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Check order of startcodes, ignore some obviously wrong ones. 

Fixes issue487.

Originally committed as revision 20643 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2009-11-28 22:51:53 +00:00
parent bbf266fdb5
commit fc23d843e1
1 changed files with 17 additions and 1 deletions
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18
libavcodec/mpeg12.c
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@ -2260,6 +2260,7 @@ static int decode_chunks(AVCodecContext *avctx,
const uint8_t *buf_ptr = buf;
const uint8_t *buf_end = buf + buf_size;
int ret, input_size;
int last_code= 0;
for(;;) {
/* find next start code */
@ -2296,8 +2297,12 @@ static int decode_chunks(AVCodecContext *avctx,
/* prepare data for next start code */
switch(start_code) {
case SEQ_START_CODE:
if(last_code == 0){
mpeg1_decode_sequence(avctx, buf_ptr,
input_size);
}else{
av_log(avctx, AV_LOG_ERROR, "ignoring SEQ_START_CODE after %X\n", last_code);
}
break;
case PICTURE_START_CODE:
@ -2310,13 +2315,18 @@ static int decode_chunks(AVCodecContext *avctx,
if(mpeg1_decode_picture(avctx,
buf_ptr, input_size) < 0)
s2->pict_type=0;
last_code= PICTURE_START_CODE;
break;
case EXT_START_CODE:
init_get_bits(&s2->gb, buf_ptr, input_size*8);
switch(get_bits(&s2->gb, 4)) {
case 0x1:
if(last_code == 0){
mpeg_decode_sequence_extension(s);
}else{
av_log(avctx, AV_LOG_ERROR, "ignoring seq ext after %X\n", last_code);
}
break;
case 0x2:
mpeg_decode_sequence_display_extension(s);
@ -2329,6 +2339,7 @@ static int decode_chunks(AVCodecContext *avctx,
break;
case 0x8:
mpeg_decode_picture_coding_extension(s);
last_code= PICTURE_START_CODE;
break;
}
break;
@ -2337,14 +2348,19 @@ static int decode_chunks(AVCodecContext *avctx,
buf_ptr, input_size);
break;
case GOP_START_CODE:
if(last_code == 0){
s2->first_field=0;
mpeg_decode_gop(avctx,
buf_ptr, input_size);
}else{
av_log(avctx, AV_LOG_ERROR, "ignoring GOP_START_CODE after %X\n", last_code);
}
break;
default:
if (start_code >= SLICE_MIN_START_CODE &&
start_code <= SLICE_MAX_START_CODE) {
start_code <= SLICE_MAX_START_CODE && last_code!=0) {
int mb_y= start_code - SLICE_MIN_START_CODE;
last_code= SLICE_MIN_START_CODE;
if(s2->last_picture_ptr==NULL){
/* Skip B-frames if we do not have reference frames and gop is not closed */