ref: 103302b3752609e28cb6ba4f706a6f6e49ffef68
dir: /silk/silk_sum_sqr_shift.c/
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#include "silk_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(
SKP_int32 *energy, /* O Energy of x, after shifting to the right */
SKP_int *shift, /* O Number of bits right shift applied to energy */
const SKP_int16 *x, /* I Input vector */
SKP_int len /* I Length of input vector */
)
{
SKP_int i, shft;
SKP_int32 nrg_tmp, nrg;
nrg = 0;
shft = 0;
len--;
for( i = 0; i < len; i += 2 ) {
nrg = SKP_SMLABB_ovflw( nrg, x[ i ], x[ i ] );
nrg = SKP_SMLABB_ovflw( nrg, x[ i + 1 ], x[ i + 1 ] );
if( nrg < 0 ) {
/* Scale down */
nrg = (SKP_int32)SKP_RSHIFT_uint( (SKP_uint32)nrg, 2 );
shft = 2;
break;
}
}
for( ; i < len; i += 2 ) {
nrg_tmp = SKP_SMULBB( x[ i ], x[ i ] );
nrg_tmp = SKP_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
nrg = (SKP_int32)SKP_ADD_RSHIFT_uint( nrg, (SKP_uint32)nrg_tmp, shft );
if( nrg < 0 ) {
/* Scale down */
nrg = (SKP_int32)SKP_RSHIFT_uint( (SKP_uint32)nrg, 2 );
shft += 2;
}
}
if( i == len ) {
/* One sample left to process */
nrg_tmp = SKP_SMULBB( x[ i ], x[ i ] );
nrg = (SKP_int32)SKP_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
}
/* Make sure to have at least one extra leading zero (two leading zeros in total) */
if( nrg & 0xC0000000 ) {
nrg = SKP_RSHIFT_uint( (SKP_uint32)nrg, 2 );
shft += 2;
}
/* Output arguments */
*shift = shft;
*energy = nrg;
}