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media/libopus/silk/NLSF2A.c@ac0c01689b40 (annotated)

media/libopus/silk/NLSF2A.c

Thu, 15 Jan 2015 15:59:08 +0100

author
Michael Schloh von Bennewitz <michael@schloh.com>
date
Thu, 15 Jan 2015 15:59:08 +0100
branch
TOR_BUG_9701
changeset 10
ac0c01689b40
permissions
-rw-r--r--

Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

michael@0 1 /***********************************************************************
michael@0 2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.
michael@0 3 Redistribution and use in source and binary forms, with or without
michael@0 4 modification, are permitted provided that the following conditions
michael@0 5 are met:
michael@0 6 - Redistributions of source code must retain the above copyright notice,
michael@0 7 this list of conditions and the following disclaimer.
michael@0 8 - Redistributions in binary form must reproduce the above copyright
michael@0 9 notice, this list of conditions and the following disclaimer in the
michael@0 10 documentation and/or other materials provided with the distribution.
michael@0 11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
michael@0 12 names of specific contributors, may be used to endorse or promote
michael@0 13 products derived from this software without specific prior written
michael@0 14 permission.
michael@0 15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
michael@0 16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
michael@0 17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
michael@0 18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
michael@0 19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
michael@0 20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
michael@0 21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
michael@0 22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
michael@0 23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0 24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
michael@0 25 POSSIBILITY OF SUCH DAMAGE.
michael@0 26 ***********************************************************************/
michael@0 27
michael@0 28 #ifdef HAVE_CONFIG_H
michael@0 29 #include "config.h"
michael@0 30 #endif
michael@0 31
michael@0 32 /* conversion between prediction filter coefficients and LSFs */
michael@0 33 /* order should be even */
michael@0 34 /* a piecewise linear approximation maps LSF <-> cos(LSF) */
michael@0 35 /* therefore the result is not accurate LSFs, but the two */
michael@0 36 /* functions are accurate inverses of each other */
michael@0 37
michael@0 38 #include "SigProc_FIX.h"
michael@0 39 #include "tables.h"
michael@0 40
michael@0 41 #define QA 16
michael@0 42
michael@0 43 /* helper function for NLSF2A(..) */
michael@0 44 static OPUS_INLINE void silk_NLSF2A_find_poly(
michael@0 45 opus_int32 *out, /* O intermediate polynomial, QA [dd+1] */
michael@0 46 const opus_int32 *cLSF, /* I vector of interleaved 2*cos(LSFs), QA [d] */
michael@0 47 opus_int dd /* I polynomial order (= 1/2 * filter order) */
michael@0 48 )
michael@0 49 {
michael@0 50 opus_int k, n;
michael@0 51 opus_int32 ftmp;
michael@0 52
michael@0 53 out[0] = silk_LSHIFT( 1, QA );
michael@0 54 out[1] = -cLSF[0];
michael@0 55 for( k = 1; k < dd; k++ ) {
michael@0 56 ftmp = cLSF[2*k]; /* QA*/
michael@0 57 out[k+1] = silk_LSHIFT( out[k-1], 1 ) - (opus_int32)silk_RSHIFT_ROUND64( silk_SMULL( ftmp, out[k] ), QA );
michael@0 58 for( n = k; n > 1; n-- ) {
michael@0 59 out[n] += out[n-2] - (opus_int32)silk_RSHIFT_ROUND64( silk_SMULL( ftmp, out[n-1] ), QA );
michael@0 60 }
michael@0 61 out[1] -= ftmp;
michael@0 62 }
michael@0 63 }
michael@0 64
michael@0 65 /* compute whitening filter coefficients from normalized line spectral frequencies */
michael@0 66 void silk_NLSF2A(
michael@0 67 opus_int16 *a_Q12, /* O monic whitening filter coefficients in Q12, [ d ] */
michael@0 68 const opus_int16 *NLSF, /* I normalized line spectral frequencies in Q15, [ d ] */
michael@0 69 const opus_int d /* I filter order (should be even) */
michael@0 70 )
michael@0 71 {
michael@0 72 /* This ordering was found to maximize quality. It improves numerical accuracy of
michael@0 73 silk_NLSF2A_find_poly() compared to "standard" ordering. */
michael@0 74 static const unsigned char ordering16[16] = {
michael@0 75 0, 15, 8, 7, 4, 11, 12, 3, 2, 13, 10, 5, 6, 9, 14, 1
michael@0 76 };
michael@0 77 static const unsigned char ordering10[10] = {
michael@0 78 0, 9, 6, 3, 4, 5, 8, 1, 2, 7
michael@0 79 };
michael@0 80 const unsigned char *ordering;
