1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #include "content/renderer/media/media_stream_audio_level_calculator.h"
7 #include "base/logging.h"
8 #include "base/stl_util.h"
14 // Calculates the maximum absolute amplitude of the audio data.
15 // Note, the return value can be bigger than std::numeric_limits<int16>::max().
16 int MaxAmplitude(const int16* audio_data, int length) {
17 int max = 0, absolute = 0;
18 for (int i = 0; i < length; ++i) {
19 absolute = std::abs(audio_data[i]);
23 // The range of int16 is [-32768, 32767], verify the |max| should not be
25 DCHECK(max <= std::abs(std::numeric_limits<int16>::min()));
32 MediaStreamAudioLevelCalculator::MediaStreamAudioLevelCalculator()
38 MediaStreamAudioLevelCalculator::~MediaStreamAudioLevelCalculator() {
41 int MediaStreamAudioLevelCalculator::Calculate(const int16* audio_data,
42 int number_of_channels,
43 int number_of_frames) {
44 DCHECK(thread_checker_.CalledOnValidThread());
45 // |level_| is updated every 10 callbacks. For the case where callback comes
46 // every 10ms, |level_| will be updated approximately every 100ms.
47 static const int kUpdateFrequency = 10;
49 int max = MaxAmplitude(audio_data, number_of_channels * number_of_frames);
50 max_amplitude_ = std::max(max_amplitude_, max);
52 if (counter_++ == kUpdateFrequency) {
53 level_ = max_amplitude_;
55 // Decay the absolute maximum amplitude by 1/4.
65 } // namespace content