gain_dequant.c revision 470e71d3649f6cac4688e83819640b012b5d38bb 
1/*
2 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11/******************************************************************
12
13 iLBC Speech Coder ANSI-C Source Code
14
15 WebRtcIlbcfix_GainDequant.c
16
17******************************************************************/
18
19#include "defines.h"
20#include "constants.h"
21
22/*----------------------------------------------------------------*
23 *  decoder for quantized gains in the gain-shape coding of
24 *  residual
25 *---------------------------------------------------------------*/
26
27WebRtc_Word16 WebRtcIlbcfix_GainDequant(
28    /* (o) quantized gain value (Q14) */
29    WebRtc_Word16 index, /* (i) quantization index */
30    WebRtc_Word16 maxIn, /* (i) maximum of unquantized gain (Q14) */
31    WebRtc_Word16 stage /* (i) The stage of the search */
32                                                ){
33  WebRtc_Word16 scale;
34  const WebRtc_Word16 *gain;
35
36  /* obtain correct scale factor */
37
38  scale=WEBRTC_SPL_ABS_W16(maxIn);
39  scale = WEBRTC_SPL_MAX(1638, scale);  /* if lower than 0.1, set it to 0.1 */
40
41  /* select the quantization table and return the decoded value */
42  gain = WebRtcIlbcfix_kGain[stage];
43
44  return((WebRtc_Word16)((WEBRTC_SPL_MUL_16_16(scale, gain[index])+8192)>>14));
45}
46