf is not supplied then data must have been allocated with
456 * av_malloc() and will on success become owned by the unit after this
457 * call or freed on error.
458 */
461 uint8_t *
data,
size_t data_size,
463
464 /**
465 * Delete a unit from a fragment and free all memory it uses.
466 *
467 * Requires position to be >= 0 and < frag->nb_units.
468 */
470 int position);
471
472
473 /**
474 * Make the content of a unit refcounted.
475 *
476 * If the unit is not refcounted, this will do a deep copy of the unit
477 * content to new refcounted buffers.
478 *
479 * It is not valid to call this function on a unit which does not have
480 * decomposed content.
481 */
484
485 /**
486 * Make the content of a unit writable so that internal fields can be
487 * modified.
488 *
489 * If it is known that there are no other references to the content of
490 * the unit, does nothing and returns success. Otherwise (including the
491 * case where the unit content is not refcounted), it does a full clone
492 * of the content (including any internal buffers) to make a new copy,
493 * and replaces the existing references inside the unit with that.
494 *
495 * It is not valid to call this function on a unit which does not have
496 * decomposed content.
497 */
500
503
504 /**
505 * keep non-vcl units even if the picture has been dropped.
506 */
508 };
509
510 /**
511 * Discard units accroding to 'skip'.
512 */
517
518
519 /**
520 * Helper function for read tracing which formats the syntax element
521 * and logs the result.
522 *
523 * Trace context should be set to the CodedBitstreamContext.
524 */
527 const char *str, const int *subscripts,
529
530 /**
531 * Helper function for write tracing which formats the syntax element
532 * and logs the result.
533 *
534 * Trace context should be set to the CodedBitstreamContext.
535 */
538 const char *str, const int *subscripts,
540
541 #endif /* AVCODEC_CBS_H */