[LAU] disappointing experience with firewire

Arnold Krille arnold at arnoldarts.de
Wed Dec 31 11:39:47 EST 2008


On Wednesday 31 December 2008 14:49:42 Susanne Schneider wrote:
> Compared to my Lexicon Omega Studio USB Device the performance of that
> FW assembly (don't want to blame a single device of that chain) just was
> disappointing, already in idlemode without any clients open the
> jackserver showed a workload of roughly 5% (128 frames/3 periods), while
> my Lexicon produces between 0.5 to 1% (128 frames/2 periods).

As Jörn pointed out this is streaming-in-kernel-space vs. streaming-in-
userspace. And probably your fw-device has _lots_ more channels. (USB1 can 
only carry four channels and USB2 has no audio-standard.)

> Opening Ardour and just replaying one of my sessions produced glitches
> where only a strong hiss could be heard. (The session itself caused a
> workload of less than 20%.) - I remember having had those hiss glitches
> in my early days in 2005 with the MAudio Transit USB and Kernel 2.6.11 -
> I never expected them coming back some day... *lol*

Did you try with higher latencies?
As long as you don't need to do software-monitoring, you don't need low-
latency for recording. It actually becomes safer to use higher latencies for 
recording as the hd has more time to store and read the data.

> I then had a look on my interrupts and had to notice the FW Card sharing
> it's interrupt (no 16) with the Nwidia Graficscard - so I might have
> found the culprit - or not? - I don't know... :-(((

Probably that is the reason. If ardour shows flashing VU-meters, your gui will 
update very often and generate lots of interrupts. This is guaranteed to 
interfere with the fw-card.
While it is definitely worth trying to use the free driver (and the only 
possibility to get support from kernel-devs and near-kernel-devs), I don't 
think this will improve your situation. I have the feeling that if you can't 
change the interrupt of either the graphics card or the pcmcia-slot, you are 
out of luck. :-(

What is the exact model of your internal ricoh fw-controller? ("lspci -nn |
grep Fire" or add your line to http://subversion.ffado.org/wiki/HostControllers 

Have fun and a happy new year,

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