gecko/media/libopus/silk/LPC_inv_pred_gain.c
Ralph Giles fcbd652345 Bug 916807 - Update opus to 1.1 prerelease. r=derf
Update our opus implementation to a prerelease of 1.1. This
brings many performance and encoder improvements and we believe
it is stable enough to switch. This import does not enable any
of the new assembly optimizations.

The imported code is https://git.xiph.org/opus.git master
commit f2446c25c6519bae190152f7a579310b83dc43fd.
2013-09-16 14:48:00 -07:00

155 lines
6.2 KiB
C

/***********************************************************************
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "SigProc_FIX.h"
#define QA 24
#define A_LIMIT SILK_FIX_CONST( 0.99975, QA )
#define MUL32_FRAC_Q(a32, b32, Q) ((opus_int32)(silk_RSHIFT_ROUND64(silk_SMULL(a32, b32), Q)))
/* Compute inverse of LPC prediction gain, and */
/* test if LPC coefficients are stable (all poles within unit circle) */
static opus_int32 LPC_inverse_pred_gain_QA( /* O Returns inverse prediction gain in energy domain, Q30 */
opus_int32 A_QA[ 2 ][ SILK_MAX_ORDER_LPC ], /* I Prediction coefficients */
const opus_int order /* I Prediction order */
)
{
opus_int k, n, mult2Q;
opus_int32 invGain_Q30, rc_Q31, rc_mult1_Q30, rc_mult2, tmp_QA;
opus_int32 *Aold_QA, *Anew_QA;
Anew_QA = A_QA[ order & 1 ];
invGain_Q30 = (opus_int32)1 << 30;
for( k = order - 1; k > 0; k-- ) {
/* Check for stability */
if( ( Anew_QA[ k ] > A_LIMIT ) || ( Anew_QA[ k ] < -A_LIMIT ) ) {
return 0;
}
/* Set RC equal to negated AR coef */
rc_Q31 = -silk_LSHIFT( Anew_QA[ k ], 31 - QA );
/* rc_mult1_Q30 range: [ 1 : 2^30 ] */
rc_mult1_Q30 = ( (opus_int32)1 << 30 ) - silk_SMMUL( rc_Q31, rc_Q31 );
silk_assert( rc_mult1_Q30 > ( 1 << 15 ) ); /* reduce A_LIMIT if fails */
silk_assert( rc_mult1_Q30 <= ( 1 << 30 ) );
/* rc_mult2 range: [ 2^30 : silk_int32_MAX ] */
mult2Q = 32 - silk_CLZ32( silk_abs( rc_mult1_Q30 ) );
rc_mult2 = silk_INVERSE32_varQ( rc_mult1_Q30, mult2Q + 30 );
/* Update inverse gain */
/* invGain_Q30 range: [ 0 : 2^30 ] */
invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
silk_assert( invGain_Q30 >= 0 );
silk_assert( invGain_Q30 <= ( 1 << 30 ) );
/* Swap pointers */
Aold_QA = Anew_QA;
Anew_QA = A_QA[ k & 1 ];
/* Update AR coefficient */
for( n = 0; n < k; n++ ) {
tmp_QA = Aold_QA[ n ] - MUL32_FRAC_Q( Aold_QA[ k - n - 1 ], rc_Q31, 31 );
Anew_QA[ n ] = MUL32_FRAC_Q( tmp_QA, rc_mult2 , mult2Q );
}
}
/* Check for stability */
if( ( Anew_QA[ 0 ] > A_LIMIT ) || ( Anew_QA[ 0 ] < -A_LIMIT ) ) {
return 0;
}
/* Set RC equal to negated AR coef */
rc_Q31 = -silk_LSHIFT( Anew_QA[ 0 ], 31 - QA );
/* Range: [ 1 : 2^30 ] */
rc_mult1_Q30 = ( (opus_int32)1 << 30 ) - silk_SMMUL( rc_Q31, rc_Q31 );
/* Update inverse gain */
/* Range: [ 0 : 2^30 ] */
invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
silk_assert( invGain_Q30 >= 0 );
silk_assert( invGain_Q30 <= 1<<30 );
return invGain_Q30;
}
/* For input in Q12 domain */
opus_int32 silk_LPC_inverse_pred_gain( /* O Returns inverse prediction gain in energy domain, Q30 */
const opus_int16 *A_Q12, /* I Prediction coefficients, Q12 [order] */
const opus_int order /* I Prediction order */
)
{
opus_int k;
opus_int32 Atmp_QA[ 2 ][ SILK_MAX_ORDER_LPC ];
opus_int32 *Anew_QA;
opus_int32 DC_resp = 0;
Anew_QA = Atmp_QA[ order & 1 ];
/* Increase Q domain of the AR coefficients */
for( k = 0; k < order; k++ ) {
DC_resp += (opus_int32)A_Q12[ k ];
Anew_QA[ k ] = silk_LSHIFT32( (opus_int32)A_Q12[ k ], QA - 12 );
}
/* If the DC is unstable, we don't even need to do the full calculations */
if( DC_resp >= 4096 ) {
return 0;
}
return LPC_inverse_pred_gain_QA( Atmp_QA, order );
}
#ifdef FIXED_POINT
/* For input in Q24 domain */
opus_int32 silk_LPC_inverse_pred_gain_Q24( /* O Returns inverse prediction gain in energy domain, Q30 */
const opus_int32 *A_Q24, /* I Prediction coefficients [order] */
const opus_int order /* I Prediction order */
)
{
opus_int k;
opus_int32 Atmp_QA[ 2 ][ SILK_MAX_ORDER_LPC ];
opus_int32 *Anew_QA;
Anew_QA = Atmp_QA[ order & 1 ];
/* Increase Q domain of the AR coefficients */
for( k = 0; k < order; k++ ) {
Anew_QA[ k ] = silk_RSHIFT32( A_Q24[ k ], 24 - QA );
}
return LPC_inverse_pred_gain_QA( Atmp_QA, order );
}
#endif