freeswitch/libs/silk/src/SKP_Silk_range_coder.c

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#include "SKP_Silk_main.h"

/* Range encoder for one symbol */
void SKP_Silk_range_encoder(
    SKP_Silk_range_coder_state      *psRC,              /* I/O  compressor data structure                   */
    const SKP_int                   data,               /* I    uncompressed data                           */
    const SKP_uint16                prob[]              /* I    cumulative density functions                */
)
{
    SKP_uint32 low_Q16, high_Q16;
    SKP_uint32 base_tmp, range_Q32;

    /* Copy structure data */
    SKP_uint32 base_Q32  = psRC->base_Q32;
    SKP_uint32 range_Q16 = psRC->range_Q16;
    SKP_int32  bufferIx  = psRC->bufferIx;
    SKP_uint8  *buffer   = psRC->buffer;

    if( psRC->error ) {
        return;
    }

    /* Update interval */
    low_Q16  = prob[ data ];
    high_Q16 = prob[ data + 1 ];
    base_tmp = base_Q32; /* save current base, to test for carry */
    base_Q32 += SKP_MUL_uint( range_Q16, low_Q16 );
    range_Q32 = SKP_MUL_uint( range_Q16, high_Q16 - low_Q16 );

    /* Check for carry */
    if( base_Q32 < base_tmp ) {
        /* Propagate carry in buffer */
        SKP_int bufferIx_tmp = bufferIx;
        while( ( ++buffer[ --bufferIx_tmp ] ) == 0 );
    }

    /* Check normalization */
    if( range_Q32 & 0xFF000000 ) {
        /* No normalization */
        range_Q16 = SKP_RSHIFT_uint( range_Q32, 16 );
    } else {
        if( range_Q32 & 0xFFFF0000 ) {
            /* Normalization of 8 bits shift */
            range_Q16 = SKP_RSHIFT_uint( range_Q32, 8 );
        } else {
            /* Normalization of 16 bits shift */
            range_Q16 = range_Q32;
            /* Make sure not to write beyond buffer */
            if( bufferIx >= psRC->bufferLength ) {
                psRC->error = RANGE_CODER_WRITE_BEYOND_BUFFER;
                return;
            }
            /* Write one byte to buffer */
            buffer[ bufferIx++ ] = (SKP_uint8)( SKP_RSHIFT_uint( base_Q32, 24 ) );
            base_Q32 = SKP_LSHIFT_ovflw( base_Q32, 8 );
        }
        /* Make sure not to write beyond buffer */
        if( bufferIx >= psRC->bufferLength ) {
            psRC->error = RANGE_CODER_WRITE_BEYOND_BUFFER;
            return;
        }
        /* Write one byte to buffer */
        buffer[ bufferIx++ ] = (SKP_uint8)( SKP_RSHIFT_uint( base_Q32, 24 ) );
        base_Q32 = SKP_LSHIFT_ovflw( base_Q32, 8 );
    }

    /* Copy structure data back */
    psRC->base_Q32  = base_Q32;
    psRC->range_Q16 = range_Q16;
    psRC->bufferIx  = bufferIx;
}

/* Range encoder for multiple symbols */
void SKP_Silk_range_encoder_multi(
    SKP_Silk_range_coder_state      *psRC,              /* I/O  compressor data structure                   */
    const SKP_int                   data[],             /* I    uncompressed data    [nSymbols]             */
    const SKP_uint16 * const        prob[],             /* I    cumulative density functions                */
    const SKP_int                   nSymbols            /* I    number of data symbols                      */
)
{
    SKP_int k;
    for( k = 0; k < nSymbols; k++ ) {
        SKP_Silk_range_encoder( psRC, data[ k ], prob[ k ] );
    }
}

/* Range decoder for one symbol */
void SKP_Silk_range_decoder(
    SKP_int                         data[],             /* O    uncompressed data                           */
    SKP_Silk_range_coder_state      *psRC,              /* I/O  compressor data structure                   */
    const SKP_uint16                prob[],             /* I    cumulative density function                 */
    SKP_int                         probIx              /* I    initial (middle) entry of cdf               */
)
{
    SKP_uint32 low_Q16, high_Q16;
    SKP_uint32 base_tmp, range_Q32;

