>     According to ktrace and such, this is where the error is occurring. 
> Looking at <sys/audioio.h>, I see that the above incoding is "obsolete".
>  What can / should I set the encoding to for this to work?  The program
> seems to output in 16-bit PCM headerless data format, and it sounds like
> that encoding would be right had it not been obsoleted.  Was it replaced
> with something else, or simply removed?  I'd greatly appreciate any
> suggestions.  Thanks in advance.
The encoding you want is AUDIO_ENCODING_SLINEAR, i.e. signed
linear.  The reason AUDIO_ENCODING_LINEAR was obsoleted was that
it didn't say anything about signed/unsigned (and in fact behaved
differently with 8 and 16 bits).
If you compile your kernel with COMPAT_12 it should still
accept AUDIO_ENCODING_LINEAR, though.

        -- Lennart