shithub: opus

ref: 242da53aa03f48939a081900a6305ff8351078a9
dir: /silk/silk_stereo_LR_to_MS.c/

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

#include "silk_main.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             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;
    opus_int16 side[ MAX_FRAME_LENGTH + 2 ];
    opus_int16 LP_mid[  MAX_FRAME_LENGTH ], HP_mid[  MAX_FRAME_LENGTH ];
    opus_int16 LP_side[ MAX_FRAME_LENGTH ], HP_side[ MAX_FRAME_LENGTH ];
    opus_int16 *mid = &x1[ -2 ];

    /* 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)SKP_RSHIFT_ROUND( sum, 1 );
        side[ n ] = (opus_int16)SKP_SAT16( SKP_RSHIFT_ROUND( diff, 1 ) );
    }

    /* Buffering */
    SKP_memcpy( mid,  state->sMid,  2 * sizeof( opus_int16 ) );
    SKP_memcpy( side, state->sSide, 2 * sizeof( opus_int16 ) );
    SKP_memcpy( state->sMid,  &mid[  frame_length ], 2 * sizeof( opus_int16 ) );
    SKP_memcpy( state->sSide, &side[ frame_length ], 2 * sizeof( opus_int16 ) );

    /* LP and HP filter mid signal */
    for( n = 0; n < frame_length; n++ ) {
        sum = SKP_RSHIFT_ROUND( SKP_ADD_LSHIFT( mid[ n ] + 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 */
    for( n = 0; n < frame_length; n++ ) {
        sum = SKP_RSHIFT_ROUND( SKP_ADD_LSHIFT( side[ n ] + 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 = SKP_SMULWB( SKP_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 = SKP_SMLABB( HP_ratio_Q14, LP_ratio_Q14, 3 );
    frac_Q16 = SKP_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 */
    min_mid_rate_bps = SKP_SMLABB( 2000, fs_kHz, 900 );
    SKP_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 = SKP_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( SKP_LSHIFT( mid_side_rates_bps[ 1 ], 1 ) - min_mid_rate_bps,
            SKP_SMULWB( SILK_FIX_CONST( 1, 16 ) + frac_3_Q16, min_mid_rate_bps ), 14+2 );
        width_Q14 = SKP_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)SKP_SMLAWB( state->smth_width_Q14, width_Q14 - state->smth_width_Q14, smooth_coef_Q16 );

    /* Reduce predictors */
    pred_Q13[ 0 ] = SKP_RSHIFT( SKP_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
    pred_Q13[ 1 ] = SKP_RSHIFT( SKP_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );

    *mid_only_flag = 0;
    if( state->width_prev_Q14 == 0 &&
        ( 8 * total_rate_bps < 13 * min_mid_rate_bps || SKP_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.05, 14 ) ) )
    {
        width_Q14 = 0;
        /* Only encode mid channel */
        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 || SKP_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.02, 14 ) ) )
    {
        width_Q14 = 0;
    } else if( state->smth_width_Q14 > SILK_FIX_CONST( 0.95, 14 ) ) {
        width_Q14 = SILK_FIX_CONST( 1, 14 );
    } else {
        width_Q14 = state->smth_width_Q14;
    }

#if 0
    DEBUG_STORE_DATA( midside.dat, &mid_side_rates_bps[ 0 ], 8 );
    DEBUG_STORE_DATA( norms0.pcm, &state->mid_side_amp_Q0[0], 8 );
    DEBUG_STORE_DATA( norms1.pcm, &state->mid_side_amp_Q0[2], 8 );
    DEBUG_STORE_DATA( width.pcm, &width_Q14, 4 );
#endif

    /* Quantize predictors */
    silk_stereo_quant_pred( state, pred_Q13, ix );

    /* Interpolate predictors and subtract prediction from side channel */
    pred0_Q13  = -state->pred_prev_Q13[ 0 ];
    pred1_Q13  = -state->pred_prev_Q13[ 1 ];
    w_Q24      =  SKP_LSHIFT( state->width_prev_Q14, 10 );
    denom_Q16  = SKP_DIV32_16( 1 << 16, STEREO_INTERP_LEN_MS * fs_kHz );
    delta0_Q13 = -SKP_RSHIFT_ROUND( SKP_SMULBB( pred_Q13[ 0 ] - state->pred_prev_Q13[ 0 ], denom_Q16 ), 16 );
    delta1_Q13 = -SKP_RSHIFT_ROUND( SKP_SMULBB( pred_Q13[ 1 ] - state->pred_prev_Q13[ 1 ], denom_Q16 ), 16 );
    deltaw_Q24 =  SKP_LSHIFT( SKP_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 = SKP_LSHIFT( SKP_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 );      /* Q11 */
        sum = SKP_SMLAWB( SKP_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 );                 /* Q8  */
        sum = SKP_SMLAWB( sum, SKP_LSHIFT( ( opus_int32 )mid[ n + 1 ], 11 ), pred1_Q13 );        /* Q8  */
        x2[ n - 1 ] = (opus_int16)SKP_SAT16( SKP_RSHIFT_ROUND( sum, 8 ) );
    }
    pred0_Q13 = -pred_Q13[ 0 ];
    pred1_Q13 = -pred_Q13[ 1 ];
    w_Q24     =  SKP_LSHIFT( width_Q14, 10 );
    for( n = STEREO_INTERP_LEN_MS * fs_kHz; n < frame_length; n++ ) {
        sum = SKP_LSHIFT( SKP_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 );      /* Q11 */
        sum = SKP_SMLAWB( SKP_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 );                 /* Q8  */
        sum = SKP_SMLAWB( sum, SKP_LSHIFT( ( opus_int32 )mid[ n + 1 ], 11 ), pred1_Q13 );        /* Q8  */
        x2[ n - 1 ] = (opus_int16)SKP_SAT16( SKP_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;
}