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#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "main.h"

#include "stack_alloc.h"

/* Convert Left/Right stereo signal to adaptive Mid/Side representation */

void silk_stereo_LR_to_MS(

    stereo_enc_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     */

    opus_int8                   ix[ 2 ][ 3 ],                   /* O    Quantization indices                        */

    opus_int8                   *mid_only_flag,                 /* O    Flag: only mid signal coded                 */

    opus_int32                  mid_side_rates_bps[],           /* O    Bitrates for mid and side signals           */

    opus_int32                  total_rate_bps,                 /* I    Total bitrate                               */

    opus_int                    prev_speech_act_Q8,             /* I    Speech activity level in previous frame     */

    opus_int                    toMono,                         /* I    Last frame before a stereo->mono transition */

    opus_int                    fs_kHz,                         /* I    Sample rate (kHz)                           */

    opus_int                    frame_length                    /* I    Number of samples                           */

)

{

    opus_int   n, is10msFrame, denom_Q16, delta0_Q13, delta1_Q13;

    opus_int32 sum, diff, smooth_coef_Q16, pred_Q13[ 2 ], pred0_Q13, pred1_Q13;

    opus_int32 LP_ratio_Q14, HP_ratio_Q14, frac_Q16, frac_3_Q16, min_mid_rate_bps, width_Q14, w_Q24, deltaw_Q24;

    VARDECL( opus_int16, side );

    VARDECL( opus_int16, LP_mid );

    VARDECL( opus_int16, HP_mid );

    VARDECL( opus_int16, LP_side );

    VARDECL( opus_int16, HP_side );

    opus_int16 *mid = &x1[ -2 ];

    SAVE_STACK;

    ALLOC( side, frame_length + 2, opus_int16 );

    /* Convert to basic mid/side signals */

    for( n = 0; n < frame_length + 2; n++ ) {

        sum  = x1[ n - 2 ] + (opus_int32)x2[ n - 2 ];

        diff = x1[ n - 2 ] - (opus_int32)x2[ n - 2 ];

        mid[  n ] = (opus_int16)silk_RSHIFT_ROUND( sum, 1 );

        side[ n ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( diff, 1 ) );

    }

    /* Buffering */

    silk_memcpy( mid,  state->sMid,  2 * sizeof( opus_int16 ) );

    silk_memcpy( side, state->sSide, 2 * sizeof( opus_int16 ) );

    silk_memcpy( state->sMid,  &mid[  frame_length ], 2 * sizeof( opus_int16 ) );

    silk_memcpy( state->sSide, &side[ frame_length ], 2 * sizeof( opus_int16 ) );

    /* LP and HP filter mid signal */

    ALLOC( LP_mid, frame_length, opus_int16 );

    ALLOC( HP_mid, frame_length, opus_int16 );

    for( n = 0; n < frame_length; n++ ) {

        sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT32( mid[ n ] + (opus_int32)mid[ n + 2 ], mid[ n + 1 ], 1 ), 2 );

        LP_mid[ n ] = sum;

        HP_mid[ n ] = mid[ n + 1 ] - sum;

    }

    /* LP and HP filter side signal */

    ALLOC( LP_side, frame_length, opus_int16 );

    ALLOC( HP_side, frame_length, opus_int16 );

    for( n = 0; n < frame_length; n++ ) {

        sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT32( side[ n ] + (opus_int32)side[ n + 2 ], side[ n + 1 ], 1 ), 2 );

        LP_side[ n ] = sum;

        HP_side[ n ] = side[ n + 1 ] - sum;

    }

    /* Find energies and predictors */

    is10msFrame = frame_length == 10 * fs_kHz;

    smooth_coef_Q16 = is10msFrame ?

        SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF / 2, 16 ) :

        SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF,     16 );

    smooth_coef_Q16 = silk_SMULWB( silk_SMULBB( prev_speech_act_Q8, prev_speech_act_Q8 ), smooth_coef_Q16 );

    pred_Q13[ 0 ] = silk_stereo_find_predictor( &LP_ratio_Q14, LP_mid, LP_side, &state->mid_side_amp_Q0[ 0 ], frame_length, smooth_coef_Q16 );

    pred_Q13[ 1 ] = silk_stereo_find_predictor( &HP_ratio_Q14, HP_mid, HP_side, &state->mid_side_amp_Q0[ 2 ], frame_length, smooth_coef_Q16 );

    /* Ratio of the norms of residual and mid signals */

    frac_Q16 = silk_SMLABB( HP_ratio_Q14, LP_ratio_Q14, 3 );

    frac_Q16 = silk_min( frac_Q16, SILK_FIX_CONST( 1, 16 ) );

    /* Determine bitrate distribution between mid and side, and possibly reduce stereo width */

    total_rate_bps -= is10msFrame ? 1200 : 600;      /* Subtract approximate bitrate for coding stereo parameters */

    if( total_rate_bps < 1 ) {

        total_rate_bps = 1;

    }

    min_mid_rate_bps = silk_SMLABB( 2000, fs_kHz, 600 );

    silk_assert( min_mid_rate_bps < 32767 );

    /* Default bitrate distribution: 8 parts for Mid and (5+3*frac) parts for Side. so: mid_rate = ( 8 / ( 13 + 3 * frac ) ) * total_ rate */

    frac_3_Q16 = silk_MUL( 3, frac_Q16 );

    mid_side_rates_bps[ 0 ] = silk_DIV32_varQ( total_rate_bps, SILK_FIX_CONST( 8 + 5, 16 ) + frac_3_Q16, 16+3 );

