Re: latency timer

["Robert Brückmann" <robert.brueckmann@stud.tu-ilmenau.de>]

> look, i've been recording huge chunks of data from a hammerfall for a
> couple of years, and my code is all out there for people to look
> at. i've even written JACK (with some help) to simplify the issue of
> writing such applications. no, i wouldn't do what you're doing. i
> wouldn't use the read/write API, for a start.
>
> i have never used the ALSA "multi" PCM devices, so i can't comment on
> how well they will work either. its possible that they add some
> additional performance penalty that affects you.

So what do think I should use instead? I need all 48 channels in perfect
sync (sample-accurate). Do you think that's impossible? The CPU-load of my
application is (with signal processing) less than 30%, but still there are
xruns sometimes. It might be that the pci bus can't handle my data.

>
> i've never recorded more than 26 channels, but i've done that *to
> disk* using less than 30% of the available CPU with no xruns in sight
> at the lowest period size. i also regularly run jackd in
> all-input-monitor mode, copying data for all 26 channels, and that
> doesn't consume more than 10-15% of the available CPU. this is on a
> dual PII-450.
>

If I run my program with only one hammerfall, then the CPU load is less than
10%, no xruns at all. Maybe the problem is not the 48 channels but the
syncing of the two hammerfalls.

> there is absolutely no reason to be messing around with the PCI bus
> settings to do multitrack recording.
>

But if the pci-bus is overloaded with the data it has to handle? It's a fact
that it worked only since I increased the pci-latency timer in the BIOS. I
am used to have these pci-performance problems with hardware from creamware
(under win98 however, but it was hardware-related), these cards needed a lot
of pci-bandwidth, too.
I wonder if I'm the first one who wants to use two hammerfalls in linux for
recording and playback at the same time.
Anyone?

Robert


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