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juce_ResamplingAudioSource.cpp
/*
==============================================================================
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
{
ResamplingAudioSource::ResamplingAudioSource (AudioSource* const inputSource,
const bool deleteInputWhenDeleted,
const int channels)
: input (inputSource, deleteInputWhenDeleted),
numChannels (channels)
{
jassert (input != nullptr);
zeromem (coefficients, sizeof (coefficients));
}
ResamplingAudioSource::~ResamplingAudioSource() {}
void ResamplingAudioSource::setResamplingRatio (const double samplesInPerOutputSample)
{
jassert (samplesInPerOutputSample > 0);
const SpinLock::ScopedLockType sl (ratioLock);
ratio = jmax (0.0, samplesInPerOutputSample);
}
void ResamplingAudioSource::prepareToPlay (int samplesPerBlockExpected, double sampleRate)
{
const SpinLock::ScopedLockType sl (ratioLock);
auto scaledBlockSize = roundToInt (samplesPerBlockExpected * ratio);
input->prepareToPlay (scaledBlockSize, sampleRate * ratio);
buffer.setSize (numChannels, scaledBlockSize + 32);
filterStates.calloc (numChannels);
srcBuffers.calloc (numChannels);
destBuffers.calloc (numChannels);
createLowPass (ratio);
flushBuffers();
}
void ResamplingAudioSource::flushBuffers()
{
const ScopedLock sl (callbackLock);
buffer.clear();
bufferPos = 0;
sampsInBuffer = 0;
subSampleOffset = 0.0;
resetFilters();
}
void ResamplingAudioSource::releaseResources()
{
input->releaseResources();
buffer.setSize (numChannels, 0);
}
void ResamplingAudioSource::getNextAudioBlock (const AudioSourceChannelInfo& info)
{
const ScopedLock sl (callbackLock);
double localRatio;
{
const SpinLock::ScopedLockType ratioSl (ratioLock);
localRatio = ratio;
}
if (! approximatelyEqual (lastRatio, localRatio))
{
createLowPass (localRatio);
lastRatio = localRatio;
}
const int sampsNeeded = roundToInt (info.numSamples * localRatio) + 3;
int bufferSize = buffer.getNumSamples();
if (bufferSize < sampsNeeded + 8)
{
bufferPos %= bufferSize;
bufferSize = sampsNeeded + 32;
buffer.setSize (buffer.getNumChannels(), bufferSize, true, true);
}
bufferPos %= bufferSize;
int endOfBufferPos = bufferPos + sampsInBuffer;
const int channelsToProcess = jmin (numChannels, info.buffer->getNumChannels());
while (sampsNeeded > sampsInBuffer)
{
endOfBufferPos %= bufferSize;
int numToDo = jmin (sampsNeeded - sampsInBuffer,
bufferSize - endOfBufferPos);
AudioSourceChannelInfo readInfo (&buffer, endOfBufferPos, numToDo);
input->getNextAudioBlock (readInfo);
if (localRatio > 1.0001)
{
// for down-sampling, pre-apply the filter..
for (int i = channelsToProcess; --i >= 0;)
applyFilter (buffer.getWritePointer (i, endOfBufferPos), numToDo, filterStates[i]);
}
sampsInBuffer += numToDo;
endOfBufferPos += numToDo;
}
for (int channel = 0; channel < channelsToProcess; ++channel)
{
destBuffers[channel] = info.buffer->getWritePointer (channel, info.startSample);
srcBuffers[channel] = buffer.getReadPointer (channel);
}
int nextPos = (bufferPos + 1) % bufferSize;
for (int m = info.numSamples; --m >= 0;)
{
jassert (sampsInBuffer > 0 && nextPos != endOfBufferPos);
const float alpha = (float) subSampleOffset;
for (int channel = 0; channel < channelsToProcess; ++channel)
*destBuffers[channel]++ = srcBuffers[channel][bufferPos]
+ alpha * (srcBuffers[channel][nextPos] - srcBuffers[channel][bufferPos]);
subSampleOffset += localRatio;
while (subSampleOffset >= 1.0)
{
if (++bufferPos >= bufferSize)
bufferPos = 0;
--sampsInBuffer;
nextPos = (bufferPos + 1) % bufferSize;
subSampleOffset -= 1.0;
}
}
if (localRatio < 0.9999)
{
// for up-sampling, apply the filter after transposing..
