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 "defs.h"
  30 #include "packet.h"
  31
  32 #ifndef CBS_PREFIX
  33 #define CBS_PREFIX cbs
  34 #endif
  35
  36 #define CBS_FUNC_PREFIX_NAME(prefix, name) ff_ ## prefix ## _ ## name
  37 #define CBS_FUNC_NAME(prefix, name) CBS_FUNC_PREFIX_NAME(prefix, name)
  38 #define CBS_FUNC(name) CBS_FUNC_NAME(CBS_PREFIX, name)
  39
  40 /*
  41  * This defines a framework for converting between a coded bitstream
  42  * and structures defining all individual syntax elements found in
  43  * such a stream.
  44  *
  45  * Conversion in both directions is possible.  Given a coded bitstream
  46  * (any meaningful fragment), it can be parsed and decomposed into
  47  * syntax elements stored in a set of codec-specific structures.
  48  * Similarly, given a set of those same codec-specific structures the
  49  * syntax elements can be serialised and combined to create a coded
  50  * bitstream.
  51  */
  52
  53 struct AVCodecContext;
  54 struct CodedBitstreamType;
  55
  56 /**
  57  * The codec-specific type of a bitstream unit.
  58  *
  59  * AV1: obu_type
  60  * H.264 / AVC: nal_unit_type
  61  * H.265 / HEVC: nal_unit_type
  62  * JPEG: marker value (without 0xff prefix)
  63  * MPEG-2: start code value (without prefix)
  64  * VP9: unused, set to zero (every unit is a frame)
  65  */
  66 typedef uint32_t CodedBitstreamUnitType;
  67
  68 /**
  69  * Coded bitstream unit structure.
  70  *
  71  * A bitstream unit the smallest element of a bitstream which
  72  * is meaningful on its own.  For example, an H.264 NAL unit.
  73  *
  74  * See the codec-specific header for the meaning of this for any
  75  * particular codec.
  76  */
  77 typedef struct CodedBitstreamUnit {
  78     /**
  79      * Codec-specific type of this unit.
  80      */
  81     CodedBitstreamUnitType type;
  82
  83     /**
  84      * Pointer to the directly-parsable bitstream form of this unit.
  85      *
  86      * May be NULL if the unit currently only exists in decomposed form.
  87      */
  88     uint8_t *data;
  89     /**
  90      * The number of bytes in the bitstream (including any padding bits
  91      * in the final byte).
  92      */
  93     size_t   data_size;
  94     /**
  95      * The number of bits which should be ignored in the final byte.
  96      *
  97      * This supports non-byte-aligned bitstreams.
  98      */
  99     size_t   data_bit_padding;
 100     /**
 101      * A reference to the buffer containing data.
 102      *
 103      * Must be set if data is not NULL.
 104      */
 105     AVBufferRef *data_ref;
 106
 107     /**
 108      * Pointer to the decomposed form of this unit.
 109      *
 110      * The type of this structure depends on both the codec and the
 111      * type of this unit.  May be NULL if the unit only exists in
 112      * bitstream form.
 113      */
 114     void *content;
 115     /**
 116      * If content is reference counted, a RefStruct reference backing content.
 117      * NULL if content is not reference counted.
 118      */
 119     void *content_ref;
 120 } CodedBitstreamUnit;
 121
 122 /**
 123  * Coded bitstream fragment structure, combining one or more units.
 124  *
 125  * This is any sequence of units.  It need not form some greater whole,
 126  * though in many cases it will.  For example, an H.264 access unit,
 127  * which is composed of a sequence of H.264 NAL units.
 128  */
 129 typedef struct CodedBitstreamFragment {
 130     /**
 131      * Pointer to the bitstream form of this fragment.
 132      *
 133      * May be NULL if the fragment only exists as component units.
 134      */
 135     uint8_t *data;
 136     /**
 137      * The number of bytes in the bitstream.
 138      *
 139      * The number of bytes in the bitstream (including any padding bits
 140      * in the final byte).
 141      */
 142     size_t   data_size;
 143     /**
 144      * The number of bits which should be ignored in the final byte.
 145      */
 146     size_t data_bit_padding;
 147     /**
 148      * A reference to the buffer containing data.
 149      *
 150      * Must be set if data is not NULL.
 151      */
 152     AVBufferRef *data_ref;
 153
 154     /**
 155      * Number of units in this fragment.
 156      *
 157      * This may be zero if the fragment only exists in bitstream form
 158      * and has not been decomposed.
 159      */
 160     int              nb_units;
 161
 162     /**
 163      * Number of allocated units.
 164      *
 165      * Must always be >= nb_units; designed for internal use by cbs.
