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Make MPC SV8 probe skip tags until stream header is found 

Originally committed as revision 19884 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Kostya Shishkov 2009-09-16 18:05:21 +00:00
parent 6f24cc0b2a
commit f53c9089f6
1 changed files with 39 additions and 20 deletions
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59
libavformat/mpc8.c
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@ -51,37 +51,56 @@ typedef struct {
int64_t samples;
} MPCContext;
static inline int64_t bs_get_v(uint8_t **bs)
{
int64_t v = 0;
int br = 0;
int c;
do {
c = **bs; (*bs)++;
v <<= 7;
v |= c & 0x7F;
br++;
if (br > 10)
return -1;
} while (c & 0x80);
return v - br;
}
static int mpc8_probe(AVProbeData *p)
{
uint8_t *bs = p->buf + 4;
uint8_t *bs_end = bs + p->buf_size;
int64_t size;
if (p->buf_size < 16)
return 0;
if (AV_RL32(p->buf) != TAG_MPCK)
return 0;
if (p->buf[4] == 'S' && p->buf[5] == 'H') {
int size = p->buf[6];
while (bs < bs_end + 3) {
int header_found = (bs[0] == 'S' && bs[1] == 'H');
if (bs[0] < 'A' || bs[0] > 'Z' || bs[1] < 'A' || bs[1] > 'Z')
return 0;
bs += 2;
size = bs_get_v(&bs);
if (size < 2)
return 0;
if (bs + size - 2 >= bs_end)
return AVPROBE_SCORE_MAX / 4 - 1; //seems to be valid MPC but no header yet
if (header_found) {
if (size < 12 || size > 30)
if (size < 11 || size > 28)
return 0;
if (!AV_RL32(&p->buf[7])) //zero CRC is invalid
return 0;
//check whether some tag follows stream header or not
if (p->buf[4 + size] < 'A' || p->buf[4 + size] > 'Z')
return 0;
if (p->buf[5 + size] < 'A' || p->buf[5 + size] > 'Z')
return 0;
if (p->buf[6 + size] < 3)
if (!AV_RL32(bs)) //zero CRC is invalid
return 0;
return AVPROBE_SCORE_MAX;
} else {
bs += size - 2;
}
}
/* file magic number should be followed by tag name which consists of
two uppercase letters */
if (p->buf[4] < 'A' || p->buf[4] > 'Z' || p->buf[5] < 'A' || p->buf[5] > 'Z')
return 0;
// tag size should be >= 3
if (p->buf[6] < 3)
return 0;
// if first tag is not stream header, that's suspicious
return AVPROBE_SCORE_MAX / 4;
return 0;
}
static inline int64_t gb_get_v(GetBitContext *gb)