mirror of
https://github.com/RaySollium99/picodrive.git
synced 2025-09-05 15:27:46 -04:00
27 lines
581 B
C
27 lines
581 B
C
|
|
int mp3_find_sync_word(const unsigned char *buf, int size)
|
|
{
|
|
const unsigned char *p, *pe;
|
|
|
|
/* find byte-aligned syncword - need 12 (MPEG 1,2) or 11 (MPEG 2.5) matching bits */
|
|
for (p = buf, pe = buf + size - 3; p <= pe; p++)
|
|
{
|
|
int pn;
|
|
if (p[0] != 0xff)
|
|
continue;
|
|
pn = p[1];
|
|
if ((pn & 0xf8) != 0xf8 || // currently must be MPEG1
|
|
(pn & 6) == 0) { // invalid layer
|
|
p++; continue;
|
|
}
|
|
pn = p[2];
|
|
if ((pn & 0xf0) < 0x20 || (pn & 0xf0) == 0xf0 || // bitrates
|
|
(pn & 0x0c) != 0) { // not 44kHz
|
|
continue;
|
|
}
|
|
|
|
return p - buf;
|
|
}
|
|
|
|
return -1;
|
|
}
|