for (int i = channelsToProcess; --i >= 0;)
applyFilter (info.buffer->getWritePointer (i, info.startSample), info.numSamples, filterStates[i]);
}
else if (localRatio <= 1.0001 && info.numSamples > 0)
{
// if the filter's not currently being applied, keep it stoked with the last couple of samples to avoid discontinuities
for (int i = channelsToProcess; --i >= 0;)
{
const float* const endOfBuffer = info.buffer->getReadPointer (i, info.startSample + info.numSamples - 1);
FilterState& fs = filterStates[i];
if (info.numSamples > 1)
{
fs.y2 = fs.x2 = *(endOfBuffer - 1);
}
else
{
fs.y2 = fs.y1;
fs.x2 = fs.x1;
}
fs.y1 = fs.x1 = *endOfBuffer;
}
}
jassert (sampsInBuffer >= 0);
}
void ResamplingAudioSource::createLowPass (const double frequencyRatio)
{
const double proportionalRate = (frequencyRatio > 1.0) ? 0.5 / frequencyRatio
: 0.5 * frequencyRatio;
const double n = 1.0 / std::tan (MathConstants<double>::pi * jmax (0.001, proportionalRate));
const double nSquared = n * n;
const double c1 = 1.0 / (1.0 + MathConstants<double>::sqrt2 * n + nSquared);
setFilterCoefficients (c1,
c1 * 2.0f,
c1,
1.0,
c1 * 2.0 * (1.0 - nSquared),
c1 * (1.0 - MathConstants<double>::sqrt2 * n + nSquared));
}
void ResamplingAudioSource::setFilterCoefficients (double c1, double c2, double c3, double c4, double c5, double c6)
{
const double a = 1.0 / c4;
c1 *= a;
c2 *= a;
c3 *= a;
c5 *= a;
c6 *= a;
coefficients[0] = c1;
coefficients[1] = c2;
coefficients[2] = c3;
coefficients[3] = c4;
coefficients[4] = c5;
coefficients[5] = c6;
}
void ResamplingAudioSource::resetFilters()
{
if (filterStates != nullptr)
filterStates.clear ((size_t) numChannels);
}
void ResamplingAudioSource::applyFilter (float* samples, int num, FilterState& fs)
{
while (--num >= 0)
{
const double in = *samples;
double out = coefficients[0] * in
+ coefficients[1] * fs.x1
+ coefficients[2] * fs.x2
- coefficients[4] * fs.y1
- coefficients[5] * fs.y2;
#if JUCE_INTEL
if (! (out < -1.0e-8 || out > 1.0e-8))
out = 0;
#endif
fs.x2 = fs.x1;
fs.x1 = in;
fs.y2 = fs.y1;
fs.y1 = out;
*samples++ = (float) out;
}
}
} // namespace juce
juce::AudioBuffer::getWritePointer
Type * getWritePointer(int channelNumber) noexcept
Definition juce_AudioSampleBuffer.h:291
juce::AudioBuffer::getNumChannels
int getNumChannels() const noexcept
Definition juce_AudioSampleBuffer.h:236
juce::AudioBuffer::getReadPointer
const Type * getReadPointer(int channelNumber) const noexcept
Definition juce_AudioSampleBuffer.h:253
juce::AudioSource::AudioSource
AudioSource()=default
juce::ResamplingAudioSource::releaseResources
void releaseResources() override
Definition juce_ResamplingAudioSource.cpp:74
juce::ResamplingAudioSource::getNextAudioBlock
void getNextAudioBlock(const AudioSourceChannelInfo &) override
Definition juce_ResamplingAudioSource.cpp:80
juce::ResamplingAudioSource::prepareToPlay
void prepareToPlay(int samplesPerBlockExpected, double sampleRate) override
Definition juce_ResamplingAudioSource.cpp:46
juce::ResamplingAudioSource::flushBuffers
void flushBuffers()
Definition juce_ResamplingAudioSource.cpp:63
juce::ResamplingAudioSource::~ResamplingAudioSource
~ResamplingAudioSource() override
Definition juce_ResamplingAudioSource.cpp:36
juce::ResamplingAudioSource::setResamplingRatio
void setResamplingRatio(double samplesInPerOutputSample)
Definition juce_ResamplingAudioSource.cpp:38
juce::ResamplingAudioSource::ResamplingAudioSource
ResamplingAudioSource(AudioSource *inputSource, bool deleteInputWhenDeleted, int numChannels=2)
Definition juce_ResamplingAudioSource.cpp:26
juce::SpinLock::ScopedLockType
GenericScopedLock< SpinLock > ScopedLockType
Definition juce_SpinLock.h:73
juce::AudioSourceChannelInfo
Definition juce_AudioSource.h:33
juce::AudioSourceChannelInfo::numSamples
int numSamples
Definition juce_AudioSource.h:81
juce::AudioSourceChannelInfo::buffer
AudioBuffer< float > * buffer
Definition juce_AudioSource.h:73
juce::AudioSourceChannelInfo::startSample
int startSample
Definition juce_AudioSource.h:77
juce::MathConstants::sqrt2
static constexpr FloatType sqrt2
Definition juce_MathsFunctions.h:153
juce::MathConstants::pi
static constexpr FloatType pi
Definition juce_MathsFunctions.h:141