libavcodec/cbs.h

   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
  25 #include "libavutil/buffer.h"
  26
  27 #include "codec_id.h"
  28 #include "codec_par.h"
  29 #include "packet.h"
  30
  31
  32 /*
  33  * This defines a framework for converting between a coded bitstream
  34  * and structures defining all individual syntax elements found in
  35  * such a stream.
  36  *
  37  * Conversion in both directions is possible.  Given a coded bitstream
  38  * (any meaningful fragment), it can be parsed and decomposed into
  39  * syntax elements stored in a set of codec-specific structures.
  40  * Similarly, given a set of those same codec-specific structures the
  41  * syntax elements can be serialised and combined to create a coded
  42  * bitstream.
  43  */
  44
  45 struct AVCodecContext;
  46 struct CodedBitstreamType;
  47
  48 /**
  49  * The codec-specific type of a bitstream unit.
  50  *
  51  * AV1: obu_type
  52  * H.264 / AVC: nal_unit_type
  53  * H.265 / HEVC: nal_unit_type
  54  * JPEG: marker value (without 0xff prefix)
  55  * MPEG-2: start code value (without prefix)
  56  * VP9: unused, set to zero (every unit is a frame)
  57  */
  58 typedef uint32_t CodedBitstreamUnitType;
  59
  60 /**
  61  * Coded bitstream unit structure.
  62  *
  63  * A bitstream unit the smallest element of a bitstream which
  64  * is meaningful on its own.  For example, an H.264 NAL unit.
  65  *
  66  * See the codec-specific header for the meaning of this for any
  67  * particular codec.
  68  */
  69 typedef struct CodedBitstreamUnit {
  70     /**
  71      * Codec-specific type of this unit.
  72      */
  73     CodedBitstreamUnitType type;
  74
  75     /**
  76      * Pointer to the directly-parsable bitstream form of this unit.
  77      *
  78      * May be NULL if the unit currently only exists in decomposed form.
  79      */
  80     uint8_t *data;
  81     /**
  82      * The number of bytes in the bitstream (including any padding bits
  83      * in the final byte).
  84      */
  85     size_t   data_size;
  86     /**
  87      * The number of bits which should be ignored in the final byte.
  88      *
  89      * This supports non-byte-aligned bitstreams.
  90      */
  91     size_t   data_bit_padding;
  92     /**
  93      * A reference to the buffer containing data.
  94      *
  95      * Must be set if data is not NULL.
  96      */
  97     AVBufferRef *data_ref;
  98
  99     /**
 100      * Pointer to the decomposed form of this unit.
 101      *
 102      * The type of this structure depends on both the codec and the
 103      * type of this unit.  May be NULL if the unit only exists in
 104      * bitstream form.
 105      */
 106     void *content;
 107     /**
 108      * If content is reference counted, a reference to the buffer containing
 109      * content.  Null if content is not reference counted.
 110      */
 111     AVBufferRef *content_ref;
 112 } CodedBitstreamUnit;
 113
 114 /**
 115  * Coded bitstream fragment structure, combining one or more units.
 116  *
 117  * This is any sequence of units.  It need not form some greater whole,
 118  * though in many cases it will.  For example, an H.264 access unit,
 119  * which is composed of a sequence of H.264 NAL units.
 120  */
 121 typedef struct CodedBitstreamFragment {
 122     /**
 123      * Pointer to the bitstream form of this fragment.
 124      *
 125      * May be NULL if the fragment only exists as component units.
 126      */
 127     uint8_t *data;
 128     /**
 129      * The number of bytes in the bitstream.
 130      *
 131      * The number of bytes in the bitstream (including any padding bits
 132      * in the final byte).
 133      */
 134     size_t   data_size;
 135     /**
 136      * The number of bits which should be ignored in the final byte.
 137      */
 138     size_t data_bit_padding;
 139     /**
 140      * A reference to the buffer containing data.
 141      *
 142      * Must be set if data is not NULL.
 143      */
 144     AVBufferRef *data_ref;
 145
 146     /**
 147      * Number of units in this fragment.
 148      *
 149      * This may be zero if the fragment only exists in bitstream form
 150      * and has not been decomposed.
 151      */
 152     int              nb_units;
 153
 154     /**
 155      * Number of allocated units.
 156      *
 157      * Must always be >= nb_units; designed for internal use by cbs.
 158      */
 159      int             nb_units_allocated;
 160
 161     /**
 162      * Pointer to an array of units of length nb_units_allocated.
 163      * Only the first nb_units are valid.
 164      *
 165      * Must be NULL if nb_units_allocated is zero.
 166      */
 167     CodedBitstreamUnit *units;
 168 } CodedBitstreamFragment;
 169
 170 /**
 171  * Context structure for coded bitstream operations.
