[PlanetCCRMA] Realtime PD Troubles

derek holzer derek@x-i.net
Wed Jan 14 02:30:03 2004


J. Scott Amort wrote:

> One question, though - are the -rt and
> -jack flags at best, redundant, or at worst (as Fernando mentioned)
> conflicting?  Doesn't plugging pd into jack guarantee real-time
> scheduling through jack making the -rt unnecessary?  

No, this really isn't the case. I run -rt and -jack both as sudo. 
Although I can't exactly tell you how, PD and Jack deal with realtime in 
different ways. You can see, for example, that PD gets DIO errors 
without an xrun, and that Jack can have xruns without PD loosing sync.

Somthing to think about is that PD's DSP is very tied up in its 
graphical processes as well. They can argue about this till the cows 
come home on the PD list, but at the bottom of it, PD is much more 
likely to get DSP errors from things occuring on the screen than many 
apps. Ardour, for example, never freaks out when I move windows or 
whatnot. But PD can and does. The -rt flag seems to reduce this greatly.

Last point is that PD, unlke Jack, cannot give realtime priviledge via 
capabilities. The -rt flag must be run as sudo or root, AFAIK.

You might post to the PD list if problems continue and one of the gurus 
there can help you more.


derek holzer ::: http://www.umatic.nl
---Oblique Strategy # 42:
-the most important thing"