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comparison: media/libopus/silk/A2NLSF.c
media/libopus/silk/A2NLSF.c
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| 1 /*********************************************************************** | |
| 2 Copyright (c) 2006-2011, Skype Limited. All rights reserved. | |
| 3 Redistribution and use in source and binary forms, with or without | |
| 4 modification, are permitted provided that the following conditions | |
| 5 are met: | |
| 6 - Redistributions of source code must retain the above copyright notice, | |
| 7 this list of conditions and the following disclaimer. | |
| 8 - Redistributions in binary form must reproduce the above copyright | |
| 9 notice, this list of conditions and the following disclaimer in the | |
| 10 documentation and/or other materials provided with the distribution. | |
| 11 - Neither the name of Internet Society, IETF or IETF Trust, nor the | |
| 12 names of specific contributors, may be used to endorse or promote | |
| 13 products derived from this software without specific prior written | |
| 14 permission. | |
| 15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
| 16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE | |
| 19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
| 20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | |
| 21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | |
| 22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | |
| 23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
| 24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
| 25 POSSIBILITY OF SUCH DAMAGE. | |
| 26 ***********************************************************************/ | |
| 27 | |
| 28 /* Conversion between prediction filter coefficients and NLSFs */ | |
| 29 /* Requires the order to be an even number */ | |
| 30 /* A piecewise linear approximation maps LSF <-> cos(LSF) */ | |
| 31 /* Therefore the result is not accurate NLSFs, but the two */ | |
| 32 /* functions are accurate inverses of each other */ | |
| 33 | |
| 34 #ifdef HAVE_CONFIG_H | |
| 35 #include "config.h" | |
| 36 #endif | |
| 37 | |
| 38 #include "SigProc_FIX.h" | |
| 39 #include "tables.h" | |
| 40 | |
| 41 /* Number of binary divisions, when not in low complexity mode */ | |
| 42 #define BIN_DIV_STEPS_A2NLSF_FIX 3 /* must be no higher than 16 - log2( LSF_COS_TAB_SZ_FIX ) */ | |
| 43 #define MAX_ITERATIONS_A2NLSF_FIX 30 | |
| 44 | |
| 45 /* Helper function for A2NLSF(..) */ | |
| 46 /* Transforms polynomials from cos(n*f) to cos(f)^n */ | |
| 47 static OPUS_INLINE void silk_A2NLSF_trans_poly( | |
| 48 opus_int32 *p, /* I/O Polynomial */ | |
| 49 const opus_int dd /* I Polynomial order (= filter order / 2 ) */ | |
| 50 ) | |
| 51 { | |
| 52 opus_int k, n; | |
| 53 | |
| 54 for( k = 2; k <= dd; k++ ) { | |
| 55 for( n = dd; n > k; n-- ) { | |
| 56 p[ n - 2 ] -= p[ n ]; | |
| 57 } | |
| 58 p[ k - 2 ] -= silk_LSHIFT( p[ k ], 1 ); | |
| 59 } | |
| 60 } | |
| 61 /* Helper function for A2NLSF(..) */ | |
| 62 /* Polynomial evaluation */ | |
| 63 static OPUS_INLINE opus_int32 silk_A2NLSF_eval_poly( /* return the polynomial evaluation, in Q16 */ | |
| 64 opus_int32 *p, /* I Polynomial, Q16 */ | |
| 65 const opus_int32 x, /* I Evaluation point, Q12 */ | |
| 66 const opus_int dd /* I Order */ | |
| 67 ) | |
| 68 { | |
