Re: [linux-audio-user] Advice needed re: latency tuning/optimization, esp. video

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Subject: Re: [linux-audio-user] Advice needed re: latency tuning/optimization, esp. video
From: Chris Metzler (cmetzler_AT_speakeasy.net)
Date: Thu Feb 19 2004 - 08:09:50 EET


OK, I can finally come back to this now.

On Tue, 17 Feb 2004 11:49:08 +0100 (MET)
Clemens Ladisch <clemens_AT_ladisch.de> wrote:
> Chris Metzler wrote:
> > Hi. I'm looking for some advice on how to deal with latency
> > introduced by graphics activity.
> > [...] So it seems that while my latency numbers are generally
> > good, video stuff can cause significant problems. This matches my
> > experience, which is that I see significant xruns in JACK (50-70ms)
> > if I minimize or open a window, or move a window, etc.
>
> Try disabling acceleration (put a line
> Option "NoAccel"
> into your driver section in XF86Config). If this helps, you can blame
> the XFree86 driver.

Bingo. It helped my latency numbers *tremendously*. Every rep during
the X11 stress tests came down to less than 1ms above the fragment
latency -- everything. Unfortunately, it also made the desktop itself
a real pain in the butt to use. I can't imagine tweaking controls in
e.g. Ardour, attempting to find a set of parameters I like for something,
given how sluggish the desktop was.

So what are my options here? It's my understanding that the driver
available from Matrox directly is the same as that for XFree86, just
with some additional support for Matrox software ("PowerDesk"); so
dumping XF86's driver in favor of one from the card maker isn't likely
to pay off. Track down another video card? Ironic given that in that
other OS, this is a highly recommended card for DAWs, and that the
reason I got it was that the mfr was considered the most friendly
to open source.

-c

P.S. CC'ing you because it took me so long to respond; hope that's
OK.

-- 
Chris Metzler			cmetzler_AT_speakeasy.snip-me.net
		(remove "snip-me." to email)

"As a child I understood how to give; I have forgotten this grace since I have become civilized." - Chief Luther Standing Bear



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