Subject: Re: Ensoniq AudioPCI 97
To: Lennart Augustsson <>
From: Nathan J. Williams <nathanw@MIT.EDU>
List: current-users
Date: 09/02/1999 18:29:46
Lennart Augustsson writes:

> > The ac97 codec on my card does not support sample rate conversion.
> >
> > Hmm, maybe somebody with an EE degree can write us a software sample
> > rate converter. ;)
> Do these new codecs only operate for certain sample rates?
> I have some USB speakers that only work at 41.1 kHz, so I've thought
> about writing a device independent sample rate converter.  (I have
> an EE degree, btw.  Not that it helps. :)

	The original spec for the AC97 codec makes them single-rate
devices (44.1? 48? I don't have my spec handy), with a later extension
for a variable-rate mode. All the AC97-based cards I've seen so far
(AudioPCI 97 and ESS Maestro-2) implement a sample rate converter in
the controller chip... I don't even know if there are any AC97
implementations that support the variable-rate mode. 

	- Nathan