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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 "nsTArray.h"
#include "mozilla/PodOperations.h"
#include "mozilla/LinkedList.h"
#include "AudioStream.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 && mFrames && mSampleRate, "Mix not called for this cycle?");
for (MixerCallback* cb = mCallbacks.getFirst();
cb != nullptr; cb = cb->getNext()) {
cb->mReceiver->MixerCallback(mMixedAudio.Elements(),
AudioSampleTypeToFormat<AudioDataValue>::Format,
mChannels,
mFrames,
mSampleRate);
}
PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
mSampleRate = mChannels = mFrames = 0;
}
/* Add a buffer to the mix. */
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);
for (uint32_t i = 0; i < aFrames * aChannels; i++) {
mMixedAudio[i] += aSamples[i];
}
}
void AddCallback(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(MixerCallbackReceiver* aReceiver)
: mReceiver(aReceiver)
{ }
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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