[Ardour-Users] jack sample rate

[John Rigg]

On Tue, Apr 22, 2008 at 07:24:48PM +0800, Ray Rashif wrote:
> Solved: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=377915
> 
> >From the looks of it, we can summarise this behaviour as per the following:
> 
> 1) Hardware limitation; most onboard chipsets have a 48KHz-only codec.
> 
> "Takashi Iwai suggested:
> 
> Check your /proc/asound/card0/codec97#0/ac97#0-0 file, whether it
> contains "VRA" in Extended ID section. If not, it's 48k-only codec."

This doesn't apply to the Delta 1010(LT) cards.
They will run at any of the common sample rates.

> 
> Your path _will_ be different, just navigate to /proc/asound/card0 and
> you'll know. For most of you it'd be "cat /proc/asound/card0/codec#0" and no
> "Extended ID section" - just "rates".
> 
> -- OR --
> 
> 2) ALSA limitation; use a different driver like OSS and/or disable RT (as
> suggested by someone else, doesn't work for me).

I'm not even sure if there is a free OSS driver for the Delta 1010.
There is one in the commercial version of OSS, but it is
more limited than the ALSA driver (eg. it couldn't sync to word clock
input last time I checked). I've been using two or three Delta 1010s
with ardour/jackd/alsa for over two years with very few problems.

> Apparently the OSS back-end does resampling. I'm taken aback as to why ALSA
> is inferior in this case - or maybe it is for the best that the users in
> concern don't use anything besides 48000Hz.
>
ALSA should definitely _not_ be doing resampling with pro/semi-pro
hardware like this. It would destroy performance.

John

> "According to Takashi, because the OSS backend resamples by default. This
> is the most appropriate behaviour for consumer-type sound applications.
> For example, if your browser plays a Flash animation with a 22kHz
> soundtrack directly to a 48kHz interface, the sound is raised in pitch
> accordingly."