title: iOS smbPitchShift doesn't work
body: <p>so I'm trying to integrate the famous smbPitchShift algorithm into my project, but the input buffer and output buffer are the same. The smbPitchShift algorithm doesn't alter the samples in the buffer.</p>
  
  <p>Here's what I'm doing in post-render callback:</p>
  
  <pre><code>OSStatus MyAURenderCallback (void                        *inRefCon,
                               AudioUnitRenderActionFlags  *ioActionFlags,
                               const AudioTimeStamp        *inTimeStamp,
                               UInt32                      inBusNumber,
                               UInt32                      inNumberFrames,
                               AudioBufferList             *ioData
                               )
  {
      if (*ioActionFlags == kAudioUnitRenderAction_PostRender) {
          NSLog(@"render");
          SBPitchShifter *self = (__bridge SBPitchShifter *)inRefCon;
  
          float *fBuffer = (float *)(malloc(sizeof(float)*inNumberFrames));
  
          int stride = 2;
          vDSP_vflt16((SInt16 *)ioData-&gt;mBuffers[0].mData, stride, (float *)fBuffer, stride, inNumberFrames);
  
          smbPitchShift(2.0, inNumberFrames, inNumberFrames, 4, self.linearPCMASBD.mSampleRate, fBuffer, fBuffer);
  
          vDSP_vfixr16((float *)fBuffer, stride, (SInt16 *)ioData-&gt;mBuffers[0].mData, stride, inNumberFrames);
  
          free(fBuffer);
      }
      return noErr;
  };
  </code></pre>
  
  <p>The sound plays just as normal, as the pitch would be set to 1. Any ideas? :)</p>