Actually, I just remember that I fixed a very similar issue with the
ASIO backend. However, it was a bit more nasty, because Pd would simply
crash if the "Delay" value was too low :-) My solution was too simply
cap the value at the hardware blocksize:
https://github.com/pure-data/pure-data/blob/3ae0388c2ba354e2b5d818c1422b7484c4a491bf/src/s_audio.c#L357
---
The problem with the Jack backend is that it caps at *Pd's* blocksize
(64 samples) - which is often lower than the Jack buffersize.
Consequently, the Jack callback might never have a chance to fill the
ring buffer.
I think the solution is simple:
In /jack_open_audio()/ replace
if (advance_samples < DEFDACBLKSIZE)
advance_samples = DEFDACBLKSIZE;
with
if (advance_samples < jack_blocksize)
advance_samples = jack_blocksize;
@Roman: can you give this a try?
Christof
On 22.03.2022 15:39, Roman Haefeli wrote:
On Tue, 2022-03-22 at 15:23 +0100, IOhannes m zmoelnig wrote:
On 3/22/22 15:06, Roman Haefeli wrote:
On Tue, 2022-03-22 at 14:56 +0100, Christof Ressi wrote:
Anyway, I can open an issue to describe that in my case DSP
only
works with callbacks on.
Yes, please! The Jack backend is supposed to work regardless of
the
"callback" setting.
But not regardless of the "delay (ms)" setting. If it is too low,
Pd
won't process audio. I don't know if there is a way to know
beforehand
what 'too low' is. It isn't necessarily a bug in Pd, I'd say.
it's probably a bug in Pd if the DSP and the GUI both freeze.
Indeed, if the buffer is set too small, then Pd GUI freezes!
From my anecdotal testing, it looks like the critical value is
predictable. As Christof said, the buffer cannot be smaller than JACK's
blocksize.
For instance with JACK @ 256 samples @ 44.1kHz (5.8ms):
- Pd works with 6ms
- Pd freezes with 5ms
I guess the dialog could be designed in a way to set a lower boundary
that is dependent on the detected JACK blocksize. I don't know,
however, if Pd is able to detect the blocksize before DSP is turned on.
Roman
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