AudioResampler.cpp

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// Copyright (c) 2008-2019 OpenShot Studios, LLC
//
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#include "AudioResampler.h"
 
using namespace std;
using namespace openshot;
 
// Default constructor, max frames to cache is 20 // resample_source(NULL), buffer_source(NULL), num_of_samples(0), new_num_of_samples(0), dest_ratio(0), source_ratio(0), resampled_buffer(NULL), isPrepared(false)
AudioResampler::AudioResampler(int numChannels)
{
    buffer = NULL;
    resample_source = NULL;
    buffer_source = NULL;
    num_of_samples = 0;
    new_num_of_samples = 0;
    dest_ratio = 0;
    source_ratio = 0;
    resampled_buffer = NULL;
    isPrepared = false;
 
    // Init buffer source
    buffer_source = new AudioBufferSource(buffer);
 
    // Init resampling source
    resample_source = new juce::ResamplingAudioSource(buffer_source, false, numChannels);
 
    // Init resampled buffer
    resampled_buffer = new juce::AudioBuffer<float>(2, 1);
    resampled_buffer->clear();
 
    // Init callback buffer
    resample_callback_buffer.buffer = resampled_buffer;
    resample_callback_buffer.numSamples = 1;
    resample_callback_buffer.startSample = 0;
}
 
// Descructor
AudioResampler::~AudioResampler()
{
    // Clean up
    if (buffer_source)
        delete buffer_source;
    if (resample_source)
        delete resample_source;
    if (resampled_buffer)
        delete resampled_buffer;
}
 
// Sets the audio buffer and updates the key settings
void AudioResampler::SetBuffer(juce::AudioBuffer<float> *new_buffer, double sample_rate, double new_sample_rate)
{
    if (sample_rate <= 0)
        sample_rate = 44100;
    if (new_sample_rate <= 0)
        new_sample_rate = 44100;
 
    // Set the sample ratio (the ratio of sample rate change)
    source_ratio = sample_rate / new_sample_rate;
 
    // Call SetBuffer with ratio
    SetBuffer(new_buffer, source_ratio);
}
 
// Sets the audio buffer and key settings
void AudioResampler::SetBuffer(juce::AudioBuffer<float> *new_buffer, double ratio)
{
    // Update buffer & buffer source
    buffer = new_buffer;
    buffer_source->setBuffer(buffer);
 
    // Set the sample ratio (the ratio of sample rate change)
    source_ratio = ratio;
    dest_ratio = 1.0 / ratio;
    num_of_samples = buffer->getNumSamples();
    new_num_of_samples = round(num_of_samples * dest_ratio);
 
    // Set resample ratio
    resample_source->setResamplingRatio(source_ratio);
 
    // Prepare to play resample source
    if (!isPrepared)
    {
        // Prepare to play the audio sources (and set the # of samples per chunk to a little more than expected)
        resample_source->prepareToPlay(num_of_samples + 10, 0);
        isPrepared = true;
    }
 
    // Resize buffer for the newly resampled data
    resampled_buffer->setSize(buffer->getNumChannels(), new_num_of_samples, true, true, true);
    resample_callback_buffer.numSamples = new_num_of_samples;
    resample_callback_buffer.startSample = 0;
    resample_callback_buffer.clearActiveBufferRegion();
}
 
// Get the resampled audio buffer
juce::AudioBuffer<float>* AudioResampler::GetResampledBuffer()
{
    // Resample the current frame's audio buffer (into the temp callback buffer)
    resample_source->getNextAudioBlock(resample_callback_buffer);
 
    // Return buffer pointer to this newly resampled buffer
    return resampled_buffer;
}