 172  */
 173 typedef struct CodedBitstreamContext {
 174     /**
 175      * Logging context to be passed to all av_log() calls associated
 176      * with this context.
 177      */
 178     void *log_ctx;
 179
 180     /**
 181      * Internal codec-specific hooks.
 182      */
 183     const struct CodedBitstreamType *codec;
 184
 185     /**
 186      * Internal codec-specific data.
 187      *
 188      * This contains any information needed when reading/writing
 189      * bitsteams which will not necessarily be present in a fragment.
 190      * For example, for H.264 it contains all currently visible
 191      * parameter sets - they are required to determine the bitstream
 192      * syntax but need not be present in every access unit.
 193      */
 194     void *priv_data;
 195
 196     /**
 197      * Array of unit types which should be decomposed when reading.
 198      *
 199      * Types not in this list will be available in bitstream form only.
 200      * If NULL, all supported types will be decomposed.
 201      */
 202     const CodedBitstreamUnitType *decompose_unit_types;
 203     /**
 204      * Length of the decompose_unit_types array.
 205      */
 206     int nb_decompose_unit_types;
 207
 208     /**
 209      * Enable trace output during read/write operations.
 210      */
 211     int trace_enable;
 212     /**
 213      * Log level to use for trace output.
 214      *
 215      * From AV_LOG_*; defaults to AV_LOG_TRACE.
 216      */
 217     int trace_level;
 218
 219     /**
 220      * Write buffer. Used as intermediate buffer when writing units.
 221      * For internal use of cbs only.
 222      */
 223     uint8_t *write_buffer;
 224     size_t   write_buffer_size;
 225 } CodedBitstreamContext;
 226
 227
 228 /**
 229  * Table of all supported codec IDs.
 230  *
 231  * Terminated by AV_CODEC_ID_NONE.
 232  */
 233 extern const enum AVCodecID ff_cbs_all_codec_ids[];
 234
 235
 236 /**
 237  * Create and initialise a new context for the given codec.
 238  */
 239 int ff_cbs_init(CodedBitstreamContext **ctx,
 240                 enum AVCodecID codec_id, void *log_ctx);
 241
 242 /**
 243  * Reset all internal state in a context.
 244  */
 245 void ff_cbs_flush(CodedBitstreamContext *ctx);
 246
 247 /**
 248  * Close a context and free all internal state.
 249  */
 250 void ff_cbs_close(CodedBitstreamContext **ctx);
 251
 252
 253 /**
 254  * Read the extradata bitstream found in codec parameters into a
 255  * fragment, then split into units and decompose.
 256  *
 257  * This also updates the internal state, so will need to be called for
 258  * codecs with extradata to read parameter sets necessary for further
 259  * parsing even if the fragment itself is not desired.
 260  *
 261  * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
 262  * before use.
 263  */
 264 int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
 265                           CodedBitstreamFragment *frag,
 266                           const AVCodecParameters *par);
 267
 268 /**
 269  * Read the extradata bitstream found in a codec context into a
 270  * fragment, then split into units and decompose.
 271  *
 272  * This acts identical to ff_cbs_read_extradata() for the case where
 273  * you already have a codec context.
 274  */
 275 int ff_cbs_read_extradata_from_codec(CodedBitstreamContext *ctx,
 276                                      CodedBitstreamFragment *frag,
 277                                      const struct AVCodecContext *avctx);
 278
 279 int ff_cbs_read_packet_side_data(CodedBitstreamContext *ctx,
 280                                  CodedBitstreamFragment *frag,
 281                                  const AVPacket *pkt);
 282
 283 /**
 284  * Read the data bitstream from a packet into a fragment, then
 285  * split into units and decompose.
 286  *
 287  * This also updates the internal state of the coded bitstream context
 288  * with any persistent data from the fragment which may be required to
 289  * read following fragments (e.g. parameter sets).
 290  *
 291  * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
 292  * before use.
 293  */
 294 int ff_cbs_read_packet(CodedBitstreamContext *ctx,
 295                        CodedBitstreamFragment *frag,
 296                        const AVPacket *pkt);
 297
 298 /**
 299  * Read a bitstream from a memory region into a fragment, then
 300  * split into units and decompose.
 301  *
 302  * This also updates the internal state of the coded bitstream context
 303  * with any persistent data from the fragment which may be required to
 304  * read following fragments (e.g. parameter sets).
 305  *
 306  * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
 307  * before use.
 308  */
 309 int ff_cbs_read(CodedBitstreamContext *ctx,
 310                 CodedBitstreamFragment *frag,
 311                 const uint8_t *data, size_t size);
 312
 313
 314 /**
 315  * Write the content of the fragment to its own internal buffer.
 316  *
 317  * Writes the content of all units and then assembles them into a new
 318  * data buffer.  When modifying the content of decomposed units, this
 319  * can be used to regenerate the bitstream form of units or the whole
 320  * fragment so that it can be extracted for other use.
