ref: fe741259c1050baa5c828444dd5a968ed658d1fb
dir: /silk/SKP_Silk_stereo_MS_to_LR.c/
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#include "SKP_Silk_main.h"
/* Convert adaptive Mid/Side representation to Left/Right stereo signal */
void SKP_Silk_stereo_MS_to_LR(
stereo_state *state, /* I/O State */
SKP_int16 x1[], /* I/O Left input signal, becomes mid signal */
SKP_int16 x2[], /* I/O Right input signal, becomes side signal */
SKP_int predictorIx, /* I Index for predictor filter */
SKP_int fs_kHz, /* I Samples rate (kHz) */
SKP_int frame_length /* I Number of samples */
)
{
SKP_int n;
SKP_int32 sum, diff, predictor_Q16, pred_Q16, delta_Q16;
/* Dequantize */
predictor_Q16 = SKP_SMLABB( -65536, predictorIx, ( 1 << 17 ) / ( STEREO_QUANT_STEPS - 1 ) );
/* Add prediction to side channel */
if( predictor_Q16 != state->predictor_prev_Q16 ) {
/* Interpolate predictor */
pred_Q16 = state->predictor_prev_Q16;
delta_Q16 = SKP_DIV32_16( predictor_Q16 - state->predictor_prev_Q16, STEREO_INTERPOL_LENGTH_MS * fs_kHz );
for( n = 0; n < STEREO_INTERPOL_LENGTH_MS * fs_kHz; n++ ) {
pred_Q16 += delta_Q16;
x2[ n ] = (SKP_int16)SKP_SAT16( SKP_SMLAWB( x2[ n ], pred_Q16, x1[ n ] ) );
}
} else {
n = 0;
}
pred_Q16 = predictor_Q16;
for( ; n < frame_length; n++ ) {
x2[ n ] = (SKP_int16)SKP_SAT16( SKP_SMLAWB( x2[ n ], pred_Q16, x1[ n ] ) );
}
state->predictor_prev_Q16 = predictor_Q16;
/* Convert to left/right signals */
for( n = 0; n < frame_length; n++ ) {
sum = x1[ n ] + (SKP_int32)x2[ n ];
diff = x1[ n ] - (SKP_int32)x2[ n ];
x1[ n ] = (SKP_int16)SKP_SAT16( sum );
x2[ n ] = (SKP_int16)SKP_SAT16( diff );
}
}