OLD | NEW |
(Empty) | |
| 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. |
| 4 |
| 5 #include "content/renderer/media/media_stream_audio_level_calculator.h" |
| 6 |
| 7 #include "base/logging.h" |
| 8 #include "base/stl_util.h" |
| 9 |
| 10 namespace content { |
| 11 |
| 12 namespace { |
| 13 |
| 14 int MaxAmplitude(const int16* audio_data, int length) { |
| 15 int max = 0, absolute = 0; |
| 16 for (int i = 0; i < length; ++i) { |
| 17 absolute = std::abs(audio_data[i]); |
| 18 if (absolute > max) |
| 19 max = absolute; |
| 20 } |
| 21 DCHECK(max <= std::numeric_limits<int16>::max()); |
| 22 return max; |
| 23 } |
| 24 |
| 25 } // namespace |
| 26 |
| 27 MediaStreamAudioLevelCalculator::MediaStreamAudioLevelCalculator() |
| 28 : counter_(0), |
| 29 max_amplitude_(0), |
| 30 level_(0) { |
| 31 } |
| 32 |
| 33 MediaStreamAudioLevelCalculator::~MediaStreamAudioLevelCalculator() { |
| 34 } |
| 35 |
| 36 int MediaStreamAudioLevelCalculator::Calculate(const int16* audio_data, |
| 37 int number_of_channels, |
| 38 int number_of_frames) { |
| 39 DCHECK(CalledOnValidThread()); |
| 40 // Permutation of bars that reprents the amplitude level of the audio signal. |
| 41 // The number of elements is 33 because we are indexing them in the range of |
| 42 // [0, 32]. |
| 43 static const int kPermutation[33] = |
| 44 {0,1,2,3,4,4,5,5,5,5,6,6,6,6,6,7,7,7,7,8,8,8,9,9,9,9,9,9,9,9,9,9,9}; |
| 45 |
| 46 // |level_| is updated every 10 callbacks. For the case where callback comes |
| 47 // every 10ms, |level_| will be updated approximately every 100ms. |
| 48 static const int kUpdateFrequency = 10; |
| 49 |
| 50 int max = MaxAmplitude(audio_data, number_of_channels * number_of_frames); |
| 51 max_amplitude_ = std::max(max_amplitude_, max); |
| 52 //std::min(max, std::numeric_limits<int16>::max())); |
| 53 |
| 54 if (counter_++ == kUpdateFrequency) { |
| 55 // Divide k16BitsMaxValue (32767) by 1000 to get in the range of [0,32] |
| 56 // which is the range of the permutation array. |
| 57 int index = static_cast<int>(max_amplitude_ / 1000); |
| 58 |
| 59 // Make it less likely that the bar stays at position 0. I.e. only if |
| 60 // its in the range 0-250 (instead of 0-1000) |
| 61 if (index == 0 && max_amplitude_ > 250) |
| 62 index = 1; |
| 63 |
| 64 // |level_| will be the value in the permutation array that the |index| is |
| 65 // pointing to. |
| 66 level_ = kPermutation[index]; |
| 67 |
| 68 // Decay the absolute maximum amplitude by 1/4. |
| 69 max_amplitude_ >>= 2; |
| 70 |
| 71 // Reset the counter. |
| 72 counter_ = 0; |
| 73 } |
| 74 |
| 75 return level_; |
| 76 } |
| 77 |
| 78 } // namespace content |
OLD | NEW |