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267 lines
10 KiB
267 lines
10 KiB
/*********************************************************************** |
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Copyright (c) 2006-2011, Skype Limited. All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
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modification, are permitted provided that the following conditions |
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are met: |
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- Redistributions of source code must retain the above copyright notice, |
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this list of conditions and the following disclaimer. |
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- Redistributions in binary form must reproduce the above copyright |
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notice, this list of conditions and the following disclaimer in the |
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documentation and/or other materials provided with the distribution. |
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- Neither the name of Internet Society, IETF or IETF Trust, nor the |
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names of specific contributors, may be used to endorse or promote |
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products derived from this software without specific prior written |
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permission. |
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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POSSIBILITY OF SUCH DAMAGE. |
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***********************************************************************/ |
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/* Conversion between prediction filter coefficients and NLSFs */ |
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/* Requires the order to be an even number */ |
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/* A piecewise linear approximation maps LSF <-> cos(LSF) */ |
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/* Therefore the result is not accurate NLSFs, but the two */ |
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/* functions are accurate inverses of each other */ |
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#ifdef HAVE_CONFIG_H |
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#include "config.h" |
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#endif |
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#include "SigProc_FIX.h" |
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#include "tables.h" |
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/* Number of binary divisions, when not in low complexity mode */ |
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#define BIN_DIV_STEPS_A2NLSF_FIX 3 /* must be no higher than 16 - log2( LSF_COS_TAB_SZ_FIX ) */ |
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#define MAX_ITERATIONS_A2NLSF_FIX 16 |
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/* Helper function for A2NLSF(..) */ |
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/* Transforms polynomials from cos(n*f) to cos(f)^n */ |
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static OPUS_INLINE void silk_A2NLSF_trans_poly( |
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opus_int32 *p, /* I/O Polynomial */ |
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const opus_int dd /* I Polynomial order (= filter order / 2 ) */ |
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) |
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{ |
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opus_int k, n; |
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for( k = 2; k <= dd; k++ ) { |
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for( n = dd; n > k; n-- ) { |
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p[ n - 2 ] -= p[ n ]; |
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} |
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p[ k - 2 ] -= silk_LSHIFT( p[ k ], 1 ); |
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} |
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} |
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/* Helper function for A2NLSF(..) */ |
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/* Polynomial evaluation */ |
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static OPUS_INLINE opus_int32 silk_A2NLSF_eval_poly( /* return the polynomial evaluation, in Q16 */ |
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opus_int32 *p, /* I Polynomial, Q16 */ |
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const opus_int32 x, /* I Evaluation point, Q12 */ |
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const opus_int dd /* I Order */ |
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) |
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{ |
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opus_int n; |
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opus_int32 x_Q16, y32; |
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y32 = p[ dd ]; /* Q16 */ |
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x_Q16 = silk_LSHIFT( x, 4 ); |
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if ( opus_likely( 8 == dd ) ) |
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{ |
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y32 = silk_SMLAWW( p[ 7 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 6 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 5 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 4 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 3 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 2 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 1 ], y32, x_Q16 ); |
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y32 = silk_SMLAWW( p[ 0 ], y32, x_Q16 ); |
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} |
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else |
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{ |
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for( n = dd - 1; n >= 0; n-- ) { |
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y32 = silk_SMLAWW( p[ n ], y32, x_Q16 ); /* Q16 */ |
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} |
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} |
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return y32; |
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} |
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static OPUS_INLINE void silk_A2NLSF_init( |
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const opus_int32 *a_Q16, |
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opus_int32 *P, |
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opus_int32 *Q, |
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const opus_int dd |
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) |
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{ |
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opus_int k; |
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/* Convert filter coefs to even and odd polynomials */ |
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P[dd] = silk_LSHIFT( 1, 16 ); |
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Q[dd] = silk_LSHIFT( 1, 16 ); |
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for( k = 0; k < dd; k++ ) { |
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P[ k ] = -a_Q16[ dd - k - 1 ] - a_Q16[ dd + k ]; /* Q16 */ |
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Q[ k ] = -a_Q16[ dd - k - 1 ] + a_Q16[ dd + k ]; /* Q16 */ |
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} |
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/* Divide out zeros as we have that for even filter orders, */ |
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/* z = 1 is always a root in Q, and */ |
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/* z = -1 is always a root in P */ |
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for( k = dd; k > 0; k-- ) { |
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P[ k - 1 ] -= P[ k ]; |
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Q[ k - 1 ] += Q[ k ]; |
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} |
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/* Transform polynomials from cos(n*f) to cos(f)^n */ |
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silk_A2NLSF_trans_poly( P, dd ); |
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silk_A2NLSF_trans_poly( Q, dd ); |
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} |
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/* Compute Normalized Line Spectral Frequencies (NLSFs) from whitening filter coefficients */ |
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/* If not all roots are found, the a_Q16 coefficients are bandwidth expanded until convergence. */ |
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void silk_A2NLSF( |
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opus_int16 *NLSF, /* O Normalized Line Spectral Frequencies in Q15 (0..2^15-1) [d] */ |
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opus_int32 *a_Q16, /* I/O Monic whitening filter coefficients in Q16 [d] */ |
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const opus_int d /* I Filter order (must be even) */ |
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) |
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{ |
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opus_int i, k, m, dd, root_ix, ffrac; |
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opus_int32 xlo, xhi, xmid; |
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opus_int32 ylo, yhi, ymid, thr; |
