title: Generate AVAudioPCMBuffer with AVAudioRecorder
body: <p>Along with iOS 10, apple released a new framework which recognizes speech. Data can be passed to this framework either by appending AVAudioPCMBuffers or giving a URL to a m4a. Currently, speech recognition works using the former but this is only possible after somebody has finished and is not in real time. Here is the code for that:</p>
  
  <pre><code>let audioSession = AVAudioSession.sharedInstance()
  var audioRecorder:AVAudioRecorder!;
  var soundURLGlobal:URL!;
  
  function setUp(){
      let recordSettings = [AVSampleRateKey : NSNumber(value: Float(44100.0)),
                            AVFormatIDKey : NSNumber(value: Int32(kAudioFormatMPEG4AAC)),
                            AVNumberOfChannelsKey : NSNumber(value: 1),
                            AVEncoderAudioQualityKey : NSNumber(value: Int32(AVAudioQuality.medium.rawValue))]
  
      let fileManager = FileManager.default()
      let urls = fileManager.urlsForDirectory(.documentDirectory, inDomains: .userDomainMask)
      let documentDirectory = urls[0] as NSURL
      let soundURL = documentDirectory.appendingPathComponent("sound.m4a")
      soundURLGlobal=soundURL;
  
  
      do {
          try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord)
          try audioRecorder = AVAudioRecorder(url: soundURL!, settings: recordSettings)
          audioRecorder.prepareToRecord()
      } catch {}
  }
  
  function start(){
      do {
          try audioSession.setActive(true)
          audioRecorder.record()
      } catch {}
  }
  
  function stop(){
      audioRecorder.stop()
      let request=SFSpeechURLRecognitionRequest(url: soundURLGlobal!)
      let recognizer=SFSpeechRecognizer();
      recognizer?.recognitionTask(with: request, resultHandler: { (result, error) in
          if(result!.isFinal){
              print(result?.bestTranscription.formattedString)
          }
      })
  
  }
  </code></pre>
  
  <p>I am trying to convert this but I cannot find where to get a AVAudioPCMBuffer. </p>
  
  <p>Thanks,</p>