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ffmpeg/libavcodec/h2645_parse.c

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/*
* H.264/HEVC common parsing code
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <string.h>
#include "config.h"
#include "libavutil/intmath.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "bytestream.h"
#include "h2645_parse.h"
int ff_h2645_extract_rbsp(const uint8_t *src, int length,
H2645NAL *nal)
{
int i, si, di;
uint8_t *dst;
#define STARTCODE_TEST \
if (i + 2 < length && src[i + 1] == 0 && src[i + 2] <= 3) { \
if (src[i + 2] != 3) { \
/* startcode, so we must be past the end */ \
length = i; \
} \
break; \
}
#if HAVE_FAST_UNALIGNED
#define FIND_FIRST_ZERO \
if (i > 0 && !src[i]) \
i--; \
while (src[i]) \
i++
#if HAVE_FAST_64BIT
for (i = 0; i + 1 < length; i += 9) {
if (!((~AV_RN64A(src + i) &
(AV_RN64A(src + i) - 0x0100010001000101ULL)) &
0x8000800080008080ULL))
continue;
FIND_FIRST_ZERO;
STARTCODE_TEST;
i -= 7;
}
#else
for (i = 0; i + 1 < length; i += 5) {
if (!((~AV_RN32A(src + i) &
(AV_RN32A(src + i) - 0x01000101U)) &
0x80008080U))
continue;
FIND_FIRST_ZERO;
STARTCODE_TEST;
i -= 3;
}
#endif /* HAVE_FAST_64BIT */
#else
for (i = 0; i + 1 < length; i += 2) {
if (src[i])
continue;
if (i > 0 && src[i - 1] == 0)
i--;
STARTCODE_TEST;
}
#endif /* HAVE_FAST_UNALIGNED */
if (i >= length - 1) { // no escaped 0
nal->data =
nal->raw_data = src;
nal->size =
nal->raw_size = length;
return length;
}
av_fast_malloc(&nal->rbsp_buffer, &nal->rbsp_buffer_size,
length + AV_INPUT_BUFFER_PADDING_SIZE);
if (!nal->rbsp_buffer)
return AVERROR(ENOMEM);
dst = nal->rbsp_buffer;
memcpy(dst, src, i);
si = di = i;
while (si + 2 < length) {
// remove escapes (very rare 1:2^22)
if (src[si + 2] > 3) {
dst[di++] = src[si++];
dst[di++] = src[si++];
} else if (src[si] == 0 && src[si + 1] == 0) {
if (src[si + 2] == 3) { // escape
dst[di++] = 0;
dst[di++] = 0;
si += 3;
continue;
} else // next start code
goto nsc;
}
dst[di++] = src[si++];
}
while (si < length)
dst[di++] = src[si++];
nsc:
memset(dst + di, 0, AV_INPUT_BUFFER_PADDING_SIZE);
nal->data = dst;
nal->size = di;
nal->raw_data = src;
nal->raw_size = si;
return si;
}
static int get_bit_length(H2645NAL *nal, int skip_trailing_zeros)
{
int size = nal->size;
int v;
while (skip_trailing_zeros && size > 0 && nal->data[size - 1] == 0)
size--;
if (!size)
return 0;
v = nal->data[size - 1];
if (size > INT_MAX / 8)
return AVERROR(ERANGE);
size *= 8;
/* remove the stop bit and following trailing zeros,
* or nothing for damaged bitstreams */
if (v)
size -= av_ctz(v) + 1;
return size;
}
/**
* @return AVERROR_INVALIDDATA if the packet is not a valid NAL unit,
* 0 if the unit should be skipped, 1 otherwise
*/
static int hevc_parse_nal_header(H2645NAL *nal, void *logctx)
{
GetBitContext *gb = &nal->gb;
int nuh_layer_id;
if (get_bits1(gb) != 0)
return AVERROR_INVALIDDATA;
nal->type = get_bits(gb, 6);
nuh_layer_id = get_bits(gb, 6);
nal->temporal_id = get_bits(gb, 3) - 1;
if (nal->temporal_id < 0)
return AVERROR_INVALIDDATA;
av_log(logctx, AV_LOG_DEBUG,
"nal_unit_type: %d, nuh_layer_id: %dtemporal_id: %d\n",
nal->type, nuh_layer_id, nal->temporal_id);
return nuh_layer_id == 0;
}
static int h264_parse_nal_header(H2645NAL *nal, void *logctx)
{
GetBitContext *gb = &nal->gb;
if (get_bits1(gb) != 0)
return AVERROR_INVALIDDATA;
nal->ref_idc = get_bits(gb, 2);
nal->type = get_bits(gb, 5);
av_log(logctx, AV_LOG_DEBUG,
