freeswitch/libs/silk/src/SKP_Silk_shell_coder.c

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#include "SKP_Silk_main.h"

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

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

SKP_INLINE void encode_split(
    SKP_Silk_range_coder_state  *sRC,           /* I/O: compressor data structure                   */
    const SKP_int               p_child1,       /* I:   pulse amplitude of first child subframe     */
    const SKP_int               p,              /* I:   pulse amplitude of current subframe         */
    const SKP_uint16            *shell_table    /* I:   table of shell cdfs                         */
)
{
    const SKP_uint16 *cdf;

    if( p > 0 ) {
        cdf = &shell_table[ SKP_Silk_shell_code_table_offsets[ p ] ];
        SKP_Silk_range_encoder( sRC, p_child1, cdf );
    }
}

SKP_INLINE void decode_split(
    SKP_int                     *p_child1,      /* O:   pulse amplitude of first child subframe     */
    SKP_int                     *p_child2,      /* O:   pulse amplitude of second child subframe    */
    SKP_Silk_range_coder_state  *sRC,           /* I/O: compressor data structure                   */
    const SKP_int               p,              /* I:   pulse amplitude of current subframe         */
    const SKP_uint16            *shell_table    /* I:   table of shell cdfs                         */
)
{
    SKP_int cdf_middle;
    const SKP_uint16 *cdf;

    if( p > 0 ) {
        cdf_middle = SKP_RSHIFT( p, 1 );
        cdf = &shell_table[ SKP_Silk_shell_code_table_offsets[ p ] ];
        SKP_Silk_range_decoder( p_child1, sRC, cdf, cdf_middle );
        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 SKP_Silk_shell_encoder(
    SKP_Silk_range_coder_state      *sRC,               /* I/O  compressor data structure                   */
    const SKP_int                   *pulses0            /* I    data: nonnegative pulse amplitudes          */
)
{
    SKP_int pulses1[ 8 ], pulses2[ 4 ], pulses3[ 2 ], pulses4[ 1 ];

    /* this function operates on one shell code frame of 16 pulses */
    SKP_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( sRC, pulses3[  0 ], pulses4[ 0 ], SKP_Silk_shell_code_table3 );

    encode_split( sRC, pulses2[  0 ], pulses3[ 0 ], SKP_Silk_shell_code_table2 );

    encode_split( sRC, pulses1[  0 ], pulses2[ 0 ], SKP_Silk_shell_code_table1 );
    encode_split( sRC, pulses0[  0 ], pulses1[ 0 ], SKP_Silk_shell_code_table0 );
    encode_split( sRC, pulses0[  2 ], pulses1[ 1 ], SKP_Silk_shell_code_table0 );

    encode_split( sRC, pulses1[  2 ], pulses2[ 1 ], SKP_Silk_shell_code_table1 );
    encode_split( sRC, pulses0[  4 ], pulses1[ 2 ], SKP_Silk_shell_code_table0 );
    encode_split( sRC, pulses0[  6 ], pulses1[ 3 ], SKP_Silk_shell_code_table0 );

    encode_split( sRC, pulses2[  2 ], pulses3[ 1 ], SKP_Silk_shell_code_table2 );

    encode_split( sRC, pulses1[  4 ], pulses2[ 2 ], SKP_Silk_shell_code_table1 );
    encode_split( sRC, pulses0[  8 ], pulses1[ 4 ], SKP_Silk_shell_code_table0 );
    encode_split( sRC, pulses0[ 10 ], pulses1[ 5 ], SKP_Silk_shell_code_table0 );

    encode_split( sRC, pulses1[  6 ], pulses2[ 3 ], SKP_Silk_shell_code_table1 );
    encode_split( sRC, pulses0[ 12 ], pulses1[ 6 ], SKP_Silk_shell_code_table0 );
    encode_split( sRC, pulses0[ 14 ], pulses1[ 7 ], SKP_Silk_shell_code_table0 );
}


/* Shell decoder, operates on one shell code frame of 16 pulses */
void SKP_Silk_shell_decoder(
    SKP_int                         *pulses0,           /* O    data: nonnegative pulse amplitudes          */
    SKP_Silk_range_coder_state      *sRC,               /* I/O  compressor data structure                   */
    const SKP_int                   pulses4             /* I    number of pulses per pulse-subframe         */
)
{
    SKP_int pulses3[ 2 ], pulses2[ 4 ], pulses1[ 8 ];

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

    decode_split( &pulses3[  0 ], &pulses3[  1 ], sRC, pulses4,      SKP_Silk_shell_code_table3 );

    decode_split( &pulses2[  0 ], &pulses2[  1 ], sRC, pulses3[ 0 ], SKP_Silk_shell_code_table2 );

    decode_split( &pulses1[  0 ], &pulses1[  1 ], sRC, pulses2[ 0 ], SKP_Silk_shell_code_table1 );
    decode_split( &pulses0[  0 ], &pulses0[  1 ], sRC, pulses1[ 0 ], SKP_Silk_shell_code_table0 );
    decode_split( &pulses0[  2 ], &pulses0[  3 ], sRC, pulses1[ 1 ], SKP_Silk_shell_code_table0 );

    decode_split( &pulses1[  2 ], &pulses1[  3 ], sRC, pulses2[ 1 ], SKP_Silk_shell_code_table1 );
    decode_split( &pulses0[  4 ], &pulses0[  5 ], sRC, pulses1[ 2 ], SKP_Silk_shell_code_table0 );
    decode_split( &pulses0[  6 ], &pulses0[  7 ], sRC, pulses1[ 3 ], SKP_Silk_shell_code_table0 );

    decode_split( &pulses2[  2 ], &pulses2[  3 ], sRC, pulses3[ 1 ], SKP_Silk_shell_code_table2 );

    decode_split( &pulses1[  4 ], &pulses1[  5 ], sRC, pulses2[ 2 ], SKP_Silk_shell_code_table1 );
    decode_split( &pulses0[  8 ], &pulses0[  9 ], sRC, pulses1[ 4 ], SKP_Silk_shell_code_table0 );
    decode_split( &pulses0[ 10 ], &pulses0[ 11 ], sRC, pulses1[ 5 ], SKP_Silk_shell_code_table0 );

    decode_split( &pulses1[  6 ], &pulses1[  7 ], sRC, pulses2[ 3 ], SKP_Silk_shell_code_table1 );
    decode_split( &pulses0[ 12 ], &pulses0[ 13 ], sRC, pulses1[ 6 ], SKP_Silk_shell_code_table0 );
    decode_split( &pulses0[ 14 ], &pulses0[ 15 ], sRC, pulses1[ 7 ], SKP_Silk_shell_code_table0 );
}