[PD] Pd + jack GUI redraw (CCRMA FC4)

[Miller Puckette]

Well, don't upgrade your kernel unless you want to do it anyway... I
think this is Pd and Jack misunderstanding each other.

Whenever it can, Pd delays graphics updates until it gets caught up with
all "real-time" operations, which are clocked off the audio system.  Pd
knows it's caught up when the audio system reports that its output
buffer is full (and its input buffer empty).  For some reason, Pd never
seems to notice when Jack is happy - I don't know enough about Jack
that I could guess why.

The reason flashing buttons "fix" the problem is that that particular
graphic update isn't queue-able, and since graphics updates cannot be
done out of order, this forces a flush of all graphics updates, whether
this would cause a click or not.  Of course, eventually I hope to have
all the graphics queue-able, which would mean the flashing button would
no longer help you.  But don't hold your breath.

Meanwhile, I'll stick it on my list to try to figure out why Pd never
believes it's idle when talking to Jack...  I never use jack myself so
would never have been aware of this if you hadn't written!

cheers
Miller



On Fri, Aug 11, 2006 at 08:51:10PM -0500, Michael Berkowski wrote:
> Hi all,
> 
> It's taken me a bit to narrow this down, and I haven't seen much in the 
> archive related to this specifically, but I wondered if someone could 
> shed some light on this GUI weirdness.
> 
> While running Pd with Jack, the GUI redraw when using the mouse is 
> highly erratic.  Typically, it will start out fine and I can move a 
> slider or numberbox smoothly, but if I hold onto it for more than a few 
> seconds, the redraw will start to pause and hang behind by increasing 
> intervals.  Meanwhile, there aren't any audio dropouts or xruns, just 
> the slow GUI.  No CPU spikes, either.
> 
> I have found that if I constantly run a metro and a flashing button, the 
> problem goes away since the GUI is forced to redraw at least as often as 
> the metro beats, but I'd like to avoid doing this.
> 
> I initially noticed this problem with the planetCCRMA pd and jack rpms 
> (which are older versions, I think).  But I have since recompiled Pd, 
> Jack, and tcl/tk from source and the problem persists.
> 
> I'm using:
> 2.6.16-1.2080.13.rdt.rhfc4.ccrmasmp (FC4
> jackd -R -d alsa -dhw:0 -r44100 -p2048 -n2  (doesn't seem to matter what 
> jack params are used, RT or not)
> pd 0.39-2 compiled with alsa and jack support.
> 
> I'd be thankful if anyone has an ideas before I try upgrading the kernel 
> as a last resort.
> 
> Best,
> Michael Berkowski
> 
> 
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