| 69 opus_int n; | |
| 70 opus_int32 x_Q16, y32; | |
| 71 | |
| 72 y32 = p[ dd ]; /* Q16 */ | |
| 73 x_Q16 = silk_LSHIFT( x, 4 ); | |
| 74 for( n = dd - 1; n >= 0; n-- ) { | |
| 75 y32 = silk_SMLAWW( p[ n ], y32, x_Q16 ); /* Q16 */ | |
| 76 } | |
| 77 return y32; | |
| 78 } | |
| 79 | |
| 80 static OPUS_INLINE void silk_A2NLSF_init( | |
| 81 const opus_int32 *a_Q16, | |
| 82 opus_int32 *P, | |
| 83 opus_int32 *Q, | |
| 84 const opus_int dd | |
| 85 ) | |
| 86 { | |
| 87 opus_int k; | |
| 88 | |
| 89 /* Convert filter coefs to even and odd polynomials */ | |
| 90 P[dd] = silk_LSHIFT( 1, 16 ); | |
| 91 Q[dd] = silk_LSHIFT( 1, 16 ); | |
| 92 for( k = 0; k < dd; k++ ) { | |
| 93 P[ k ] = -a_Q16[ dd - k - 1 ] - a_Q16[ dd + k ]; /* Q16 */ | |
| 94 Q[ k ] = -a_Q16[ dd - k - 1 ] + a_Q16[ dd + k ]; /* Q16 */ | |
| 95 } | |
| 96 | |
| 97 /* Divide out zeros as we have that for even filter orders, */ | |
| 98 /* z = 1 is always a root in Q, and */ | |
| 99 /* z = -1 is always a root in P */ | |
| 100 for( k = dd; k > 0; k-- ) { | |
| 101 P[ k - 1 ] -= P[ k ]; | |
| 102 Q[ k - 1 ] += Q[ k ]; | |
| 103 } | |
| 104 | |
| 105 /* Transform polynomials from cos(n*f) to cos(f)^n */ | |
| 106 silk_A2NLSF_trans_poly( P, dd ); | |
| 107 silk_A2NLSF_trans_poly( Q, dd ); | |
| 108 } | |
| 109 | |
| 110 /* Compute Normalized Line Spectral Frequencies (NLSFs) from whitening filter coefficients */ | |
| 111 /* If not all roots are found, the a_Q16 coefficients are bandwidth expanded until convergence. */ | |
| 112 void silk_A2NLSF( | |
| 113 opus_int16 *NLSF, /* O Normalized Line Spectral Frequencies in Q15 (0..2^15-1) [d] */ | |
| 114 opus_int32 *a_Q16, /* I/O Monic whitening filter coefficients in Q16 [d] */ | |
| 115 const opus_int d /* I Filter order (must be even) */ | |
| 116 ) | |
| 117 { | |
| 118 opus_int i, k, m, dd, root_ix, ffrac; | |
| 119 opus_int32 xlo, xhi, xmid; | |
| 120 opus_int32 ylo, yhi, ymid, thr; | |
| 121 opus_int32 nom, den; | |
| 122 opus_int32 P[ SILK_MAX_ORDER_LPC / 2 + 1 ]; | |
| 123 opus_int32 Q[ SILK_MAX_ORDER_LPC / 2 + 1 ]; | |
| 124 opus_int32 *PQ[ 2 ]; | |
| 125 opus_int32 *p; | |
| 126 | |
| 127 /* Store pointers to array */ | |
| 128 PQ[ 0 ] = P; | |
| 129 PQ[ 1 ] = Q; | |
| 130 | |
| 131 dd = silk_RSHIFT( d, 1 ); | |
| 132 | |
| 133 silk_A2NLSF_init( a_Q16, P, Q, dd ); | |
| 134 | |
| 135 /* Find roots, alternating between P and Q */ | |
| 136 p = P; /* Pointer to polynomial */ | |
| 137 | |
| 138 xlo = silk_LSFCosTab_FIX_Q12[ 0 ]; /* Q12*/ | |
| 139 ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); | |
| 140 | |
| 141 if( ylo < 0 ) { | |
| 142 /* Set the first NLSF to zero and move on to the next */ | |
| 143 NLSF[ 0 ] = 0; | |
| 144 p = Q; /* Pointer to polynomial */ | |
| 145 ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); | |
| 146 root_ix = 1; /* Index of current root */ | |
| 147 } else { | |
| 148 root_ix = 0; /* Index of current root */ | |
| 149 } | |
| 150 k = 1; /* Loop counter */ | |
| 151 i = 0; /* Counter for bandwidth expansions applied */ | |
| 152 thr = 0; | |
| 153 while( 1 ) { | |
| 154 /* Evaluate polynomial */ | |
| 155 xhi = silk_LSFCosTab_FIX_Q12[ k ]; /* Q12 */ | |
| 156 yhi = silk_A2NLSF_eval_poly( p, xhi, dd ); | |
| 157 | |
| 158 /* Detect zero crossing */ | |
| 159 if( ( ylo <= 0 && yhi >= thr ) || ( ylo >= 0 && yhi <= -thr ) ) { | |
