/* * 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 */