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