OGG loads as a naked file, but not if embedded in an IFF.

I can now load and play AIFF, WAV, and OGG files using libsndfile and 
libao.  Now I'm moving on to loading and playing files embedded in an IFF 
file.  This is presenting a problem.  Playing an AIFF embedded in an IFF 
works fine.  Playing an OGG embedded in the same IFF fails. 
Specifically, it appears that sf_open_fd() can't figure out what it's 
being told to load.  Except for extra code to tell the player function 
what offset to start at, the player function in the IFF-embedded player 
program is functionally identical to the one in the standalone player 
program.

I have the test code in a Github repo at 
https://github.com/DavidGriffith/blorbsnd.  Would someone please help me 
out?

-- 
David Griffith
[email protected]