render.cpp

inline juce::String renderFile(juce::File inputFile, juce::File outputFile)
{
    if (!outputFile.hasFileExtension(("wav")))
        return "output file must be .wav";
    juce::AudioFormatManager fman;
    fman.registerBasicFormats();
    auto reader = std::unique_ptr<juce::AudioFormatReader>(fman.createReaderFor(inputFile));
    if (reader == nullptr)
        return "could not create input file reader";
    juce::WavAudioFormat wavformat;
    if (outputFile.existsAsFile())
        outputFile.deleteFile();
    auto ostream = outputFile.createOutputStream();
    // writer is for .wav, 32 bit float samples and the same channel count and sample rate as the
    // input file
    auto writer = std::unique_ptr<juce::AudioFormatWriter>(wavformat.createWriterFor(
        ostream.release(), reader->sampleRate, reader->numChannels, 32, {}, 0));
    if (!writer)
        return "could not create output file writer";
    uint32_t processingBufferSize = 4096;

    juce::dsp::Chorus<float> chorus;
    juce::dsp::ProcessSpec spec{reader->sampleRate, processingBufferSize, reader->numChannels};
    chorus.prepare(spec);

    juce::AudioBuffer<float> processingBuffer(reader->numChannels, processingBufferSize);
    processingBuffer.clear();
    auto outsampleCounter = 0;
    while (outsampleCounter < reader->lengthInSamples)
    {
        // process exact number of samples
        int samplesToProcess =
            std::min<int64_t>(processingBufferSize, reader->lengthInSamples - outsampleCounter);
        processingBuffer.setSize(processingBuffer.getNumChannels(), samplesToProcess, false, true,
                                 true);
        reader->read(&processingBuffer, 0, samplesToProcess, outsampleCounter, true, true);

        // do our actual processing of the buffer
        juce::dsp::AudioBlock<float> block(processingBuffer);
        juce::dsp::ProcessContextReplacing<float> ctx(block);
        chorus.process(ctx);

        // write to output file
        writer->writeFromAudioSampleBuffer(processingBuffer, 0, samplesToProcess);

        outsampleCounter += processingBufferSize;
    }
    return "rendered ok";
}