/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVCODEC_CBS_H
#define AVCODEC_CBS_H
#include <stddef.h>
#include <stdint.h>
#include "avcodec.h"
/*
* This defines a framework for converting between a coded bitstream
* and structures defining all individual syntax elements found in
* such a stream.
*
* Conversion in both directions is possible. Given a coded bitstream
* (any meaningful fragment), it can be parsed and decomposed into
* syntax elements stored in a set of codec-specific structures.
* Similarly, given a set of those same codec-specific structures the
* syntax elements can be serialised and combined to create a coded
* bitstream.
*/
struct CodedBitstreamType;
/**
* The codec-specific type of a bitstream unit.
*
* H.264 / AVC: nal_unit_type
* H.265 / HEVC: nal_unit_type
* MPEG-2: start code value (without prefix)
*/
typedef uint32_t CodedBitstreamUnitType;
/**
* Coded bitstream unit structure.
*
* A bitstream unit the smallest element of a bitstream which
* is meaningful on its own. For example, an H.264 NAL unit.
*
* See the codec-specific header for the meaning of this for any
* particular codec.
*/
typedef struct CodedBitstreamUnit {
/**
* Codec-specific type of this unit.
*/
CodedBitstreamUnitType type;
/**
* Pointer to the directly-parsable bitstream form of this unit.
*
* May be NULL if the unit currently only exists in decomposed form.
*/
uint8_t *data;
/**
* The number of bytes in the bitstream (including any padding bits
* in the final byte).
*/
size_t data_size;
/**
* The number of bits which should be ignored in the final byte.
*
* This supports non-byte-aligned bitstreams.
*/
size_t data_bit_padding;
/**
* Pointer to the decomposed form of this unit.
*
* The type of this structure depends on both the codec and the
* type of this unit. May be NULL if the unit only exists in
* bitstream form.
*/
void *content;
/**
* Whether the content was supplied externally.
*
* If so, it should not be freed when freeing the unit.
*/
int content_external;
} CodedBitstreamUnit;
/**
* Coded bitstream fragment structure, combining one or more units.
*
* This is any sequence of units. It need not form some greater whole,
* though in many cases it will. For example, an H.264 access unit,
* which is composed of a sequence of H.264 NAL units.
*/
typedef struct CodedBitstreamFragment {
/**
* Pointer to the bitstream form of this fragment.
*
* May be NULL if the fragment only exists as component units.
*/
uint8_t *data;
/**
* The number of bytes in the bitstream.
*
* The number of bytes in the bitstream (including any padding bits
* in the final byte).
*/
size_t data_size;
/**
* The number of bits which should be ignored in the final byte.
*/
size_t data_bit_padding;
/**
* Number of units in this fragment.
*
* This may be zero if the fragment only exists in bitstream form
* and has not been decomposed.
*/
int nb_units;
/**
* Pointer to an array of units of length nb_units.
*
* Must be NULL if nb_units is zero.
*/
CodedBitstreamUnit *units;
} CodedBitstreamFragment;
/**
* Context structure for coded bitstream operations.
*/
typedef struct CodedBitstreamContext {
/**
* Logging context to be passed to all av_log() calls associated
* with this context.
*/
void *log_ctx;
/**
* Internal codec-specific hooks.
*/
const struct CodedBitstreamType *codec;
/**
* Internal codec-specific data.
*
* This contains any information needed when reading/writing
* bitsteams which will not necessarily be present in a fragment.
* For example, for H.264 it contains all currently visible
* parameter sets - they are required to determine the bitstream
* syntax but need not be present in every access unit.
*/
void *priv_data;
/**
* Array of unit types which should be decomposed when reading.
*
* Types not in this list will be available in bitstream form only.
* If NULL, all supported types will be decomposed.
*/
CodedBitstreamUnitType *decompose_unit_types;
/**
* Length of the decompose_unit_types array.
*/
int nb_decompose_unit_types;
/**
* Enable trace output during read/write operations.
*/
int trace_enable;
/**
* Log level to use for trace output.
*
* From AV_LOG_*; defaults to AV_LOG_TRACE.
*/
int trace_level;
} CodedBitstreamContext;
/**
* Create and initialise a new context for the given codec.
*/
int ff_cbs_init(CodedBitstreamContext **ctx,
enum AVCodecID codec_id, void *log_ctx);
/**
* Close a context and free all internal state.
*/
void ff_cbs_close(CodedBitstreamContext **ctx);
/**
* Read the extradata bitstream found in codec parameters into a
* fragment, then split into units and decompose.
*
* This also updates the internal state, so will need to be called for
* codecs with extradata to read parameter sets necessary for further
* parsing even if the fragment itself is not desired.
*/
int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
const AVCodecParameters *par);
/**
* Read the data bitstream from a packet into a fragment, then
* split into units and decompose.
*
* This also updates the internal state of the coded bitstream context
* with any persistent data from the fragment which may be required to
* read following fragments (e.g. parameter sets).
*/
int ff_cbs_read_packet(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
const AVPacket *pkt);
/**
* Read a bitstream from a memory region into a fragment, then
* split into units and decompose.
*
* This also updates the internal state of the coded bitstream context
* with any persistent data from the fragment which may be required to
* read following fragments (e.g. parameter sets).
*/
int ff_cbs_read(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
const uint8_t *data, size_t size);
/**
* Write the content of the fragment to its own internal buffer.
*
* Writes the content of all units and then assembles them into a new
* data buffer. When modifying the content of decomposed units, this
* can be used to regenerate the bitstream form of units or the whole
* fragment so that it can be extracted for other use.
*
* This also updates the internal state of the coded bitstream context
* with any persistent data from the fragment which may be required to
* write following fragments (e.g. parameter sets).
*/
int ff_cbs_write_fragment_data(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag);
/**
* Write the bitstream of a fragment to the extradata in codec parameters.
*
* This replaces any existing extradata in the structure.
*/
int ff_cbs_write_extradata(CodedBitstreamContext *ctx,
AVCodecParameters *par,
CodedBitstreamFragment *frag);
/**
* Write the bitstream of a fragment to a packet.
*/
int ff_cbs_write_packet(CodedBitstreamContext *ctx,
AVPacket *pkt,
CodedBitstreamFragment *frag);
/**
* Free all allocated memory in a fragment.
*/
void ff_cbs_fragment_uninit(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag);
/**
* Insert a new unit into a fragment with the given content.
*
* The content structure continues to be owned by the caller, and
* will not be freed when the unit is.
*/
int ff_cbs_insert_unit_content(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int position,
CodedBitstreamUnitType type,
void *content);
/**
* Insert a new unit into a fragment with the given data bitstream.
*
* The data buffer will be owned by the unit after this operation.
*/
int ff_cbs_insert_unit_data(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int position,
CodedBitstreamUnitType type,
uint8_t *data, size_t data_size);
/**
* Delete a unit from a fragment and free all memory it uses.
*/
int ff_cbs_delete_unit(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int position);
#endif /* AVCODEC_CBS_H */