title: calling objective c method from callback
body: <p>first of all I am newbie! 
  I am trying to get audio data from microphone and apply filter. the filter I found is an objective c methods based NVDSP filter. the filter method and the callback function coming from microphone is down below. But I dont know how to connect the dots. how can I call objective c method which is FilterData from the performRender callback? </p>
  
  <pre><code>static OSStatus performRender (void                     *inRefCon,
                             AudioUnitRenderActionFlags   *ioActionFlags,
                             const AudioTimeStamp         *inTimeStamp,
                             UInt32                       inBusNumber,
                             UInt32                       inNumberFrames,
                             AudioBufferList              *ioData)
  {
      UInt32 bus1 = 1;
      CheckError(AudioUnitRender(effectState.rioUnit,
                             ioActionFlags,
                             inTimeStamp,
                             bus1,
                             inNumberFrames,
                             ioData), "Couldn't render from RemoteIO unit");
  
  
  //how can I call the method here to apply filter on ioData-&gt;mBuffers[0].mData ? 
  //is this logical ? what should I do for best performance?
  
  
      return noErr;
  }
  
  
  
  @implementation ViewController
  
  ...
  ...
  -(float *) FilterData_rawSamples:(float *)samples
  {
      // setup Highpass filter
      NVHighpassFilter *HPF;
      HPF = [[NVHighpassFilter alloc] initWithSamplingRate:samplingRate];
  
      HPF.cornerFrequency = 17500.0f;
      HPF.Q = 0.5f;
  
      [HPF filterData:samples numFrames:(UInt32)theFileLengthInFrames numChannels:1];
      return samples;
  }
  ...
  ...
  
  @end
  </code></pre>
  
  <p>thanksin advance</p>