SILK fixes following last codec WG meeting

decoder:
- fixed incorrect scaling of filter states for the smallest quantization
  step sizes
- NLSF2A now limits the prediction gain of LPC filters

encoder:
- increased damping of LTP coefficients in LTP analysis
- increased white noise fraction in noise shaping LPC analysis
- introduced maximum total prediction gain.  Used by Burg's method to
  exit early if prediction gain is exceeded.  This improves packet
  loss robustness and numerical robustness in Burg's method
- Prefiltered signal is now in int32 Q10 domain, from int16 Q0
- Increased max number of iterations in CBR gain control loop from 5 to 6
- Removed useless code from LTP scaling control
- Optimization: smarter LPC loop unrolling
- Switched default win32 compile mode to be floating-point

resampler:
- made resampler have constant delay of 0.75 ms; removed delay
  compensation from silk code.
- removed obsolete table entries (~850 Bytes)
- increased downsampling filter order from 16 to 18/24/36 (depending on
  frequency ratio)
- reoptimized filter coefficients

1 files changed, 23 insertions, 30 deletions

diff --git a/silk/LPC_inv_pred_gain.c b/silk/LPC_inv_pred_gain.c
index 249da318..db529d14 100644
--- a/silk/LPC_inv_pred_gain.c
+++ b/silk/LPC_inv_pred_gain.c
@@ -38,24 +38,22 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 /* Compute inverse of LPC prediction gain, and                          */
 /* test if LPC coefficients are stable (all poles within unit circle)   */
-static opus_int LPC_inverse_pred_gain_QA(                   /* O   Returns 1 if unstable, otherwise 0          */
-    opus_int32           *invGain_Q30,                      /* O   Inverse prediction gain, Q30 energy domain  */
-    opus_int32           A_QA[ 2 ][ SILK_MAX_ORDER_LPC ],   /* I   Prediction coefficients                     */
-    const opus_int       order                              /* I   Prediction order                            */
+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 rc_Q31, rc_mult1_Q30, rc_mult2, tmp_QA;
+    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 = ( 1 << 30 );
+    invGain_Q30 = 1 << 30;
     for( k = order - 1; k > 0; k-- ) {
         /* Check for stability */
         if( ( Anew_QA[ k ] > A_LIMIT ) || ( Anew_QA[ k ] < -A_LIMIT ) ) {
-            *invGain_Q30 = 0;
-            return 1;
+            return 0;
         }
 
         /* Set RC equal to negated AR coef */
@@ -72,9 +70,9 @@ static opus_int LPC_inverse_pred_gain_QA(                   /* O   Returns 1 if
 
         /* 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 ) );
+        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;
@@ -89,8 +87,7 @@ static opus_int LPC_inverse_pred_gain_QA(                   /* O   Returns 1 if
 
     /* Check for stability */
     if( ( Anew_QA[ 0 ] > A_LIMIT ) || ( Anew_QA[ 0 ] < -A_LIMIT ) ) {
-        *invGain_Q30 = 0;
-        return 1;
+        return 0;
     }
 
     /* Set RC equal to negated AR coef */
@@ -101,16 +98,15 @@ static opus_int LPC_inverse_pred_gain_QA(                   /* O   Returns 1 if
 
     /* 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 );
+    invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
+    silk_assert( invGain_Q30 >= 0     );
+    silk_assert( invGain_Q30 <= 1<<30 );
 
-    return 0;
+    return invGain_Q30;
 }
 
 /* For input in Q12 domain */
-opus_int silk_LPC_inverse_pred_gain(                /* O   Returns 1 if unstable, otherwise 0                           */
-    opus_int32                  *invGain_Q30,       /* O   Inverse prediction gain, Q30 energy 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                                             */
 )
@@ -118,30 +114,27 @@ opus_int silk_LPC_inverse_pred_gain(                /* O   Returns 1 if unstable
     opus_int   k;
     opus_int32 Atmp_QA[ 2 ][ SILK_MAX_ORDER_LPC ];
     opus_int32 *Anew_QA;
-    opus_int32 DC_resp=0;
+    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_LSHIFT( (opus_int32)A_Q12[ k ], QA - 12 );
+        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 ) {
-       *invGain_Q30 = 0;
-       return 1;
+        return 0;
     }
-    return LPC_inverse_pred_gain_QA( invGain_Q30, Atmp_QA, order );
+    return LPC_inverse_pred_gain_QA( Atmp_QA, order );
 }
 
 #ifdef FIXED_POINT
 
 /* For input in Q24 domain */
-/* This function is only used by the fixed-point build */
-opus_int silk_LPC_inverse_pred_gain_Q24(            /* O    Returns 1 if unstable, otherwise 0                          */
-    opus_int32                  *invGain_Q30,       /* O    Inverse prediction gain, Q30 energy domain                  */
-    const opus_int32            *A_Q24,             /* I    Prediction coefficients, Q24 [order]                        */
+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                                            */
 )
 {
@@ -153,9 +146,9 @@ opus_int silk_LPC_inverse_pred_gain_Q24(            /* O    Returns 1 if unstabl
 
     /* Increase Q domain of the AR coefficients */
     for( k = 0; k < order; k++ ) {
-        Anew_QA[ k ] = silk_RSHIFT( A_Q24[ k ], 24 - QA );
+        Anew_QA[ k ] = silk_RSHIFT32( A_Q24[ k ], 24 - QA );
     }
 
-    return LPC_inverse_pred_gain_QA( invGain_Q30, Atmp_QA, order );
+    return LPC_inverse_pred_gain_QA( Atmp_QA, order );
 }
 #endif