 166      */
 167      int             nb_units_allocated;
 168
 169     /**
 170      * Pointer to an array of units of length nb_units_allocated.
 171      * Only the first nb_units are valid.
 172      *
 173      * Must be NULL if nb_units_allocated is zero.
 174      */
 175     CodedBitstreamUnit *units;
 176 } CodedBitstreamFragment;
 177
 178
 179 struct CodedBitstreamContext;
 180 struct GetBitContext;
 181 struct PutBitContext;
 182
 183 /**
 184  * Callback type for read tracing.
 185  *
 186  * @param ctx         User-set trace context.
 187  * @param gbc         A GetBitContext set at the start of the syntax
 188  *                    element.  This is a copy, the callee does not
 189  *                    need to preserve it.
 190  * @param length      Length in bits of the syntax element.
 191  * @param name        String name of the syntax elements.
 192  * @param subscripts  If the syntax element is an array, a pointer to
 193  *                    an array of subscripts into the array.
 194  * @param value       Parsed value of the syntax element.
 195  */
 196 typedef void (*CBSTraceReadCallback)(void *trace_context,
 197                                      struct GetBitContext *gbc,
 198                                      int start_position,
 199                                      const char *name,
 200                                      const int *subscripts,
 201                                      int64_t value);
 202
 203 /**
 204  * Callback type for write tracing.
 205  *
 206  * @param ctx         User-set trace context.
 207  * @param pbc         A PutBitContext set at the end of the syntax
 208  *                    element.  The user must not modify this, but may
 209  *                    inspect it to determine state.
 210  * @param length      Length in bits of the syntax element.
 211  * @param name        String name of the syntax elements.
 212  * @param subscripts  If the syntax element is an array, a pointer to
 213  *                    an array of subscripts into the array.
 214  * @param value       Written value of the syntax element.
 215  */
 216 typedef void (*CBSTraceWriteCallback)(void *trace_context,
 217                                       struct PutBitContext *pbc,
 218                                       int start_position,
 219                                       const char *name,
 220                                       const int *subscripts,
 221                                       int64_t value);
 222
 223 /**
 224  * Context structure for coded bitstream operations.
 225  */
 226 typedef struct CodedBitstreamContext {
 227     /**
 228      * Logging context to be passed to all av_log() calls associated
 229      * with this context.
 230      */
 231     void *log_ctx;
 232
 233     /**
 234      * Internal codec-specific hooks.
 235      */
 236     const struct CodedBitstreamType *codec;
 237
 238     /**
 239      * Internal codec-specific data.
 240      *
 241      * This contains any information needed when reading/writing
 242      * bitsteams which will not necessarily be present in a fragment.
 243      * For example, for H.264 it contains all currently visible
 244      * parameter sets - they are required to determine the bitstream
 245      * syntax but need not be present in every access unit.
 246      */
 247     void *priv_data;
 248
 249     /**
 250      * Array of unit types which should be decomposed when reading.
 251      *
 252      * Types not in this list will be available in bitstream form only.
 253      * If NULL, all supported types will be decomposed.
 254      */
 255     const CodedBitstreamUnitType *decompose_unit_types;
 256     /**
 257      * Length of the decompose_unit_types array.
 258      */
 259     int nb_decompose_unit_types;
 260
 261     /**
 262      * Enable trace output during read/write operations.
 263      */
 264     int trace_enable;
 265     /**
 266      * Log level to use for default trace output.
 267      *
 268      * From AV_LOG_*; defaults to AV_LOG_TRACE.
 269      */
 270     int trace_level;
 271     /**
 272      * User context pointer to pass to trace callbacks.
 273      */
 274     void *trace_context;
 275     /**
 276      * Callback for read tracing.
 277      *
 278      * If tracing is enabled then this is called once for each syntax
 279      * element parsed.
 280      */
 281     CBSTraceReadCallback  trace_read_callback;
 282     /**
 283      * Callback for write tracing.
 284      *
 285      * If tracing is enabled then this is called once for each syntax
 286      * element written.
 287      */
 288     CBSTraceWriteCallback trace_write_callback;
 289
 290     /**
 291      * Write buffer. Used as intermediate buffer when writing units.
 292      * For internal use of cbs only.
 293      */
 294     uint8_t *write_buffer;
 295     size_t   write_buffer_size;
 296 } CodedBitstreamContext;
 297
 298
 299 /**
 300  * Table of all supported codec IDs.
 301  *
 302  * Terminated by AV_CODEC_ID_NONE.
 303  */
 304 extern const enum AVCodecID CBS_FUNC(all_codec_ids)[];
 305
 306
 307 /**
 308  * Create and initialise a new context for the given codec.
