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ac3dec: unroll inner loop in exponent decoding. 46% faster decode_exponents().

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Originally committed as revision 16018 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-12-06 15:46:23 +00:00
parent 806703243e
commit 96f229d6c0
1 changed files with 6 additions and 3 deletions
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9
libavcodec/ac3dec.c
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@ -390,12 +390,15 @@ static int decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
/* convert to absolute exps and expand groups */ /* convert to absolute exps and expand groups */
prevexp = absexp; prevexp = absexp;
for(i=0; i<ngrps*3; i++) { for(i=0,j=0; i<ngrps*3; i++) {
prevexp += dexp[i] - 2; prevexp += dexp[i] - 2;
if (prevexp < 0 || prevexp > 24) if (prevexp < 0 || prevexp > 24)
return -1; return -1;
for(j=0; j<group_size; j++) { switch (group_size) {
dexps[(i*group_size)+j] = prevexp; case 4: dexps[j++] = prevexp;
dexps[j++] = prevexp;
case 2: dexps[j++] = prevexp;
case 1: dexps[j++] = prevexp;
} }
} }
return 0; return 0;