2 * This file is part of FFmpeg.
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.
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.
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
25 #include "libavutil/buffer.h"
31 * This defines a framework for converting between a coded bitstream
32 * and structures defining all individual syntax elements found in
35 * Conversion in both directions is possible. Given a coded bitstream
36 * (any meaningful fragment), it can be parsed and decomposed into
37 * syntax elements stored in a set of codec-specific structures.
38 * Similarly, given a set of those same codec-specific structures the
39 * syntax elements can be serialised and combined to create a coded
43 struct CodedBitstreamType;
46 * The codec-specific type of a bitstream unit.
48 * H.264 / AVC: nal_unit_type
49 * H.265 / HEVC: nal_unit_type
50 * MPEG-2: start code value (without prefix)
51 * VP9: unused, set to zero (every unit is a frame)
53 typedef uint32_t CodedBitstreamUnitType;
56 * Coded bitstream unit structure.
58 * A bitstream unit the smallest element of a bitstream which
59 * is meaningful on its own. For example, an H.264 NAL unit.
61 * See the codec-specific header for the meaning of this for any
64 typedef struct CodedBitstreamUnit {
66 * Codec-specific type of this unit.
68 CodedBitstreamUnitType type;
71 * Pointer to the directly-parsable bitstream form of this unit.
73 * May be NULL if the unit currently only exists in decomposed form.
77 * The number of bytes in the bitstream (including any padding bits
82 * The number of bits which should be ignored in the final byte.
84 * This supports non-byte-aligned bitstreams.
86 size_t data_bit_padding;
88 * A reference to the buffer containing data.
90 * Must be set if data is not NULL.
92 AVBufferRef *data_ref;
95 * Pointer to the decomposed form of this unit.
97 * The type of this structure depends on both the codec and the
98 * type of this unit. May be NULL if the unit only exists in
103 * If content is reference counted, a reference to the buffer containing
104 * content. Null if content is not reference counted.
106 AVBufferRef *content_ref;
107 } CodedBitstreamUnit;
110 * Coded bitstream fragment structure, combining one or more units.
112 * This is any sequence of units. It need not form some greater whole,
113 * though in many cases it will. For example, an H.264 access unit,
114 * which is composed of a sequence of H.264 NAL units.
116 typedef struct CodedBitstreamFragment {
118 * Pointer to the bitstream form of this fragment.
120 * May be NULL if the fragment only exists as component units.
124 * The number of bytes in the bitstream.
126 * The number of bytes in the bitstream (including any padding bits
127 * in the final byte).
131 * The number of bits which should be ignored in the final byte.
133 size_t data_bit_padding;
135 * A reference to the buffer containing data.
137 * Must be set if data is not NULL.
139 AVBufferRef *data_ref;
142 * Number of units in this fragment.
144 * This may be zero if the fragment only exists in bitstream form
145 * and has not been decomposed.
149 * Pointer to an array of units of length nb_units.
151 * Must be NULL if nb_units is zero.
153 CodedBitstreamUnit *units;
154 } CodedBitstreamFragment;
157 * Context structure for coded bitstream operations.
159 typedef struct CodedBitstreamContext {
161 * Logging context to be passed to all av_log() calls associated
167 * Internal codec-specific hooks.
169 const struct CodedBitstreamType *codec;
172 * Internal codec-specific data.
174 * This contains any information needed when reading/writing
175 * bitsteams which will not necessarily be present in a fragment.
176 * For example, for H.264 it contains all currently visible
177 * parameter sets - they are required to determine the bitstream
178 * syntax but need not be present in every access unit.
183 * Array of unit types which should be decomposed when reading.
185 * Types not in this list will be available in bitstream form only.
186 * If NULL, all supported types will be decomposed.
188 CodedBitstreamUnitType *decompose_unit_types;
190 * Length of the decompose_unit_types array.
192 int nb_decompose_unit_types;
195 * Enable trace output during read/write operations.
199 * Log level to use for trace output.
201 * From AV_LOG_*; defaults to AV_LOG_TRACE.
204 } CodedBitstreamContext;
208 * Table of all supported codec IDs.
210 * Terminated by AV_CODEC_ID_NONE.
