133 lines
5.6 KiB
C
133 lines
5.6 KiB
C
/***********************************************************************
|
|
Copyright (c) 2006-2010, Skype Limited. All rights reserved.
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, (subject to the limitations in the disclaimer below)
|
|
are permitted provided that the following conditions are met:
|
|
- Redistributions of source code must retain the above copyright notice,
|
|
this list of conditions and the following disclaimer.
|
|
- Redistributions in binary form must reproduce the above copyright
|
|
notice, this list of conditions and the following disclaimer in the
|
|
documentation and/or other materials provided with the distribution.
|
|
- Neither the name of Skype Limited, nor the names of specific
|
|
contributors, may be used to endorse or promote products derived from
|
|
this software without specific prior written permission.
|
|
NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
|
|
BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
|
|
CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
|
|
BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
|
|
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
|
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
|
|
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
***********************************************************************/
|
|
|
|
#include "SKP_Silk_typedef.h"
|
|
#include "SKP_Silk_SigProc_FIX.h"
|
|
|
|
#define LPC_STABILIZE_LPC_MAX_ABS_VALUE_Q16 ( ( (SKP_int32)SKP_int16_MAX ) << 4 )
|
|
|
|
/* LPC stabilizer, for a single input data vector */
|
|
void SKP_Silk_LPC_stabilize(
|
|
SKP_int16 *a_Q12, /* O stabilized LPC vector [L] */
|
|
SKP_int32 *a_Q16, /* I LPC vector [L] */
|
|
const SKP_int32 bwe_Q16, /* I Bandwidth expansion factor */
|
|
const SKP_int L /* I Number of LPC parameters in the input vector */
|
|
)
|
|
{
|
|
SKP_int32 maxabs, absval, sc_Q16;
|
|
SKP_int i, idx = 0;
|
|
SKP_int32 invGain_Q30;
|
|
|
|
SKP_Silk_bwexpander_32( a_Q16, L, bwe_Q16 );
|
|
|
|
/***************************/
|
|
/* Limit range of the LPCs */
|
|
/***************************/
|
|
/* Limit the maximum absolute value of the prediction coefficients */
|
|
while( SKP_TRUE ) {
|
|
/* Find maximum absolute value and its index */
|
|
maxabs = SKP_int32_MIN;
|
|
for( i = 0; i < L; i++ ) {
|
|
absval = SKP_abs( a_Q16[ i ] );
|
|
if( absval > maxabs ) {
|
|
maxabs = absval;
|
|
idx = i;
|
|
}
|
|
}
|
|
|
|
if( maxabs >= LPC_STABILIZE_LPC_MAX_ABS_VALUE_Q16 ) {
|
|
/* Reduce magnitude of prediction coefficients */
|
|
sc_Q16 = SKP_DIV32( SKP_int32_MAX, SKP_RSHIFT( maxabs, 4 ) );
|
|
sc_Q16 = 65536 - sc_Q16;
|
|
sc_Q16 = SKP_DIV32( sc_Q16, idx + 1 );
|
|
sc_Q16 = 65536 - sc_Q16;
|
|
sc_Q16 = SKP_LSHIFT( SKP_SMULWB( sc_Q16, 32604 ), 1 ); // 0.995 in Q16
|
|
SKP_Silk_bwexpander_32( a_Q16, L, sc_Q16 );
|
|
} else {
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* Convert to 16 bit Q12 */
|
|
for( i = 0; i < L; i++ ) {
|
|
a_Q12[ i ] = (SKP_int16)SKP_RSHIFT_ROUND( a_Q16[ i ], 4 );
|
|
}
|
|
|
|
/**********************/
|
|
/* Ensure stable LPCs */
|
|
/**********************/
|
|
while( SKP_Silk_LPC_inverse_pred_gain( &invGain_Q30, a_Q12, L ) == 1 ) {
|
|
SKP_Silk_bwexpander( a_Q12, L, 65339 ); // 0.997 in Q16
|
|
}
|
|
}
|
|
|
|
void SKP_Silk_LPC_fit(
|
|
SKP_int16 *a_QQ, /* O Stabilized LPC vector, Q(24-rshift) [L] */
|
|
SKP_int32 *a_Q24, /* I LPC vector [L] */
|
|
const SKP_int QQ, /* I Q domain of output LPC vector */
|
|
const SKP_int L /* I Number of LPC parameters in the input vector */
|
|
)
|
|
{
|
|
SKP_int i, rshift, idx = 0;
|
|
SKP_int32 maxabs, absval, sc_Q16;
|
|
|
|
rshift = 24 - QQ;
|
|
|
|
/***************************/
|
|
/* Limit range of the LPCs */
|
|
/***************************/
|
|
/* Limit the maximum absolute value of the prediction coefficients */
|
|
while( SKP_TRUE ) {
|
|
/* Find maximum absolute value and its index */
|
|
maxabs = SKP_int32_MIN;
|
|
for( i = 0; i < L; i++ ) {
|
|
absval = SKP_abs( a_Q24[ i ] );
|
|
if( absval > maxabs ) {
|
|
maxabs = absval;
|
|
idx = i;
|
|
}
|
|
}
|
|
|
|
maxabs = SKP_RSHIFT( maxabs, rshift );
|
|
if( maxabs >= SKP_int16_MAX ) {
|
|
/* Reduce magnitude of prediction coefficients */
|
|
sc_Q16 = 65470 - SKP_DIV32( SKP_MUL( 65470 >> 2, maxabs - SKP_int16_MAX ),
|
|
SKP_RSHIFT32( SKP_MUL( maxabs, idx + 1), 2 ) );
|
|
SKP_Silk_bwexpander_32( a_Q24, L, sc_Q16 );
|
|
} else {
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* Convert to 16 bit Q(24-rshift) */
|
|
SKP_assert( rshift > 0 );
|
|
SKP_assert( rshift < 31 );
|
|
for( i = 0; i < L; i++ ) {
|
|
a_QQ[ i ] = (SKP_int16)SKP_RSHIFT_ROUND( a_Q24[ i ], rshift );
|
|
}
|
|
}
|