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Fix incorrectly constructed Dirac parse units that caused A/V sync loss.

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Fixes issue 694.
patch by Anuradha Suraparaju, anuradha rd.bbc.co uk

Originally committed as revision 16261 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Anuradha Suraparaju 2008-12-22 00:01:39 +00:00 committed by Diego Biurrun
parent c4ff7c53e0
commit 64bfc5845b
3 changed files with 192 additions and 20 deletions
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203
libavcodec/dirac_parser.c
View File

@ -1,7 +1,8 @@
/*
* Dirac parser
*
* Copyright (c) 2007 Marco Gerards <marco@gnu.org>
* Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
* Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
*
* This file is part of FFmpeg.
*
@ -34,42 +35,200 @@
* Finds the end of the current frame in the bitstream.
* @return the position of the first byte of the next frame or -1
*/
static int find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
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;
int i = 0;
for (i = 0; i < buf_size; i++) {
state = (state << 8) | buf[i];
if (state == DIRAC_PARSE_INFO_PREFIX) {
pc->frame_start_found ^= 1;
if (!pc->frame_start_found) {
pc->state = -1;
return i - 3;
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;
}
return END_NOT_FOUND;
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)
{
uint8_t *start = pc->buffer + offset;
uint8_t *end = pc->buffer + pc->index;
if (start < pc->buffer || (start+13 > end))
return 0;
pu->pu_type = start[4];
pu->next_pu_offset = AV_RB32(start+5);
pu->prev_pu_offset = AV_RB32(start+9);
if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
pu->next_pu_offset = 13;
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) {
memcpy(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));
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);
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 -= 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) {
uint8_t *cur_pu = pc->buffer +
pc->index - 13 - pu1.prev_pu_offset;
int pts = AV_RB32(cur_pu + 13);
if (s->last_pts == 0 && s->last_dts == 0)
s->dts = pts - 1;
else
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 = FF_B_TYPE;
/* 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)
{
ParseContext *pc = s->priv_data;
DiracParseContext *pc = s->priv_data;
int next;
*poutbuf = NULL;
*poutbuf_size = 0;
if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
next = buf_size;
}else{
*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 (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
*poutbuf = NULL;
*poutbuf_size = 0;
if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {
return buf_size;
}
}
@ -79,10 +238,18 @@ static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
return next;
}
static void dirac_parse_close(AVCodecParserContext *s)
{
DiracParseContext *pc = s->priv_data;
if (pc->buffer_size > 0)
av_free(pc->buffer);
}
AVCodecParser dirac_parser = {
{ CODEC_ID_DIRAC },
sizeof(ParseContext),
sizeof(DiracParseContext),
NULL,
dirac_parse,
ff_parse_close,
dirac_parse_close,
};

6
libavcodec/libdiracdec.c
View File

@ -88,10 +88,12 @@ static int libdirac_decode_frame(AVCodecContext *avccontext,
*data_size = 0;
if (buf_size>0)
if (buf_size>0) {
/* set data to decode into buffer */
dirac_buffer (p_dirac_params->p_decoder, buf, buf+buf_size);
if ((buf[4] &0x08) == 0x08 && (buf[4] & 0x03))
avccontext->has_b_frames = 1;
}
while (1) {
/* parse data and process result */
DecoderState state = dirac_parse (p_dirac_params->p_decoder);

3
libavcodec/libschroedingerdec.c
View File

@ -235,6 +235,9 @@ static int libschroedinger_decode_frame(AVCodecContext *avccontext,
do {
if ((enc_buf = FfmpegFindNextSchroParseUnit(&parse_ctx))) {
/* Push buffer into decoder. */
if (SCHRO_PARSE_CODE_IS_PICTURE(enc_buf->data[4]) &&
SCHRO_PARSE_CODE_NUM_REFS(enc_buf->data[4]) > 0)
avccontext->has_b_frames = 1;
state = schro_decoder_push (decoder, enc_buf);
if (state == SCHRO_DECODER_FIRST_ACCESS_UNIT)
libschroedinger_handle_first_access_unit(avccontext);