michael@0 81 opus_int k, i, dd;
michael@0 82 opus_int32 cos_LSF_QA[ SILK_MAX_ORDER_LPC ];
michael@0 83 opus_int32 P[ SILK_MAX_ORDER_LPC / 2 + 1 ], Q[ SILK_MAX_ORDER_LPC / 2 + 1 ];
michael@0 84 opus_int32 Ptmp, Qtmp, f_int, f_frac, cos_val, delta;
michael@0 85 opus_int32 a32_QA1[ SILK_MAX_ORDER_LPC ];
michael@0 86 opus_int32 maxabs, absval, idx=0, sc_Q16;
michael@0 87
michael@0 88 silk_assert( LSF_COS_TAB_SZ_FIX == 128 );
michael@0 89 silk_assert( d==10||d==16 );
michael@0 90
michael@0 91 /* convert LSFs to 2*cos(LSF), using piecewise linear curve from table */
michael@0 92 ordering = d == 16 ? ordering16 : ordering10;
michael@0 93 for( k = 0; k < d; k++ ) {
michael@0 94 silk_assert(NLSF[k] >= 0 );
michael@0 95
michael@0 96 /* f_int on a scale 0-127 (rounded down) */
michael@0 97 f_int = silk_RSHIFT( NLSF[k], 15 - 7 );
michael@0 98
michael@0 99 /* f_frac, range: 0..255 */
michael@0 100 f_frac = NLSF[k] - silk_LSHIFT( f_int, 15 - 7 );
michael@0 101
michael@0 102 silk_assert(f_int >= 0);
michael@0 103 silk_assert(f_int < LSF_COS_TAB_SZ_FIX );
michael@0 104
michael@0 105 /* Read start and end value from table */
michael@0 106 cos_val = silk_LSFCosTab_FIX_Q12[ f_int ]; /* Q12 */
michael@0 107 delta = silk_LSFCosTab_FIX_Q12[ f_int + 1 ] - cos_val; /* Q12, with a range of 0..200 */
michael@0 108
michael@0 109 /* Linear interpolation */
michael@0 110 cos_LSF_QA[ordering[k]] = silk_RSHIFT_ROUND( silk_LSHIFT( cos_val, 8 ) + silk_MUL( delta, f_frac ), 20 - QA ); /* QA */
michael@0 111 }
michael@0 112
michael@0 113 dd = silk_RSHIFT( d, 1 );
michael@0 114
michael@0 115 /* generate even and odd polynomials using convolution */
michael@0 116 silk_NLSF2A_find_poly( P, &cos_LSF_QA[ 0 ], dd );
michael@0 117 silk_NLSF2A_find_poly( Q, &cos_LSF_QA[ 1 ], dd );
michael@0 118
michael@0 119 /* convert even and odd polynomials to opus_int32 Q12 filter coefs */
michael@0 120 for( k = 0; k < dd; k++ ) {
michael@0 121 Ptmp = P[ k+1 ] + P[ k ];
michael@0 122 Qtmp = Q[ k+1 ] - Q[ k ];
michael@0 123
michael@0 124 /* the Ptmp and Qtmp values at this stage need to fit in int32 */
michael@0 125 a32_QA1[ k ] = -Qtmp - Ptmp; /* QA+1 */
michael@0 126 a32_QA1[ d-k-1 ] = Qtmp - Ptmp; /* QA+1 */
michael@0 127 }
michael@0 128
michael@0 129 /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
michael@0 130 for( i = 0; i < 10; i++ ) {
michael@0 131 /* Find maximum absolute value and its index */
michael@0 132 maxabs = 0;
michael@0 133 for( k = 0; k < d; k++ ) {
michael@0 134 absval = silk_abs( a32_QA1[k] );
michael@0 135 if( absval > maxabs ) {
michael@0 136 maxabs = absval;
michael@0 137 idx = k;
michael@0 138 }
michael@0 139 }
michael@0 140 maxabs = silk_RSHIFT_ROUND( maxabs, QA + 1 - 12 ); /* QA+1 -> Q12 */
michael@0 141
michael@0 142 if( maxabs > silk_int16_MAX ) {
michael@0 143 /* Reduce magnitude of prediction coefficients */
michael@0 144 maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
michael@0 145 sc_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
michael@0 146 silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
michael@0 147 silk_bwexpander_32( a32_QA1, d, sc_Q16 );
michael@0 148 } else {
michael@0 149 break;
michael@0 150 }
michael@0 151 }
michael@0 152
michael@0 153 if( i == 10 ) {
michael@0 154 /* Reached the last iteration, clip the coefficients */
michael@0 155 for( k = 0; k < d; k++ ) {
michael@0 156 a_Q12[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a32_QA1[ k ], QA + 1 - 12 ) ); /* QA+1 -> Q12 */
michael@0 157 a32_QA1[ k ] = silk_LSHIFT( (opus_int32)a_Q12[ k ], QA + 1 - 12 );
michael@0 158 }
michael@0 159 } else {
michael@0 160 for( k = 0; k < d; k++ ) {
michael@0 161 a_Q12[ k ] = (opus_int16)silk_RSHIFT_ROUND( a32_QA1[ k ], QA + 1 - 12 ); /* QA+1 -> Q12 */
michael@0 162 }
michael@0 163 }
michael@0 164
michael@0 165 for( i = 0; i < MAX_LPC_STABILIZE_ITERATIONS; i++ ) {
michael@0 166 if( silk_LPC_inverse_pred_gain( a_Q12, d ) < SILK_FIX_CONST( 1.0 / MAX_PREDICTION_POWER_GAIN, 30 ) ) {
michael@0 167 /* Prediction coefficients are (too close to) unstable; apply bandwidth expansion */
michael@0 168 /* on the unscaled coefficients, convert to Q12 and measure again */
michael@0 169 silk_bwexpander_32( a32_QA1, d, 65536 - silk_LSHIFT( 2, i ) );
michael@0 170 for( k = 0; k < d; k++ ) {
michael@0 171 a_Q12[ k ] = (opus_int16)silk_RSHIFT_ROUND( a32_QA1[ k ], QA + 1 - 12 ); /* QA+1 -> Q12 */
michael@0 172 }
michael@0 173 } else {
michael@0 174 break;
michael@0 175 }
michael@0 176 }
michael@0 177 }
michael@0 178

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