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FFmpeg4/libavcodec/dirac_parser.c

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/*
* Dirac parser
*
* Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
* Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
*
* 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
*/
/**
* @file
* Dirac Parser
* @author Marco Gerards <marco@gnu.org>
*/
#include <string.h>
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "parser.h"
#define DIRAC_PARSE_INFO_PREFIX 0x42424344
/**
* Find the end of the current frame in the bitstream.
* @return the position of the first byte of the next frame or -1
*/
typedef struct DiracParseContext {
int state;
int is_synced;
int sync_offset;
int header_bytes_needed;
int overread_index;
int buffer_size;
int index;
uint8_t *buffer;
int dirac_unit_size;
uint8_t *dirac_unit;
} DiracParseContext;
static int find_frame_end(DiracParseContext *pc,
const uint8_t *buf, int buf_size)
{
uint32_t state = pc->state;
int i = 0;
if (!pc->is_synced) {
for (i = 0; i < buf_size; i++) {
state = (state << 8) | buf[i];
if (state == DIRAC_PARSE_INFO_PREFIX) {
state = -1;
pc->is_synced = 1;
pc->header_bytes_needed = 9;
pc->sync_offset = i;
break;
}
}
}
if (pc->is_synced) {
pc->sync_offset = 0;
for (; i < buf_size; i++) {
if (state == DIRAC_PARSE_INFO_PREFIX) {
if ((buf_size - i) >= pc->header_bytes_needed) {
pc->state = -1;
return i + pc->header_bytes_needed;
} else {
pc->header_bytes_needed = 9 - (buf_size - i);
break;
}
} else
state = (state << 8) | buf[i];
}
}
pc->state = state;
return -1;
}
typedef struct DiracParseUnit {
int next_pu_offset;
int prev_pu_offset;
uint8_t pu_type;
} DiracParseUnit;
static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
int offset)
{
int i;
int8_t *start;
static const uint8_t valid_pu_types[] = {
0x00, 0x10, 0x20, 0x30, 0x08, 0x48, 0xC8, 0xE8, 0x0A, 0x0C, 0x0D, 0x0E,
0x4C, 0x09, 0xCC, 0x88, 0xCB
};
if (offset < 0 || pc->index - 13 < offset)
return 0;
start = pc->buffer + offset;
pu->pu_type = start[4];
pu->next_pu_offset = AV_RB32(start + 5);
pu->prev_pu_offset = AV_RB32(start + 9);
/* Check for valid parse code */
for (i = 0; i < 17; i++)
if (valid_pu_types[i] == pu->pu_type)
break;
if (i == 17)
return 0;
if (pu->pu_type == 0x10 && pu->next_pu_offset == 0x00)
pu->next_pu_offset = 13; /* The length of a parse info header */
/* Check if the parse offsets are somewhat sane */
if ((pu->next_pu_offset && pu->next_pu_offset < 13) ||
(pu->prev_pu_offset && pu->prev_pu_offset < 13))
return 0;
return 1;
}
static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
int next, const uint8_t **buf, int *buf_size)
{
int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
s->dts == AV_NOPTS_VALUE);
DiracParseContext *pc = s->priv_data;
if (pc->overread_index) {
memmove(pc->buffer, pc->buffer + pc->overread_index,
pc->index - pc->overread_index);
pc->index -= pc->overread_index;
pc->overread_index = 0;
if (*buf_size == 0 && pc->buffer[4] == 0x10) {
*buf = pc->buffer;
*buf_size = pc->index;
return 0;
}
}
if (next == -1) {
/* Found a possible frame start but not a frame end */
void *new_buffer =
av_fast_realloc(pc->buffer, &pc->buffer_size,
pc->index + (*buf_size - pc->sync_offset));
if (!new_buffer)
return AVERROR(ENOMEM);
pc->buffer = new_buffer;
memcpy(pc->buffer + pc->index, (*buf + pc->sync_offset),
*buf_size - pc->sync_offset);
pc->index += *buf_size - pc->sync_offset;
return -1;
} else {
/* Found a possible frame start and a possible frame end */
DiracParseUnit pu1, pu;
void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
pc->index + next);
if (!new_buffer)
return AVERROR(ENOMEM);
pc->buffer = new_buffer;
memcpy(pc->buffer + pc->index, *buf, next);
pc->index += next;
/* Need to check if we have a valid Parse Unit. We can't go by the
* sync pattern 'BBCD' alone because arithmetic coding of the residual
* and motion data can cause the pattern triggering a false start of
* frame. So check if the previous parse offset of the next parse unit
* is equal to the next parse offset of the current parse unit then
* we can be pretty sure that we have a valid parse unit */
if (!unpack_parse_unit(&pu1, pc, pc->index - 13) ||
!unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
pu.next_pu_offset != pu1.prev_pu_offset ||
pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset
) {
pc->index -= 9;
*buf_size = next - 9;
pc->header_bytes_needed = 9;
return -1;
}
/* All non-frame data must be accompanied by frame data. This is to
* ensure that pts is set correctly. So if the current parse unit is
* not frame data, wait for frame data to come along */
pc->dirac_unit = pc->buffer + pc->index - 13 -
pu1.prev_pu_offset - pc->dirac_unit_size;
pc->dirac_unit_size += pu.next_pu_offset;
if ((pu.pu_type & 0x08) != 0x08) {
pc->header_bytes_needed = 9;
*buf_size = next;
return -1;
}
/* Get the picture number to set the pts and dts*/
if (parse_timing_info && pu1.prev_pu_offset >= 13) {
uint8_t *cur_pu = pc->buffer +
pc->index - 13 - pu1.prev_pu_offset;
int64_t pts = AV_RB32(cur_pu + 13);
if (s->last_pts == 0 && s->last_dts == 0)
s->dts = pts - 1;
else if (s->last_dts != AV_NOPTS_VALUE)
s->dts = s->last_dts + 1;
s->pts = pts;
if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
avctx->has_b_frames = 1;
}
if (avctx->has_b_frames && s->pts == s->dts)
s->pict_type = AV_PICTURE_TYPE_B;
/* Finally have a complete Dirac data unit */
*buf = pc->dirac_unit;
*buf_size = pc->dirac_unit_size;
pc->dirac_unit_size = 0;
pc->overread_index = pc->index - 13;
pc->header_bytes_needed = 9;
}
return next;
}
static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
const uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size)
{
DiracParseContext *pc = s->priv_data;
int next;
*poutbuf = NULL;
*poutbuf_size = 0;
if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
next = buf_size;
*poutbuf = buf;
*poutbuf_size = buf_size;
/* Assume that data has been packetized into an encapsulation unit. */
} else {
next = find_frame_end(pc, buf, buf_size);
if (!pc->is_synced && next == -1)
/* No frame start found yet. So throw away the entire buffer. */
return buf_size;
if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0)
return buf_size;
}
*poutbuf = buf;
*poutbuf_size = buf_size;
return next;
}
static void dirac_parse_close(AVCodecParserContext *s)
{
DiracParseContext *pc = s->priv_data;
if (pc->buffer_size > 0)
av_freep(&pc->buffer);
}
AVCodecParser ff_dirac_parser = {
.codec_ids = { AV_CODEC_ID_DIRAC },
.priv_data_size = sizeof(DiracParseContext),
.parser_parse = dirac_parse,
.parser_close = dirac_parse_close,
};
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