genadee / ataudioprocessinglibrary Goto Github PK

// The code is looking complex, but calculation done per vectorized block, 
// so it's quite outperformer the sample-by-sample approach.

// ParabolicWM oscillator;
// oscillator.init(sampleRate, channelCount, calculationBlockSize, oversamplingFactor);

void process(AUAudioFrameCount frameCount, AUAudioFrameCount bufferOffset) override {
    AudioBuffer *out = outBufferListPtr->mBuffers;
    
    for (int frameOffset = 0; frameOffset < frameCount; frameOffset+=calculationBlockSize) {
        // to improve performance per block calculation is used
        
        //
        // Fill the rest of the output from the previous iteration
        // (in the case of variable framerate)
        //
        
        if (frameCount - frameOffset < preGenWriteIndex) {
            preGenWriteIndex = frameCount - frameOffset;
        }
        
        if (preGenWriteIndex != 0) {
            for (int channel = 0; channel < numberOfChannels; ++channel) {
                sample_t *outChannel = (sample_t *)out[channel].mData;
                memcpy(outChannel+frameOffset, &oscillator.output[channel][postGenWriteIndex],
                       preGenWriteIndex*sizeof(sample_t));
            }
        }
        
        if (preGenWriteIndex + frameOffset == frameCount) {
            postGenWriteIndex += preGenWriteIndex;
            break;
        }

        //
        // calculate the block
        // here should be your DSP
        //
        oscillator.calculateBlock(440, 0.5, 1);
        
        //
        // copy the output
        //
        if (frameCount - frameOffset < calculationBlockSize) {
            postGenWriteIndex = frameCount - frameOffset - preGenWriteIndex;
        }

        for (int channel = 0; channel < numberOfChannels; ++channel) {
            sample_t *outChannel = (sample_t *)out[channel].mData;
            memcpy(outChannel+frameOffset+preGenWriteIndex, &oscillator.output[channel][0],
                postGenWriteIndex*sizeof(sample_t));
        }
    }
    
    preGenWriteIndex = calculationBlockSize - postGenWriteIndex;
}