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opus_int32 nom, den; |
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opus_int32 P[ SILK_MAX_ORDER_LPC / 2 + 1 ]; |
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opus_int32 Q[ SILK_MAX_ORDER_LPC / 2 + 1 ]; |
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opus_int32 *PQ[ 2 ]; |
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opus_int32 *p; |
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/* Store pointers to array */ |
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PQ[ 0 ] = P; |
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PQ[ 1 ] = Q; |
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dd = silk_RSHIFT( d, 1 ); |
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silk_A2NLSF_init( a_Q16, P, Q, dd ); |
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/* Find roots, alternating between P and Q */ |
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p = P; /* Pointer to polynomial */ |
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xlo = silk_LSFCosTab_FIX_Q12[ 0 ]; /* Q12*/ |
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ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); |
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if( ylo < 0 ) { |
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/* Set the first NLSF to zero and move on to the next */ |
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NLSF[ 0 ] = 0; |
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p = Q; /* Pointer to polynomial */ |
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ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); |
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root_ix = 1; /* Index of current root */ |
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} else { |
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root_ix = 0; /* Index of current root */ |
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} |
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k = 1; /* Loop counter */ |
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i = 0; /* Counter for bandwidth expansions applied */ |
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thr = 0; |
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while( 1 ) { |
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/* Evaluate polynomial */ |
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xhi = silk_LSFCosTab_FIX_Q12[ k ]; /* Q12 */ |
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yhi = silk_A2NLSF_eval_poly( p, xhi, dd ); |
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/* Detect zero crossing */ |
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if( ( ylo <= 0 && yhi >= thr ) || ( ylo >= 0 && yhi <= -thr ) ) { |
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if( yhi == 0 ) { |
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/* If the root lies exactly at the end of the current */ |
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/* interval, look for the next root in the next interval */ |
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thr = 1; |
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} else { |
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thr = 0; |
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} |
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/* Binary division */ |
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ffrac = -256; |
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for( m = 0; m < BIN_DIV_STEPS_A2NLSF_FIX; m++ ) { |
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/* Evaluate polynomial */ |
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xmid = silk_RSHIFT_ROUND( xlo + xhi, 1 ); |
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ymid = silk_A2NLSF_eval_poly( p, xmid, dd ); |
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/* Detect zero crossing */ |
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if( ( ylo <= 0 && ymid >= 0 ) || ( ylo >= 0 && ymid <= 0 ) ) { |
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/* Reduce frequency */ |
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xhi = xmid; |
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yhi = ymid; |
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} else { |
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/* Increase frequency */ |
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xlo = xmid; |
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ylo = ymid; |
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ffrac = silk_ADD_RSHIFT( ffrac, 128, m ); |
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} |
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} |
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/* Interpolate */ |
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if( silk_abs( ylo ) < 65536 ) { |
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/* Avoid dividing by zero */ |
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den = ylo - yhi; |
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nom = silk_LSHIFT( ylo, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) + silk_RSHIFT( den, 1 ); |
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if( den != 0 ) { |
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ffrac += silk_DIV32( nom, den ); |
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} |
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} else { |
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/* No risk of dividing by zero because abs(ylo - yhi) >= abs(ylo) >= 65536 */ |
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ffrac += silk_DIV32( ylo, silk_RSHIFT( ylo - yhi, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) ); |
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} |
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NLSF[ root_ix ] = (opus_int16)silk_min_32( silk_LSHIFT( (opus_int32)k, 8 ) + ffrac, silk_int16_MAX ); |
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silk_assert( NLSF[ root_ix ] >= 0 ); |
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root_ix++; /* Next root */ |
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if( root_ix >= d ) { |
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/* Found all roots */ |
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break; |
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} |
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/* Alternate pointer to polynomial */ |
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p = PQ[ root_ix & 1 ]; |
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/* Evaluate polynomial */ |
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xlo = silk_LSFCosTab_FIX_Q12[ k - 1 ]; /* Q12*/ |
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ylo = silk_LSHIFT( 1 - ( root_ix & 2 ), 12 ); |
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} else { |
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/* Increment loop counter */ |
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k++; |
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xlo = xhi; |
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ylo = yhi; |
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thr = 0; |
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if( k > LSF_COS_TAB_SZ_FIX ) { |
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i++; |
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if( i > MAX_ITERATIONS_A2NLSF_FIX ) { |
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/* Set NLSFs to white spectrum and exit */ |
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NLSF[ 0 ] = (opus_int16)silk_DIV32_16( 1 << 15, d + 1 ); |
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for( k = 1; k < d; k++ ) { |
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NLSF[ k ] = (opus_int16)silk_ADD16( NLSF[ k-1 ], NLSF[ 0 ] ); |
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} |
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return; |
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} |
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/* Error: Apply progressively more bandwidth expansion and run again */ |
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silk_bwexpander_32( a_Q16, d, 65536 - silk_LSHIFT( 1, i ) ); |
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silk_A2NLSF_init( a_Q16, P, Q, dd ); |
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p = P; /* Pointer to polynomial */ |
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xlo = silk_LSFCosTab_FIX_Q12[ 0 ]; /* Q12*/ |
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ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); |
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if( ylo < 0 ) { |
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/* Set the first NLSF to zero and move on to the next */ |
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NLSF[ 0 ] = 0; |
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p = Q; /* Pointer to polynomial */ |
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ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); |
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root_ix = 1; /* Index of current root */ |
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} else { |
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root_ix = 0; /* Index of current root */ |
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} |
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k = 1; /* Reset loop counter */ |
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} |
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} |
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} |
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}
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