gecko/content/media/AudioMixer.h

86 lines
2.6 KiB
C++

/* -*- 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"
namespace mozilla {
typedef void(*MixerFunc)(AudioDataValue* aMixedBuffer,
AudioSampleFormat aFormat,
uint32_t aChannels,
uint32_t aFrames);
/**
* 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.
*
* 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(MixerFunc aCallback)
: mCallback(aCallback),
mFrames(0),
mChannels(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() {
mCallback(mMixedAudio.Elements(),
AudioSampleTypeToFormat<AudioDataValue>::Format,
mChannels,
mFrames);
PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
mChannels = mFrames = 0;
}
/* Add a buffer to the mix. aSamples is interleaved. */
void Mix(AudioDataValue* aSamples, uint32_t aChannels, uint32_t aFrames) {
if (!mFrames && !mChannels) {
mFrames = aFrames;
mChannels = aChannels;
EnsureCapacityAndSilence();
}
MOZ_ASSERT(aFrames == mFrames);
MOZ_ASSERT(aChannels == mChannels);
for (uint32_t i = 0; i < aFrames * aChannels; i++) {
mMixedAudio[i] += aSamples[i];
}
}
private:
void EnsureCapacityAndSilence() {
if (mFrames * mChannels > mMixedAudio.Length()) {
mMixedAudio.SetLength(mFrames* mChannels);
}
PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
}
/* Function that is called when the mixing is done. */
MixerFunc mCallback;
/* Number of frames for this mixing block. */
uint32_t mFrames;
/* Number of channels for this mixing block. */
uint32_t mChannels;
/* Buffer containing the mixed audio data. */
nsTArray<AudioDataValue> mMixedAudio;
};
}
#endif // MOZILLA_AUDIOMIXER_H_