src/third_party/opus/silk/shell_coder.c

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

#include "main.h"

/* shell coder; pulse-subframe length is hardcoded */

static OPUS_INLINE void combine_pulses(
    opus_int         *out,   /* O    combined pulses vector [len] */
    const opus_int   *in,    /* I    input vector       [2 * len] */
    const opus_int   len     /* I    number of OUTPUT samples     */
)
{
    opus_int k;
    for( k = 0; k < len; k++ ) {
        out[ k ] = in[ 2 * k ] + in[ 2 * k + 1 ];
    }
}

static OPUS_INLINE void encode_split(
    ec_enc                      *psRangeEnc,    /* I/O  compressor data structure                   */
    const opus_int              p_child1,       /* I    pulse amplitude of first child subframe     */
    const opus_int              p,              /* I    pulse amplitude of current subframe         */
    const opus_uint8            *shell_table    /* I    table of shell cdfs                         */
)
{
    if( p > 0 ) {
        ec_enc_icdf( psRangeEnc, p_child1, &shell_table[ silk_shell_code_table_offsets[ p ] ], 8 );
    }
}

static OPUS_INLINE void decode_split(
    opus_int16                  *p_child1,      /* O    pulse amplitude of first child subframe     */
    opus_int16                  *p_child2,      /* O    pulse amplitude of second child subframe    */
    ec_dec                      *psRangeDec,    /* I/O  Compressor data structure                   */
    const opus_int              p,              /* I    pulse amplitude of current subframe         */
    const opus_uint8            *shell_table    /* I    table of shell cdfs                         */
)
{
    if( p > 0 ) {
        p_child1[ 0 ] = ec_dec_icdf( psRangeDec, &shell_table[ silk_shell_code_table_offsets[ p ] ], 8 );
        p_child2[ 0 ] = p - p_child1[ 0 ];
    } else {
        p_child1[ 0 ] = 0;
        p_child2[ 0 ] = 0;
    }
}

/* Shell encoder, operates on one shell code frame of 16 pulses */
void silk_shell_encoder(
    ec_enc                      *psRangeEnc,                    /* I/O  compressor data structure                   */
    const opus_int              *pulses0                        /* I    data: nonnegative pulse amplitudes          */
)
{
    opus_int pulses1[ 8 ], pulses2[ 4 ], pulses3[ 2 ], pulses4[ 1 ];

    /* this function operates on one shell code frame of 16 pulses */
    silk_assert( SHELL_CODEC_FRAME_LENGTH == 16 );

    /* tree representation per pulse-subframe */
    combine_pulses( pulses1, pulses0, 8 );
    combine_pulses( pulses2, pulses1, 4 );
    combine_pulses( pulses3, pulses2, 2 );
    combine_pulses( pulses4, pulses3, 1 );

    encode_split( psRangeEnc, pulses3[  0 ], pulses4[ 0 ], silk_shell_code_table3 );

    encode_split( psRangeEnc, pulses2[  0 ], pulses3[ 0 ], silk_shell_code_table2 );

    encode_split( psRangeEnc, pulses1[  0 ], pulses2[ 0 ], silk_shell_code_table1 );
    encode_split( psRangeEnc, pulses0[  0 ], pulses1[ 0 ], silk_shell_code_table0 );
    encode_split( psRangeEnc, pulses0[  2 ], pulses1[ 1 ], silk_shell_code_table0 );

    encode_split( psRangeEnc, pulses1[  2 ], pulses2[ 1 ], silk_shell_code_table1 );
    encode_split( psRangeEnc, pulses0[  4 ], pulses1[ 2 ], silk_shell_code_table0 );
    encode_split( psRangeEnc, pulses0[  6 ], pulses1[ 3 ], silk_shell_code_table0 );

    encode_split( psRangeEnc, pulses2[  2 ], pulses3[ 1 ], silk_shell_code_table2 );

    encode_split( psRangeEnc, pulses1[  4 ], pulses2[ 2 ], silk_shell_code_table1 );
    encode_split( psRangeEnc, pulses0[  8 ], pulses1[ 4 ], silk_shell_code_table0 );
    encode_split( psRangeEnc, pulses0[ 10 ], pulses1[ 5 ], silk_shell_code_table0 );

    encode_split( psRangeEnc, pulses1[  6 ], pulses2[ 3 ], silk_shell_code_table1 );
    encode_split( psRangeEnc, pulses0[ 12 ], pulses1[ 6 ], silk_shell_code_table0 );
    encode_split( psRangeEnc, pulses0[ 14 ], pulses1[ 7 ], silk_shell_code_table0 );
}


/* Shell decoder, operates on one shell code frame of 16 pulses */
void silk_shell_decoder(
    opus_int16                  *pulses0,                       /* O    data: nonnegative pulse amplitudes          */
    ec_dec                      *psRangeDec,                    /* I/O  Compressor data structure                   */
    const opus_int              pulses4                         /* I    number of pulses per pulse-subframe         */
)
{
    opus_int16 pulses3[ 2 ], pulses2[ 4 ], pulses1[ 8 ];

    /* this function operates on one shell code frame of 16 pulses */
    silk_assert( SHELL_CODEC_FRAME_LENGTH == 16 );

    decode_split( &pulses3[  0 ], &pulses3[  1 ], psRangeDec, pulses4,      silk_shell_code_table3 );

    decode_split( &pulses2[  0 ], &pulses2[  1 ], psRangeDec, pulses3[ 0 ], silk_shell_code_table2 );

    decode_split( &pulses1[  0 ], &pulses1[  1 ], psRangeDec, pulses2[ 0 ], silk_shell_code_table1 );
    decode_split( &pulses0[  0 ], &pulses0[  1 ], psRangeDec, pulses1[ 0 ], silk_shell_code_table0 );
    decode_split( &pulses0[  2 ], &pulses0[  3 ], psRangeDec, pulses1[ 1 ], silk_shell_code_table0 );

    decode_split( &pulses1[  2 ], &pulses1[  3 ], psRangeDec, pulses2[ 1 ], silk_shell_code_table1 );
    decode_split( &pulses0[  4 ], &pulses0[  5 ], psRangeDec, pulses1[ 2 ], silk_shell_code_table0 );
    decode_split( &pulses0[  6 ], &pulses0[  7 ], psRangeDec, pulses1[ 3 ], silk_shell_code_table0 );

    decode_split( &pulses2[  2 ], &pulses2[  3 ], psRangeDec, pulses3[ 1 ], silk_shell_code_table2 );

    decode_split( &pulses1[  4 ], &pulses1[  5 ], psRangeDec, pulses2[ 2 ], silk_shell_code_table1 );
    decode_split( &pulses0[  8 ], &pulses0[  9 ], psRangeDec, pulses1[ 4 ], silk_shell_code_table0 );
    decode_split( &pulses0[ 10 ], &pulses0[ 11 ], psRangeDec, pulses1[ 5 ], silk_shell_code_table0 );

    decode_split( &pulses1[  6 ], &pulses1[  7 ], psRangeDec, pulses2[ 3 ], silk_shell_code_table1 );
    decode_split( &pulses0[ 12 ], &pulses0[ 13 ], psRangeDec, pulses1[ 6 ], silk_shell_code_table0 );
    decode_split( &pulses0[ 14 ], &pulses0[ 15 ], psRangeDec, pulses1[ 7 ], silk_shell_code_table0 );
}