1 // Copyright 2013 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 // MSVC++ requires this to be set before any other includes to get M_PI. 6 #define _USE_MATH_DEFINES 7 #include <cmath> 8 9 #include "media/base/audio_hash.h" 10 11 #include "base/strings/stringprintf.h" 12 #include "media/base/audio_bus.h" 13 14 namespace media { 15 16 AudioHash::AudioHash() 17 : audio_hash_(), 18 sample_count_(0) { 19 } 20 21 AudioHash::~AudioHash() {} 22 23 void AudioHash::Update(const AudioBus* audio_bus, int frames) { 24 // Use uint32 to ensure overflow is a defined operation. 25 for (uint32 ch = 0; ch < static_cast<uint32>(audio_bus->channels()); ++ch) { 26 const float* channel = audio_bus->channel(ch); 27 for (uint32 i = 0; i < static_cast<uint32>(frames); ++i) { 28 const uint32 kSampleIndex = sample_count_ + i; 29 const uint32 kHashIndex = 30 (kSampleIndex * (ch + 1)) % arraysize(audio_hash_); 31 32 // Mix in a sine wave with the result so we ensure that sequences of empty 33 // buffers don't result in an empty hash. 34 if (ch == 0) { 35 audio_hash_[kHashIndex] += 36 channel[i] + sin(2.0 * M_PI * M_PI * kSampleIndex); 37 } else { 38 audio_hash_[kHashIndex] += channel[i]; 39 } 40 } 41 } 42 43 sample_count_ += static_cast<uint32>(frames); 44 } 45 46 std::string AudioHash::ToString() const { 47 std::string result; 48 for (size_t i = 0; i < arraysize(audio_hash_); ++i) 49 result += base::StringPrintf("%.2f,", audio_hash_[i]); 50 return result; 51 } 52 53 } // namespace media 54
