Quickies for Audio

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General

• Error code -12780 [permalink]
  Sometimes you get error code -12780, and it's completely undocumented ( rdar://20194243 - please document this stupid code plzkthx).

  Thanks to Dave DeLong: It’s a CoreMedia error: “Returned when caller passes incorrect input or output parameters”

  So it's a paramErr, but for CoreMedia. Something, somewhere, internally went amiss, and it's interpreting an argument as invalid.

  Here are situations I've either encountered or seen on the net:

  • Passing a nil AVAsset due to a MPMediaItem not being local. Workaround is to download from the cloud. No way to force a download
  • Your audio session category is incorrect for whatever it is you're doing
  • You may need to convert a path based on NSSearchPathForDirectoriesInDomains explicitly to a file URL
  • Consecutive calls to startRecordingToOutputFileURL.
  • Recording video with device orientation of UIDeviceOrientationFaceUp, UIDeviceOrientationFaceDown, or UIDeviceOrientationUnknown.
  • Trying to play Protected music (even though the AVAsset returns NO from hasProtectedContent. Sigh).
  • Got any more? let me know.

• Getting the duration of an audio file [permalink]
  

  #import <AudioToolbox/AudioToolbox.h>
  ...
  - (NSTimeInterval) voiceCueLength {
      NSTimeInterval length = 0.0;
      NSURL *audioURL = [NSURL fileURLWithPath: self.pathToVoiceCue];
  
      OSStatus result = noErr;
  
      AudioFileID audioFile = NULL;
      result = AudioFileOpenURL ((CFURLRef)audioURL,
                                 kAudioFileReadPermission,
                                 0, // hint
                                 &audioFile);
      if (result != noErr) goto bailout;
  
      //Get file length
      NSTimeInterval seconds;
      UInt32 propertySize = sizeof (seconds);
      result = AudioFileGetProperty (audioFile,
                                     kAudioFilePropertyEstimatedDuration,
                                     &propertySize,
                                     &seconds);
      if (result != noErr) goto bailout;
  
      length = seconds;
  
    bailout:
      if (audioFile) AudioFileClose (audioFile);
      return length;
  } // voiceCueLength
  

  And Link with the AudioToolbox framework.

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