ref: c9d5bea13e3cb7381bfa897a45d8bab4e7b767a7
dir: /silk/float/warped_autocorrelation_FLP.c/
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "main_FLP.h"
/* Autocorrelations for a warped frequency axis */
void silk_warped_autocorrelation_FLP(
silk_float *corr, /* O Result [order + 1] */
const silk_float *input, /* I Input data to correlate */
const silk_float warping, /* I Warping coefficient */
const opus_int length, /* I Length of input */
const opus_int order /* I Correlation order (even) */
)
{
opus_int n, i;
double tmp1, tmp2;
double state[ MAX_SHAPE_LPC_ORDER + 1 ] = { 0 };
double C[ MAX_SHAPE_LPC_ORDER + 1 ] = { 0 };
/* Order must be even */
celt_assert( ( order & 1 ) == 0 );
/* Loop over samples */
for( n = 0; n < length; n++ ) {
tmp1 = input[ n ];
/* Loop over allpass sections */
for( i = 0; i < order; i += 2 ) {
/* Output of allpass section */
tmp2 = state[ i ] + warping * ( state[ i + 1 ] - tmp1 );
state[ i ] = tmp1;
C[ i ] += state[ 0 ] * tmp1;
/* Output of allpass section */
tmp1 = state[ i + 1 ] + warping * ( state[ i + 2 ] - tmp2 );
state[ i + 1 ] = tmp2;
C[ i + 1 ] += state[ 0 ] * tmp2;
}
state[ order ] = tmp1;
C[ order ] += state[ 0 ] * tmp1;
}
/* Copy correlations in silk_float output format */
for( i = 0; i < order + 1; i++ ) {
corr[ i ] = ( silk_float )C[ i ];
}
}