source/modules/juce_audio_basics/sources/juce_ResamplingAudioSource.h

   1 /*
   2   ==============================================================================
   3
   4    This file is part of the JUCE library.
   5    Copyright (c) 2022 - Raw Material Software Limited
   6
   7    JUCE is an open source library subject to commercial or open-source
   8    licensing.
   9
  10    The code included in this file is provided under the terms of the ISC license
  11    http://www.isc.org/downloads/software-support-policy/isc-license. Permission
  12    To use, copy, modify, and/or distribute this software for any purpose with or
  13    without fee is hereby granted provided that the above copyright notice and
  14    this permission notice appear in all copies.
  15
  16    JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
  17    EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
  18    DISCLAIMED.
  19
  20   ==============================================================================
  21 */
  22
  23 namespace juce
  24 {
  25
  26 //==============================================================================
  27 /**
  28     A type of AudioSource that takes an input source and changes its sample rate.
  29
  30     @see AudioSource, LagrangeInterpolator, CatmullRomInterpolator
  31
  32     @tags{Audio}
  33 */
  34 class JUCE_API  ResamplingAudioSource  : public AudioSource
  35 {
  36 public:
  37     //==============================================================================
  38     /** Creates a ResamplingAudioSource for a given input source.
  39
  40         @param inputSource              the input source to read from
  41         @param deleteInputWhenDeleted   if true, the input source will be deleted when
  42                                         this object is deleted
  43         @param numChannels              the number of channels to process
  44     */
  45     ResamplingAudioSource (AudioSource* inputSource,
  46                            bool deleteInputWhenDeleted,
  47                            int numChannels = 2);
  48
  49     /** Destructor. */
  50     ~ResamplingAudioSource() override;
  51
  52     /** Changes the resampling ratio.
  53
  54         (This value can be changed at any time, even while the source is running).
  55
  56         @param samplesInPerOutputSample     if set to 1.0, the input is passed through; higher
  57                                             values will speed it up; lower values will slow it
  58                                             down. The ratio must be greater than 0
  59     */
  60     void setResamplingRatio (double samplesInPerOutputSample);
  61
  62     /** Returns the current resampling ratio.
  63
  64         This is the value that was set by setResamplingRatio().
  65     */
  66     double getResamplingRatio() const noexcept                  { return ratio; }
  67
  68     /** Clears any buffers and filters that the resampler is using. */
  69     void flushBuffers();
  70
  71     //==============================================================================
  72     void prepareToPlay (int samplesPerBlockExpected, double sampleRate) override;
  73     void releaseResources() override;
  74     void getNextAudioBlock (const AudioSourceChannelInfo&) override;
  75
  76 private:
  77     //==============================================================================
  78     OptionalScopedPointer<AudioSource> input;
  79     double ratio = 1.0, lastRatio = 1.0;
  80     AudioBuffer<float> buffer;
  81     int bufferPos = 0, sampsInBuffer = 0;
  82     double subSampleOffset = 0.0;
  83     double coefficients[6];
  84     SpinLock ratioLock;
  85     CriticalSection callbackLock;
  86     const int numChannels;
  87     HeapBlock<float*> destBuffers;
  88     HeapBlock<const float*> srcBuffers;
  89
  90     void setFilterCoefficients (double c1, double c2, double c3, double c4, double c5, double c6);
  91     void createLowPass (double proportionalRate);
  92
  93     struct FilterState
  94     {
  95         double x1, x2, y1, y2;
  96     };
  97
  98     HeapBlock<FilterState> filterStates;
  99     void resetFilters();
 100
 101     void applyFilter (float* samples, int num, FilterState& fs);
 102
 103     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ResamplingAudioSource)
 104 };
 105
 106 } // namespace juce