1885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/*********************************************************************** 2885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgCopyright (c) 2006-2011, Skype Limited. All rights reserved. 3885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgRedistribution and use in source and binary forms, with or without 4885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgmodification, are permitted provided that the following conditions 5885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgare met: 6885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org- Redistributions of source code must retain the above copyright notice, 7885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgthis list of conditions and the following disclaimer. 8885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org- Redistributions in binary form must reproduce the above copyright 9885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgnotice, this list of conditions and the following disclaimer in the 10885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgdocumentation and/or other materials provided with the distribution. 11e3ea049fcaee2247e45f0ce793d4313babb4ef69tlegrand@chromium.org- Neither the name of Internet Society, IETF or IETF Trust, nor the 12885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgnames of specific contributors, may be used to endorse or promote 13885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgproducts derived from this software without specific prior written 14885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgpermission. 15e3ea049fcaee2247e45f0ce793d4313babb4ef69tlegrand@chromium.orgTHIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 16885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgAND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgIMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 19885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgLIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgCONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgSUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 22885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgINTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgCONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 24885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 25885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgPOSSIBILITY OF SUCH DAMAGE. 26885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org***********************************************************************/ 27885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 28885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org#ifdef HAVE_CONFIG_H 29885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org#include "config.h" 30885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org#endif 31885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 32885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* conversion between prediction filter coefficients and LSFs */ 33885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* order should be even */ 34885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* a piecewise linear approximation maps LSF <-> cos(LSF) */ 35885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* therefore the result is not accurate LSFs, but the two */ 36885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* functions are accurate inverses of each other */ 37885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 38885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org#include "SigProc_FIX.h" 39885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org#include "tables.h" 40885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 41885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org#define QA 16 42885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 43885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* helper function for NLSF2A(..) */ 443c3902f0ac13428394f14f78f0fab05ef3468d69tlegrand@google.comstatic OPUS_INLINE void silk_NLSF2A_find_poly( 45885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 *out, /* O intermediate polynomial, QA [dd+1] */ 46885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org const opus_int32 *cLSF, /* I vector of interleaved 2*cos(LSFs), QA [d] */ 47885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int dd /* I polynomial order (= 1/2 * filter order) */ 48885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org) 49885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org{ 50885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int k, n; 51885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 ftmp; 52885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 53885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org out[0] = silk_LSHIFT( 1, QA ); 54885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org out[1] = -cLSF[0]; 55885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 1; k < dd; k++ ) { 56885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org ftmp = cLSF[2*k]; /* QA*/ 57885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org out[k+1] = silk_LSHIFT( out[k-1], 1 ) - (opus_int32)silk_RSHIFT_ROUND64( silk_SMULL( ftmp, out[k] ), QA ); 58885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( n = k; n > 1; n-- ) { 59885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org out[n] += out[n-2] - (opus_int32)silk_RSHIFT_ROUND64( silk_SMULL( ftmp, out[n-1] ), QA ); 60885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 61885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org out[1] -= ftmp; 62885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 63885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org} 64885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 65885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org/* compute whitening filter coefficients from normalized line spectral frequencies */ 66885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.orgvoid silk_NLSF2A( 67885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int16 *a_Q12, /* O monic whitening filter coefficients in Q12, [ d ] */ 68885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org const opus_int16 *NLSF, /* I normalized line spectral frequencies in Q15, [ d ] */ 69885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org const opus_int d /* I filter order (should be even) */ 70885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org) 71885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org{ 72885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* This ordering was found to maximize quality. It improves numerical accuracy of 73885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_NLSF2A_find_poly() compared to "standard" ordering. */ 74885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org static const unsigned char ordering16[16] = { 75885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 0, 15, 8, 7, 4, 11, 12, 3, 2, 13, 10, 5, 6, 9, 14, 1 76885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org }; 77885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org static const unsigned char ordering10[10] = { 78885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 0, 9, 6, 3, 4, 5, 8, 1, 2, 7 79885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org }; 80885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org const unsigned char *ordering; 81885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int k, i, dd; 82885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 cos_LSF_QA[ SILK_MAX_ORDER_LPC ]; 83885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 P[ SILK_MAX_ORDER_LPC / 2 + 1 ], Q[ SILK_MAX_ORDER_LPC / 2 + 1 ]; 84885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 Ptmp, Qtmp, f_int, f_frac, cos_val, delta; 85885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 a32_QA1[ SILK_MAX_ORDER_LPC ]; 86885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org opus_int32 maxabs, absval, idx=0, sc_Q16; 