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Multiple ExtAudioFileRefs pointing to the same file
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Multiple ExtAudioFileRefs pointing to the same file


  • Subject: Multiple ExtAudioFileRefs pointing to the same file
  • From: Christopher Liscio <email@hidden>
  • Date: Tue, 10 Mar 2009 17:10:01 -0400

I am working with a desktop application on Mac OS X 10.5(.6) that creates two ExtAudioFileRef instances, in two separate threads. Both of the instances point to the same file on disk. The main thread's instance is used for audio playback, and the auxiliary thread reads the file in its entirety for drawing purposes.

Everything seems to behave OK, except for my call to ExtAudioFileGetProperty( ... kExtAudioFileProperty_FileLengthFrames ... ). In the main thread, this function always returns the correct value of ~8 million frames for a particular file. Sometimes, in the second thread, kExtAudioFileProperty_FileLengthFrames comes back as ~150 million for the same file.

When the second thread is done reading the file, it correctly stops after only ~8 million frames. So, the issue appears to be localized to reading the FileLengthFrames property.

This error is not easily reproducible, either. It only happens when reading M4A files, and only about 10% of the time. It doesn't appear to be specific to any one file, either.

Is it fair to say that >1 ExtAudioFileRef pointing to the same file on disk is not supported, and should be considered unsafe? Or, is this a bug in ExtAudioFile that I should file?

Thanks in advance,

Chris Liscio
http://SuperMegaUltraGroovy.com
Acoustic measurement software for Mac OS X -- http://www.FuzzMeasure.com
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