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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 MOZILLA_AUDIOMIXER_H_
#define MOZILLA_AUDIOMIXER_H_
#include "AudioSampleFormat.h"
#include "AudioStream.h"
#include "nsTArray.h"
#include "mozilla/LinkedList.h"
#include "mozilla/NotNull.h"
#include "mozilla/PodOperations.h"
namespace mozilla {
struct MixerCallbackReceiver {
virtual void MixerCallback(AudioDataValue* aMixedBuffer,
AudioSampleFormat aFormat, uint32_t aChannels,
uint32_t aFrames, uint32_t aSampleRate) = 0;
};
/**
* This class mixes multiple streams of audio together to output a single audio
* stream.
*
* AudioMixer::Mix is to be called repeatedly with buffers that have the same
* length, sample rate, sample format and channel count. This class works with
* interleaved and plannar buffers, but the buffer mixed must be of the same
* type during a mixing cycle.
*
* When all the tracks have been mixed, calling FinishMixing will call back with
* a buffer containing the mixed audio data.
*
* This class is not thread safe.
*/
class AudioMixer {
public:
AudioMixer() : mFrames(0), mChannels(0), mSampleRate(0) {}
~AudioMixer() {
MixerCallback* cb;
while ((cb = mCallbacks.popFirst())) {
delete cb;
}
}
void StartMixing() { mSampleRate = mChannels = mFrames = 0; }
/* Get the data from the mixer. This is supposed to be called when all the
* tracks have been mixed in. The caller should not hold onto the data. */
void FinishMixing() {
MOZ_ASSERT(mChannels && mSampleRate, "Mix not called for this cycle?");
for (MixerCallback* cb = mCallbacks.getFirst(); cb != nullptr;
cb = cb->getNext()) {
MixerCallbackReceiver* receiver = cb->mReceiver;
MOZ_ASSERT(receiver);
receiver->MixerCallback(mMixedAudio.Elements(),
AudioSampleTypeToFormat<AudioDataValue>::Format,
mChannels, mFrames, mSampleRate);
}
PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
mSampleRate = mChannels = mFrames = 0;
}
/* Add a buffer to the mix. The buffer can be null if there's nothing to mix
* but the callback is still needed. */
void Mix(AudioDataValue* aSamples, uint32_t aChannels, uint32_t aFrames,
uint32_t aSampleRate) {
if (!mFrames && !mChannels) {
mFrames = aFrames;
mChannels = aChannels;
mSampleRate = aSampleRate;
EnsureCapacityAndSilence();
}
MOZ_ASSERT(aFrames == mFrames);
MOZ_ASSERT(aChannels == mChannels);
MOZ_ASSERT(aSampleRate == mSampleRate);
if (!aSamples) {
return;
}
for (uint32_t i = 0; i < aFrames * aChannels; i++) {
mMixedAudio[i] += aSamples[i];
}
}
void AddCallback(NotNull<MixerCallbackReceiver*> aReceiver) {
mCallbacks.insertBack(new MixerCallback(aReceiver));
}
bool FindCallback(MixerCallbackReceiver* aReceiver) {
for (MixerCallback* cb = mCallbacks.getFirst(); cb != nullptr;
cb = cb->getNext()) {
if (cb->mReceiver == aReceiver) {
return true;
}
}
return false;
}
bool RemoveCallback(MixerCallbackReceiver* aReceiver) {
for (MixerCallback* cb = mCallbacks.getFirst(); cb != nullptr;
cb = cb->getNext()) {
if (cb->mReceiver == aReceiver) {
cb->remove();
delete cb;
return true;
}
}
return false;
}
private:
void EnsureCapacityAndSilence() {
if (mFrames * mChannels > mMixedAudio.Length()) {
mMixedAudio.SetLength(mFrames * mChannels);
}
PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
}
class MixerCallback : public LinkedListElement<MixerCallback> {
public:
explicit MixerCallback(NotNull<MixerCallbackReceiver*> aReceiver)
: mReceiver(aReceiver) {}
NotNull<MixerCallbackReceiver*> mReceiver;
};
/* Function that is called when the mixing is done. */
LinkedList<MixerCallback> mCallbacks;
/* Number of frames for this mixing block. */
uint32_t mFrames;
/* Number of channels for this mixing block. */
uint32_t mChannels;
/* Sample rate the of the mixed data. */
uint32_t mSampleRate;
/* Buffer containing the mixed audio data. */
nsTArray<AudioDataValue> mMixedAudio;
};
} // namespace mozilla
#endif // MOZILLA_AUDIOMIXER_H_
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