The Tor Browser: media/libopus/silk/stereo_MS_to

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

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     2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.

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    26 ***********************************************************************/

    28 #ifdef HAVE_CONFIG_H

    29 #include "config.h"

    30 #endif

    32 #include "main.h"

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

    35 void silk_stereo_MS_to_LR(

    36     stereo_dec_state            *state,                         /* I/O  State                                       */

    37     opus_int16                  x1[],                           /* I/O  Left input signal, becomes mid signal       */

    38     opus_int16                  x2[],                           /* I/O  Right input signal, becomes side signal     */

    39     const opus_int32            pred_Q13[],                     /* I    Predictors                                  */

    40     opus_int                    fs_kHz,                         /* I    Samples rate (kHz)                          */

    41     opus_int                    frame_length                    /* I    Number of samples                           */

    42 )

    43 {

    44     opus_int   n, denom_Q16, delta0_Q13, delta1_Q13;

    45     opus_int32 sum, diff, pred0_Q13, pred1_Q13;

    47     /* Buffering */

    48     silk_memcpy( x1, state->sMid,  2 * sizeof( opus_int16 ) );

    49     silk_memcpy( x2, state->sSide, 2 * sizeof( opus_int16 ) );

    50     silk_memcpy( state->sMid,  &x1[ frame_length ], 2 * sizeof( opus_int16 ) );

    51     silk_memcpy( state->sSide, &x2[ frame_length ], 2 * sizeof( opus_int16 ) );

    53     /* Interpolate predictors and add prediction to side channel */

    54     pred0_Q13  = state->pred_prev_Q13[ 0 ];

    55     pred1_Q13  = state->pred_prev_Q13[ 1 ];

    56     denom_Q16  = silk_DIV32_16( (opus_int32)1 << 16, STEREO_INTERP_LEN_MS * fs_kHz );

    57     delta0_Q13 = silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 0 ] - state->pred_prev_Q13[ 0 ], denom_Q16 ), 16 );

    58     delta1_Q13 = silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 1 ] - state->pred_prev_Q13[ 1 ], denom_Q16 ), 16 );

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

    60         pred0_Q13 += delta0_Q13;

    61         pred1_Q13 += delta1_Q13;

    62         sum = silk_LSHIFT( silk_ADD_LSHIFT( x1[ n ] + x1[ n + 2 ], x1[ n + 1 ], 1 ), 9 );       /* Q11 */

    63         sum = silk_SMLAWB( silk_LSHIFT( (opus_int32)x2[ n + 1 ], 8 ), sum, pred0_Q13 );         /* Q8  */

    64         sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)x1[ n + 1 ], 11 ), pred1_Q13 );        /* Q8  */

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

    66     }

    67     pred0_Q13 = pred_Q13[ 0 ];

    68     pred1_Q13 = pred_Q13[ 1 ];

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

    70         sum = silk_LSHIFT( silk_ADD_LSHIFT( x1[ n ] + x1[ n + 2 ], x1[ n + 1 ], 1 ), 9 );       /* Q11 */

    71         sum = silk_SMLAWB( silk_LSHIFT( (opus_int32)x2[ n + 1 ], 8 ), sum, pred0_Q13 );         /* Q8  */

    72         sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)x1[ n + 1 ], 11 ), pred1_Q13 );        /* Q8  */

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

    74     }

    75     state->pred_prev_Q13[ 0 ] = pred_Q13[ 0 ];

    76     state->pred_prev_Q13[ 1 ] = pred_Q13[ 1 ];

    78     /* Convert to left/right signals */

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

    80         sum  = x1[ n + 1 ] + (opus_int32)x2[ n + 1 ];

    81         diff = x1[ n + 1 ] - (opus_int32)x2[ n + 1 ];

    82         x1[ n + 1 ] = (opus_int16)silk_SAT16( sum );

    83         x2[ n + 1 ] = (opus_int16)silk_SAT16( diff );

    84     }

    85 }

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