    /* Copy structure data */
    SKP_uint32 base_Q32  = psRC->base_Q32;
    SKP_uint32 range_Q16 = psRC->range_Q16;
    SKP_int32  bufferIx  = psRC->bufferIx;
    SKP_uint8  *buffer   = &psRC->buffer[ 4 ];

    if( psRC->error ) {
        /* Set output to zero */
        *data = 0;
        return;
    }

    high_Q16 = prob[ probIx ];
    base_tmp = SKP_MUL_uint( range_Q16, high_Q16 );
    if( base_tmp > base_Q32 ) {
        while( 1 ) {
            low_Q16 = prob[ --probIx ];
            base_tmp = SKP_MUL_uint( range_Q16, low_Q16 );
            if( base_tmp <= base_Q32 ) {
                break;
            }
            high_Q16 = low_Q16;
            /* Test for out of range */
            if( high_Q16 == 0 ) {
                psRC->error = RANGE_CODER_CDF_OUT_OF_RANGE;
                /* Set output to zero */
                *data = 0;
                return;
            }
        }
    } else {
        while( 1 ) {
            low_Q16  = high_Q16;
            high_Q16 = prob[ ++probIx ];
            base_tmp = SKP_MUL_uint( range_Q16, high_Q16 );
            if( base_tmp > base_Q32 ) {
                probIx--;
                break;
            }
            /* Test for out of range */
            if( high_Q16 == 0xFFFF ) {
                psRC->error = RANGE_CODER_CDF_OUT_OF_RANGE;
                /* Set output to zero */
                *data = 0;
                return;
            }
        }
    }
    *data = probIx;
    base_Q32 -= SKP_MUL_uint( range_Q16, low_Q16 );
    range_Q32 = SKP_MUL_uint( range_Q16, high_Q16 - low_Q16 );

    /* Check normalization */
    if( range_Q32 & 0xFF000000 ) {
        /* No normalization */
        range_Q16 = SKP_RSHIFT_uint( range_Q32, 16 );
    } else {
        if( range_Q32 & 0xFFFF0000 ) {
            /* Normalization of 8 bits shift */
            range_Q16 = SKP_RSHIFT_uint( range_Q32, 8 );
            /* Check for errors */
            if( SKP_RSHIFT_uint( base_Q32, 24 ) ) {
                psRC->error = RANGE_CODER_NORMALIZATION_FAILED;
                /* Set output to zero */
                *data = 0;
                return;
            }
        } else {
            /* Normalization of 16 bits shift */
            range_Q16 = range_Q32;
            /* Check for errors */
            if( SKP_RSHIFT( base_Q32, 16 ) ) {
                psRC->error = RANGE_CODER_NORMALIZATION_FAILED;
                /* Set output to zero */
                *data = 0;
                return;
            }
            /* Update base */
            base_Q32 = SKP_LSHIFT_uint( base_Q32, 8 );
            /* Make sure not to read beyond buffer */
            if( bufferIx < psRC->bufferLength ) {
                /* Read one byte from buffer */
                base_Q32 |= (SKP_uint32)buffer[ bufferIx++ ];
            }
        }
        /* Update base */
        base_Q32 = SKP_LSHIFT_uint( base_Q32, 8 );
        /* Make sure not to read beyond buffer */
        if( bufferIx < psRC->bufferLength ) {
            /* Read one byte from buffer */
            base_Q32 |= (SKP_uint32)buffer[ bufferIx++ ];
        }
    }

    /* Check for zero interval length */
    if( range_Q16 == 0 ) {
        psRC->error = RANGE_CODER_ZERO_INTERVAL_WIDTH;
        /* Set output to zero */
        *data = 0;
        return;
    }

    /* Copy structure data back */
    psRC->base_Q32  = base_Q32;
    psRC->range_Q16 = range_Q16;
    psRC->bufferIx  = bufferIx;
}

/* Range decoder for multiple symbols */
void SKP_Silk_range_decoder_multi(
    SKP_int                         data[],             /* O    uncompressed data                [nSymbols] */
    SKP_Silk_range_coder_state      *psRC,              /* I/O  compressor data structure                   */
    const SKP_uint16 * const        prob[],             /* I    cumulative density functions                */
    const SKP_int                   probStartIx[],      /* I    initial (middle) entries of cdfs [nSymbols] */
    const SKP_int                   nSymbols            /* I    number of data symbols                      */
)
{
    SKP_int k;
    for( k = 0; k < nSymbols; k++ ) {
        SKP_Silk_range_decoder( &data[ k ], psRC, prob[ k ], probStartIx[ k ] );
    }
}

/* Initialize range encoder */
void SKP_Silk_range_enc_init(
    SKP_Silk_range_coder_state      *psRC               /* O    compressor data structure                   */
)
{
    /* Initialize structure */
    psRC->bufferLength = MAX_ARITHM_BYTES;
    psRC->range_Q16    = 0x0000FFFF;
    psRC->bufferIx     = 0;
    psRC->base_Q32     = 0;
    psRC->error        = 0;
}

