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      1 /***********************************************************************
      2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.
      3 Redistribution and use in source and binary forms, with or without
      4 modification, are permitted provided that the following conditions
      5 are met:
      6 - Redistributions of source code must retain the above copyright notice,
      7 this list of conditions and the following disclaimer.
      8 - Redistributions in binary form must reproduce the above copyright
      9 notice, this list of conditions and the following disclaimer in the
     10 documentation and/or other materials provided with the distribution.
     11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
     12 names of specific contributors, may be used to endorse or promote
     13 products derived from this software without specific prior written
     14 permission.
     15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
     16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
     19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     25 POSSIBILITY OF SUCH DAMAGE.
     26 ***********************************************************************/
     27 
     28 #ifdef HAVE_CONFIG_H
     29 #include "config.h"
     30 #endif
     31 
     32 #include "main.h"
     33 #include "stack_alloc.h"
     34 
     35 /* Convert Left/Right stereo signal to adaptive Mid/Side representation */
     36 void silk_stereo_LR_to_MS(
     37     stereo_enc_state            *state,                         /* I/O  State                                       */
     38     opus_int16                  x1[],                           /* I/O  Left input signal, becomes mid signal       */
     39     opus_int16                  x2[],                           /* I/O  Right input signal, becomes side signal     */
     40     opus_int8                   ix[ 2 ][ 3 ],                   /* O    Quantization indices                        */
     41     opus_int8                   *mid_only_flag,                 /* O    Flag: only mid signal coded                 */
     42     opus_int32                  mid_side_rates_bps[],           /* O    Bitrates for mid and side signals           */
     43     opus_int32                  total_rate_bps,                 /* I    Total bitrate                               */
     44     opus_int                    prev_speech_act_Q8,             /* I    Speech activity level in previous frame     */
     45     opus_int                    toMono,                         /* I    Last frame before a stereo->mono transition */
     46     opus_int                    fs_kHz,                         /* I    Sample rate (kHz)                           */
     47     opus_int                    frame_length                    /* I    Number of samples                           */
     48 )
     49 {
     50     opus_int   n, is10msFrame, denom_Q16, delta0_Q13, delta1_Q13;
     51     opus_int32 sum, diff, smooth_coef_Q16, pred_Q13[ 2 ], pred0_Q13, pred1_Q13;
     52     opus_int32 LP_ratio_Q14, HP_ratio_Q14, frac_Q16, frac_3_Q16, min_mid_rate_bps, width_Q14, w_Q24, deltaw_Q24;
     53     VARDECL( opus_int16, side );
     54     VARDECL( opus_int16, LP_mid );
     55     VARDECL( opus_int16, HP_mid );
     56     VARDECL( opus_int16, LP_side );
     57     VARDECL( opus_int16, HP_side );
     58     opus_int16 *mid = &x1[ -2 ];
     59     SAVE_STACK;
     60 
     61     ALLOC( side, frame_length + 2, opus_int16 );
     62     /* Convert to basic mid/side signals */
     63     for( n = 0; n < frame_length + 2; n++ ) {
     64         sum  = x1[ n - 2 ] + (opus_int32)x2[ n - 2 ];
     65         diff = x1[ n - 2 ] - (opus_int32)x2[ n - 2 ];
     66         mid[  n ] = (opus_int16)silk_RSHIFT_ROUND( sum, 1 );
     67         side[ n ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( diff, 1 ) );
     68     }
     69 
     70     /* Buffering */
     71     silk_memcpy( mid,  state->sMid,  2 * sizeof( opus_int16 ) );
     72     silk_memcpy( side, state->sSide, 2 * sizeof( opus_int16 ) );
     73     silk_memcpy( state->sMid,  &mid[  frame_length ], 2 * sizeof( opus_int16 ) );
     74     silk_memcpy( state->sSide, &side[ frame_length ], 2 * sizeof( opus_int16 ) );
     75 
     76     /* LP and HP filter mid signal */
     77     ALLOC( LP_mid, frame_length, opus_int16 );
     78     ALLOC( HP_mid, frame_length, opus_int16 );
     79     for( n = 0; n < frame_length; n++ ) {
     80         sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 2 );
     81         LP_mid[ n ] = sum;
     82         HP_mid[ n ] = mid[ n + 1 ] - sum;
     83     }
     84 
     85     /* LP and HP filter side signal */
     86     ALLOC( LP_side, frame_length, opus_int16 );
     87     ALLOC( HP_side, frame_length, opus_int16 );
     88     for( n = 0; n < frame_length; n++ ) {
     89         sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT( side[ n ] + side[ n + 2 ], side[ n + 1 ], 1 ), 2 );
     90         LP_side[ n ] = sum;
     91         HP_side[ n ] = side[ n + 1 ] - sum;
     92     }
     93 
     94     /* Find energies and predictors */
     95     is10msFrame = frame_length == 10 * fs_kHz;
     96     smooth_coef_Q16 = is10msFrame ?
