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FFmpeg/libavcodec/cbs_mpeg2.c
Andreas Rheinhardt a105b11a9d avcodec/cbs: Add specialization for ff_cbs_(read|write)_unsigned() 
These functions allow not only to read and write unsigned values,
but also to check ranges and to emit trace output which can be
beautified when processing arrays (indices like "[i]" are replaced
by their actual numbers).

Yet lots of callers actually only need something simpler:
Their range is only implicitly restricted by the amount
of bits used and they are not part of arrays, hence don't
need this beautification.

This commit adds specializations for these callers;
this is very beneficial size-wise (it reduced the size
of .text by 23312 bytes here), as a call is now cheaper.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2023-07-30 21:36:31 +02:00

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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
* 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
*/
#include "libavutil/avassert.h"
#include "cbs.h"
#include "cbs_internal.h"
#include "cbs_mpeg2.h"
#include "startcode.h"
#define HEADER(name) do { \
ff_cbs_trace_header(ctx, name); \
} while (0)
#define CHECK(call) do { \
err = (call); \
if (err < 0) \
return err; \
} while (0)
#define FUNC_NAME(rw, codec, name) cbs_ ## codec ## _ ## rw ## _ ## name
#define FUNC_MPEG2(rw, name) FUNC_NAME(rw, mpeg2, name)
#define FUNC(name) FUNC_MPEG2(READWRITE, name)
#define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)
#define uir(width, name) \
xui(width, name, current->name, 1, MAX_UINT_BITS(width), 0, )
#define uis(width, name, subs, ...) \
xui(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define uirs(width, name, subs, ...) \
xui(width, name, current->name, 1, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define xui(width, name, var, range_min, range_max, subs, ...) \
xuia(width, #name, var, range_min, range_max, subs, __VA_ARGS__)
#define sis(width, name, subs, ...) \
xsi(width, name, current->name, subs, __VA_ARGS__)
#define marker_bit() \
bit("marker_bit", 1)
#define bit(string, value) do { \
av_unused uint32_t bit = value; \
xuia(1, string, bit, value, value, 0, ); \
} while (0)
#define READ
#define READWRITE read
#define RWContext GetBitContext
#define ui(width, name) do { \
uint32_t value; \
CHECK(ff_cbs_read_simple_unsigned(ctx, rw, width, #name, \
&value)); \
current->name = value; \
} while (0)
#define xuia(width, string, var, range_min, range_max, subs, ...) do { \
uint32_t value; \
CHECK(ff_cbs_read_unsigned(ctx, rw, width, string, \
SUBSCRIPTS(subs, __VA_ARGS__), \
&value, range_min, range_max)); \
var = value; \
} while (0)
#define xsi(width, name, var, subs, ...) do { \
int32_t value; \
CHECK(ff_cbs_read_signed(ctx, rw, width, #name, \
SUBSCRIPTS(subs, __VA_ARGS__), &value, \
MIN_INT_BITS(width), \
MAX_INT_BITS(width))); \
var = value; \
} while (0)
#define nextbits(width, compare, var) \
(get_bits_left(rw) >= width && \
(var = show_bits(rw, width)) == (compare))
#define infer(name, value) do { \
current->name = value; \
} while (0)
#include "cbs_mpeg2_syntax_template.c"
#undef READ
#undef READWRITE
#undef RWContext
#undef ui
#undef xuia
#undef xsi
#undef nextbits
#undef infer
#define WRITE
#define READWRITE write
#define RWContext PutBitContext
#define ui(width, name) do { \
CHECK(ff_cbs_write_simple_unsigned(ctx, rw, width, #name, \
current->name)); \
} while (0)
#define xuia(width, string, var, range_min, range_max, subs, ...) do { \
CHECK(ff_cbs_write_unsigned(ctx, rw, width, string, \
SUBSCRIPTS(subs, __VA_ARGS__), \
var, range_min, range_max)); \
} while (0)
#define xsi(width, name, var, subs, ...) do { \
CHECK(ff_cbs_write_signed(ctx, rw, width, #name, \
SUBSCRIPTS(subs, __VA_ARGS__), var, \
MIN_INT_BITS(width), \
MAX_INT_BITS(width))); \
} while (0)
#define nextbits(width, compare, var) (var)
#define infer(name, value) do { \
if (current->name != (value)) { \
av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
"%s does not match inferred value: " \
"%"PRId64", but should be %"PRId64".\n", \
#name, (int64_t)current->name, (int64_t)(value)); \
} \
} while (0)
#include "cbs_mpeg2_syntax_template.c"
#undef WRITE
#undef READWRITE
#undef RWContext
#undef ui
#undef xuia
#undef xsi
#undef nextbits
#undef infer
static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int header)
{
const uint8_t *start;
uint32_t start_code = -1;
int err;
start = avpriv_find_start_code(frag->data, frag->data + frag->data_size,
&start_code);
if (start_code >> 8 != 0x000001) {
// No start code found.
