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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_LSHIFT32( x1[ n ] + (opus_int32)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_LSHIFT32( x1[ n ] + (opus_int32)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 );

    }

}