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//#ifdef HAVE_CONFIG_H
#include "../config.h"
//#endif

#include "main.h"

/* Convert adaptive Mid/Side representation to Left/Right stereo signal */
void silk_stereo_MS_to_LR(
    stereo_dec_state            *state,                         /* I/O  State                                       */
    opus_int16                  x1[],                           /* I/O  Left input signal, becomes mid signal       */
    opus_int16                  x2[],                           /* I/O  Right input signal, becomes side signal     */
    const opus_int32            pred_Q13[],                     /* I    Predictors                                  */
    opus_int                    fs_kHz,                         /* I    Samples rate (kHz)                          */
    opus_int                    frame_length                    /* I    Number of samples                           */
) {
    opus_int   n, denom_Q16, delta0_Q13, delta1_Q13;
    opus_int32 sum, diff, pred0_Q13, pred1_Q13;

    /* Buffering */
    silk_memcpy(x1, state->sMid,  2 * sizeof(opus_int16));
    silk_memcpy(x2, state->sSide, 2 * sizeof(opus_int16));
    silk_memcpy(state->sMid,  &x1[ frame_length ], 2 * sizeof(opus_int16));
    silk_memcpy(state->sSide, &x2[ frame_length ], 2 * sizeof(opus_int16));

    /* Interpolate predictors and add prediction to side channel */
    pred0_Q13  = state->pred_prev_Q13[ 0 ];
    pred1_Q13  = state->pred_prev_Q13[ 1 ];
    denom_Q16  = silk_DIV32_16((opus_int32)1 << 16, STEREO_INTERP_LEN_MS * fs_kHz);
    delta0_Q13 = silk_RSHIFT_ROUND(silk_SMULBB(pred_Q13[ 0 ] - state->pred_prev_Q13[ 0 ], denom_Q16), 16);
    delta1_Q13 = silk_RSHIFT_ROUND(silk_SMULBB(pred_Q13[ 1 ] - state->pred_prev_Q13[ 1 ], denom_Q16), 16);
    for (n = 0; n < STEREO_INTERP_LEN_MS * fs_kHz; n++) {
        pred0_Q13 += delta0_Q13;
        pred1_Q13 += delta1_Q13;
        sum = silk_LSHIFT(silk_ADD_LSHIFT(x1[ n ] + x1[ n + 2 ], x1[ n + 1 ], 1), 9);           /* Q11 */
        sum = silk_SMLAWB(silk_LSHIFT((opus_int32)x2[ n + 1 ], 8), sum, pred0_Q13);             /* Q8  */
        sum = silk_SMLAWB(sum, silk_LSHIFT((opus_int32)x1[ n + 1 ], 11), pred1_Q13);            /* Q8  */
        x2[ n + 1 ] = (opus_int16)silk_SAT16(silk_RSHIFT_ROUND(sum, 8));
    }
    pred0_Q13 = pred_Q13[ 0 ];
    pred1_Q13 = pred_Q13[ 1 ];
    for (n = STEREO_INTERP_LEN_MS * fs_kHz; n < frame_length; n++) {
        sum = silk_LSHIFT(silk_ADD_LSHIFT(x1[ n ] + x1[ n + 2 ], x1[ n + 1 ], 1), 9);           /* Q11 */
        sum = silk_SMLAWB(silk_LSHIFT((opus_int32)x2[ n + 1 ], 8), sum, pred0_Q13);             /* Q8  */
        sum = silk_SMLAWB(sum, silk_LSHIFT((opus_int32)x1[ n + 1 ], 11), pred1_Q13);            /* Q8  */
        x2[ n + 1 ] = (opus_int16)silk_SAT16(silk_RSHIFT_ROUND(sum, 8));
    }
    state->pred_prev_Q13[ 0 ] = pred_Q13[ 0 ];
    state->pred_prev_Q13[ 1 ] = pred_Q13[ 1 ];

    /* Convert to left/right signals */
    for (n = 0; n < frame_length; n++) {
        sum  = x1[ n + 1 ] + (opus_int32)x2[ n + 1 ];
        diff = x1[ n + 1 ] - (opus_int32)x2[ n + 1 ];
        x1[ n + 1 ] = (opus_int16)silk_SAT16(sum);
        x2[ n + 1 ] = (opus_int16)silk_SAT16(diff);
    }
}
