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* 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
* 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
#include "avcodec.h"
#include "cbs.h"
#include "get_bits.h"
#include "put_bits.h"
enum CBSContentType {
// Unit content is a simple structure.
// Unit content contains some references to other structures, but all
// managed via buffer reference counting. The descriptor defines the
// structure offsets of every buffer reference.
// Unit content is something more complex. The descriptor defines
// special functions to manage the content.
enum {
// Maximum number of unit types described by the same unit type
// descriptor.
// Maximum number of reference buffer offsets in any one unit.
// Special value used in a unit type descriptor to indicate that it
// applies to a large range of types rather than a set of discrete
// values.
typedef const struct CodedBitstreamUnitTypeDescriptor {
// Number of entries in the unit_types array, or the special value
// CBS_UNIT_TYPE_RANGE to indicate that the range fields should be
// used instead.
int nb_unit_types;
// Array of unit types that this entry describes.
const CodedBitstreamUnitType unit_types[CBS_MAX_UNIT_TYPES];
// Start and end of unit type range, used if nb_unit_types is
const CodedBitstreamUnitType unit_type_range_start;
const CodedBitstreamUnitType unit_type_range_end;
// The type of content described.
enum CBSContentType content_type;
// The size of the structure which should be allocated to contain
// the decomposed content of this type of unit.
size_t content_size;
// Number of entries in the ref_offsets array. Only used if the
int nb_ref_offsets;
// The structure must contain two adjacent elements:
// type *field;
// AVBufferRef *field_ref;
// where field points to something in the buffer referred to by
// field_ref. This offset is then set to offsetof(struct, field).
size_t ref_offsets[CBS_MAX_REF_OFFSETS];
void (*content_free)(void *opaque, uint8_t *data);
int (*content_clone)(AVBufferRef **ref, CodedBitstreamUnit *unit);
} CodedBitstreamUnitTypeDescriptor;
typedef struct CodedBitstreamType {
enum AVCodecID codec_id;
// A class for the private data, used to declare private AVOptions.
// This field is NULL for types that do not declare any options.
// If this field is non-NULL, the first member of the filter private data
// must be a pointer to AVClass.
const AVClass *priv_class;
size_t priv_data_size;
// List of unit type descriptors for this codec.
// Terminated by a descriptor with nb_unit_types equal to zero.
const CodedBitstreamUnitTypeDescriptor *unit_types;
// Split frag->data into coded bitstream units, creating the
// frag->units array. Fill data but not content on each unit.
// The header argument should be set if the fragment came from
// a header block, which may require different parsing for some
// codecs (e.g. the AVCC header in H.264).
int (*split_fragment)(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int header);
// Read the unit->data bitstream and decompose it, creating
// unit->content.
int (*read_unit)(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit);
// Write the data bitstream from unit->content into pbc.
// Return value AVERROR(ENOSPC) indicates that pbc was too small.
int (*write_unit)(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc);
// Read the data from all of frag->units and assemble it into
// a bitstream for the whole fragment.
int (*assemble_fragment)(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag);
// Reset the codec internal state.
void (*flush)(CodedBitstreamContext *ctx);
// Free the codec internal state.
void (*close)(CodedBitstreamContext *ctx);
} CodedBitstreamType;
// Helper functions for trace output.
void ff_cbs_trace_header(CodedBitstreamContext *ctx,
const char *name);
void ff_cbs_trace_syntax_element(CodedBitstreamContext *ctx, int position,
const char *name, const int *subscripts,
const char *bitstring, int64_t value);
// Helper functions for read/write of common bitstream elements, including
// generation of trace output.
int ff_cbs_read_unsigned(CodedBitstreamContext *ctx, GetBitContext *gbc,
int width, const char *name,
const int *subscripts, uint32_t *write_to,
uint32_t range_min, uint32_t range_max);
int ff_cbs_write_unsigned(CodedBitstreamContext *ctx, PutBitContext *pbc,
int width, const char *name,
const int *subscripts, uint32_t value,
uint32_t range_min, uint32_t range_max);
int ff_cbs_read_signed(CodedBitstreamContext *ctx, GetBitContext *gbc,
int width, const char *name,
const int *subscripts, int32_t *write_to,
int32_t range_min, int32_t range_max);
int ff_cbs_write_signed(CodedBitstreamContext *ctx, PutBitContext *pbc,
int width, const char *name,
const int *subscripts, int32_t value,
int32_t range_min, int32_t range_max);
// The largest unsigned value representable in N bits, suitable for use as
// range_max in the above functions.
#define MAX_UINT_BITS(length) ((UINT64_C(1) << (length)) - 1)
// The largest signed value representable in N bits, suitable for use as
// range_max in the above functions.
#define MAX_INT_BITS(length) ((INT64_C(1) << ((length) - 1)) - 1)
// The smallest signed value representable in N bits, suitable for use as
// range_min in the above functions.
#define MIN_INT_BITS(length) (-(INT64_C(1) << ((length) - 1)))
#define CBS_UNIT_TYPE_POD(type, structure) { \
.nb_unit_types = 1, \
.unit_types = { type }, \
.content_type = CBS_CONTENT_TYPE_POD, \
.content_size = sizeof(structure), \
#define CBS_UNIT_TYPE_INTERNAL_REF(type, structure, ref_field) { \
.nb_unit_types = 1, \
.unit_types = { type }, \
.content_size = sizeof(structure), \
.nb_ref_offsets = 1, \
.ref_offsets = { offsetof(structure, ref_field) }, \
#define CBS_UNIT_TYPE_COMPLEX(type, structure, free_func) { \
.nb_unit_types = 1, \
.unit_types = { type }, \
.content_type = CBS_CONTENT_TYPE_COMPLEX, \
.content_size = sizeof(structure), \
.content_free = free_func, \
#define CBS_UNIT_TYPE_END_OF_LIST { .nb_unit_types = 0 }
extern const CodedBitstreamType ff_cbs_type_av1;
extern const CodedBitstreamType ff_cbs_type_h264;
extern const CodedBitstreamType ff_cbs_type_h265;
extern const CodedBitstreamType ff_cbs_type_jpeg;
extern const CodedBitstreamType ff_cbs_type_mpeg2;
extern const CodedBitstreamType ff_cbs_type_vp9;