    /* If Mid bitrate below minimum, reduce stereo width */

    if( mid_side_rates_bps[ 0 ] < min_mid_rate_bps ) {

        mid_side_rates_bps[ 0 ] = min_mid_rate_bps;

        mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ];

        /* width = 4 * ( 2 * side_rate - min_rate ) / ( ( 1 + 3 * frac ) * min_rate ) */

        width_Q14 = silk_DIV32_varQ( silk_LSHIFT( mid_side_rates_bps[ 1 ], 1 ) - min_mid_rate_bps,

            silk_SMULWB( SILK_FIX_CONST( 1, 16 ) + frac_3_Q16, min_mid_rate_bps ), 14+2 );

        width_Q14 = silk_LIMIT( width_Q14, 0, SILK_FIX_CONST( 1, 14 ) );

    } else {

        mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ];

        width_Q14 = SILK_FIX_CONST( 1, 14 );

    }

    /* Smoother */

    state->smth_width_Q14 = (opus_int16)silk_SMLAWB( state->smth_width_Q14, width_Q14 - state->smth_width_Q14, smooth_coef_Q16 );

    /* At very low bitrates or for inputs that are nearly amplitude panned, switch to panned-mono coding */

    *mid_only_flag = 0;

    if( toMono ) {

        /* Last frame before stereo->mono transition; collapse stereo width */

        width_Q14 = 0;

        pred_Q13[ 0 ] = 0;

        pred_Q13[ 1 ] = 0;

        silk_stereo_quant_pred( pred_Q13, ix );

    } else if( state->width_prev_Q14 == 0 &&

        ( 8 * total_rate_bps < 13 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.05, 14 ) ) )

    {

        /* Code as panned-mono; previous frame already had zero width */

        /* Scale down and quantize predictors */

        pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );

        pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );

        silk_stereo_quant_pred( pred_Q13, ix );

        /* Collapse stereo width */

        width_Q14 = 0;

        pred_Q13[ 0 ] = 0;

        pred_Q13[ 1 ] = 0;

        mid_side_rates_bps[ 0 ] = total_rate_bps;

        mid_side_rates_bps[ 1 ] = 0;

        *mid_only_flag = 1;

    } else if( state->width_prev_Q14 != 0 &&

        ( 8 * total_rate_bps < 11 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.02, 14 ) ) )

    {

        /* Transition to zero-width stereo */

        /* Scale down and quantize predictors */

        pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );

        pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );

        silk_stereo_quant_pred( pred_Q13, ix );

        /* Collapse stereo width */

        width_Q14 = 0;

        pred_Q13[ 0 ] = 0;

        pred_Q13[ 1 ] = 0;

    } else if( state->smth_width_Q14 > SILK_FIX_CONST( 0.95, 14 ) ) {

        /* Full-width stereo coding */

        silk_stereo_quant_pred( pred_Q13, ix );

        width_Q14 = SILK_FIX_CONST( 1, 14 );

    } else {

        /* Reduced-width stereo coding; scale down and quantize predictors */

        pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );

        pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );

        silk_stereo_quant_pred( pred_Q13, ix );

        width_Q14 = state->smth_width_Q14;

    }

    /* Make sure to keep on encoding until the tapered output has been transmitted */

    if( *mid_only_flag == 1 ) {

        state->silent_side_len += frame_length - STEREO_INTERP_LEN_MS * fs_kHz;

        if( state->silent_side_len < LA_SHAPE_MS * fs_kHz ) {

            *mid_only_flag = 0;

        } else {

            /* Limit to avoid wrapping around */

            state->silent_side_len = 10000;

        }

    } else {

        state->silent_side_len = 0;

    }

    if( *mid_only_flag == 0 && mid_side_rates_bps[ 1 ] < 1 ) {

        mid_side_rates_bps[ 1 ] = 1;

        mid_side_rates_bps[ 0 ] = silk_max_int( 1, total_rate_bps - mid_side_rates_bps[ 1 ]);

    }

    /* Interpolate predictors and subtract prediction from side channel */

    pred0_Q13  = -state->pred_prev_Q13[ 0 ];

    pred1_Q13  = -state->pred_prev_Q13[ 1 ];

    w_Q24      =  silk_LSHIFT( state->width_prev_Q14, 10 );

    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 );

    deltaw_Q24 =  silk_LSHIFT( silk_SMULWB( width_Q14 - state->width_prev_Q14, denom_Q16 ), 10 );

    for( n = 0; n < STEREO_INTERP_LEN_MS * fs_kHz; n++ ) {

        pred0_Q13 += delta0_Q13;

        pred1_Q13 += delta1_Q13;

        w_Q24   += deltaw_Q24;

        sum = silk_LSHIFT( silk_ADD_LSHIFT32( mid[ n ] + (opus_int32)mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 );    /* Q11 */

        sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 );               /* Q8  */

        sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ 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 ];

    w_Q24     =  silk_LSHIFT( width_Q14, 10 );

    for( n = STEREO_INTERP_LEN_MS * fs_kHz; n < frame_length; n++ ) {

        sum = silk_LSHIFT( silk_ADD_LSHIFT32( mid[ n ] + (opus_int32)mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 );    /* Q11 */

        sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 );               /* Q8  */

        sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 );       /* Q8  */

        x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) );

    }

    state->pred_prev_Q13[ 0 ] = (opus_int16)pred_Q13[ 0 ];

    state->pred_prev_Q13[ 1 ] = (opus_int16)pred_Q13[ 1 ];

    state->width_prev_Q14     = (opus_int16)width_Q14;

    RESTORE_STACK;

}