return AVERROR_INVALIDDATA;
}
do {
CodedBitstreamUnitType unit_type = start_code & 0xff;
const uint8_t *end;
size_t unit_size;
// Reset start_code to ensure that avpriv_find_start_code()
// really reads a new start code and does not reuse the old
// start code in any way (as e.g. happens when there is a
// Sequence End unit at the very end of a packet).
start_code = UINT32_MAX;
end = avpriv_find_start_code(start--, frag->data + frag->data_size,
&start_code);
// start points to the byte containing the start_code_identifier
// (may be the last byte of fragment->data); end points to the byte
// following the byte containing the start code identifier (or to
// the end of fragment->data).
if (start_code >> 8 == 0x000001) {
// Unit runs from start to the beginning of the start code
// pointed to by end (including any padding zeroes).
unit_size = (end - 4) - start;
} else {
// We didn't find a start code, so this is the final unit.
unit_size = end - start;
}
err = ff_cbs_append_unit_data(frag, unit_type, (uint8_t*)start,
unit_size, frag->data_ref);
if (err < 0)
return err;
start = end;
// Do we have a further unit to add to the fragment?
} while ((start_code >> 8) == 0x000001);
return 0;
}
static int cbs_mpeg2_read_unit(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit)
{
GetBitContext gbc;
int err;
err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
if (err < 0)
return err;
err = ff_cbs_alloc_unit_content(ctx, unit);
if (err < 0)
return err;
if (MPEG2_START_IS_SLICE(unit->type)) {
MPEG2RawSlice *slice = unit->content;
int pos, len;
err = cbs_mpeg2_read_slice_header(ctx, &gbc, &slice->header);
if (err < 0)
return err;
if (!get_bits_left(&gbc))
return AVERROR_INVALIDDATA;
pos = get_bits_count(&gbc);
len = unit->data_size;
slice->data_size = len - pos / 8;
slice->data_ref = av_buffer_ref(unit->data_ref);
if (!slice->data_ref)
return AVERROR(ENOMEM);
slice->data = unit->data + pos / 8;
slice->data_bit_start = pos % 8;
} else {
switch (unit->type) {
#define START(start_code, type, read_func, free_func) \
case start_code: \
{ \
type *header = unit->content; \
err = cbs_mpeg2_read_ ## read_func(ctx, &gbc, header); \
if (err < 0) \
return err; \
} \
break;
START(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
picture_header, &cbs_mpeg2_free_picture_header);
START(MPEG2_START_USER_DATA, MPEG2RawUserData,
user_data, &cbs_mpeg2_free_user_data);
START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader,
sequence_header, NULL);
START(MPEG2_START_EXTENSION, MPEG2RawExtensionData,
extension_data, NULL);
START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
group_of_pictures_header, NULL);
START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd,
sequence_end, NULL);
#undef START
default:
return AVERROR(ENOSYS);
}
}
return 0;
}
static int cbs_mpeg2_write_header(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
int err;
switch (unit->type) {
#define START(start_code, type, func) \
case start_code: \
err = cbs_mpeg2_write_ ## func(ctx, pbc, unit->content); \
break;
START(MPEG2_START_PICTURE, MPEG2RawPictureHeader, picture_header);
START(MPEG2_START_USER_DATA, MPEG2RawUserData, user_data);
START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader, sequence_header);
START(MPEG2_START_EXTENSION, MPEG2RawExtensionData, extension_data);
START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
group_of_pictures_header);
START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd, sequence_end);
#undef START
default:
av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for start "
"code %02"PRIx32".\n", unit->type);
return AVERROR_PATCHWELCOME;
}
return err;
}
static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
MPEG2RawSlice *slice = unit->content;
int err;
err = cbs_mpeg2_write_slice_header(ctx, pbc, &slice->header);
if (err < 0)
return err;
if (slice->data) {
size_t rest = slice->data_size - (slice->data_bit_start + 7) / 8;
uint8_t *pos = slice->data + slice->data_bit_start / 8;
av_assert0(slice->data_bit_start >= 0 &&
slice->data_size > slice->data_bit_start / 8);
if (slice->data_size * 8 + 8 > put_bits_left(pbc))
return AVERROR(ENOSPC);
// First copy the remaining bits of the first byte
if (slice->data_bit_start % 8)
put_bits(pbc, 8 - slice->data_bit_start % 8,
*pos++ & MAX_UINT_BITS(8 - slice->data_bit_start % 8));
if (put_bits_count(pbc) % 8 == 0) {
// If the writer is aligned at this point,
// memcpy can be used to improve performance.
