[PD] Pd 0.52-1 - frozen dsp and gui in ubuntu 20.04

Roman Haefeli reduzent at gmail.com
Tue Mar 22 15:00:54 CET 2022


On Tue, 2022-03-22 at 10:45 -0300, Bruno Rohde wrote:
> > Turn OFF (or ON) the "use callbacks" checkbox in the audio dialog.
> 
> That did the trick, with callbacks ON DSP works. I never used it
> before, and to be honest, I don't know what this does, but for now it
> solved the problem.
> Could you (or someone) explain briefly what this is for? Is there any
> impact elsewhere (maybe performance) by using it enabled?

From what I understand, using callbacks means that Pd processes audio
as soon as it is provided by JACK. This means, Pd doesn't add
additional latency as JACK client. But it also means, that when Pd
isn't quick enought with writing back processed data, the whole JACK
process with all clients experiences a drop-out.

Without callbacks, Pd is less tightly coupled to JACK and uses a
ringbuffer for input and output. The size of the ringbuffer is set in
the 'delay(ms)' setting in the audio settings. From my experience,
setting it too low causes Pd to not process audio at all. In my
experience, this value is below 5ms, but this probably depends on
JACK's blocksize setting. 

Roman
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