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Fixes an overflow in limit_warped_coefs()

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For large values of maxabs_Q20, silk_MUL( maxabs_Q20, ind + 1 ) could
overflow.
This commit is contained in:
Jean-Marc Valin 2016-07-25 11:05:00 -04:00
parent ee44ff86c6
commit 07ca5cc776
1 changed files with 7 additions and 4 deletions
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11
silk/fixed/noise_shape_analysis_FIX.c
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@ -65,6 +65,7 @@ static OPUS_INLINE void limit_warped_coefs(
opus_int i, iter, ind = 0; opus_int i, iter, ind = 0;
opus_int32 tmp, maxabs_Q24, chirp_Q16, gain_Q16; opus_int32 tmp, maxabs_Q24, chirp_Q16, gain_Q16;
opus_int32 nom_Q16, den_Q24; opus_int32 nom_Q16, den_Q24;
opus_int32 limit_Q20, maxabs_Q20;
/* Convert to monic coefficients */ /* Convert to monic coefficients */
lambda_Q16 = -lambda_Q16; lambda_Q16 = -lambda_Q16;
@ -78,7 +79,7 @@ static OPUS_INLINE void limit_warped_coefs(
for( i = 0; i < order; i++ ) { for( i = 0; i < order; i++ ) {
coefs_Q24[ i ] = silk_SMULWW( gain_Q16, coefs_Q24[ i ] ); coefs_Q24[ i ] = silk_SMULWW( gain_Q16, coefs_Q24[ i ] );
} }
limit_Q20 = silk_RSHIFT(limit_Q24, 4);
for( iter = 0; iter < 10; iter++ ) { for( iter = 0; iter < 10; iter++ ) {
/* Find maximum absolute value */ /* Find maximum absolute value */
maxabs_Q24 = -1; maxabs_Q24 = -1;
@ -89,7 +90,9 @@ static OPUS_INLINE void limit_warped_coefs(
ind = i; ind = i;
} }
} }
if( maxabs_Q24 <= limit_Q24 ) { /* Use Q20 to avoid any overflow when multiplying by (ind + 1) later. */
maxabs_Q20 = silk_RSHIFT(maxabs_Q24, 4);
if( maxabs_Q20 <= limit_Q20 ) {
/* Coefficients are within range - done */ /* Coefficients are within range - done */
return; return;
} }
@ -105,8 +108,8 @@ static OPUS_INLINE void limit_warped_coefs(
/* Apply bandwidth expansion */ /* Apply bandwidth expansion */
chirp_Q16 = SILK_FIX_CONST( 0.99, 16 ) - silk_DIV32_varQ( chirp_Q16 = SILK_FIX_CONST( 0.99, 16 ) - silk_DIV32_varQ(
silk_SMULWB( maxabs_Q24 - limit_Q24, silk_SMLABB( SILK_FIX_CONST( 0.8, 10 ), SILK_FIX_CONST( 0.1, 10 ), iter ) ), silk_SMULWB( maxabs_Q20 - limit_Q20, silk_SMLABB( SILK_FIX_CONST( 0.8, 10 ), SILK_FIX_CONST( 0.1, 10 ), iter ) ),
silk_MUL( maxabs_Q24, ind + 1 ), 22 ); silk_MUL( maxabs_Q20, ind + 1 ), 22 );
silk_bwexpander_32( coefs_Q24, order, chirp_Q16 ); silk_bwexpander_32( coefs_Q24, order, chirp_Q16 );
/* Convert to monic warped coefficients */ /* Convert to monic warped coefficients */