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Rewrite h261_probe().

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New code can detect h261 startcodes even when the first is damaged or not at the
begin. It also passes probetest v2 & v3.

Originally committed as revision 19845 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2009-09-14 21:29:19 +00:00
parent 05bdd33a12
commit 89c4e176f6
1 changed files with 28 additions and 6 deletions
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34
libavformat/raw.c
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@ -489,14 +489,36 @@ static int h263_probe(AVProbeData *p)
#if CONFIG_H261_DEMUXER
static int h261_probe(AVProbeData *p)
{
int code;
const uint8_t *d;
uint32_t code= -1;
int i;
int valid_psc=0;
int invalid_psc=0;
int next_gn=0;
int src_fmt=0;
GetBitContext gb;
d = p->buf;
code = (d[0] << 12) | (d[1] << 4) | (d[2] >> 4);
if (code == 0x10) {
return 50;
init_get_bits(&gb, p->buf, p->buf_size*8);
for(i=0; i<p->buf_size*8; i++){
code = (code<<1) + get_bits1(&gb);
if ((code & 0xffff0000) == 0x10000) {
int gn= (code>>12)&0xf;
if(!gn)
src_fmt= code&8;
if(gn != next_gn) invalid_psc++;
else valid_psc++;
if(src_fmt){ // CIF
next_gn= (gn+1 )%13;
}else{ //QCIF
next_gn= (gn+1+!!gn)% 7;
}
}
}
if(valid_psc > 2*invalid_psc + 4){
return 50;
}else if(valid_psc > 2*invalid_psc + 2)
return 25;
return 0;
}
#endif