Hi,
the subprocess managed by the [pd~] object is "driven" by the parent
process (= the main Pd process). If the subprocess blocks, so does the
parent process! However, one thing you can do is increase the FIFO size
(-fifo) to give the subprocess more "leeway".
Are you doing the FFT on the whole audio file at once? If you are doing
large computations that interrupt audio processing, one key technique is
to spread the computation over multiple scheduler ticks.
Christof
On 23.03.2025 21:27, Pier Bar wrote:
Hello Pd community,
I've encountered an interesting behavior regarding CPU management in
Pure Data using [pd~], and I'd appreciate your insights or confirmations.
Here's my scenario:
I'm running a computationally "intensive" FFT analysis with sigmund~
(similar to the 17.partialtracer example, but without using data
structures), on a 4-second audio array. This analysis is causing
"Audio I/O Error" warnings and audible dropouts when executed within
the main Pd patch, DSP active, latency ~50ms... Increasing the latency
further would solve the problem, but I would like to find another
solution.
Initially, I attempted to resolve this by offloading the computation
into a subprocess via [pd~]. However, despite what seemed to be a
correct configuration (no audio signals shared, only control messages
exchanged, -nogui option used), I still observed audio dropouts and
"Audio I/O Error" warnings in the main patch.
otherwise when running two completely separate instances of Pd
manually, that is two versions of Pd, 0.55-1 and 0.55-2 (one dedicated
to real-time audio and another solely for the FFT analysis, without
using [pd~]), my system (macOS Apple Silicon M3) handled both
processes simultaneously without any audio dropouts or errors.
This behavior suggests to me that perhaps the subprocess initiated by
[pd~] might not provide complete isolation at the OS level,
potentially causing implicit timing interactions leading to audio
dropouts. Conversely, manually running two independent Pd instances
seems to solve the problem... would this be the best way (using OSC)?
I'm curious if others have had similar experiences or can offer any
clarification or alternative configurations to better achieve
isolation within a single Pd instance.
Thanks very much in advance for your thoughts!
Best regards,
Pierpaolo Barbiero
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