diff options
Diffstat (limited to 'thirdparty/opus/silk/fixed/burg_modified_FIX.c')
| -rw-r--r-- | thirdparty/opus/silk/fixed/burg_modified_FIX.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/thirdparty/opus/silk/fixed/burg_modified_FIX.c b/thirdparty/opus/silk/fixed/burg_modified_FIX.c index 4878553b65..17d0e0993c 100644 --- a/thirdparty/opus/silk/fixed/burg_modified_FIX.c +++ b/thirdparty/opus/silk/fixed/burg_modified_FIX.c @@ -150,8 +150,11 @@ void silk_burg_modified_c( C_first_row[ k ] = silk_MLA( C_first_row[ k ], x1, x_ptr[ n - k - 1 ] ); /* Q( -rshifts ) */ C_last_row[ k ] = silk_MLA( C_last_row[ k ], x2, x_ptr[ subfr_length - n + k ] ); /* Q( -rshifts ) */ Atmp1 = silk_RSHIFT_ROUND( Af_QA[ k ], QA - 17 ); /* Q17 */ - tmp1 = silk_MLA( tmp1, x_ptr[ n - k - 1 ], Atmp1 ); /* Q17 */ - tmp2 = silk_MLA( tmp2, x_ptr[ subfr_length - n + k ], Atmp1 ); /* Q17 */ + /* We sometimes have get overflows in the multiplications (even beyond +/- 2^32), + but they cancel each other and the real result seems to always fit in a 32-bit + signed integer. This was determined experimentally, not theoretically (unfortunately). */ + tmp1 = silk_MLA_ovflw( tmp1, x_ptr[ n - k - 1 ], Atmp1 ); /* Q17 */ + tmp2 = silk_MLA_ovflw( tmp2, x_ptr[ subfr_length - n + k ], Atmp1 ); /* Q17 */ } tmp1 = -tmp1; /* Q17 */ tmp2 = -tmp2; /* Q17 */ @@ -200,12 +203,14 @@ void silk_burg_modified_c( /* Max prediction gain exceeded; set reflection coefficient such that max prediction gain is exactly hit */ tmp2 = ( (opus_int32)1 << 30 ) - silk_DIV32_varQ( minInvGain_Q30, invGain_Q30, 30 ); /* Q30 */ rc_Q31 = silk_SQRT_APPROX( tmp2 ); /* Q15 */ - /* Newton-Raphson iteration */ - rc_Q31 = silk_RSHIFT32( rc_Q31 + silk_DIV32( tmp2, rc_Q31 ), 1 ); /* Q15 */ - rc_Q31 = silk_LSHIFT32( rc_Q31, 16 ); /* Q31 */ - if( num < 0 ) { - /* Ensure adjusted reflection coefficients has the original sign */ - rc_Q31 = -rc_Q31; + if( rc_Q31 > 0 ) { + /* Newton-Raphson iteration */ + rc_Q31 = silk_RSHIFT32( rc_Q31 + silk_DIV32( tmp2, rc_Q31 ), 1 ); /* Q15 */ + rc_Q31 = silk_LSHIFT32( rc_Q31, 16 ); /* Q31 */ + if( num < 0 ) { + /* Ensure adjusted reflection coefficients has the original sign */ + rc_Q31 = -rc_Q31; + } } invGain_Q30 = minInvGain_Q30; reached_max_gain = 1; |