Subject: Re: [linux-audio-dev] Low Latencies. Which hardware to use?
From: Josh Green (jgreen_AT_users.sourceforge.net)
Date: Mon Jun 11 2001 - 23:37:39 EEST
Alexander Ehlert wrote:
>
> So what kind of buffer settings are you using with alsa? Reading the
> source the alsa xg driver seems to allow 64 frames fragment size, but
> trying to set it with buffer_rate_near always gives me a frame size around
> 200. Can't recall the exact amount atm.
> I have a dual machine, too. Are all your soundcards pci btw? My SB AWE
> is ISA, maybe that's the problem? I think I'll get myself the
> new RME card with multiface. Paul: How about writing a driver together?
> At least it seems that this card is already available in germany. Do you
> think RME would actually provide hardware for writing a driver or do
> I still have to purchase it :)
>
> Cheers, Alex
I have an ISA SB AWE 32 and I get pretty good low latency results (Linux
2.4.5 with low latency patch). You mentioned that you didn't have a low
latency patched kernel? I would start be getting your kernel patched :)
When I tested my machine with Benno's latencytest program (wrote about
it in a previous thread) I got < 4ms latency with a patched kernel.
Whereas I got a lot of large spikes with an unpatched kernel, they were
still <12ms though and in the disk read/write tests. I've only tried a
few real time related programs (the UltraMaster software sequencer comes
to mind). Programs need to run at higher scheduling priority for you to
expect good lowlatency performance. Most real time Linux programs have
this option, but must be run as root. Maybe try out the latencytest
program to see the results for your machine
(http://www.gardena.net/benno/linux/audio/). Lates..
Josh Green
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