MSHFAudioProcessing.m

#import "public/MSHFAudioProcessing.h"

@implementation MSHFAudioProcessing

- (id)initWithBufferSize:(int)bufferSize {
  self = [super init];

  numberOfFrames = bufferSize;
  numberOfFramesOver2 = numberOfFrames / 2;
  fftNormFactor = -1.0 / 256.0;

  outReal = (float *)malloc(sizeof(float) * numberOfFramesOver2);
  outImaginary = (float *)malloc(sizeof(float) * numberOfFramesOver2);
  out = (float *)malloc(sizeof(float) * numberOfFramesOver2);
  output.realp = outReal;
  output.imagp = outImaginary;

  bufferLog2 = round(log2(numberOfFrames));
  fftSetup = vDSP_create_fftsetup(bufferLog2, kFFTRadix2);
  window = (float *)malloc(sizeof(float) * numberOfFrames);

  vDSP_hann_window(window, numberOfFrames, vDSP_HANN_NORM);

  return self;
}

-(void)dealloc {
    free(out);
    free(outReal);
    free(outImaginary);
    free(window);
    
    vDSP_destroy_fftsetup(fftSetup);
}

- (void)process:(float *)data withLength:(int)length {
  if (!self.delegate)
    return;

  if (self.fft && length == numberOfFrames) {
    vDSP_vmul(data, 1, window, 1, data, 1, numberOfFrames);
    vDSP_ctoz((COMPLEX *)data, 2, &output, 1, numberOfFramesOver2);
    vDSP_fft_zrip(fftSetup, &output, 1, bufferLog2, FFT_FORWARD);
    vDSP_zvabs(&output, 1, out, 1, numberOfFramesOver2);
    vDSP_vsmul(out, 1, &fftNormFactor, out, 1, numberOfFramesOver2);
    [self.delegate setSampleData:out length:numberOfFramesOver2 / 8];
  } else {
    [self.delegate setSampleData:data length:length];
  }
}

@end