Add copy of opus library in deps/third_party.

opus/silk/stereo_quant_pred.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 "main.h"
+
+/* Quantize mid/side predictors */
+void silk_stereo_quant_pred(
+    opus_int32                  pred_Q13[],                     /* I/O  Predictors (out: quantized)                 */
+    opus_int8                   ix[ 2 ][ 3 ]                    /* O    Quantization indices                        */
+)
+{
+    opus_int   i, j, n;
+    opus_int32 low_Q13, step_Q13, lvl_Q13, err_min_Q13, err_Q13, quant_pred_Q13 = 0;
+
+    /* Quantize */
+    for( n = 0; n < 2; n++ ) {
+        /* Brute-force search over quantization levels */
+        err_min_Q13 = silk_int32_MAX;
+        for( i = 0; i < STEREO_QUANT_TAB_SIZE - 1; i++ ) {
+            low_Q13 = silk_stereo_pred_quant_Q13[ i ];
+            step_Q13 = silk_SMULWB( silk_stereo_pred_quant_Q13[ i + 1 ] - low_Q13,
+                SILK_FIX_CONST( 0.5 / STEREO_QUANT_SUB_STEPS, 16 ) );
+            for( j = 0; j < STEREO_QUANT_SUB_STEPS; j++ ) {
+                lvl_Q13 = silk_SMLABB( low_Q13, step_Q13, 2 * j + 1 );
+                err_Q13 = silk_abs( pred_Q13[ n ] - lvl_Q13 );
+                if( err_Q13 < err_min_Q13 ) {
+                    err_min_Q13 = err_Q13;
+                    quant_pred_Q13 = lvl_Q13;
+                    ix[ n ][ 0 ] = i;
+                    ix[ n ][ 1 ] = j;
+                } else {
+                    /* Error increasing, so we're past the optimum */
+                    goto done;
+                }
+            }
+        }
+        done:
+        ix[ n ][ 2 ]  = silk_DIV32_16( ix[ n ][ 0 ], 3 );
+        ix[ n ][ 0 ] -= ix[ n ][ 2 ] * 3;
+        pred_Q13[ n ] = quant_pred_Q13;
+    }
+
+    /* Subtract second from first predictor (helps when actually applying these) */
+    pred_Q13[ 0 ] -= pred_Q13[ 1 ];
+}