280 lines
12 KiB
C
Executable File
280 lines
12 KiB
C
Executable File
/***********************************************************************
|
|
Copyright (c) 2006-2012, 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.
|
|
***********************************************************************/
|
|
|
|
/* Conversion between prediction filter coefficients and NLSFs */
|
|
/* Requires the order to be an even number */
|
|
/* A piecewise linear approximation maps LSF <-> cos(LSF) */
|
|
/* Therefore the result is not accurate NLSFs, but the two */
|
|
/* function are accurate inverses of each other */
|
|
|
|
#include "SKP_Silk_SigProc_FIX.h"
|
|
|
|
/* Number of binary divisions */
|
|
#define BIN_DIV_STEPS_A2NLSF_FIX 3 /* must be no higher than 16 - log2( LSF_COS_TAB_SZ_FIX ) */
|
|
#define QPoly 16
|
|
#define MAX_ITERATIONS_A2NLSF_FIX 30
|
|
|
|
/* Flag for using 2x as many cosine sampling points, reduces the risk of missing a root */
|
|
#define OVERSAMPLE_COSINE_TABLE 0
|
|
|
|
/* Helper function for A2NLSF(..) */
|
|
/* Transforms polynomials from cos(n*f) to cos(f)^n */
|
|
SKP_INLINE void SKP_Silk_A2NLSF_trans_poly(
|
|
SKP_int32 *p, /* I/O Polynomial */
|
|
const SKP_int dd /* I Polynomial order (= filter order / 2 ) */
|
|
)
|
|
{
|
|
SKP_int k, n;
|
|
|
|
for( k = 2; k <= dd; k++ ) {
|
|
for( n = dd; n > k; n-- ) {
|
|
p[ n - 2 ] -= p[ n ];
|
|
}
|
|
p[ k - 2 ] -= SKP_LSHIFT( p[ k ], 1 );
|
|
}
|
|
}
|
|
/* Helper function for A2NLSF(..) */
|
|
/* Polynomial evaluation */
|
|
SKP_INLINE SKP_int32 SKP_Silk_A2NLSF_eval_poly( /* return the polynomial evaluation, in QPoly */
|
|
SKP_int32 *p, /* I Polynomial, QPoly */
|
|
const SKP_int32 x, /* I Evaluation point, Q12 */
|
|
const SKP_int dd /* I Order */
|
|
)
|
|
{
|
|
SKP_int n;
|
|
SKP_int32 x_Q16, y32;
|
|
|
|
y32 = p[ dd ]; /* QPoly */
|
|
x_Q16 = SKP_LSHIFT( x, 4 );
|
|
for( n = dd - 1; n >= 0; n-- ) {
|
|
y32 = SKP_SMLAWW( p[ n ], y32, x_Q16 ); /* QPoly */
|
|
}
|
|
return y32;
|
|
}
|
|
|
|
SKP_INLINE void SKP_Silk_A2NLSF_init(
|
|
const SKP_int32 *a_Q16,
|
|
SKP_int32 *P,
|
|
SKP_int32 *Q,
|
|
const SKP_int dd
|
|
)
|
|
{
|
|
SKP_int k;
|
|
|
|
/* Convert filter coefs to even and odd polynomials */
|
|
P[dd] = SKP_LSHIFT( 1, QPoly );
|
|
Q[dd] = SKP_LSHIFT( 1, QPoly );
|
|
for( k = 0; k < dd; k++ ) {
|
|
#if( QPoly < 16 )
|
|
P[ k ] = SKP_RSHIFT_ROUND( -a_Q16[ dd - k - 1 ] - a_Q16[ dd + k ], 16 - QPoly ); /* QPoly */
|
|
Q[ k ] = SKP_RSHIFT_ROUND( -a_Q16[ dd - k - 1 ] + a_Q16[ dd + k ], 16 - QPoly ); /* QPoly */
|
|
#elif( QPoly == 16 )
|
|
P[ k ] = -a_Q16[ dd - k - 1 ] - a_Q16[ dd + k ]; // QPoly
|
|
Q[ k ] = -a_Q16[ dd - k - 1 ] + a_Q16[ dd + k ]; // QPoly
|
|
#else
|
|
P[ k ] = SKP_LSHIFT( -a_Q16[ dd - k - 1 ] - a_Q16[ dd + k ], QPoly - 16 ); /* QPoly */
|
|
