1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/AudioMixer.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,95 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this file,
1.7 + * You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef MOZILLA_AUDIOMIXER_H_
1.10 +#define MOZILLA_AUDIOMIXER_H_
1.11 +
1.12 +#include "AudioSampleFormat.h"
1.13 +#include "nsTArray.h"
1.14 +#include "mozilla/PodOperations.h"
1.15 +
1.16 +namespace mozilla {
1.17 +typedef void(*MixerFunc)(AudioDataValue* aMixedBuffer,
1.18 + AudioSampleFormat aFormat,
1.19 + uint32_t aChannels,
1.20 + uint32_t aFrames,
1.21 + uint32_t aSampleRate);
1.22 +
1.23 +/**
1.24 + * This class mixes multiple streams of audio together to output a single audio
1.25 + * stream.
1.26 + *
1.27 + * AudioMixer::Mix is to be called repeatedly with buffers that have the same
1.28 + * length, sample rate, sample format and channel count.
1.29 + *
1.30 + * When all the tracks have been mixed, calling FinishMixing will call back with
1.31 + * a buffer containing the mixed audio data.
1.32 + *
1.33 + * This class is not thread safe.
1.34 + */
1.35 +class AudioMixer
1.36 +{
1.37 +public:
1.38 + AudioMixer(MixerFunc aCallback)
1.39 + : mCallback(aCallback),
1.40 + mFrames(0),
1.41 + mChannels(0),
1.42 + mSampleRate(0)
1.43 + { }
1.44 +
1.45 + /* Get the data from the mixer. This is supposed to be called when all the
1.46 + * tracks have been mixed in. The caller should not hold onto the data. */
1.47 + void FinishMixing() {
1.48 + mCallback(mMixedAudio.Elements(),
1.49 + AudioSampleTypeToFormat<AudioDataValue>::Format,
1.50 + mChannels,
1.51 + mFrames,
1.52 + mSampleRate);
1.53 + PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
1.54 + mSampleRate = mChannels = mFrames = 0;
1.55 + }
1.56 +
1.57 + /* Add a buffer to the mix. aSamples is interleaved. */
1.58 + void Mix(AudioDataValue* aSamples,
1.59 + uint32_t aChannels,
1.60 + uint32_t aFrames,
1.61 + uint32_t aSampleRate) {
1.62 + if (!mFrames && !mChannels) {
1.63 + mFrames = aFrames;
1.64 + mChannels = aChannels;
1.65 + mSampleRate = aSampleRate;
1.66 + EnsureCapacityAndSilence();
1.67 + }
1.68 +
1.69 + MOZ_ASSERT(aFrames == mFrames);
1.70 + MOZ_ASSERT(aChannels == mChannels);
1.71 + MOZ_ASSERT(aSampleRate == mSampleRate);
1.72 +
1.73 + for (uint32_t i = 0; i < aFrames * aChannels; i++) {
1.74 + mMixedAudio[i] += aSamples[i];
1.75 + }
1.76 + }
1.77 +private:
1.78 + void EnsureCapacityAndSilence() {
1.79 + if (mFrames * mChannels > mMixedAudio.Length()) {
1.80 + mMixedAudio.SetLength(mFrames* mChannels);
1.81 + }
1.82 + PodZero(mMixedAudio.Elements(), mMixedAudio.Length());
1.83 + }
1.84 +
1.85 + /* Function that is called when the mixing is done. */
1.86 + MixerFunc mCallback;
1.87 + /* Number of frames for this mixing block. */
1.88 + uint32_t mFrames;
1.89 + /* Number of channels for this mixing block. */
1.90 + uint32_t mChannels;
1.91 + /* Sample rate the of the mixed data. */
1.92 + uint32_t mSampleRate;
1.93 + /* Buffer containing the mixed audio data. */
1.94 + nsTArray<AudioDataValue> mMixedAudio;
1.95 +};
1.96 +}
1.97 +
1.98 +#endif // MOZILLA_AUDIOMIXER_H_
