Add copy of opus library in deps/third_party.

opus/silk/float/levinsondurbin_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_FLP.h"
+
+/* Solve the normal equations using the Levinson-Durbin recursion */
+silk_float silk_levinsondurbin_FLP(         /* O    prediction error energy                                     */
+    silk_float          A[],                /* O    prediction coefficients    [order]                          */
+    const silk_float    corr[],             /* I    input auto-correlations [order + 1]                         */
+    const opus_int      order               /* I    prediction order                                            */
+)
+{
+    opus_int   i, mHalf, m;
+    silk_float min_nrg, nrg, t, km, Atmp1, Atmp2;
+
+    min_nrg = 1e-12f * corr[ 0 ] + 1e-9f;
+    nrg = corr[ 0 ];
+    nrg = silk_max_float(min_nrg, nrg);
+    A[ 0 ] = corr[ 1 ] / nrg;
+    nrg -= A[ 0 ] * corr[ 1 ];
+    nrg = silk_max_float(min_nrg, nrg);
+
+    for( m = 1; m < order; m++ )
+    {
+        t = corr[ m + 1 ];
+        for( i = 0; i < m; i++ ) {
+            t -= A[ i ] * corr[ m - i ];
+        }
+
+        /* reflection coefficient */
+        km = t / nrg;
+
+        /* residual energy */
+        nrg -= km * t;
+        nrg = silk_max_float(min_nrg, nrg);
+
+        mHalf = m >> 1;
+        for( i = 0; i < mHalf; i++ ) {
+            Atmp1 = A[ i ];
+            Atmp2 = A[ m - i - 1 ];
+            A[ m - i - 1 ] -= km * Atmp1;
+            A[ i ]         -= km * Atmp2;
+        }
+        if( m & 1 ) {
+            A[ mHalf ]     -= km * A[ mHalf ];
+        }
+        A[ m ] = km;
+    }
+
+    /* return the residual energy */
+    return nrg;
+}
+