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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef DOM_MEDIA_AUDIBILITYMONITOR_H_
#define DOM_MEDIA_AUDIBILITYMONITOR_H_
#include <cstdint>
#include "AudioSampleFormat.h"
#include "WebAudioUtils.h"
#include "AudioBlock.h"
#include "MediaData.h"
namespace mozilla {
class AudibilityMonitor {
public:
// ≈ 20 * log10(pow(2, 12)), noise floor of 12bit audio
const float AUDIBILITY_THREHSOLD = -72.;
AudibilityMonitor(uint32_t aSamplerate, float aSilenceDurationSeconds)
: mSamplerate(aSamplerate),
mSilenceDurationSeconds(aSilenceDurationSeconds),
mSilentFramesInARow(0),
mEverAudible(false) {}
void Process(const AudioData* aData) {
ProcessInterleaved(aData->Data(), aData->mChannels);
}
void Process(const AudioBlock& aData) {
if (aData.IsNull() || aData.IsMuted()) {
mSilentFramesInARow += aData.GetDuration();
return;
}
ProcessPlanar(aData.ChannelData<float>(), aData.GetDuration());
}
void ProcessPlanar(const nsTArray<const float*>& aPlanar, TrackTime aFrames) {
uint32_t lastFrameAudibleAccrossChannels = 0;
for (uint32_t channel = 0; channel < aPlanar.Length(); channel++) {
uint32_t lastSampleAudible = 0;
for (uint32_t frame = 0; frame < aFrames; frame++) {
float dbfs = dom::WebAudioUtils::ConvertLinearToDecibels(
abs(aPlanar[channel][frame]), -100.f);
if (dbfs > AUDIBILITY_THREHSOLD) {
mEverAudible = true;
mSilentFramesInARow = 0;
lastSampleAudible = frame;
}
}
lastFrameAudibleAccrossChannels =
std::max(lastFrameAudibleAccrossChannels, lastSampleAudible);
}
mSilentFramesInARow += aFrames - lastFrameAudibleAccrossChannels - 1;
}
void ProcessInterleaved(const Span<AudioDataValue>& aInterleaved,
size_t aChannels) {
MOZ_ASSERT(aInterleaved.Length() % aChannels == 0);
uint32_t frameCount = aInterleaved.Length() / aChannels;
AudioDataValue* samples = aInterleaved.Elements();
uint32_t readIndex = 0;
for (uint32_t i = 0; i < frameCount; i++) {
bool atLeastOneAudible = false;
for (uint32_t j = 0; j < aChannels; j++) {
float dbfs = dom::WebAudioUtils::ConvertLinearToDecibels(
abs(AudioSampleToFloat(samples[readIndex++])), -100.f);
if (dbfs > AUDIBILITY_THREHSOLD) {
atLeastOneAudible = true;
}
}
if (atLeastOneAudible) {
mSilentFramesInARow = 0;
mEverAudible = true;
} else {
mSilentFramesInARow++;
}
}
}
// A stream is considered audible if there was audible content in the last
// `mSilenceDurationSeconds` seconds, or it has never been audible for now.
bool RecentlyAudible() {
return mEverAudible && (static_cast<float>(mSilentFramesInARow) /
mSamplerate) < mSilenceDurationSeconds;
}
private:
const uint32_t mSamplerate;
const float mSilenceDurationSeconds;
uint64_t mSilentFramesInARow;
bool mEverAudible;
};
}; // namespace mozilla
#endif // DOM_MEDIA_AUDIBILITYMONITOR_H_