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// Copyright 2013 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.
// MSVC++ requires this to be set before any other includes to get M_PI.
#define _USE_MATH_DEFINES
#include <cmath>
#include "media/base/audio_hash.h"
#include "base/strings/stringprintf.h"
#include "media/base/audio_bus.h"
namespace media {
AudioHash::AudioHash()
: audio_hash_(),
sample_count_(0) {
}
AudioHash::~AudioHash() {}
void AudioHash::Update(const AudioBus* audio_bus, int frames) {
// Use uint32 to ensure overflow is a defined operation.
for (uint32 ch = 0; ch < static_cast<uint32>(audio_bus->channels()); ++ch) {
const float* channel = audio_bus->channel(ch);
for (uint32 i = 0; i < static_cast<uint32>(frames); ++i) {
const uint32 kSampleIndex = sample_count_ + i;
const uint32 kHashIndex =
(kSampleIndex * (ch + 1)) % arraysize(audio_hash_);
// Mix in a sine wave with the result so we ensure that sequences of empty
// buffers don't result in an empty hash.
if (ch == 0) {
audio_hash_[kHashIndex] +=
channel[i] + sin(2.0 * M_PI * M_PI * kSampleIndex);
} else {
audio_hash_[kHashIndex] += channel[i];
}
}
}
sample_count_ += static_cast<uint32>(frames);
}
std::string AudioHash::ToString() const {
std::string result;
for (size_t i = 0; i < arraysize(audio_hash_); ++i)
result += base::StringPrintf("%.2f,", audio_hash_[i]);
return result;
}
} // namespace media
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