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AudioCallbackDriver is the only client to benefit from a callback. StartMixing() is now required if reusing the AudioMixer because getting the mixed data after mixing no longer collapses the duration to zero. Differential Revision: https://phabricator.services.mozilla.com/D198221
112 lines
3.6 KiB
C++
112 lines
3.6 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 "AudioSegment.h"
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#include "AudioStream.h"
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#include "nsTArray.h"
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#include "mozilla/NotNull.h"
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#include "mozilla/PodOperations.h"
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namespace mozilla {
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struct MixerCallbackReceiver {
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// MixerCallback MAY modify aMixedBuffer but MUST clear
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// aMixedBuffer->mBuffer if its data is to live longer than the duration of
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// the callback.
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virtual void MixerCallback(AudioChunk* aMixedBuffer,
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uint32_t aSampleRate) = 0;
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};
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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. This class works with
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* planar buffers.
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*
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* When all the tracks have been mixed, calling MixedChunk() will provide
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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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public:
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AudioMixer() { mChunk.mBufferFormat = AUDIO_OUTPUT_FORMAT; }
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~AudioMixer() = default;
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void StartMixing() {
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mChunk.mDuration = 0;
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mSampleRate = 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 MAY modify the chunk but MUST clear
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* mBuffer if its data needs to survive the next call to Mix(). */
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AudioChunk* MixedChunk() {
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MOZ_ASSERT(mSampleRate, "Mix not called for this cycle?");
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mSampleRate = 0;
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return &mChunk;
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};
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/* Add a buffer to the mix. The buffer can be null if there's nothing to mix
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* but the callback is still needed. */
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void Mix(AudioDataValue* aSamples, uint32_t aChannels, uint32_t aFrames,
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uint32_t aSampleRate) {
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if (!mChunk.mDuration) {
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mChunk.mDuration = aFrames;
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MOZ_ASSERT(aChannels > 0);
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mChunk.mChannelData.SetLength(aChannels);
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mSampleRate = aSampleRate;
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EnsureCapacityAndSilence();
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}
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MOZ_ASSERT(aFrames == mChunk.mDuration);
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MOZ_ASSERT(aChannels == mChunk.ChannelCount());
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MOZ_ASSERT(aSampleRate == mSampleRate);
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if (!aSamples) {
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return;
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}
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for (uint32_t i = 0; i < aFrames * aChannels; i++) {
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mChunk.ChannelDataForWrite<AudioDataValue>(0)[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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uint32_t sampleCount = mChunk.mDuration * mChunk.ChannelCount();
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if (!mChunk.mBuffer || sampleCount > mSampleCapacity) {
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CheckedInt<size_t> bufferSize(sizeof(AudioDataValue));
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bufferSize *= sampleCount;
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mChunk.mBuffer = SharedBuffer::Create(bufferSize);
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mSampleCapacity = sampleCount;
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}
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MOZ_ASSERT(!mChunk.mBuffer->IsShared());
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mChunk.mChannelData[0] =
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static_cast<SharedBuffer*>(mChunk.mBuffer.get())->Data();
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for (size_t i = 1; i < mChunk.ChannelCount(); ++i) {
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mChunk.mChannelData[i] =
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mChunk.ChannelData<AudioDataValue>()[0] + i * mChunk.mDuration;
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}
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PodZero(mChunk.ChannelDataForWrite<AudioDataValue>(0), sampleCount);
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}
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/* Buffer containing the mixed audio data. */
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AudioChunk mChunk;
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/* Size allocated for mChunk.mBuffer. */
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uint32_t mSampleCapacity = 0;
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/* Sample rate the of the mixed data. */
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uint32_t mSampleRate = 0;
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};
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} // namespace mozilla
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#endif // MOZILLA_AUDIOMIXER_H_
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