 321  *
 322  * This also updates the internal state of the coded bitstream context
 323  * with any persistent data from the fragment which may be required to
 324  * write following fragments (e.g. parameter sets).
 325  */
 326 int ff_cbs_write_fragment_data(CodedBitstreamContext *ctx,
 327                                CodedBitstreamFragment *frag);
 328
 329 /**
 330  * Write the bitstream of a fragment to the extradata in codec parameters.
 331  *
 332  * Modifies context and fragment as ff_cbs_write_fragment_data does and
 333  * replaces any existing extradata in the structure.
 334  */
 335 int ff_cbs_write_extradata(CodedBitstreamContext *ctx,
 336                            AVCodecParameters *par,
 337                            CodedBitstreamFragment *frag);
 338
 339 /**
 340  * Write the bitstream of a fragment to a packet.
 341  *
 342  * Modifies context and fragment as ff_cbs_write_fragment_data does.
 343  *
 344  * On success, the packet's buf is unreferenced and its buf, data and
 345  * size fields are set to the corresponding values from the newly updated
 346  * fragment; other fields are not touched.  On failure, the packet is not
 347  * touched at all.
 348  */
 349 int ff_cbs_write_packet(CodedBitstreamContext *ctx,
 350                         AVPacket *pkt,
 351                         CodedBitstreamFragment *frag);
 352
 353
 354 /**
 355  * Free the units contained in a fragment as well as the fragment's
 356  * own data buffer, but not the units array itself.
 357  */
 358 void ff_cbs_fragment_reset(CodedBitstreamFragment *frag);
 359
 360 /**
 361  * Free the units array of a fragment in addition to what
 362  * ff_cbs_fragment_reset does.
 363  */
 364 void ff_cbs_fragment_free(CodedBitstreamFragment *frag);
 365
 366 /**
 367  * Allocate a new internal content buffer of the given size in the unit.
 368  *
 369  * The content will be zeroed.
 370  */
 371 int ff_cbs_alloc_unit_content(CodedBitstreamUnit *unit,
 372                               size_t size,
 373                               void (*free)(void *opaque, uint8_t *content));
 374
 375 /**
 376  * Allocate a new internal content buffer matching the type of the unit.
 377  *
 378  * The content will be zeroed.
 379  */
 380 int ff_cbs_alloc_unit_content2(CodedBitstreamContext *ctx,
 381                                CodedBitstreamUnit *unit);
 382
 383 /**
 384  * Insert a new unit into a fragment with the given content.
 385  *
 386  * The content structure continues to be owned by the caller if
 387  * content_buf is not supplied.
 388  */
 389 int ff_cbs_insert_unit_content(CodedBitstreamFragment *frag,
 390                                int position,
 391                                CodedBitstreamUnitType type,
 392                                void *content,
 393                                AVBufferRef *content_buf);
 394
 395 /**
 396  * Add a new unit to a fragment with the given data bitstream.
 397  *
 398  * If data_buf is not supplied then data must have been allocated with
 399  * av_malloc() and will on success become owned by the unit after this
 400  * call or freed on error.
 401  */
 402 int ff_cbs_append_unit_data(CodedBitstreamFragment *frag,
 403                             CodedBitstreamUnitType type,
 404                             uint8_t *data, size_t data_size,
 405                             AVBufferRef *data_buf);
 406
 407 /**
 408  * Delete a unit from a fragment and free all memory it uses.
 409  *
 410  * Requires position to be >= 0 and < frag->nb_units.
 411  */
 412 void ff_cbs_delete_unit(CodedBitstreamFragment *frag,
 413                         int position);
 414
 415
 416 /**
 417  * Make the content of a unit refcounted.
 418  *
 419  * If the unit is not refcounted, this will do a deep copy of the unit
 420  * content to new refcounted buffers.
 421  *
 422  * It is not valid to call this function on a unit which does not have
 423  * decomposed content.
 424  */
 425 int ff_cbs_make_unit_refcounted(CodedBitstreamContext *ctx,
 426                                 CodedBitstreamUnit *unit);
 427
 428 /**
 429  * Make the content of a unit writable so that internal fields can be
 430  * modified.
 431  *
 432  * If it is known that there are no other references to the content of
 433  * the unit, does nothing and returns success.  Otherwise (including the
 434  * case where the unit content is not refcounted), it does a full clone
 435  * of the content (including any internal buffers) to make a new copy,
 436  * and replaces the existing references inside the unit with that.
 437  *
 438  * It is not valid to call this function on a unit which does not have
 439  * decomposed content.
 440  */
 441 int ff_cbs_make_unit_writable(CodedBitstreamContext *ctx,
 442                               CodedBitstreamUnit *unit);
 443
 444
 445 #endif /* AVCODEC_CBS_H */