 309  */
 310 int CBS_FUNC(init)(CodedBitstreamContext **ctx,
 311                 enum AVCodecID codec_id, void *log_ctx);
 312
 313 /**
 314  * Reset all internal state in a context.
 315  */
 316 void CBS_FUNC(flush)(CodedBitstreamContext *ctx);
 317
 318 /**
 319  * Close a context and free all internal state.
 320  */
 321 void CBS_FUNC(close)(CodedBitstreamContext **ctx);
 322
 323
 324 /**
 325  * Read the extradata bitstream found in codec parameters into a
 326  * fragment, then split into units and decompose.
 327  *
 328  * This also updates the internal state, so will need to be called for
 329  * codecs with extradata to read parameter sets necessary for further
 330  * parsing even if the fragment itself is not desired.
 331  *
 332  * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
 333  * before use.
 334  */
 335 int CBS_FUNC(read_extradata)(CodedBitstreamContext *ctx,
 336                           CodedBitstreamFragment *frag,
 337                           const AVCodecParameters *par);
 338
 339 /**
 340  * Read the extradata bitstream found in a codec context into a
 341  * fragment, then split into units and decompose.
 342  *
 343  * This acts identical to ff_cbs_read_extradata() for the case where
 344  * you already have a codec context.
 345  */
 346 int CBS_FUNC(read_extradata_from_codec)(CodedBitstreamContext *ctx,
 347                                      CodedBitstreamFragment *frag,
 348                                      const struct AVCodecContext *avctx);
 349
 350 int CBS_FUNC(read_packet_side_data)(CodedBitstreamContext *ctx,
 351                                  CodedBitstreamFragment *frag,
 352                                  const AVPacket *pkt);
 353
 354 /**
 355  * Read the data bitstream from a packet into a fragment, then
 356  * split into units and decompose.
 357  *
 358  * This also updates the internal state of the coded bitstream context
 359  * with any persistent data from the fragment which may be required to
 360  * read following fragments (e.g. parameter sets).
 361  *
 362  * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
 363  * before use.
 364  */
 365 int CBS_FUNC(read_packet)(CodedBitstreamContext *ctx,
 366                        CodedBitstreamFragment *frag,
 367                        const AVPacket *pkt);
 368
 369 /**
 370  * Read a bitstream from a memory region into a fragment, then
 371  * split into units and decompose.
 372  *
 373  * This also updates the internal state of the coded bitstream context
 374  * with any persistent data from the fragment which may be required to
 375  * read following fragments (e.g. parameter sets).
 376  *
 377  * The fragment must have been zeroed or reset via ff_cbs_fragment_reset
 378  * before use.
 379  */
 380 int CBS_FUNC(read)(CodedBitstreamContext *ctx,
 381                 CodedBitstreamFragment *frag,
 382                 const AVBufferRef *buf,
 383                 const uint8_t *data, size_t size);
 384
 385
 386 /**
 387  * Write the content of the fragment to its own internal buffer.
 388  *
 389  * Writes the content of all units and then assembles them into a new
 390  * data buffer.  When modifying the content of decomposed units, this
 391  * can be used to regenerate the bitstream form of units or the whole
 392  * fragment so that it can be extracted for other use.
 393  *
 394  * This also updates the internal state of the coded bitstream context
 395  * with any persistent data from the fragment which may be required to
 396  * write following fragments (e.g. parameter sets).
 397  */
 398 int CBS_FUNC(write_fragment_data)(CodedBitstreamContext *ctx,
 399                                CodedBitstreamFragment *frag);
 400
 401 /**
 402  * Write the bitstream of a fragment to the extradata in codec parameters.
 403  *
 404  * Modifies context and fragment as ff_cbs_write_fragment_data does and
 405  * replaces any existing extradata in the structure.
 406  */
 407 int CBS_FUNC(write_extradata)(CodedBitstreamContext *ctx,
 408                            AVCodecParameters *par,
 409                            CodedBitstreamFragment *frag);
 410
 411 /**
 412  * Write the bitstream of a fragment to a packet.
 413  *
 414  * Modifies context and fragment as ff_cbs_write_fragment_data does.
 415  *
 416  * On success, the packet's buf is unreferenced and its buf, data and
 417  * size fields are set to the corresponding values from the newly updated
 418  * fragment; other fields are not touched.  On failure, the packet is not
 419  * touched at all.
 420  */
 421 int CBS_FUNC(write_packet)(CodedBitstreamContext *ctx,
 422                         AVPacket *pkt,
 423                         CodedBitstreamFragment *frag);
 424
 425
 426 /**
 427  * Free the units contained in a fragment as well as the fragment's
 428  * own data buffer, but not the units array itself.
