ref: 683592180f64f5723274a9105be2f3af6208a901
dir: /silk/sum_sqr_shift.c/
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "SigProc_FIX.h"
/* Compute number of bits to right shift the sum of squares of a vector */
/* of int16s to make it fit in an int32 */
void silk_sum_sqr_shift(
opus_int32 *energy, /* O Energy of x, after shifting to the right */
opus_int *shift, /* O Number of bits right shift applied to energy */
const opus_int16 *x, /* I Input vector */
opus_int len /* I Length of input vector */
)
{
opus_int i, shft;
opus_uint32 nrg_tmp;
opus_int32 nrg;
/* Do a first run with the maximum shift we could have. */
shft = 31-silk_CLZ32(len);
/* Let's be conservative with rounding and start with nrg=len. */
nrg = len;
for( i = 0; i < len - 1; i += 2 ) {
nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
nrg_tmp = silk_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
}
if( i < len ) {
/* One sample left to process */
nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
}
silk_assert( nrg >= 0 );
/* Make sure the result will fit in a 32-bit signed integer with two bits
of headroom. */
shft = silk_max_32(0, shft+3 - silk_CLZ32(nrg));
nrg = 0;
for( i = 0 ; i < len - 1; i += 2 ) {
nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
nrg_tmp = silk_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
}
if( i < len ) {
/* One sample left to process */
nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
}
silk_assert( nrg >= 0 );
/* Output arguments */
*shift = shft;
*energy = nrg;
}