Chris@69: /***********************************************************************
Chris@69: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
Chris@69: Redistribution and use in source and binary forms, with or without
Chris@69: modification, are permitted provided that the following conditions
Chris@69: are met:
Chris@69: - Redistributions of source code must retain the above copyright notice,
Chris@69: this list of conditions and the following disclaimer.
Chris@69: - Redistributions in binary form must reproduce the above copyright
Chris@69: notice, this list of conditions and the following disclaimer in the
Chris@69: documentation and/or other materials provided with the distribution.
Chris@69: - Neither the name of Internet Society, IETF or IETF Trust, nor the
Chris@69: names of specific contributors, may be used to endorse or promote
Chris@69: products derived from this software without specific prior written
Chris@69: permission.
Chris@69: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
Chris@69: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
Chris@69: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
Chris@69: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
Chris@69: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
Chris@69: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
Chris@69: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
Chris@69: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
Chris@69: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
Chris@69: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
Chris@69: POSSIBILITY OF SUCH DAMAGE.
Chris@69: ***********************************************************************/
Chris@69: 
Chris@69: #ifdef HAVE_CONFIG_H
Chris@69: #include "config.h"
Chris@69: #endif
Chris@69: 
Chris@69: #include "SigProc_FIX.h"
Chris@69: #include "define.h"
Chris@69: 
Chris@69: #define QA                          24
Chris@69: #define A_LIMIT                     SILK_FIX_CONST( 0.99975, QA )
Chris@69: 
Chris@69: #define MUL32_FRAC_Q(a32, b32, Q)   ((opus_int32)(silk_RSHIFT_ROUND64(silk_SMULL(a32, b32), Q)))
Chris@69: 
Chris@69: /* Compute inverse of LPC prediction gain, and                          */
Chris@69: /* test if LPC coefficients are stable (all poles within unit circle)   */
Chris@69: static opus_int32 LPC_inverse_pred_gain_QA_c(               /* O   Returns inverse prediction gain in energy domain, Q30    */
Chris@69:     opus_int32           A_QA[ SILK_MAX_ORDER_LPC ],        /* I   Prediction coefficients                                  */
Chris@69:     const opus_int       order                              /* I   Prediction order                                         */
Chris@69: )
Chris@69: {
Chris@69:     opus_int   k, n, mult2Q;
Chris@69:     opus_int32 invGain_Q30, rc_Q31, rc_mult1_Q30, rc_mult2, tmp1, tmp2;
Chris@69: 
Chris@69:     invGain_Q30 = SILK_FIX_CONST( 1, 30 );
Chris@69:     for( k = order - 1; k > 0; k-- ) {
Chris@69:         /* Check for stability */
Chris@69:         if( ( A_QA[ k ] > A_LIMIT ) || ( A_QA[ k ] < -A_LIMIT ) ) {
Chris@69:             return 0;
Chris@69:         }
Chris@69: 
Chris@69:         /* Set RC equal to negated AR coef */
Chris@69:         rc_Q31 = -silk_LSHIFT( A_QA[ k ], 31 - QA );
Chris@69: 
Chris@69:         /* rc_mult1_Q30 range: [ 1 : 2^30 ] */
Chris@69:         rc_mult1_Q30 = silk_SUB32( SILK_FIX_CONST( 1, 30 ), silk_SMMUL( rc_Q31, rc_Q31 ) );
Chris@69:         silk_assert( rc_mult1_Q30 > ( 1 << 15 ) );                   /* reduce A_LIMIT if fails */
Chris@69:         silk_assert( rc_mult1_Q30 <= ( 1 << 30 ) );
Chris@69: 
Chris@69:         /* Update inverse gain */
