Subject: Re: SPDIF and NetBSD 4.0?
To: Jukka Marin <>
From: Giles Lean <>
List: netbsd-users
Date: 12/11/2007 22:34:34
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

  (I could tolerate it as background when output in the next room &
  could pause it when the phone rang, but in front of the speakers?
  Ugh.  My DVD player made a better digital source, and it's pretty
  bad when used for that purpose.)

What would be really excellent would be if NetBSD's uaudio device were
updated to handle devices with multiple endpoints such as the M-Audio
Transit, which /does/ sound good but can't be used on NetBSD.

The Transit is a very flawed device: it needs a firmware download each
time it's plugged in.  I wrote a firmware loader for NetBSD, but there
is (was?) a limitation in the USB kenel code that the port could not be
reset (needed for the firmware to "take" so I had to kludge it by half
unplugging the unit (to remove the data connections while retaining
power) and then plugging it back in to simulate a reset.

Then the uaudio driver couldn't handle the device anyway, so it was all
moot as I lacked time to attack the uadio driver.

I now use the Transit on OS X, but there I only use the firmware loader
from M-Audio and the OS X audio driver: the audio kernel driver M-Audio
supplies is a cause of crackles, pops, and pauses.  Under Windows XP,
their drivers work well, but I don't have a Windows machine anymore.
(Linux is also supposed to be able to handle the device: I haven't
tried as I have no Linux systems in regular use.)

Other possibilities: Logitech (formerly Slim Devices) Squeezebox: neat
gadget but it's not audiophile material, and can use a NetBSD machine as
a server but isn't controllable from one as far as I know (it has its
own remote).  (Upmarket option: Logitec Transporter, which for USD$2K
ought to do the job and do it well.)

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

Sorry for the length of the rant.  I'm a consumer with an unmet
need^H^H^H^H want.

Good luck,


P.S. If anyone wants to buy a Zoltrix card with optical inputs and
outputs, or an as-new Logitech branded Squeezebox, feel free to talk to
me.  I'm in Melbourne, Australia -- shipping within Oz is reasonable,
overseas, probably not.

P.P.S. If someone with appropriate skills and time wants a M-Audio
Transit to make the uaudio driver work with it, I'll buy you one.  You
don't need to be in Oz for that.  All I'd ask is that if you don't
succeed (or run out of time or whatever) that you be prepared to post
the device on to someone else who wants to try, or failing that, to