     97         SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF / 2, 16 ) :
     98         SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF,     16 );
     99     smooth_coef_Q16 = silk_SMULWB( silk_SMULBB( prev_speech_act_Q8, prev_speech_act_Q8 ), smooth_coef_Q16 );
    100 
    101     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 );
    102     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 );
    103     /* Ratio of the norms of residual and mid signals */
    104     frac_Q16 = silk_SMLABB( HP_ratio_Q14, LP_ratio_Q14, 3 );
    105     frac_Q16 = silk_min( frac_Q16, SILK_FIX_CONST( 1, 16 ) );
    106 
    107     /* Determine bitrate distribution between mid and side, and possibly reduce stereo width */
    108     total_rate_bps -= is10msFrame ? 1200 : 600;      /* Subtract approximate bitrate for coding stereo parameters */
    109     if( total_rate_bps < 1 ) {
    110         total_rate_bps = 1;
    111     }
    112     min_mid_rate_bps = silk_SMLABB( 2000, fs_kHz, 900 );
    113     silk_assert( min_mid_rate_bps < 32767 );
    114     /* Default bitrate distribution: 8 parts for Mid and (5+3*frac) parts for Side. so: mid_rate = ( 8 / ( 13 + 3 * frac ) ) * total_ rate */
    115     frac_3_Q16 = silk_MUL( 3, frac_Q16 );
    116     mid_side_rates_bps[ 0 ] = silk_DIV32_varQ( total_rate_bps, SILK_FIX_CONST( 8 + 5, 16 ) + frac_3_Q16, 16+3 );
    117     /* If Mid bitrate below minimum, reduce stereo width */
    118     if( mid_side_rates_bps[ 0 ] < min_mid_rate_bps ) {
    119         mid_side_rates_bps[ 0 ] = min_mid_rate_bps;
    120         mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ];
    121         /* width = 4 * ( 2 * side_rate - min_rate ) / ( ( 1 + 3 * frac ) * min_rate ) */
    122         width_Q14 = silk_DIV32_varQ( silk_LSHIFT( mid_side_rates_bps[ 1 ], 1 ) - min_mid_rate_bps,
    123             silk_SMULWB( SILK_FIX_CONST( 1, 16 ) + frac_3_Q16, min_mid_rate_bps ), 14+2 );
    124         width_Q14 = silk_LIMIT( width_Q14, 0, SILK_FIX_CONST( 1, 14 ) );
    125     } else {
    126         mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ];
    127         width_Q14 = SILK_FIX_CONST( 1, 14 );
    128     }
    129 
    130     /* Smoother */
    131     state->smth_width_Q14 = (opus_int16)silk_SMLAWB( state->smth_width_Q14, width_Q14 - state->smth_width_Q14, smooth_coef_Q16 );
    132 
    133     /* At very low bitrates or for inputs that are nearly amplitude panned, switch to panned-mono coding */
    134     *mid_only_flag = 0;
    135     if( toMono ) {
    136         /* Last frame before stereo->mono transition; collapse stereo width */
    137         width_Q14 = 0;
    138         pred_Q13[ 0 ] = 0;
    139         pred_Q13[ 1 ] = 0;
    140         silk_stereo_quant_pred( pred_Q13, ix );
    141     } else if( state->width_prev_Q14 == 0 &&
    142         ( 8 * total_rate_bps < 13 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.05, 14 ) ) )
    143     {
    144         /* Code as panned-mono; previous frame already had zero width */
    145         /* Scale down and quantize predictors */
    146         pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
    147         pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );
    148         silk_stereo_quant_pred( pred_Q13, ix );
    149         /* Collapse stereo width */
    150         width_Q14 = 0;
    151         pred_Q13[ 0 ] = 0;
    152         pred_Q13[ 1 ] = 0;
    153         mid_side_rates_bps[ 0 ] = total_rate_bps;
    154         mid_side_rates_bps[ 1 ] = 0;
    155         *mid_only_flag = 1;
    156     } else if( state->width_prev_Q14 != 0 &&
    157         ( 8 * total_rate_bps < 11 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.02, 14 ) ) )
    158     {
    159         /* Transition to zero-width stereo */
    160         /* Scale down and quantize predictors */