 429  */
 430 void CBS_FUNC(fragment_reset)(CodedBitstreamFragment *frag);
 431
 432 /**
 433  * Free the units array of a fragment in addition to what
 434  * ff_cbs_fragment_reset does.
 435  */
 436 void CBS_FUNC(fragment_free)(CodedBitstreamFragment *frag);
 437
 438 /**
 439  * Allocate a new internal content buffer matching the type of the unit.
 440  *
 441  * The content will be zeroed.
 442  */
 443 int CBS_FUNC(alloc_unit_content)(CodedBitstreamContext *ctx,
 444                               CodedBitstreamUnit *unit);
 445
 446 /**
 447  * Insert a new unit into a fragment with the given content.
 448  *
 449  * If content_ref is supplied, it has to be a RefStruct reference
 450  * backing content; the user keeps ownership of the supplied reference.
 451  * The content structure continues to be owned by the caller if
 452  * content_ref is not supplied.
 453  */
 454 int CBS_FUNC(insert_unit_content)(CodedBitstreamFragment *frag,
 455                                int position,
 456                                CodedBitstreamUnitType type,
 457                                void *content,
 458                                void *content_ref);
 459
 460 /**
 461  * Add a new unit to a fragment with the given data bitstream.
 462  *
 463  * If data_buf is not supplied then data must have been allocated with
 464  * av_malloc() and will on success become owned by the unit after this
 465  * call or freed on error.
 466  */
 467 int CBS_FUNC(append_unit_data)(CodedBitstreamFragment *frag,
 468                             CodedBitstreamUnitType type,
 469                             uint8_t *data, size_t data_size,
 470                             AVBufferRef *data_buf);
 471
 472 /**
 473  * Delete a unit from a fragment and free all memory it uses.
 474  *
 475  * Requires position to be >= 0 and < frag->nb_units.
 476  */
 477 void CBS_FUNC(delete_unit)(CodedBitstreamFragment *frag,
 478                         int position);
 479
 480
 481 /**
 482  * Make the content of a unit refcounted.
 483  *
 484  * If the unit is not refcounted, this will do a deep copy of the unit
 485  * content to new refcounted buffers.
 486  *
 487  * It is not valid to call this function on a unit which does not have
 488  * decomposed content.
 489  */
 490 int CBS_FUNC(make_unit_refcounted)(CodedBitstreamContext *ctx,
 491                                 CodedBitstreamUnit *unit);
 492
 493 /**
 494  * Make the content of a unit writable so that internal fields can be
 495  * modified.
 496  *
 497  * If it is known that there are no other references to the content of
 498  * the unit, does nothing and returns success.  Otherwise (including the
 499  * case where the unit content is not refcounted), it does a full clone
 500  * of the content (including any internal buffers) to make a new copy,
 501  * and replaces the existing references inside the unit with that.
 502  *
 503  * It is not valid to call this function on a unit which does not have
 504  * decomposed content.
 505  */
 506 int CBS_FUNC(make_unit_writable)(CodedBitstreamContext *ctx,
 507                               CodedBitstreamUnit *unit);
 508
 509 enum CbsDiscardFlags {
 510     DISCARD_FLAG_NONE = 0,
 511
 512     /**
 513      * keep non-vcl units even if the picture has been dropped.
 514      */
 515     DISCARD_FLAG_KEEP_NON_VCL = 0x01,
 516 };
 517
 518 /**
 519  * Discard units according to 'skip'.
 520  */
 521 void CBS_FUNC(discard_units)(CodedBitstreamContext *ctx,
 522                           CodedBitstreamFragment *frag,
 523                           enum AVDiscard skip,
 524                           int flags);
 525
 526
 527 /**
 528  * Helper function for read tracing which formats the syntax element
 529  * and logs the result.
 530  *
 531  * Trace context should be set to the CodedBitstreamContext.
 532  */
 533 void CBS_FUNC(trace_read_log)(void *trace_context,
 534                            struct GetBitContext *gbc, int length,
 535                            const char *str, const int *subscripts,
 536                            int64_t value);
 537
 538 /**
 539  * Helper function for write tracing which formats the syntax element
 540  * and logs the result.
 541  *
 542  * Trace context should be set to the CodedBitstreamContext.
 543  */
 544 void CBS_FUNC(trace_write_log)(void *trace_context,
 545                             struct PutBitContext *pbc, int length,
 546                             const char *str, const int *subscripts,
 547                             int64_t value);
 548
 549 #endif /* AVCODEC_CBS_H */