"nal_unit_type: %d, nal_ref_idc: %d\n",
nal->type, nal->ref_idc);
return 1;
}
static int find_next_start_code(const uint8_t *buf, const uint8_t *next_avc)
{
int i = 0;
if (buf + 3 >= next_avc)
return next_avc - buf;
while (buf + i + 3 < next_avc) {
if (buf[i] == 0 && buf[i + 1] == 0 && buf[i + 2] == 1)
break;
i++;
}
return i + 3;
}
int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
void *logctx, int is_nalff, int nal_length_size,
enum AVCodecID codec_id)
{
GetByteContext bc;
int consumed, ret = 0;
size_t next_avc = is_nalff ? 0 : length;
bytestream2_init(&bc, buf, length);
pkt->nb_nals = 0;
while (bytestream2_get_bytes_left(&bc) >= 4) {
H2645NAL *nal;
int extract_length = 0;
int skip_trailing_zeros = 1;
/*
* Only parse an AVC1 length field if one is expected at the current
* buffer position. There are unfortunately streams with multiple
* NAL units covered by the length field. Those NAL units are delimited
* by Annex B start code prefixes. ff_h2645_extract_rbsp() detects it
* correctly and consumes only the first NAL unit. The additional NAL
* units are handled here in the Annex B parsing code.
*/
if (bytestream2_tell(&bc) == next_avc) {
int i;
for (i = 0; i < nal_length_size; i++)
extract_length = (extract_length << 8) | bytestream2_get_byte(&bc);
if (extract_length > bytestream2_get_bytes_left(&bc)) {
av_log(logctx, AV_LOG_ERROR,
"Invalid NAL unit size (%d > %d).\n",
extract_length, bytestream2_get_bytes_left(&bc));
return AVERROR_INVALIDDATA;
}
// keep track of the next AVC1 length field
next_avc = bytestream2_tell(&bc) + extract_length;
} else {
/*
* expected to return immediately except for streams with mixed
* NAL unit coding
*/
int buf_index = find_next_start_code(bc.buffer, buf + next_avc);
bytestream2_skip(&bc, buf_index);
/*
* break if an AVC1 length field is expected at the current buffer
* position
*/
if (bytestream2_tell(&bc) == next_avc)
continue;
if (bytestream2_get_bytes_left(&bc) > 0) {
extract_length = bytestream2_get_bytes_left(&bc);
} else if (pkt->nb_nals == 0) {
av_log(logctx, AV_LOG_ERROR, "No NAL unit found\n");
return AVERROR_INVALIDDATA;
} else {
break;
}
}
if (pkt->nals_allocated < pkt->nb_nals + 1) {
int new_size = pkt->nals_allocated + 1;
H2645NAL *tmp = av_realloc_array(pkt->nals, new_size, sizeof(*tmp));
if (!tmp)
return AVERROR(ENOMEM);
pkt->nals = tmp;
memset(pkt->nals + pkt->nals_allocated, 0,
(new_size - pkt->nals_allocated) * sizeof(*tmp));
pkt->nals_allocated = new_size;
}
nal = &pkt->nals[pkt->nb_nals++];
consumed = ff_h2645_extract_rbsp(bc.buffer, extract_length, nal);
if (consumed < 0)
return consumed;
bytestream2_skip(&bc, consumed);
/* see commit 3566042a0 */
if (bytestream2_get_bytes_left(&bc) >= 4 &&
bytestream2_peek_be32(&bc) == 0x000001E0)
skip_trailing_zeros = 0;
nal->size_bits = get_bit_length(nal, skip_trailing_zeros);
ret = init_get_bits(&nal->gb, nal->data, nal->size_bits);
if (ret < 0)
return ret;
if (codec_id == AV_CODEC_ID_HEVC)
ret = hevc_parse_nal_header(nal, logctx);
else
ret = h264_parse_nal_header(nal, logctx);
if (ret <= 0) {
if (ret < 0) {
av_log(logctx, AV_LOG_ERROR, "Invalid NAL unit %d, skipping.\n",
nal->type);
}
pkt->nb_nals--;
}
}
return 0;
}
void ff_h2645_packet_uninit(H2645Packet *pkt)
{
int i;
for (i = 0; i < pkt->nals_allocated; i++)
av_freep(&pkt->nals[i].rbsp_buffer);
av_freep(&pkt->nals);
pkt->nals_allocated = 0;
}
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