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Move autocorrelation function from flacenc.c to lpc.c. Also rename the

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corresponding dsputil functions and remove their dependency on the FLAC
encoder.
Fixes Issue1486.

Originally committed as revision 20266 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles
2009-10-17 21:00:39 +00:00
parent a4cb675124
commit fde82ca7e4
7 changed files with 72 additions and 77 deletions
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64
libavcodec/lpc.c
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@@ -26,6 +26,68 @@
#include "lpc.h"
/**
* Apply Welch window function to audio block
*/
static void apply_welch_window(const int32_t *data, int len, double *w_data)
{
int i, n2;
double w;
double c;
assert(!(len&1)); //the optimization in r11881 does not support odd len
//if someone wants odd len extend the change in r11881
n2 = (len >> 1);
c = 2.0 / (len - 1.0);
w_data+=n2;
data+=n2;
for(i=0; i<n2; i++) {
w = c - n2 + i;
w = 1.0 - (w * w);
w_data[-i-1] = data[-i-1] * w;
w_data[+i ] = data[+i ] * w;
}
}
/**
* Calculates autocorrelation data from audio samples
* A Welch window function is applied before calculation.
*/
void ff_lpc_compute_autocorr(const int32_t *data, int len, int lag,
double *autoc)
{
int i, j;
double tmp[len + lag + 1];
double *data1= tmp + lag;
apply_welch_window(data, len, data1);
for(j=0; j<lag; j++)
data1[j-lag]= 0.0;
data1[len] = 0.0;
for(j=0; j<lag; j+=2){
double sum0 = 1.0, sum1 = 1.0;
for(i=j; i<len; i++){
sum0 += data1[i] * data1[i-j];
sum1 += data1[i] * data1[i-j-1];
}
autoc[j ] = sum0;
autoc[j+1] = sum1;
}
if(j==lag){
double sum = 1.0;
for(i=j-1; i<len; i+=2){
sum += data1[i ] * data1[i-j ]
+ data1[i+1] * data1[i-j+1];
}
autoc[j] = sum;
}
}
/**
* Quantize LPC coefficients
*/
@@ -115,7 +177,7 @@ int ff_lpc_calc_coefs(DSPContext *s,
assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && use_lpc > 0);
if(use_lpc == 1){
s->flac_compute_autocorr(samples, blocksize, max_order, autoc);
s->lpc_compute_autocorr(samples, blocksize, max_order, autoc);
compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);