/* Initialize range decoder */
void SKP_Silk_range_dec_init(
    SKP_Silk_range_coder_state      *psRC,              /* O    compressor data structure                   */
    const SKP_uint8                 buffer[],           /* I    buffer for compressed data [bufferLength]   */
    const SKP_int32                 bufferLength        /* I    buffer length (in bytes)                    */
)
{
    /* check input */
    if( bufferLength > MAX_ARITHM_BYTES ) {
        psRC->error = RANGE_CODER_DEC_PAYLOAD_TOO_LONG;
        return;
    }
    /* Initialize structure */
    /* Copy to internal buffer */
    SKP_memcpy( psRC->buffer, buffer, bufferLength * sizeof( SKP_uint8 ) );
    psRC->bufferLength = bufferLength;
    psRC->bufferIx = 0;
    psRC->base_Q32 =
        SKP_LSHIFT_uint( (SKP_uint32)buffer[ 0 ], 24 ) |
        SKP_LSHIFT_uint( (SKP_uint32)buffer[ 1 ], 16 ) |
        SKP_LSHIFT_uint( (SKP_uint32)buffer[ 2 ],  8 ) |
                         (SKP_uint32)buffer[ 3 ];
    psRC->range_Q16 = 0x0000FFFF;
    psRC->error     = 0;
}

/* Determine length of bitstream */
SKP_int SKP_Silk_range_coder_get_length(                /* O    returns number of BITS in stream            */
    const SKP_Silk_range_coder_state    *psRC,          /* I    compressed data structure                   */
    SKP_int                             *nBytes         /* O    number of BYTES in stream                   */
)
{
    SKP_int nBits;

    /* Number of bits in stream */
    nBits = SKP_LSHIFT( psRC->bufferIx, 3 ) + SKP_Silk_CLZ32( psRC->range_Q16 - 1 ) - 14;

    *nBytes = SKP_RSHIFT( nBits + 7, 3 );

    /* Return number of bits in bitstream */
    return nBits;
}

/* Write shortest uniquely decodable stream to buffer, and determine its length */
void SKP_Silk_range_enc_wrap_up(
    SKP_Silk_range_coder_state      *psRC               /* I/O  compressed data structure                   */
)
{
    SKP_int bufferIx_tmp, bits_to_store, bits_in_stream, nBytes, mask;
    SKP_uint32 base_Q24;

    /* Lower limit of interval, shifted 8 bits to the right */
    base_Q24 = SKP_RSHIFT_uint( psRC->base_Q32, 8 );

    bits_in_stream = SKP_Silk_range_coder_get_length( psRC, &nBytes );

    /* Number of additional bits (1..9) required to be stored to stream */
    bits_to_store = bits_in_stream - SKP_LSHIFT( psRC->bufferIx, 3 );
    /* Round up to required resolution */
    base_Q24 += SKP_RSHIFT_uint(  0x00800000, bits_to_store - 1 );
    base_Q24 &= SKP_LSHIFT_ovflw( 0xFFFFFFFF, 24 - bits_to_store );

    /* Check for carry */
    if( base_Q24 & 0x01000000 ) {
        /* Propagate carry in buffer */
        bufferIx_tmp = psRC->bufferIx;
        while( ( ++( psRC->buffer[ --bufferIx_tmp ] ) ) == 0 );
    }

    /* Store to stream, making sure not to write beyond buffer */
    if( psRC->bufferIx < psRC->bufferLength ) {
        psRC->buffer[ psRC->bufferIx++ ] = (SKP_uint8)SKP_RSHIFT_uint( base_Q24, 16 );
        if( bits_to_store > 8 ) {
            if( psRC->bufferIx < psRC->bufferLength ) {
                psRC->buffer[ psRC->bufferIx++ ] = (SKP_uint8)SKP_RSHIFT_uint( base_Q24, 8 );
            }
        }
    }

    /* Fill up any remaining bits in the last byte with 1s */
    if( bits_in_stream & 7 ) {
        mask = SKP_RSHIFT( 0xFF, bits_in_stream & 7 );
        if( nBytes - 1 < psRC->bufferLength ) {
            psRC->buffer[ nBytes - 1 ] |= mask;
        }
    }
}

/* Check that any remaining bits in the last byte are set to 1 */
void SKP_Silk_range_coder_check_after_decoding(
    SKP_Silk_range_coder_state      *psRC               /* I/O  compressed data structure                   */
)
{
    SKP_int bits_in_stream, nBytes, mask;

    bits_in_stream = SKP_Silk_range_coder_get_length( psRC, &nBytes );

    /* Make sure not to read beyond buffer */
    if( nBytes - 1 >= psRC->bufferLength ) {
        psRC->error = RANGE_CODER_DECODER_CHECK_FAILED;
        return;
    }

    /* Test any remaining bits in last byte */
    if( bits_in_stream & 7 ) {
        mask = SKP_RSHIFT( 0xFF, bits_in_stream & 7 );
        if( ( psRC->buffer[ nBytes - 1 ] & mask ) != mask ) {
            psRC->error = RANGE_CODER_DECODER_CHECK_FAILED;
            return;
        }
    }
}