`fluid.ampfeature~` can break when it receives a `nan`

[rconstanzo]

As outlined in this thread on the discourse when fluid.ampfeature~ receives a nan its own output breaks.

What was the expected result?

The envelope follower should get pulled in that direction but not ultimately fail.

What was the actual result?

The object stops working until audio is restarted.

What operating system were you using?

Mac

Operating system version

macOS 13.4.1

FluCoMa Version

1.0.6

[tremblap]

now looking at this: the only question here is what to replace NaN with. traditionally it is by 0 but in this case I wonder if that is the best choice. Paging @AlexHarker for a strong opinion about this. then @weefuzzy for another. then @rconstanzo for another.

[tremblap]

I'd check for NaN at line 45 of algo:public:envelop.hpp with something as dirty as std::isnan but hey ideas will abound I'm sure

[rconstanzo]

I have no direct opinion as I know little about the implications. I imagine a zero would not be good here as that would be "loud", so maybe like -70 or -99 or something more in that range. But as I said, I have little clue of what the implications would be.

[tremblap]

it is at the input, so it would be 0 as assuming NaN is silence

[tremblap]

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[tremblap]

test patch

[rconstanzo]

it is at the input, so it would be 0 as assuming NaN is silence

Yeah that makes sense, I was (obviously) thinking output.

[AlexHarker]

There is nothing dirty about std::isnan(). It is self documenting, is portable and should be reliable.

My more general disagreement is with fixing Nans by default although I do tend to do it to in cases where it might cause unrecoverable errors (e.g. a filter memory in some cases). Otherwise I consider it better practice to fix nans upstream. I dislike max fixing them in places where I think the user should already have avoided them (especially as this adds performance cost)

[tremblap]

In this case it is at the input, as if a nan is sent in, the hpf will blow unrecoverable. so 0 would be a good replacement in that case?

[weefuzzy]

My 2c: If we have to fix them (and avoiding exploding filters has something to be said for it) then 0 isn't the right choice here, because it's unpredictably saying that the input might have changed significantly even when we have no actual information to that effect.

I think I'd be more inclined to track the last 'valid' input sample and repeat that in the case of a NaN. For constant NaNs this will drag the HPF output quickly to 0 but won't explode it, for the odd NaN it shouldn't affect the detector too much.

With that said I do also tend towards the view that prevention is better than cure here: adding a clear or reset message would, IMO, be more virtuous (but non-trivial).

Agree that std::isnan is the correct test here. Nothing at all dirty about it: we should rely on standard library authors to have implemented this properly and portably.

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[rconstanzo]

Can't test this patch (no filter.butterworth~ here), but what you're describing sounds good, especially in that it keeps the envelope followers where they ought to be.

I would, personally, prefer something that treats the NaNs at the input as often it's not clear where an issue emerged (e.g. playlist~ randomly puking out a NaN sometimes for no good reason), so a clear or reset message will be of little use in a blown-up/frozen patch.

[weefuzzy]

Ah, sorry – filter is a C74 package (muy useful, IMO). Can be installed by package manager.

[rconstanzo]

Ah nice, didn't realize. Seems handy indeed! (should be native!).