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skip junk in mp3_helix, refactor find_sync_word

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git-svn-id: file:///home/notaz/opt/svn/PicoDrive@889 be3aeb3a-fb24-0410-a615-afba39da0efa
This commit is contained in:
notaz 2010-09-08 20:52:13 +00:00
parent cf82669f50
commit 7c18e34a74
13 changed files with 86 additions and 82 deletions
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29
platform/common/mp3.c Normal file
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@ -0,0 +1,29 @@
#include "mp3.h"
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;
}