ref: 81592731016180584d0de28be13965aa5b80ea0d
dir: /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 additional bits (1..9) required to be stored to 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;
}
}
}