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