    161         pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
    162         pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );
    163         silk_stereo_quant_pred( pred_Q13, ix );
    164         /* Collapse stereo width */
    165         width_Q14 = 0;
    166         pred_Q13[ 0 ] = 0;
    167         pred_Q13[ 1 ] = 0;
    168     } else if( state->smth_width_Q14 > SILK_FIX_CONST( 0.95, 14 ) ) {
    169         /* Full-width stereo coding */
    170         silk_stereo_quant_pred( pred_Q13, ix );
    171         width_Q14 = SILK_FIX_CONST( 1, 14 );
    172     } else {
    173         /* Reduced-width stereo coding; scale down and quantize predictors */
    174         pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
    175         pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );
    176         silk_stereo_quant_pred( pred_Q13, ix );
    177         width_Q14 = state->smth_width_Q14;
    178     }
    179 
    180     /* Make sure to keep on encoding until the tapered output has been transmitted */
    181     if( *mid_only_flag == 1 ) {
    182         state->silent_side_len += frame_length - STEREO_INTERP_LEN_MS * fs_kHz;
    183         if( state->silent_side_len < LA_SHAPE_MS * fs_kHz ) {
    184             *mid_only_flag = 0;
    185         } else {
    186             /* Limit to avoid wrapping around */
    187             state->silent_side_len = 10000;
    188         }
    189     } else {
    190         state->silent_side_len = 0;
    191     }
    192 
    193     if( *mid_only_flag == 0 && mid_side_rates_bps[ 1 ] < 1 ) {
    194         mid_side_rates_bps[ 1 ] = 1;
    195         mid_side_rates_bps[ 0 ] = silk_max_int( 1, total_rate_bps - mid_side_rates_bps[ 1 ]);
    196     }
    197 
    198     /* Interpolate predictors and subtract prediction from side channel */
    199     pred0_Q13  = -state->pred_prev_Q13[ 0 ];
    200     pred1_Q13  = -state->pred_prev_Q13[ 1 ];
    201     w_Q24      =  silk_LSHIFT( state->width_prev_Q14, 10 );
    202     denom_Q16  = silk_DIV32_16( (opus_int32)1 << 16, STEREO_INTERP_LEN_MS * fs_kHz );
    203     delta0_Q13 = -silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 0 ] - state->pred_prev_Q13[ 0 ], denom_Q16 ), 16 );
    204     delta1_Q13 = -silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 1 ] - state->pred_prev_Q13[ 1 ], denom_Q16 ), 16 );
    205     deltaw_Q24 =  silk_LSHIFT( silk_SMULWB( width_Q14 - state->width_prev_Q14, denom_Q16 ), 10 );
    206     for( n = 0; n < STEREO_INTERP_LEN_MS * fs_kHz; n++ ) {
    207         pred0_Q13 += delta0_Q13;
    208         pred1_Q13 += delta1_Q13;
    209         w_Q24   += deltaw_Q24;
    210         sum = silk_LSHIFT( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 );    /* Q11 */
    211         sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 );               /* Q8  */
    212         sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 );       /* Q8  */
    213         x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) );
    214     }
    215 
    216     pred0_Q13 = -pred_Q13[ 0 ];
    217     pred1_Q13 = -pred_Q13[ 1 ];
    218     w_Q24     =  silk_LSHIFT( width_Q14, 10 );
    219     for( n = STEREO_INTERP_LEN_MS * fs_kHz; n < frame_length; n++ ) {
    220         sum = silk_LSHIFT( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 );    /* Q11 */
    221         sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 );               /* Q8  */
    222         sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 );       /* Q8  */
    223         x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) );
    224     }
    225     state->pred_prev_Q13[ 0 ] = (opus_int16)pred_Q13[ 0 ];
    226     state->pred_prev_Q13[ 1 ] = (opus_int16)pred_Q13[ 1 ];
    227     state->width_prev_Q14     = (opus_int16)width_Q14;
    228     RESTORE_STACK;
    229 }
    230