// This is the normal case.
flush_put_bits(pbc);
memcpy(put_bits_ptr(pbc), pos, rest);
skip_put_bytes(pbc, rest);
} else {
// If not, we have to copy manually:
for (; rest > 3; rest -= 4, pos += 4)
put_bits32(pbc, AV_RB32(pos));
for (; rest; rest--, pos++)
put_bits(pbc, 8, *pos);
// Align with zeros
put_bits(pbc, 8 - put_bits_count(pbc) % 8, 0);
}
}
return 0;
}
static int cbs_mpeg2_write_unit(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
if (MPEG2_START_IS_SLICE(unit->type))
return cbs_mpeg2_write_slice (ctx, unit, pbc);
else
return cbs_mpeg2_write_header(ctx, unit, pbc);
}
static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag)
{
uint8_t *data;
size_t size, dp;
int i;
size = 0;
for (i = 0; i < frag->nb_units; i++)
size += 3 + frag->units[i].data_size;
frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
if (!frag->data_ref)
return AVERROR(ENOMEM);
data = frag->data_ref->data;
dp = 0;
for (i = 0; i < frag->nb_units; i++) {
CodedBitstreamUnit *unit = &frag->units[i];
data[dp++] = 0;
data[dp++] = 0;
data[dp++] = 1;
memcpy(data + dp, unit->data, unit->data_size);
dp += unit->data_size;
}
av_assert0(dp == size);
memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
frag->data = data;
frag->data_size = size;
return 0;
}
static const CodedBitstreamUnitTypeDescriptor cbs_mpeg2_unit_types[] = {
CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
extra_information_picture.extra_information),
{
.nb_unit_types = CBS_UNIT_TYPE_RANGE,
.unit_type.range.start = 0x01,
.unit_type.range.end = 0xaf,
.content_type = CBS_CONTENT_TYPE_INTERNAL_REFS,
.content_size = sizeof(MPEG2RawSlice),
.type.ref = { .nb_offsets = 2,
.offsets = { offsetof(MPEG2RawSlice, header.extra_information_slice.extra_information),
offsetof(MPEG2RawSlice, data) } },
},
CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_USER_DATA, MPEG2RawUserData,
user_data),
CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader),
CBS_UNIT_TYPE_POD(MPEG2_START_EXTENSION, MPEG2RawExtensionData),
CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd),
CBS_UNIT_TYPE_POD(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader),
CBS_UNIT_TYPE_END_OF_LIST
};
const CodedBitstreamType ff_cbs_type_mpeg2 = {
.codec_id = AV_CODEC_ID_MPEG2VIDEO,
.priv_data_size = sizeof(CodedBitstreamMPEG2Context),
.unit_types = cbs_mpeg2_unit_types,
.split_fragment = &cbs_mpeg2_split_fragment,
.read_unit = &cbs_mpeg2_read_unit,
.write_unit = &cbs_mpeg2_write_unit,
.assemble_fragment = &cbs_mpeg2_assemble_fragment,
};
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