[PD] glitches when streaming UDP

[Roman Haefeli]

Hey all

I'm working on a patch that transmits audio through UDP. The patch runs
totally smooth on macOS (10.10 and 10.11) with Pd 0.48-1 and JACK as
back-end. On the Linux machines I tested (all Ubuntu 16.04) with the
same version of Pd I get a lot of glitches, although I'm using very
similar Jack settings (128 frames/period, 3 periods). Glitches happen
more frequently when UDP streaming is on, but don't completely
disappear when I stop UDP transmission. So, relatively to macOS, Pd
seems to be more prone to glitches on Linux. 

Just to be sure that my Linux machine is up to task I tuned it with the
help of [1]. I get very stable performance with softwares like Ardour,
even under load. It's only Pd that creates glitches. I also observed
that Pd experiences drop outs while jack reports not glitches. I
believe to have observed that ardour only glitches when jack does. So,
it seems Pd is less "tightly coupled" to jack, does that sound right? 

Is there anything I can do to tune Pd for stable low latency (on
Linux)? 

BTW: What happened to those messages when running with -rt:

"priority 6 scheduling enabled.
priority 8 scheduling enabled."

Roman


[1] https://github.com/raboof/realtimeconfigquickscan

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