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7c18e34a74
git-svn-id: file:///home/notaz/opt/svn/PicoDrive@889 be3aeb3a-fb24-0410-a615-afba39da0efa
29 lines
599 B
C
29 lines
599 B
C
#include "mp3.h"
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int mp3_find_sync_word(const unsigned char *buf, int size)
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{
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const unsigned char *p, *pe;
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/* find byte-aligned syncword - need 12 (MPEG 1,2) or 11 (MPEG 2.5) matching bits */
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for (p = buf, pe = buf + size - 3; p <= pe; p++)
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{
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int pn;
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if (p[0] != 0xff)
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continue;
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pn = p[1];
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if ((pn & 0xf8) != 0xf8 || // currently must be MPEG1
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(pn & 6) == 0) { // invalid layer
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p++; continue;
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}
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pn = p[2];
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if ((pn & 0xf0) < 0x20 || (pn & 0xf0) == 0xf0 || // bitrates
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(pn & 0x0c) != 0) { // not 44kHz
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continue;
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}
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return p - buf;
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}
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return -1;
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}
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