Q[ k ] = SKP_LSHIFT( -a_Q16[ dd - k - 1 ] + a_Q16[ dd + k ], QPoly - 16 ); /* QPoly */
|
|
#endif
|
|
}
|
|
|
|
/* Divide out zeros as we have that for even filter orders, */
|
|
/* z = 1 is always a root in Q, and */
|
|
/* z = -1 is always a root in P */
|
|
for( k = dd; k > 0; k-- ) {
|
|
P[ k - 1 ] -= P[ k ];
|
|
Q[ k - 1 ] += Q[ k ];
|
|
}
|
|
|
|
/* Transform polynomials from cos(n*f) to cos(f)^n */
|
|
SKP_Silk_A2NLSF_trans_poly( P, dd );
|
|
SKP_Silk_A2NLSF_trans_poly( Q, dd );
|
|
}
|
|
|
|
/* Compute Normalized Line Spectral Frequencies (NLSFs) from whitening filter coefficients */
|
|
/* If not all roots are found, the a_Q16 coefficients are bandwidth expanded until convergence. */
|
|
void SKP_Silk_A2NLSF(
|
|
SKP_int *NLSF, /* O Normalized Line Spectral Frequencies, Q15 (0 - (2^15-1)), [d] */
|
|
SKP_int32 *a_Q16, /* I/O Monic whitening filter coefficients in Q16 [d] */
|
|
const SKP_int d /* I Filter order (must be even) */
|
|
)
|
|
{
|
|
SKP_int i, k, m, dd, root_ix, ffrac;
|
|
SKP_int32 xlo, xhi, xmid;
|
|
SKP_int32 ylo, yhi, ymid;
|
|
SKP_int32 nom, den;
|
|
SKP_int32 P[ SKP_Silk_MAX_ORDER_LPC / 2 + 1 ];
|
|
SKP_int32 Q[ SKP_Silk_MAX_ORDER_LPC / 2 + 1 ];
|
|
SKP_int32 *PQ[ 2 ];
|
|
SKP_int32 *p;
|
|
|
|
/* Store pointers to array */
|
|
PQ[ 0 ] = P;
|
|
PQ[ 1 ] = Q;
|
|
|
|
dd = SKP_RSHIFT( d, 1 );
|
|
|
|
SKP_Silk_A2NLSF_init( a_Q16, P, Q, dd );
|
|
|
|
/* Find roots, alternating between P and Q */
|
|
p = P; /* Pointer to polynomial */
|
|
|
|
xlo = SKP_Silk_LSFCosTab_FIX_Q12[ 0 ]; // Q12
|
|
ylo = SKP_Silk_A2NLSF_eval_poly( p, xlo, dd );
|
|
|
|
if( ylo < 0 ) {
|
|
/* Set the first NLSF to zero and move on to the next */
|
|
NLSF[ 0 ] = 0;
|
|
p = Q; /* Pointer to polynomial */
|
|
ylo = SKP_Silk_A2NLSF_eval_poly( p, xlo, dd );
|
|
root_ix = 1; /* Index of current root */
|
|
} else {
|
|
root_ix = 0; /* Index of current root */
|
|
}
|
|
k = 1; /* Loop counter */
|
|
i = 0; /* Counter for bandwidth expansions applied */
|
|
while( 1 ) {
|
|
/* Evaluate polynomial */
|
|
#if OVERSAMPLE_COSINE_TABLE
|
|
xhi = SKP_Silk_LSFCosTab_FIX_Q12[ k >> 1 ] +
|
|
( ( SKP_Silk_LSFCosTab_FIX_Q12[ ( k + 1 ) >> 1 ] -
|
|
SKP_Silk_LSFCosTab_FIX_Q12[ k >> 1 ] ) >> 1 ); /* Q12 */
|
|
#else
|
|
xhi = SKP_Silk_LSFCosTab_FIX_Q12[ k ]; /* Q12 */
|
|
#endif
|
|
yhi = SKP_Silk_A2NLSF_eval_poly( p, xhi, dd );
|
|
|
|
/* Detect zero crossing */
|
|
if( ( ylo <= 0 && yhi >= 0 ) || ( ylo >= 0 && yhi <= 0 ) ) {
|
|
/* Binary division */
|
|
#if OVERSAMPLE_COSINE_TABLE
|
|
ffrac = -128;
|
|
#else
|
|
ffrac = -256;
|
|
#endif
|
|
for( m = 0; m < BIN_DIV_STEPS_A2NLSF_FIX; m++ ) {
|
|
/* Evaluate polynomial */
|
|
xmid = SKP_RSHIFT_ROUND( xlo + xhi, 1 );
|
|
ymid = SKP_Silk_A2NLSF_eval_poly( p, xmid, dd );
|
|
|
|
/* Detect zero crossing */
|
|
if( ( ylo <= 0 && ymid >= 0 ) || ( ylo >= 0 && ymid <= 0 ) ) {
|
|
/* Reduce frequency */