Chris@69:         /* invGain_Q30 range: [ 0 : 2^30 ] */
Chris@69:         invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
Chris@69:         silk_assert( invGain_Q30 >= 0           );
Chris@69:         silk_assert( invGain_Q30 <= ( 1 << 30 ) );
Chris@69:         if( invGain_Q30 < SILK_FIX_CONST( 1.0f / MAX_PREDICTION_POWER_GAIN, 30 ) ) {
Chris@69:             return 0;
Chris@69:         }
Chris@69: 
Chris@69:         /* rc_mult2 range: [ 2^30 : silk_int32_MAX ] */
Chris@69:         mult2Q = 32 - silk_CLZ32( silk_abs( rc_mult1_Q30 ) );
Chris@69:         rc_mult2 = silk_INVERSE32_varQ( rc_mult1_Q30, mult2Q + 30 );
Chris@69: 
Chris@69:         /* Update AR coefficient */
Chris@69:         for( n = 0; n < (k + 1) >> 1; n++ ) {
Chris@69:             opus_int64 tmp64;
Chris@69:             tmp1 = A_QA[ n ];
Chris@69:             tmp2 = A_QA[ k - n - 1 ];
Chris@69:             tmp64 = silk_RSHIFT_ROUND64( silk_SMULL( silk_SUB_SAT32(tmp1,
Chris@69:                   MUL32_FRAC_Q( tmp2, rc_Q31, 31 ) ), rc_mult2 ), mult2Q);
Chris@69:             if( tmp64 > silk_int32_MAX || tmp64 < silk_int32_MIN ) {
Chris@69:                return 0;
Chris@69:             }
Chris@69:             A_QA[ n ] = ( opus_int32 )tmp64;
Chris@69:             tmp64 = silk_RSHIFT_ROUND64( silk_SMULL( silk_SUB_SAT32(tmp2,
Chris@69:                   MUL32_FRAC_Q( tmp1, rc_Q31, 31 ) ), rc_mult2), mult2Q);
Chris@69:             if( tmp64 > silk_int32_MAX || tmp64 < silk_int32_MIN ) {
Chris@69:                return 0;
Chris@69:             }
Chris@69:             A_QA[ k - n - 1 ] = ( opus_int32 )tmp64;
Chris@69:         }
Chris@69:     }
Chris@69: 
Chris@69:     /* Check for stability */
Chris@69:     if( ( A_QA[ k ] > A_LIMIT ) || ( A_QA[ k ] < -A_LIMIT ) ) {
Chris@69:         return 0;
Chris@69:     }
Chris@69: 
Chris@69:     /* Set RC equal to negated AR coef */
Chris@69:     rc_Q31 = -silk_LSHIFT( A_QA[ 0 ], 31 - QA );
Chris@69: 
Chris@69:     /* Range: [ 1 : 2^30 ] */
Chris@69:     rc_mult1_Q30 = silk_SUB32( SILK_FIX_CONST( 1, 30 ), silk_SMMUL( rc_Q31, rc_Q31 ) );
Chris@69: 
Chris@69:     /* Update inverse gain */
Chris@69:     /* Range: [ 0 : 2^30 ] */
Chris@69:     invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
Chris@69:     silk_assert( invGain_Q30 >= 0           );
Chris@69:     silk_assert( invGain_Q30 <= ( 1 << 30 ) );
Chris@69:     if( invGain_Q30 < SILK_FIX_CONST( 1.0f / MAX_PREDICTION_POWER_GAIN, 30 ) ) {
Chris@69:         return 0;
Chris@69:     }
Chris@69: 
Chris@69:     return invGain_Q30;
Chris@69: }
Chris@69: 
Chris@69: /* For input in Q12 domain */
Chris@69: opus_int32 silk_LPC_inverse_pred_gain_c(            /* O   Returns inverse prediction gain in energy domain, Q30        */
Chris@69:     const opus_int16            *A_Q12,             /* I   Prediction coefficients, Q12 [order]                         */
Chris@69:     const opus_int              order               /* I   Prediction order                                             */
Chris@69: )
Chris@69: {
Chris@69:     opus_int   k;
Chris@69:     opus_int32 Atmp_QA[ SILK_MAX_ORDER_LPC ];
Chris@69:     opus_int32 DC_resp = 0;
Chris@69: 
Chris@69:     /* Increase Q domain of the AR coefficients */
Chris@69:     for( k = 0; k < order; k++ ) {
Chris@69:         DC_resp += (opus_int32)A_Q12[ k ];
Chris@69:         Atmp_QA[ k ] = silk_LSHIFT32( (opus_int32)A_Q12[ k ], QA - 12 );
Chris@69:     }
Chris@69:     /* If the DC is unstable, we don't even need to do the full calculations */
Chris@69:     if( DC_resp >= 4096 ) {
Chris@69:         return 0;
Chris@69:     }
Chris@69:     return LPC_inverse_pred_gain_QA_c( Atmp_QA, order );
Chris@69: }