[PD] glitches when streaming UDP

[Lorenzo Sutton]

On 30/01/2018 11:07, Roman Haefeli wrote:
> On Mon, 2018-01-29 at 10:25 +0100, Roman Haefeli wrote:
> 
>> 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).
> 
> Update:
> My personal, somewhat outdated laptop from 2007 has absolutely stable
> performance with same patch, same Pd version, same OS, same kernel. To
> be clear: It's only Pd that performs well on one computer and not so
> well on others. I get glitch-free audio with Ardour on all tested
> computers. So I wonder what circumstances affect specifically Pd. It's
> a pity the most powerful computer I have access to is in its current
> state not suitable for Pd projects :-(

One thing to try from totally non-scientific personal experience would 
be to look into CPU scaling stuff when using Pd. The fact that an old 
machine works well possibly hints that this might be the culprit, so 
worth trying. I experimented with this when pushing my Granita 
granulator with realtime input being fed to the buffer and trying to 
eliminate as much as possilbe "smart" CPU stuff improved things quite a 
lot... On my previous laptop I could set various governors on my current 
one there is only powersave and performance, the latter should work, but 
also trying to set a fixed frequency... You have to experiment a bit.

Kernel documentation:
https://www.kernel.org/doc/html/v4.14/admin-guide/pm/cpufreq.html

Arch-specific but possibly some interesting general information:
https://wiki.archlinux.org/index.php/CPU_frequency_scaling

Also for Debian (and possibly Ubuntu):
https://wiki.debian.org/HowTo/CpuFrequencyScaling

Red Hat:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/power_management_guide/cpufreq_governors

My two cents.
Lorenzo