2011-10-10 0:27:53
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2011-10-10 0:27:53
/** This structure contains the data a format has to probe a file. */
typedef struct AVProbeData {
const char *filename;
unsigned char *buf; /**< Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero. */
int buf_size; /**< Size of buf except extra allocated bytes */
} AVProbeData;
h264的探测函数:
static int h264_probe(AVProbeData *p)
{
uint32_t code= -1;
int sps=0, pps=0, idr=0, res=0, sli=0;
int i;
for(i=0; i<p->buf_size; i++){
code = (code<<8) + p->buf[i];
if ((code & 0xffffff00) == 0x100) {
int ref_idc= (code>>5)&3;
int type = code & 0x1F;
static const int8_t ref_zero[32]={
2, 0, 0, 0, 0,-1, 1,-1,
-1, 1, 1, 1, 1,-1, 2, 2,
2, 2, 2, 0, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2
};
if(code & 0x80) //forbidden bit
return 0;
if(ref_zero[type] == 1 && ref_idc)
return 0;
if(ref_zero[type] ==-1 && !ref_idc)
return 0;
if(ref_zero[type] == 2)
res++;
switch(type){
case 1: sli++; break;
case 5: idr++; break;
case 7:
if(p->buf[i+2]&0x0F)
return 0;
sps++;
break;
case 8: pps++; break;
}
}
}
if(sps && pps && (idr||sli>3) && res<(sps+pps+idr))
return AVPROBE_SCORE_MAX/2+1; // +1 for .mpg
return 0;
}
解析是否为H.264
/** This structure contains the data a format has to probe a file. */
typedef struct AVProbeData {
const char *filename;
unsigned char *buf; /**< Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero. */
int buf_size; /**< Size of buf except extra allocated bytes */
} AVProbeData;
h264的探测函数:
static int h264_probe(AVProbeData *p)
{
uint32_t code= -1;
int sps=0, pps=0, idr=0, res=0, sli=0;
int i;
for(i=0; i<p->buf_size; i++){
code = (code<<8) + p->buf[i];
if ((code & 0xffffff00) == 0x100) {
int ref_idc= (code>>5)&3;
int type = code & 0x1F;
static const int8_t ref_zero[32]={
2, 0, 0, 0, 0,-1, 1,-1,
-1, 1, 1, 1, 1,-1, 2, 2,
2, 2, 2, 0, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2
};
if(code & 0x80) //forbidden bit
return 0;
if(ref_zero[type] == 1 && ref_idc)
return 0;
if(ref_zero[type] ==-1 && !ref_idc)
return 0;
if(ref_zero[type] == 2)
res++;
switch(type){
case 1: sli++; break;
case 5: idr++; break;
case 7:
if(p->buf[i+2]&0x0F)
return 0;
sps++;
break;
case 8: pps++; break;
}
}
}
if(sps && pps && (idr||sli>3) && res<(sps+pps+idr))
return AVPROBE_SCORE_MAX/2+1; // +1 for .mpg
return 0;
}
解析是否为H.264
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