git-svn-id: http://webrtc.googlecode.com/svn/trunk@4 4adac7df-926f-26a2-2b94-8c16560cd09d

modules/audio_coding/codecs/CNG/main/source/cng_helpfuns.c

@@ -0,0 +1,64 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+
+#include "webrtc_cng.h"
+#include "signal_processing_library.h"
+#include "typedefs.h"
+#include "cng_helpfuns.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+void WebRtcCng_K2a16( 
+    WebRtc_Word16 *k,           /* Q15.    */
+    int            useOrder,
+    WebRtc_Word16 *a            /* Q12.    */
+)
+{
+    WebRtc_Word16 any[WEBRTC_SPL_MAX_LPC_ORDER+1];
+    WebRtc_Word16 *aptr, *aptr2, *anyptr;
+    G_CONST WebRtc_Word16 *kptr;
+    int m, i;
+    
+    kptr = k;
+    *a   = 4096;  /* i.e., (Word16_MAX >> 3)+1 */
+     *any = *a;
+    a[1] = (*k+4) >> 3;
+    for( m=1; m<useOrder; m++ )
+    {
+        kptr++;
+        aptr = a;
+        aptr++;
+        aptr2 = &a[m];
+        anyptr = any;
+        anyptr++;
+
+        any[m+1] = (*kptr+4) >> 3;
+        for( i=0; i<m; i++ ) {
+            *anyptr++ = (*aptr++) + (WebRtc_Word16)( (( (WebRtc_Word32)(*aptr2--) * (WebRtc_Word32)*kptr )+16384) >> 15);
+        }
+
+        aptr   = a;
+        anyptr = any;
+        for( i=0; i<(m+2); i++ ){
+            *aptr++ = *anyptr++;
+        }
+    }
+}
+
+
+#ifdef __cplusplus
+}
+#endif
+