filmstro_audiohelpers_OutputSourcePlayer.h

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/*
 ==============================================================================
 Copyright (c) 2017, Filmstro Ltd. - Daniel Walz
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 ==============================================================================
 \class        OutputSourcePlayer
 \file         filmstro_audiobasics_OutputSourcePlayer.h
 \brief        An AudioSourcePlayer which handles changes of the sample rate

 \author       Daniel Walz / Filmstro Ltd.
 \date         December 19th 2016

 \description  An AudioSourcePlayer which handles changes of the sample rate

 ==============================================================================
 */


#ifndef filmstro_audiobasics_OutputSourcePlayer_h
#define filmstro_audiobasics_OutputSourcePlayer_h

class OutputSourcePlayer : public juce::AudioSourcePlayer
{
public:
    OutputSourcePlayer (double sampleRate, int channels=2)
    : internalSampleRate (sampleRate),
    deviceSampleRate (0.0),
    numChannels (channels),
    outputDevice (nullptr)
    {

    }

    void setSource (juce::AudioSource* newSource)
    {
        const juce::ScopedLock sl (readLock);
        juce::AudioSourcePlayer::setSource (newSource);
    }

    void audioDeviceIOCallback (const float **inputChannelData, int totalNumInputChannels,
                                float **outputChannelData, int totalNumOutputChannels,
                                int numSamples) override
    {
        if (getCurrentSource()) {
            const juce::ScopedLock sl (readLock);

            if (outputDevice != nullptr) {
                if (fabs (deviceSampleRate - outputDevice->getCurrentSampleRate ()) > 1.0) {
                    deviceSampleRate = outputDevice->getCurrentSampleRate();
                    resampler->setResamplingRatio (deviceSampleRate != 0 ?
                                                   internalSampleRate / deviceSampleRate :
                                                   1.0);
                    resampler->flushBuffers ();
                }
            }
            juce::AudioBuffer<float> buffer (outputChannelData,
                                             totalNumOutputChannels,
                                             numSamples);
            juce::AudioSourceChannelInfo bufferToFill (&buffer, 0, numSamples);
            resampler->getNextAudioBlock (bufferToFill);
        }
        else {
            juce::AudioSourcePlayer::audioDeviceIOCallback (inputChannelData,
                                                            totalNumInputChannels,
                                                            outputChannelData,
                                                            totalNumOutputChannels,
                                                            numSamples);
        }
    }

    void audioDeviceAboutToStart (juce::AudioIODevice *device) override
    {
        outputDevice = device;
        resampler = new juce::ResamplingAudioSource (getCurrentSource(), false);
        resampler->prepareToPlay (device->getCurrentBufferSizeSamples(),
                                  device->getCurrentSampleRate());
        juce::AudioSourcePlayer::audioDeviceAboutToStart (device);
    }

    void audioDeviceStopped () override
    {
        juce::AudioSourcePlayer::audioDeviceStopped();
        resampler = nullptr;
        outputDevice = nullptr;
    }



private:
    double  internalSampleRate;

    double  deviceSampleRate;

    int     numChannels;

    juce::AudioIODevice*    outputDevice;

    juce::ScopedPointer<juce::ResamplingAudioSource> resampler;

    juce::CriticalSection readLock;
};


#endif /* filmstro_audiobasics_OutputSourcePlayer_h */