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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_