juce_ResamplingAudioSource.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
class JUCE_API  ResamplingAudioSource  : public AudioSource
{
public:
    //==============================================================================
    ResamplingAudioSource (AudioSource* inputSource,
                           bool deleteInputWhenDeleted,
                           int numChannels = 2);
 
    ~ResamplingAudioSource() override;
 
    void setResamplingRatio (double samplesInPerOutputSample);
 
    double getResamplingRatio() const noexcept                  { return ratio; }
 
    void flushBuffers();
 
    //==============================================================================
    void prepareToPlay (int samplesPerBlockExpected, double sampleRate) override;
    void releaseResources() override;
    void getNextAudioBlock (const AudioSourceChannelInfo&) override;
 
private:
    //==============================================================================
    OptionalScopedPointer<AudioSource> input;
    double ratio = 1.0, lastRatio = 1.0;
    AudioBuffer<float> buffer;
    int bufferPos = 0, sampsInBuffer = 0;
    double subSampleOffset = 0.0;
    double coefficients[6];
    SpinLock ratioLock;
    CriticalSection callbackLock;
    const int numChannels;
    HeapBlock<float*> destBuffers;
    HeapBlock<const float*> srcBuffers;
 
    void setFilterCoefficients (double c1, double c2, double c3, double c4, double c5, double c6);
    void createLowPass (double proportionalRate);
 
    struct FilterState
    {
        double x1, x2, y1, y2;
    };
 
    HeapBlock<FilterState> filterStates;
    void resetFilters();
 
    void applyFilter (float* samples, int num, FilterState& fs);
 
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ResamplingAudioSource)
};
 
} // namespace juce