michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef MOZILLA_AUDIOMIXER_H_
michael@0: #define MOZILLA_AUDIOMIXER_H_
michael@0: 
michael@0: #include "AudioSampleFormat.h"
michael@0: #include "nsTArray.h"
michael@0: #include "mozilla/PodOperations.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: typedef void(*MixerFunc)(AudioDataValue* aMixedBuffer,
michael@0:                          AudioSampleFormat aFormat,
michael@0:                          uint32_t aChannels,
michael@0:                          uint32_t aFrames,
michael@0:                          uint32_t aSampleRate);
michael@0: 
michael@0: /**
michael@0:  * This class mixes multiple streams of audio together to output a single audio
michael@0:  * stream.
michael@0:  *
michael@0:  * AudioMixer::Mix is to be called repeatedly with buffers that have the same
michael@0:  * length, sample rate, sample format and channel count.
michael@0:  *
michael@0:  * When all the tracks have been mixed, calling FinishMixing will call back with
michael@0:  * a buffer containing the mixed audio data.
michael@0:  *
michael@0:  * This class is not thread safe.
michael@0:  */
michael@0: class AudioMixer
michael@0: {
michael@0: public:
michael@0:   AudioMixer(MixerFunc aCallback)
michael@0:     : mCallback(aCallback),
michael@0:       mFrames(0),
michael@0:       mChannels(0),
michael@0:       mSampleRate(0)
michael@0:   { }
michael@0: 
michael@0:   /* Get the data from the mixer. This is supposed to be called when all the
michael@0:    * tracks have been mixed in. The caller should not hold onto the data. */
michael@0:   void FinishMixing() {
michael@0:     mCallback(mMixedAudio.Elements(),
michael@0:               AudioSampleTypeToFormat<AudioDataValue>::Format,
michael@0:               mChannels,
michael@0:               mFrames,
michael@0:               mSampleRate);
michael@0:     PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
michael@0:     mSampleRate = mChannels = mFrames = 0;
michael@0:   }
michael@0: 
michael@0:   /* Add a buffer to the mix. aSamples is interleaved. */
michael@0:   void Mix(AudioDataValue* aSamples,
michael@0:            uint32_t aChannels,
michael@0:            uint32_t aFrames,
michael@0:            uint32_t aSampleRate) {
michael@0:     if (!mFrames && !mChannels) {
michael@0:       mFrames = aFrames;
michael@0:       mChannels = aChannels;
michael@0:       mSampleRate = aSampleRate;
michael@0:       EnsureCapacityAndSilence();
michael@0:     }
michael@0: 
michael@0:     MOZ_ASSERT(aFrames == mFrames);
michael@0:     MOZ_ASSERT(aChannels == mChannels);
michael@0:     MOZ_ASSERT(aSampleRate == mSampleRate);
michael@0: 
michael@0:     for (uint32_t i = 0; i < aFrames * aChannels; i++) {
michael@0:       mMixedAudio[i] += aSamples[i];
michael@0:     }
michael@0:   }
michael@0: private:
michael@0:   void EnsureCapacityAndSilence() {
michael@0:     if (mFrames * mChannels > mMixedAudio.Length()) {
michael@0:       mMixedAudio.SetLength(mFrames* mChannels);
michael@0:     }
michael@0:     PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
michael@0:   }
michael@0: 
michael@0:   /* Function that is called when the mixing is done. */
michael@0:   MixerFunc mCallback;
michael@0:   /* Number of frames for this mixing block. */
michael@0:   uint32_t mFrames;
michael@0:   /* Number of channels for this mixing block. */
michael@0:   uint32_t mChannels;
michael@0:   /* Sample rate the of the mixed data. */
michael@0:   uint32_t mSampleRate;
michael@0:   /* Buffer containing the mixed audio data. */
michael@0:   nsTArray<AudioDataValue> mMixedAudio;
michael@0: };
michael@0: }
michael@0: 
michael@0: #endif // MOZILLA_AUDIOMIXER_H_