ref: 25f7f35555168f3426b9aad1efefab466f365af6
dir: /silk/silk_autocorr.c/
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "silk_SigProc_FIX.h"
/* Compute autocorrelation */
void silk_autocorr(
opus_int32 *results, /* O Result (length correlationCount) */
opus_int *scale, /* O Scaling of the correlation vector */
const opus_int16 *inputData, /* I Input data to correlate */
const opus_int inputDataSize, /* I Length of input */
const opus_int correlationCount /* I Number of correlation taps to compute */
)
{
opus_int i, lz, nRightShifts, corrCount;
opus_int64 corr64;
corrCount = SKP_min_int( inputDataSize, correlationCount );
/* compute energy (zero-lag correlation) */
corr64 = silk_inner_prod16_aligned_64( inputData, inputData, inputDataSize );
/* deal with all-zero input data */
corr64 += 1;
/* number of leading zeros */
lz = silk_CLZ64( corr64 );
/* scaling: number of right shifts applied to correlations */
nRightShifts = 35 - lz;
*scale = nRightShifts;
if( nRightShifts <= 0 ) {
results[ 0 ] = SKP_LSHIFT( (opus_int32)SKP_CHECK_FIT32( corr64 ), -nRightShifts );
/* compute remaining correlations based on int32 inner product */
for( i = 1; i < corrCount; i++ ) {
results[ i ] = SKP_LSHIFT( silk_inner_prod_aligned( inputData, inputData + i, inputDataSize - i ), -nRightShifts );
}
} else {
results[ 0 ] = (opus_int32)SKP_CHECK_FIT32( SKP_RSHIFT64( corr64, nRightShifts ) );
/* compute remaining correlations based on int64 inner product */
for( i = 1; i < corrCount; i++ ) {
results[ i ] = (opus_int32)SKP_CHECK_FIT32( SKP_RSHIFT64( silk_inner_prod16_aligned_64( inputData, inputData + i, inputDataSize - i ), nRightShifts ) );
}
}
}