1/*
2 *  Copyright (c) 2014 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#include "webrtc/modules/audio_processing/rms_level.h"
12
13#include <assert.h>
14#include <math.h>
15
16namespace webrtc {
17
18static const float kMaxSquaredLevel = 32768 * 32768;
19
20RMSLevel::RMSLevel()
21    : sum_square_(0),
22      sample_count_(0) {}
23
24RMSLevel::~RMSLevel() {}
25
26void RMSLevel::Reset() {
27  sum_square_ = 0;
28  sample_count_ = 0;
29}
30
31void RMSLevel::Process(const int16_t* data, int length) {
32  for (int i = 0; i < length; ++i) {
33    sum_square_ += data[i] * data[i];
34  }
35  sample_count_ += length;
36}
37
38void RMSLevel::ProcessMuted(int length) {
39  sample_count_ += length;
40}
41
42int RMSLevel::RMS() {
43  if (sample_count_ == 0 || sum_square_ == 0) {
44    Reset();
45    return kMinLevel;
46  }
47
48  // Normalize by the max level.
49  float rms = sum_square_ / (sample_count_ * kMaxSquaredLevel);
50  // 20log_10(x^0.5) = 10log_10(x)
51  rms = 10 * log10(rms);
52  assert(rms <= 0);
53  if (rms < -kMinLevel)
54    rms = -kMinLevel;
55
56  rms = -rms;
57  Reset();
58  return static_cast<int>(rms + 0.5);
59}
60
61}  // namespace webrtc
62