| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "content/renderer/media/media_stream_audio_level_calculator.h" |
| |
| #include "base/logging.h" |
| #include "base/stl_util.h" |
| |
| namespace content { |
| |
| namespace { |
| |
| // Calculates the maximum absolute amplitude of the audio data. |
| // Note, the return value can be bigger than std::numeric_limits<int16>::max(). |
| int MaxAmplitude(const int16* audio_data, int length) { |
| int max = 0, absolute = 0; |
| for (int i = 0; i < length; ++i) { |
| absolute = std::abs(audio_data[i]); |
| if (absolute > max) |
| max = absolute; |
| } |
| // The range of int16 is [-32768, 32767], verify the |max| should not be |
| // bigger than 32768. |
| DCHECK(max <= std::abs(std::numeric_limits<int16>::min())); |
| |
| return max; |
| } |
| |
| } // namespace |
| |
| MediaStreamAudioLevelCalculator::MediaStreamAudioLevelCalculator() |
| : counter_(0), |
| max_amplitude_(0), |
| level_(0) { |
| } |
| |
| MediaStreamAudioLevelCalculator::~MediaStreamAudioLevelCalculator() { |
| } |
| |
| int MediaStreamAudioLevelCalculator::Calculate( |
| const int16* audio_data, |
| int number_of_channels, |
| int number_of_frames, |
| bool force_report_nonzero_energy) { |
| DCHECK(thread_checker_.CalledOnValidThread()); |
| // |level_| is updated every 10 callbacks. For the case where callback comes |
| // every 10ms, |level_| will be updated approximately every 100ms. |
| static const int kUpdateFrequency = 10; |
| |
| int max = MaxAmplitude(audio_data, number_of_channels * number_of_frames); |
| max_amplitude_ = std::max(max_amplitude_, max); |
| |
| if (counter_++ == kUpdateFrequency) { |
| level_ = (max_amplitude_ == 0 ? |
| force_report_nonzero_energy : max_amplitude_); |
| |
| // Decay the absolute maximum amplitude by 1/4. |
| max_amplitude_ >>= 2; |
| |
| // Reset the counter. |
| counter_ = 0; |
| } |
| |
| return level_; |
| } |
| |
| } // namespace content |