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

modules/audio_coding/codecs/iLBC/main/source/gain_dequant.c

@@ -0,0 +1,45 @@
+/*
+ *  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.
+ */
+
+/******************************************************************
+
+ iLBC Speech Coder ANSI-C Source Code
+
+ WebRtcIlbcfix_GainDequant.c
+
+******************************************************************/
+
+#include "defines.h"
+#include "constants.h"
+
+/*----------------------------------------------------------------*
+ *  decoder for quantized gains in the gain-shape coding of
+ *  residual
+ *---------------------------------------------------------------*/
+
+WebRtc_Word16 WebRtcIlbcfix_GainDequant(
+    /* (o) quantized gain value (Q14) */
+    WebRtc_Word16 index, /* (i) quantization index */
+    WebRtc_Word16 maxIn, /* (i) maximum of unquantized gain (Q14) */
+    WebRtc_Word16 stage /* (i) The stage of the search */
+                                                ){
+  WebRtc_Word16 scale;
+  const WebRtc_Word16 *gain;
+
+  /* obtain correct scale factor */
+
+  scale=WEBRTC_SPL_ABS_W16(maxIn);
+  scale = WEBRTC_SPL_MAX(1638, scale);  /* if lower than 0.1, set it to 0.1 */
+
+  /* select the quantization table and return the decoded value */
+  gain = WebRtcIlbcfix_kGain[stage];
+
+  return((WebRtc_Word16)((WEBRTC_SPL_MUL_16_16(scale, gain[index])+8192)>>14));
+}