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optimize encode_residual_lpc() 

37%/45%/90% faster on core2/k8/p4, making flac encoding overall 15%/17%/40% faster at compression_level>=8 (less at low levels).

Originally committed as revision 10585 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Loren Merritt 2007-09-25 23:30:29 +00:00
parent 7ecae905b6
commit f74471e043
1 changed files with 11 additions and 6 deletions
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17
libavcodec/flacenc.c
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@ -838,17 +838,22 @@ static void encode_residual_lpc(int32_t *res, const int32_t *smp, int n,
int order, const int32_t *coefs, int shift)
{
int i, j;
int32_t pred;
for(i=0; i<order; i++) {
res[i] = smp[i];
}
for(i=order; i<n; i++) {
pred = 0;
for(j=0; j<order; j++) {
pred += coefs[j] * smp[i-j-1];
for(i=order; i<n; i+=2) {
int32_t c = coefs[0];
int32_t p0 = 0, p1 = c*smp[i];
for(j=1; j<order; j++) {
int32_t s = smp[i-j];
p0 += c*s;
c = coefs[j];
p1 += c*s;
}
res[i] = smp[i] - (pred >> shift);
p0 += c*smp[i-order];
res[i+0] = smp[i+0] - (p0 >> shift);
res[i+1] = smp[i+1] - (p1 >> shift);
}
}