godot/thirdparty/opus/silk/LPC_inv_pred_gain.c
Rémi Verschelde d9a291f641 ogg/vorbis/opus: Make them modules and unbundle thirdparty libs
Took the opportunity to undo the Godot changed made to the
opus source. The opus module should eventually be built in its
own environment to avoid polluting others with too many include
dirs and defines.

TODO: Fix the platform/ stuff for opus.
2016-10-15 11:50:40 +02:00

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