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xylophone21 Sep 13, 2021
score 越大，可能性越高
```c
static int mov_probe(const AVProbeData *p)
{
int64_t offset;
uint32_t tag;
int score = 0;
int moov_offset = -1;
/* check file header */
offset = 0;
for (;;) {
int64_t size;
int minsize = 8;
/* ignore invalid offset */
if ((offset + 8ULL) > (unsigned int)p->buf_size)
break;
size = AV_RB32(p->buf + offset);
if (size == 1 && offset + 16 <= (unsigned int)p->buf_size) {
size = AV_RB64(p->buf+offset + 8);
minsize = 16;
} else if (size == 0) {
size = p->buf_size - offset;
}
if (size < minsize) {
offset += 4;
continue;
}
tag = AV_RL32(p->buf + offset + 4);
switch(tag) {
/* check for obvious tags */
case MKTAG('m','o','o','v'):
moov_offset = offset + 4;
case MKTAG('m','d','a','t'):
case MKTAG('p','n','o','t'): /* detect movs with preview pics like ew.mov and april.mov */
case MKTAG('u','d','t','a'): /* Packet Video PVAuthor adds this and a lot of more junk */
case MKTAG('f','t','y','p'):
if (tag == MKTAG('f','t','y','p') &&
( AV_RL32(p->buf + offset + 8) == MKTAG('j','p','2',' ')
|| AV_RL32(p->buf + offset + 8) == MKTAG('j','p','x',' ')
)) {
score = FFMAX(score, 5);
} else {
score = AVPROBE_SCORE_MAX;
}
break;
/* those are more common words, so rate then a bit less */
case MKTAG('e','d','i','w'): /* xdcam files have reverted first tags */
case MKTAG('w','i','d','e'):
case MKTAG('f','r','e','e'):
case MKTAG('j','u','n','k'):
case MKTAG('p','i','c','t'):
score = FFMAX(score, AVPROBE_SCORE_MAX - 5);
break;
case MKTAG(0x82,0x82,0x7f,0x7d):
case MKTAG('s','k','i','p'):
case MKTAG('u','u','i','d'):
case MKTAG('p','r','f','l'):
/* if we only find those cause probedata is too small at least rate them */
score = FFMAX(score, AVPROBE_SCORE_EXTENSION);
break;
}
if (size > INT64_MAX - offset)
break;
offset += size;
}
if (score > AVPROBE_SCORE_MAX - 50 && moov_offset != -1) {
/* moov atom in the header - we should make sure that this is not a
* MOV-packed MPEG-PS */
offset = moov_offset;
while (offset < (p->buf_size - 16)) { /* Sufficient space */
/* We found an actual hdlr atom */
if (AV_RL32(p->buf + offset ) == MKTAG('h','d','l','r') &&
AV_RL32(p->buf + offset + 8) == MKTAG('m','h','l','r') &&
AV_RL32(p->buf + offset + 12) == MKTAG('M','P','E','G')) {
av_log(NULL, AV_LOG_WARNING, "Found media data tag MPEG indicating this is a MOV-packed MPEG-PS.\n");
/* We found a media handler reference atom describing an
* MPEG-PS-in-MOV, return a
* low score to force expanding the probe window until
* mpegps_probe finds what it needs */
return 5;
} else {
/* Keep looking */
offset += 2;
}
}
}
return score;
}
```
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