Subject: Re: SPDIF and NetBSD 4.0?
To: Giles Lean <>
From: Simon Truss <>
List: netbsd-users
Date: 12/11/2007 21:09:38
Giles Lean wrote:
> Jukka Marin <> wrote:
>> Does NetBSD support digital (SPDIF) audio output with some audio
>> card(s)?
> Yes -- I haven't tested with 4.0, but used a Zoltrix card with the
> cmpci(4) driver on earlier releases. I expect other drivers work too.
> Typical issues:
> o most chips resample 44.1kHz audio to 44kHz (you may or may not care)
> o the sound quality from the Zoltix card (which wasn't resampling) is
>   the worst digital source I've had the mispleasure of listening to,
>   even when fed into a good quality DAC

> If anyone finds a card with an optical SPDIF output that will emit a bit
> perfect stream at 44.1kHz or 48kHz depending on source (and preferably
> at either 16 and 24 bit again depending on source) I want to hear about
> it!

I use a C-Media 8738 (under linux) for about 4years without trouble. I 
hacked the driver to support raw 32bit transfers and did the framing in 
software. My tests showed that with several GB of audio data transferred 
I had no loss of sync. The chips have a PLL so you can adjust the sample 
clock to a reference time source under software control. databooks are 
available online at no cost. These chips should be up to the job.

It is however shocking just how badly some cards can be designed and 
built given how few components boards like this need.