87885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 88885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_assert( LSF_COS_TAB_SZ_FIX == 128 ); 89885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_assert( d==10||d==16 ); 90885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 91885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* convert LSFs to 2*cos(LSF), using piecewise linear curve from table */ 92885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org ordering = d == 16 ? ordering16 : ordering10; 93885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 0; k < d; k++ ) { 94885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_assert(NLSF[k] >= 0 ); 95885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 96885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* f_int on a scale 0-127 (rounded down) */ 97885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org f_int = silk_RSHIFT( NLSF[k], 15 - 7 ); 98885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 99885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* f_frac, range: 0..255 */ 100885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org f_frac = NLSF[k] - silk_LSHIFT( f_int, 15 - 7 ); 101885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 102885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_assert(f_int >= 0); 103885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_assert(f_int < LSF_COS_TAB_SZ_FIX ); 104885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 105885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Read start and end value from table */ 106885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org cos_val = silk_LSFCosTab_FIX_Q12[ f_int ]; /* Q12 */ 107885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org delta = silk_LSFCosTab_FIX_Q12[ f_int + 1 ] - cos_val; /* Q12, with a range of 0..200 */ 108885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 109885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Linear interpolation */ 110885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org cos_LSF_QA[ordering[k]] = silk_RSHIFT_ROUND( silk_LSHIFT( cos_val, 8 ) + silk_MUL( delta, f_frac ), 20 - QA ); /* QA */ 111885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 112885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 113885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org dd = silk_RSHIFT( d, 1 ); 114885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 115885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* generate even and odd polynomials using convolution */ 116885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_NLSF2A_find_poly( P, &cos_LSF_QA[ 0 ], dd ); 117885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_NLSF2A_find_poly( Q, &cos_LSF_QA[ 1 ], dd ); 118885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 119885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* convert even and odd polynomials to opus_int32 Q12 filter coefs */ 120885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 0; k < dd; k++ ) { 121885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org Ptmp = P[ k+1 ] + P[ k ]; 122885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org Qtmp = Q[ k+1 ] - Q[ k ]; 123885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 124885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* the Ptmp and Qtmp values at this stage need to fit in int32 */ 125885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org a32_QA1[ k ] = -Qtmp - Ptmp; /* QA+1 */ 126885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org a32_QA1[ d-k-1 ] = Qtmp - Ptmp; /* QA+1 */ 127885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 128885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 129885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */ 130885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( i = 0; i < 10; i++ ) { 131885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Find maximum absolute value and its index */ 132885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org maxabs = 0; 133885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 0; k < d; k++ ) { 134885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org absval = silk_abs( a32_QA1[k] ); 135885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org if( absval > maxabs ) { 136885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org maxabs = absval; 137885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org idx = k; 138885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 139885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 140885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org maxabs = silk_RSHIFT_ROUND( maxabs, QA + 1 - 12 ); /* QA+1 -> Q12 */ 141885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 142885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org if( maxabs > silk_int16_MAX ) { 143885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Reduce magnitude of prediction coefficients */ 144885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */ 145885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org sc_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ), 146885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) ); 147885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_bwexpander_32( a32_QA1, d, sc_Q16 ); 148885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } else { 149885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org break; 150885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 151885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 152885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 153885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org if( i == 10 ) { 154885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Reached the last iteration, clip the coefficients */ 155885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 0; k < d; k++ ) { 156885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org a_Q12[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a32_QA1[ k ], QA + 1 - 12 ) ); /* QA+1 -> Q12 */ 157885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org a32_QA1[ k ] = silk_LSHIFT( (opus_int32)a_Q12[ k ], QA + 1 - 12 ); 158885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 159885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } else { 160885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 0; k < d; k++ ) { 161885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org a_Q12[ k ] = (opus_int16)silk_RSHIFT_ROUND( a32_QA1[ k ], QA + 1 - 12 ); /* QA+1 -> Q12 */ 162885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 163885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 164885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 165885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( i = 0; i < MAX_LPC_STABILIZE_ITERATIONS; i++ ) { 166885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org if( silk_LPC_inverse_pred_gain( a_Q12, d ) < SILK_FIX_CONST( 1.0 / MAX_PREDICTION_POWER_GAIN, 30 ) ) { 167885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* Prediction coefficients are (too close to) unstable; apply bandwidth expansion */ 168885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org /* on the unscaled coefficients, convert to Q12 and measure again */ 169885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org silk_bwexpander_32( a32_QA1, d, 65536 - silk_LSHIFT( 2, i ) ); 170885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org for( k = 0; k < d; k++ ) { 171885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org a_Q12[ k ] = (opus_int16)silk_RSHIFT_ROUND( a32_QA1[ k ], QA + 1 - 12 ); /* QA+1 -> Q12 */ 172885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 173885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } else { 174885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org break; 175885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 176885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org } 177885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org} 178885f2ff5a7a7d6a73432d26a6c0ae9147e6b452sergeyu@chromium.org 179