Wednesday, February 11, 2004

How does the system match up the right decompressor component? Going through the AudioCodec sample code has confused me on a pretty basic point. How does the system know to match up a particular audio stream with a particular codec? The AudioCodec classes have no facility for reading/writing files, nor do I see any "probe" (like in I/OKit) where a codec can test a stream and decide if it matches or not. For a hint, I looked at the OggVorbis QT component source. Even though it is based on the Carbon Sound Manager, there's a LOT of similarity between it and the CoreAudio stuff. Anyway, near as I can tell the only way the system knows that a file should be handed off to the OggVorbis component is via the filename extension (.ogg). If you remove ".ogg" from a filename, you can't play it from QT, import it into QT, preview it from the Finder, or drag-n-drop it into iTunes. That's because the .ogg extension is defined as part of the QT Importer/Exporter interface. Do I really need to write those too just to test? Any hints on how to proceed would be appreciated. 10:20:02 PM    comment []

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