|
|
xhi = xmid;
|
|
yhi = ymid;
|
|
} else {
|
|
/* Increase frequency */
|
|
xlo = xmid;
|
|
ylo = ymid;
|
|
#if OVERSAMPLE_COSINE_TABLE
|
|
ffrac = SKP_ADD_RSHIFT( ffrac, 64, m );
|
|
#else
|
|
ffrac = SKP_ADD_RSHIFT( ffrac, 128, m );
|
|
#endif
|
|
}
|
|
}
|
|
|
|
/* Interpolate */
|
|
if( SKP_abs( ylo ) < 65536 ) {
|
|
/* Avoid dividing by zero */
|
|
den = ylo - yhi;
|
|
nom = SKP_LSHIFT( ylo, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) + SKP_RSHIFT( den, 1 );
|
|
if( den != 0 ) {
|
|
ffrac += SKP_DIV32( nom, den );
|
|
}
|
|
} else {
|
|
/* No risk of dividing by zero because abs(ylo - yhi) >= abs(ylo) >= 65536 */
|
|
ffrac += SKP_DIV32( ylo, SKP_RSHIFT( ylo - yhi, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) );
|
|
}
|
|
#if OVERSAMPLE_COSINE_TABLE
|
|
NLSF[ root_ix ] = (SKP_int)SKP_min_32( SKP_LSHIFT( (SKP_int32)k, 7 ) + ffrac, SKP_int16_MAX );
|
|
#else
|
|
NLSF[ root_ix ] = (SKP_int)SKP_min_32( SKP_LSHIFT( (SKP_int32)k, 8 ) + ffrac, SKP_int16_MAX );
|
|
#endif
|
|
|
|
SKP_assert( NLSF[ root_ix ] >= 0 );
|
|
SKP_assert( NLSF[ root_ix ] <= 32767 );
|
|
|
|
root_ix++; /* Next root */
|
|
if( root_ix >= d ) {
|
|
/* Found all roots */
|
|
break;
|
|
}
|
|
/* Alternate pointer to polynomial */
|
|
p = PQ[ root_ix & 1 ];
|
|
|
|
/* Evaluate polynomial */
|
|
#if OVERSAMPLE_COSINE_TABLE
|
|
xlo = SKP_Silk_LSFCosTab_FIX_Q12[ ( k - 1 ) >> 1 ] +
|
|
( ( SKP_Silk_LSFCosTab_FIX_Q12[ k >> 1 ] -
|
|
SKP_Silk_LSFCosTab_FIX_Q12[ ( k - 1 ) >> 1 ] ) >> 1 ); // Q12
|
|
#else
|
|
xlo = SKP_Silk_LSFCosTab_FIX_Q12[ k - 1 ]; // Q12
|
|
#endif
|
|
ylo = SKP_LSHIFT( 1 - ( root_ix & 2 ), 12 );
|
|
} else {
|
|
/* Increment loop counter */
|
|
k++;
|
|
xlo = xhi;
|
|
ylo = yhi;
|
|
|
|
#if OVERSAMPLE_COSINE_TABLE
|
|
if( k > 2 * LSF_COS_TAB_SZ_FIX ) {
|
|
#else
|
|
if( k > LSF_COS_TAB_SZ_FIX ) {
|
|
#endif
|
|
i++;
|
|
if( i > MAX_ITERATIONS_A2NLSF_FIX ) {
|
|
/* Set NLSFs to white spectrum and exit */
|
|
NLSF[ 0 ] = SKP_DIV32_16( 1 << 15, d + 1 );
|
|
for( k = 1; k < d; k++ ) {
|
|
NLSF[ k ] = SKP_SMULBB( k + 1, NLSF[ 0 ] );
|
|
}
|
|
return;
|
|
}
|
|
|
|
/* Error: Apply progressively more bandwidth expansion and run again */
|
|
SKP_Silk_bwexpander_32( a_Q16, d, 65536 - SKP_SMULBB( 10 + i, i ) ); // 10_Q16 = 0.00015
|
|
|
|
SKP_Silk_A2NLSF_init( a_Q16, P, Q, dd );
|
|
p = P; /* Pointer to polynomial */
|
|
xlo = SKP_Silk_LSFCosTab_FIX_Q12[ 0 ]; // Q12
|
|
ylo = SKP_Silk_A2NLSF_eval_poly( p, xlo, dd );
|
|
if( ylo < 0 ) {
|
|
/* Set the first NLSF to zero and move on to the next */
|
|
NLSF[ 0 ] = 0;
|
|
p = Q; /* Pointer to polynomial */
|
|
ylo = SKP_Silk_A2NLSF_eval_poly( p, xlo, dd );
|
|
root_ix = 1; /* Index of current root */
|
|
} else {
|
|
root_ix = 0; /* Index of current root */
|
|
}
|
|
k = 1; /* Reset loop counter */
|
|
}
|
|
}
|
|
}
|
|
}
|