Add copy of opus library in deps/third_party.

opus/silk/float/LPC_inv_pred_gain_FLP.c

+/***********************************************************************
+Copyright (c) 2006-2011, Skype Limited. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+- Redistributions of source code must retain the above copyright notice,
+this list of conditions and the following disclaimer.
+- Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+- Neither the name of Internet Society, IETF or IETF Trust, nor the 
+names of specific contributors, may be used to endorse or promote
+products derived from this software without specific prior written
+permission.
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS”
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+***********************************************************************/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "SigProc_FIX.h"
+#include "SigProc_FLP.h"
+
+#define RC_THRESHOLD        0.9999f
+
+/* compute inverse of LPC prediction gain, and                          */
+/* test if LPC coefficients are stable (all poles within unit circle)   */
+/* this code is based on silk_a2k_FLP()                                 */
+silk_float silk_LPC_inverse_pred_gain_FLP(  /* O    return inverse prediction gain, energy domain               */
+    const silk_float    *A,                 /* I    prediction coefficients [order]                             */
+    opus_int32          order               /* I    prediction order                                            */
+)
+{
+    opus_int   k, n;
+    double     invGain, rc, rc_mult1, rc_mult2;
+    silk_float Atmp[ 2 ][ SILK_MAX_ORDER_LPC ];
+    silk_float *Aold, *Anew;
+
+    Anew = Atmp[ order & 1 ];
+    silk_memcpy( Anew, A, order * sizeof(silk_float) );
+
+    invGain = 1.0;
+    for( k = order - 1; k > 0; k-- ) {
+        rc = -Anew[ k ];
+        if( rc > RC_THRESHOLD || rc < -RC_THRESHOLD ) {
+            return 0.0f;
+        }
+        rc_mult1 = 1.0f - rc * rc;
+        rc_mult2 = 1.0f / rc_mult1;
+        invGain *= rc_mult1;
+        /* swap pointers */
+        Aold = Anew;
+        Anew = Atmp[ k & 1 ];
+        for( n = 0; n < k; n++ ) {
+            Anew[ n ] = (silk_float)( ( Aold[ n ] - Aold[ k - n - 1 ] * rc ) * rc_mult2 );
+        }
+    }
+    rc = -Anew[ 0 ];
+    if( rc > RC_THRESHOLD || rc < -RC_THRESHOLD ) {
+        return 0.0f;
+    }
+    rc_mult1 = 1.0f - rc * rc;
+    invGain *= rc_mult1;
+    return (silk_float)invGain;
+}