ZynAddSubFx glitch on high sample rate

[zynskeywolf]

A rare glitch appears with ZynAddSubFx with very specific scenarios. It Might be related to the envelopes in ZynAddSubFx, but it happens too randomly to be sure.

Steps to reproduce:

• Set the playback sample rate to 192 kHz (currently doable in .lmmsrc.xml)
• Open this project. (Updated)
• Enable the oscilloscope and press play

Expected behavior:
The sound sounds, then goes to silence.

Actual behavior:
You can see a gradually appearing DC offset in the output.
Putting in a reverb in Zyn produces even more crazy things.

Tested in 1.3.0-alpha.1.606+g75d6be2ea (Linux/x86_64, Qt 5.15.13, GCC 14.1.1 20240507)

[zonkmachine]

I can confirm the issue.

Putting in a reverb in Zyn produces even more crazy things.

That's what you'd get with a floating point error. A good candidate to trouble shoot with the WANT_DEBUG_FPE debug option.

[zonkmachine]

That's what you'd get with a floating point error. A good candidate to trouble shoot with the WANT_DEBUG_FPE debug option.

Tested with -DWANT_DEBUG_FPE=ON and nothing showed up.

Change samplerate to 48000, bit depth to 16, and oversampling to 8x.

I get the same result no matter what bit depth setting I use.

[zonkmachine]

Oversampling was removed in #7228

[zynskeywolf]

Oversampling was removed in #7228

It's not an issue with the oversampling feature, it's a ZynAddSubFx bug when using high sample rates in general.

[zynskeywolf]

Updated the original post to be reproducible without the removed setting.

[zonkmachine]

Set the playback sample rate to 192 kHz (currently doable in .lmmsrc.xml)

Are you sure this setting isn't just a feature in #7125 ?

OK. I tested the issue above on #7125 and can confirm the issue.

[zynskeywolf]

Are you sure this setting isn't just a feature in #7125 ?

Well it is, but that pr is open, thus not in newest master.

[zonkmachine]

Well it is, but that pr is open, thus not in newest master.

Ah, right! Now I found it. samplerate=""/>. I learnt something new.

Enable the oscilloscope and press play

Interesting. I do get the bug but it doesn't show up on export.