ref: 5d7b03669cb067c8848dfad642357c86e46e806a
dir: /silk/silk_stereo_quant_pred.c/
/***********************************************************************
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***********************************************************************/
#include "silk_main.h"
/* Quantize mid/side predictors */
void silk_stereo_quant_pred(
stereo_enc_state *state, /* I/O State */
SKP_int32 pred_Q13[], /* I/O Predictors (out: quantized) */
SKP_int8 ix[ 2 ][ 4 ] /* O Quantization indices */
)
{
SKP_int i, j, n;
SKP_int32 low_Q13, step_Q13, lvl_Q13, err_min_Q13, err_Q13, quant_pred_Q13 = 0;
/* Quantize */
for( n = 0; n < 2; n++ ) {
/* Brute-force search over quantization levels */
err_min_Q13 = SKP_int32_MAX;
for( i = 0; i < STEREO_QUANT_TAB_SIZE - 1; i++ ) {
low_Q13 = silk_stereo_pred_quant_Q13[ i ];
step_Q13 = SKP_SMULWB( silk_stereo_pred_quant_Q13[ i + 1 ] - low_Q13,
SILK_FIX_CONST( 0.5 / STEREO_QUANT_SUB_STEPS, 16 ) );
for( j = 0; j < STEREO_QUANT_SUB_STEPS; j++ ) {
lvl_Q13 = SKP_SMLABB( low_Q13, step_Q13, 2 * j + 1 );
err_Q13 = SKP_abs( pred_Q13[ n ] - lvl_Q13 );
if( err_Q13 < err_min_Q13 ) {
err_min_Q13 = err_Q13;
quant_pred_Q13 = lvl_Q13;
ix[ n ][ 0 ] = i;
ix[ n ][ 1 ] = j;
} else {
/* Error increasing, so we're past the optimum */
goto done;
}
}
}
done:
ix[ n ][ 2 ] = SKP_DIV32_16( ix[ n ][ 0 ], 3 );
ix[ n ][ 0 ] -= ix[ n ][ 2 ] * 3;
pred_Q13[ n ] = quant_pred_Q13;
}
/* Subtract second from first predictor (helps when actually applying these) */
pred_Q13[ 0 ] -= pred_Q13[ 1 ];
}