Fluid.transients~ spike-y/glitchy CPU use?

rodrigo.constanzo · September 12, 2024, 2:12pm

Before posting this as a git issue, wanted to check here to see if I’m missing something.

It seems like fluid.transients~ likes to make pops all over the audio when it’s loaded up. As in, if I’m using something like this in a patch, the audio starts crackling like crazy, even with the (average) CPU usage very low.

Here’s a simple patch showing what I mean:

<pre><code>
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ScA0e3ud3uoevPAE
-----------end_max5_patcher-----------
</code></pre>

(I pasted a few more instances just to exacerbate the issue)

And here’s a video showing what I mean (filmed with my phone in case the audio driver doesn’t capture the glitches):

It sounds like what happens when you have audio in interrupt on and have a metro banging like crazy somewhere, but that’s not the case here, it’s just overdrive on.

Is this normal/expected behavior?

rodrigo.constanzo · September 12, 2024, 2:23pm

Here’s a more real-world use case to show the weirdness.

With moderate cpu usage (~30% average) the audio becomes unusable. AND the CPU spiking is so much that it even impacts non-Max audio?!

weefuzzy · September 12, 2024, 9:39pm

Unfortunately, that’s built in to the algorithm that transients uses and, despite trying quite hard, I didn’t find I way to calm it down appreciably

The algo is, lamentably, much more expensive in direct proportion to the number of transients it finds because each time it finds one it is synthesising audio at profligate* expense. The higher the order and blocksize, the more awful that will be. So, if nothing else, the average CPU reports from Max won’t be giving the full impression of how hard the processor is getting smacked.

* At the very least, quadratic w.r.t. order, IIRC. Or maybe even blocksize, which would be even worse.

rodrigo.constanzo · September 12, 2024, 10:00pm

Hmm, good (and bad) to know.

I’ll play with it a bit more to see if I can get something that sounds alright without turning everything else into popcorn.

Also bananas how far reaching the CPU usage is, as this is a pretty fast computer (m2 pro)…

weefuzzy · September 12, 2024, 10:06pm

Fingers crossed. Getting the order and blocksize down as much as you can is the key!

rodrigo.constanzo · September 13, 2024, 12:37pm

Ok dialed those down and it’s less…popcorn. What I’ll do is wrap it up in a poly~ as in SP-Tools I’ve bundled fluid.transients~ and fluid.hpss~ together as different modes of the same object. And I’ll make fluid.hpss~ the default so you don’t accidentally get popcorn unless you really want it.