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lavc: Add coded bitstream read/write API
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Mark Thompson
274
libavcodec/cbs.h
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274
libavcodec/cbs.h
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/*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVCODEC_CBS_H
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#define AVCODEC_CBS_H
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#include <stddef.h>
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#include <stdint.h>
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#include "avcodec.h"
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struct CodedBitstreamType;
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/**
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* Coded bitstream unit structure.
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*
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* A bitstream unit the the smallest element of a bitstream which
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* is meaningful on its own. For example, an H.264 NAL unit.
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*
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* See the codec-specific header for the meaning of this for any
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* particular codec.
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*/
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typedef struct CodedBitstreamUnit {
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/**
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* Codec-specific type of this unit.
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*/
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uint32_t type;
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/**
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* Pointer to the bitstream form of this unit.
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*
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* May be NULL if the unit currently only exists in decomposed form.
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*/
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uint8_t *data;
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/**
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* The number of bytes in the bitstream (including any padding bits
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* in the final byte).
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*/
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size_t data_size;
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/**
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* The number of bits which should be ignored in the final byte.
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*
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* This supports non-byte-aligned bitstreams.
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*/
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size_t data_bit_padding;
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/**
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* Pointer to the decomposed form of this unit.
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*
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* The type of this structure depends on both the codec and the
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* type of this unit. May be NULL if the unit only exists in
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* bitstream form.
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*/
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void *content;
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/**
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* Whether the content was supplied externally.
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*
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* If so, it should not be freed when freeing the unit.
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*/
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int content_external;
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} CodedBitstreamUnit;
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/**
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* Coded bitstream fragment structure, combining one or more units.
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*
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* This is any sequence of units. It need not form some greater whole,
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* though in many cases it will. For example, an H.264 access unit,
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* which is composed of a sequence of H.264 NAL units.
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*/
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typedef struct CodedBitstreamFragment {
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/**
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* Pointer to the bitstream form of this fragment.
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*
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* May be NULL if the fragment only exists as component units.
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*/
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uint8_t *data;
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/**
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* The number of bytes in the bitstream.
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*
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* The number of bytes in the bitstream (including any padding bits
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* in the final byte).
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*/
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size_t data_size;
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/**
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* The number of bits which should be ignored in the final byte.
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*/
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size_t data_bit_padding;
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/**
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* Number of units in this fragment.
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*
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* This may be zero if the fragment only exists in bistream form
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* and has not been decomposed.
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*/
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int nb_units;
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/**
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* Pointer to an array of units of length nb_units.
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*
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* Must be NULL if nb_units is zero.
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*/
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CodedBitstreamUnit *units;
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} CodedBitstreamFragment;
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/**
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* Context structure for coded bitstream operations.
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*/
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typedef struct CodedBitstreamContext {
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/**
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* Logging context to be passed to all av_log() calls associated
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* with this context.
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*/
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void *log_ctx;
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/**
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* Internal codec-specific hooks.
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*/
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const struct CodedBitstreamType *codec;
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/**
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* Internal codec-specific data.
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*
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* This contains any information needed when reading/writing
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* bitsteams which will not necessarily be present in a fragment.
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* For example, for H.264 it contains all currently visible
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* parameter sets - they are required to determine the bitstream
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* syntax but need not be present in every access unit.
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*/
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void *priv_data;
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/**
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* Array of unit types which should be decomposed when reading.
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*
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* Types not in this list will be available in bitstream form only.
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* If NULL, all supported types will be decomposed.
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*/
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uint32_t *decompose_unit_types;
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/**
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* Length of the decompose_unit_types array.
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*/
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int nb_decompose_unit_types;
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/**
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* Enable trace output during read/write operations.
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*/
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int trace_enable;
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/**
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* Log level to use for trace output.
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*
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* From AV_LOG_*; defaults to AV_LOG_TRACE.
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*/
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int trace_level;
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} CodedBitstreamContext;
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/**
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* Initialise a new context for the given codec.
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*/
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int ff_cbs_init(CodedBitstreamContext *ctx,
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enum AVCodecID codec_id, void *log_ctx);
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/**
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* Close a context and free all internal state.
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*/
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void ff_cbs_close(CodedBitstreamContext *ctx);
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/**
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* Read the extradata bitstream found in codec parameters into a
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* fragment, then split into units and decompose.
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*
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* This also updates the internal state, so will need to be called for
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* codecs with extradata to read parameter sets necessary for further
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* parsing even if the fragment itself is not desired.
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*/
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int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag,
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const AVCodecParameters *par);
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/**
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* Read the data bitstream from a packet into a fragment, then
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* split into units and decompose.
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*/
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int ff_cbs_read_packet(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag,
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const AVPacket *pkt);
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/**
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* Read a bitstream from a memory region into a fragment, then
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* split into units and decompose.
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*/
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int ff_cbs_read(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag,
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const uint8_t *data, size_t size);
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/**
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* Write the content of the fragment to its own internal buffer.
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*
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* Writes the content of all units and then assembles them into a new
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* data buffer. When modifying the content of decomposed units, this
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* can be used to regenerate the bitstream form of units or the whole
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* fragment so that it can be extracted for other use.
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*/
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int ff_cbs_write_fragment_data(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag);
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/**
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* Write the bitstream of a fragment to the extradata in codec parameters.
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*/
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int ff_cbs_write_extradata(CodedBitstreamContext *ctx,
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AVCodecParameters *par,
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CodedBitstreamFragment *frag);
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/**
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* Write the bitstream of a fragment to a packet.
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*/
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int ff_cbs_write_packet(CodedBitstreamContext *ctx,
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AVPacket *pkt,
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CodedBitstreamFragment *frag);
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/**
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* Free all allocated memory in a fragment.
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*/
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void ff_cbs_fragment_uninit(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag);
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/**
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* Insert a new unit into a fragment with the given content.
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*
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* The content structure continues to be owned by the caller, and
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* will not be freed when the unit is.
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*/
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int ff_cbs_insert_unit_content(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag,
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int position, uint32_t type,
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void *content);
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/**
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* Insert a new unit into a fragment with the given data bitstream.
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*
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* The data buffer will be owned by the unit after this operation.
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*/
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int ff_cbs_insert_unit_data(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag,
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int position, uint32_t type,
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uint8_t *data, size_t data_size);
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/**
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* Delete a unit from a fragment and free all memory it uses.
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*/
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int ff_cbs_delete_unit(CodedBitstreamContext *ctx,
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CodedBitstreamFragment *frag,
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int position);
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#endif /* AVCODEC_CBS_H */
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