[PD] [nbuntil]: an non-blocking [until] replacement

[Roman Haefeli]

Hi all

Audio drop-outs happen, when Pd needs more time to do something than is
available (i.e. the configured audio buffer size). The underlying
reasons are manifold, often it is because something requiring lots of
CPU power is processed in zero logical time. For such of those problems,
that can be divided into smaller tasks or those that already are of an
iterative nature, [nbuntil] may provide a solution to avoid audio
drop-outs.

[nbuntil] works similar to the regular [until], but unlike the original,
it breaks Pd's principle of "depth first". It measures how much time
each iteration requires and delays the next iteration by this time. By
employing [nbuntil], many kinds of tasks can be performed without
causing drop-outs, that would otherwise block Pd for a certain amount of
time. 

Example applications include loading presets or dynamic creation of
parts "in the background". Yet, I use it to pre-calculate a set of
tables while audio is running. I could imagine using it to create an
emulation of a threaded [soundfiler], though a proof of concept is yet
lacking and needs to be created. Contrary to Miller's suggestion of
using a [readsf~] in an upsampled subpatch, [nbuntil]'s adaptive
approach uses the maximum available CPU power. 

I'm curios to see whether other people find it useful and even find use
cases I haven't thought of yet. Despite its rather simple design, I
can't remember having seen this approach discussed here on the list. I'd
also be interested if similar or different approaches have been used,
but not yet discussed here.

I'm currently not in the urgent need of a vanilla pseudo-threaded
[soundfiler], but if there is enough interest, I'd be happy to dedicate
some time to it (not totally sure, that it would work, though).

Roman


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