ios - Read encoded frames from audio file with ExtAudioFileSeek and ExtAudioFileRead

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I'm getting audio (PCM) from the microphone using TheAmazingAudioEngine and putting it in a buffer;

Using TPAACAudioConverter I'm reading audio from my buffer and writing to a temp file (AAC);

In the processing thread of TPAACAudioConverter I replaced this:

OSStatus status = ExtAudioFileWrite(destinationFile, numFrames, &fillBufList);
with this:
OSStatus status = ExtAudioFileWrite(destinationFile, numFrames, &fillBufList);
UInt32 framesWritten = numFrames;
totalFramesWritten += framesWritten;
AudioBufferList readData;
readData.mNumberBuffers = 1;
ExtAudioFileSeek(destinationFile, totalFramesWritten - framesWritten);
OSStatus readStatus = ExtAudioFileRead(destinationFile, &numFrames, &readData);
ExtAudioFileSeek(destinationFile, totalFramesWritten);
NSLog(@"Bytes read=%d", numFrames);
but what I get is 0 numFrames read from file.


   
    
     Any idea on what I may be doing wrong or any suggestion on alternative paths to achieve what I need?
    
    
     I don't quite get what are you doing: writing to
     
      destinationFile
     
     , then immediately re-reading what you've just written?
    
    –
    
     user3078414
    
    
     
      Jul 18, 2016 at 12:58
     
    
    
     From what I understand encoding happen on ExtAudioFileWrite so I'm trying to use this write/read loop to get the encoded data. This is one of different way I'm trying to achieve the goal exposed in the first part of the question and also here
     
      stackoverflow.com/questions/38430805/…
     
     .
    
    –
    
     Francesco Papagno
    
    
     
      Jul 19, 2016 at 7:19
     
    
    
     The issue is that whatever ExtAudioFile does under the hood doesn't allow for seeking on a file that is open for writing.  If you look at the documentation for
     
      ExtAudioFileSeek
     
     it says "This function's behavior with files open for writing is currently undefined".
    
    
     You can solve this by using the more extensible (and difficult)
     
      Audio File Services
     
     and the
     
      Audio Converter Services
     
     directly instead of the convenient Extended audio file services.
    
    
     I abandoned this approach and reused the AQRecorder class from the SpeakHere example by Apple.
    
    
     The project is available here
     
      https://github.com/robovm/apple-ios-samples/tree/master/SpeakHere
     
     .
    
    
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