| 160 if( yhi == 0 ) { | |
| 161 /* If the root lies exactly at the end of the current */ | |
| 162 /* interval, look for the next root in the next interval */ | |
| 163 thr = 1; | |
| 164 } else { | |
| 165 thr = 0; | |
| 166 } | |
| 167 /* Binary division */ | |
| 168 ffrac = -256; | |
| 169 for( m = 0; m < BIN_DIV_STEPS_A2NLSF_FIX; m++ ) { | |
| 170 /* Evaluate polynomial */ | |
| 171 xmid = silk_RSHIFT_ROUND( xlo + xhi, 1 ); | |
| 172 ymid = silk_A2NLSF_eval_poly( p, xmid, dd ); | |
| 173 | |
| 174 /* Detect zero crossing */ | |
| 175 if( ( ylo <= 0 && ymid >= 0 ) || ( ylo >= 0 && ymid <= 0 ) ) { | |
| 176 /* Reduce frequency */ | |
| 177 xhi = xmid; | |
| 178 yhi = ymid; | |
| 179 } else { | |
| 180 /* Increase frequency */ | |
| 181 xlo = xmid; | |
| 182 ylo = ymid; | |
| 183 ffrac = silk_ADD_RSHIFT( ffrac, 128, m ); | |
| 184 } | |
| 185 } | |
| 186 | |
| 187 /* Interpolate */ | |
| 188 if( silk_abs( ylo ) < 65536 ) { | |
| 189 /* Avoid dividing by zero */ | |
| 190 den = ylo - yhi; | |
| 191 nom = silk_LSHIFT( ylo, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) + silk_RSHIFT( den, 1 ); | |
| 192 if( den != 0 ) { | |
| 193 ffrac += silk_DIV32( nom, den ); | |
| 194 } | |
| 195 } else { | |
| 196 /* No risk of dividing by zero because abs(ylo - yhi) >= abs(ylo) >= 65536 */ | |
| 197 ffrac += silk_DIV32( ylo, silk_RSHIFT( ylo - yhi, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) ); | |
| 198 } | |
| 199 NLSF[ root_ix ] = (opus_int16)silk_min_32( silk_LSHIFT( (opus_int32)k, 8 ) + ffrac, silk_int16_MAX ); | |
| 200 | |
| 201 silk_assert( NLSF[ root_ix ] >= 0 ); | |
| 202 | |
| 203 root_ix++; /* Next root */ | |
| 204 if( root_ix >= d ) { | |
| 205 /* Found all roots */ | |
| 206 break; | |
| 207 } | |
| 208 /* Alternate pointer to polynomial */ | |
| 209 p = PQ[ root_ix & 1 ]; | |
| 210 | |
| 211 /* Evaluate polynomial */ | |
| 212 xlo = silk_LSFCosTab_FIX_Q12[ k - 1 ]; /* Q12*/ | |
| 213 ylo = silk_LSHIFT( 1 - ( root_ix & 2 ), 12 ); | |
| 214 } else { | |
| 215 /* Increment loop counter */ | |
| 216 k++; | |
| 217 xlo = xhi; | |
| 218 ylo = yhi; | |
| 219 thr = 0; | |
| 220 | |
| 221 if( k > LSF_COS_TAB_SZ_FIX ) { | |
| 222 i++; | |
| 223 if( i > MAX_ITERATIONS_A2NLSF_FIX ) { | |
| 224 /* Set NLSFs to white spectrum and exit */ | |
| 225 NLSF[ 0 ] = (opus_int16)silk_DIV32_16( 1 << 15, d + 1 ); | |
| 226 for( k = 1; k < d; k++ ) { | |
| 227 NLSF[ k ] = (opus_int16)silk_SMULBB( k + 1, NLSF[ 0 ] ); | |
| 228 } | |
| 229 return; | |
| 230 } | |
| 231 | |
| 232 /* Error: Apply progressively more bandwidth expansion and run again */ | |
| 233 silk_bwexpander_32( a_Q16, d, 65536 - silk_SMULBB( 10 + i, i ) ); /* 10_Q16 = 0.00015*/ | |
| 234 | |
| 235 silk_A2NLSF_init( a_Q16, P, Q, dd ); | |
| 236 p = P; /* Pointer to polynomial */ | |
| 237 xlo = silk_LSFCosTab_FIX_Q12[ 0 ]; /* Q12*/ | |
| 238 ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); | |
| 239 if( ylo < 0 ) { | |
| 240 /* Set the first NLSF to zero and move on to the next */ | |
| 241 NLSF[ 0 ] = 0; | |
| 242 p = Q; /* Pointer to polynomial */ | |
| 243 ylo = silk_A2NLSF_eval_poly( p, xlo, dd ); | |
| 244 root_ix = 1; /* Index of current root */ | |
| 245 } else { | |
| 246 root_ix = 0; /* Index of current root */ | |
| 247 } | |
| 248 k = 1; /* Reset loop counter */ | |
| 249 } | |
| 250 } | |
| 251 } | |
| 252 } |