212 extern const enum AVCodecID ff_cbs_all_codec_ids[];
216 * Create and initialise a new context for the given codec.
218 int ff_cbs_init(CodedBitstreamContext **ctx,
219 enum AVCodecID codec_id, void *log_ctx);
222 * Close a context and free all internal state.
224 void ff_cbs_close(CodedBitstreamContext **ctx);
228 * Read the extradata bitstream found in codec parameters into a
229 * fragment, then split into units and decompose.
231 * This also updates the internal state, so will need to be called for
232 * codecs with extradata to read parameter sets necessary for further
233 * parsing even if the fragment itself is not desired.
235 int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
236 CodedBitstreamFragment *frag,
237 const AVCodecParameters *par);
240 * Read the data bitstream from a packet into a fragment, then
241 * split into units and decompose.
243 * This also updates the internal state of the coded bitstream context
244 * with any persistent data from the fragment which may be required to
245 * read following fragments (e.g. parameter sets).
247 int ff_cbs_read_packet(CodedBitstreamContext *ctx,
248 CodedBitstreamFragment *frag,
249 const AVPacket *pkt);
252 * Read a bitstream from a memory region into a fragment, then
253 * split into units and decompose.
255 * This also updates the internal state of the coded bitstream context
256 * with any persistent data from the fragment which may be required to
257 * read following fragments (e.g. parameter sets).
259 int ff_cbs_read(CodedBitstreamContext *ctx,
260 CodedBitstreamFragment *frag,
261 const uint8_t *data, size_t size);
265 * Write the content of the fragment to its own internal buffer.
267 * Writes the content of all units and then assembles them into a new
268 * data buffer. When modifying the content of decomposed units, this
269 * can be used to regenerate the bitstream form of units or the whole
270 * fragment so that it can be extracted for other use.
272 * This also updates the internal state of the coded bitstream context
273 * with any persistent data from the fragment which may be required to
274 * write following fragments (e.g. parameter sets).
276 int ff_cbs_write_fragment_data(CodedBitstreamContext *ctx,
277 CodedBitstreamFragment *frag);
280 * Write the bitstream of a fragment to the extradata in codec parameters.
282 * This replaces any existing extradata in the structure.
284 int ff_cbs_write_extradata(CodedBitstreamContext *ctx,
285 AVCodecParameters *par,
286 CodedBitstreamFragment *frag);
289 * Write the bitstream of a fragment to a packet.
291 int ff_cbs_write_packet(CodedBitstreamContext *ctx,
293 CodedBitstreamFragment *frag);
297 * Free all allocated memory in a fragment.
299 void ff_cbs_fragment_uninit(CodedBitstreamContext *ctx,
300 CodedBitstreamFragment *frag);
304 * Allocate a new internal content buffer of the given size in the unit.
306 * The content will be zeroed.
308 int ff_cbs_alloc_unit_content(CodedBitstreamContext *ctx,
309 CodedBitstreamUnit *unit,
311 void (*free)(void *unit, uint8_t *content));
314 * Allocate a new internal data buffer of the given size in the unit.
316 * The data buffer will have input padding.
318 int ff_cbs_alloc_unit_data(CodedBitstreamContext *ctx,
319 CodedBitstreamUnit *unit,
323 * Insert a new unit into a fragment with the given content.
325 * The content structure continues to be owned by the caller if
326 * content_buf is not supplied.
328 int ff_cbs_insert_unit_content(CodedBitstreamContext *ctx,
329 CodedBitstreamFragment *frag,
331 CodedBitstreamUnitType type,
333 AVBufferRef *content_buf);
336 * Insert a new unit into a fragment with the given data bitstream.
338 * If data_buf is not supplied then data must have been allocated with
339 * av_malloc() and will become owned by the unit after this call.
341 int ff_cbs_insert_unit_data(CodedBitstreamContext *ctx,
342 CodedBitstreamFragment *frag,
344 CodedBitstreamUnitType type,
345 uint8_t *data, size_t data_size,
346 AVBufferRef *data_buf);
349 * Delete a unit from a fragment and free all memory it uses.
351 int ff_cbs_delete_unit(CodedBitstreamContext *ctx,
352 CodedBitstreamFragment *frag,
356 #endif /* AVCODEC_CBS_H */