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2.5x faster compute_autocorr()

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overall flac encoding: 15-50% faster on core2, 8-30% on k8, 2-20% on p4 (depending on compression_level)

Originally committed as revision 10606 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Loren Merritt 2007-09-28 06:06:18 +00:00
parent 7e1e297ee3
commit 28e968c4a4
1 changed files with 17 additions and 8 deletions
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25
libavcodec/flacenc.c
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@ -607,21 +607,30 @@ static void apply_welch_window(const int32_t *data, int len, double *w_data)
static void compute_autocorr(const int32_t *data, int len, int lag,
double *autoc)
{
int i, lag_ptr;
int i, j;
double tmp[len + lag];
double *data1= tmp + lag;
apply_welch_window(data, len, data1);
for(i=0; i<lag; i++){
autoc[i] = 1.0;
data1[i-lag]= 0.0;
for(j=0; j<lag; j++)
data1[j-lag]= 0.0;
for(j=0; j<lag; j+=2){
double sum0 = 1.0, sum1 = 1.0;
for(i=0; i<len; i++){
sum0 += data1[i] * data1[i-j];
sum1 += data1[i] * data1[i-j-1];
}
autoc[j ] = sum0;
autoc[j+1] = sum1;
}
for(i=0; i<len; i++){
for(lag_ptr= i-lag; lag_ptr<=i; lag_ptr++){
autoc[i-lag_ptr] += data1[i] * data1[lag_ptr];
}
if(j==lag){
double sum = 1.0;
for(i=0; i<len; i++)
sum += data1[i] * data1[i-j];
autoc[j] = sum;
}
}