XM Bugs - Lowpass Filter gets stuck

steffest / BassoonTracker

Webbased old-school Amiga music tracker in plain old javascript - Plays and edits Amiga Mod files and FastTracker XM files

http://www.stef.be/bassoontracker/

MIT License

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XM Bugs - Lowpass Filter gets stuck #10

Closed steffest closed 5 years ago

steffest commented 5 years ago

Split from #8

Some songs have a bug where a lowpass filter is enabled and remains even after loading new songs (gets "stuck"):

vogue-ambient light.zip (Pattern 9) lesnik-hot dogs 3.xm (happens immediately in Pattern 1) lamb-happiness.xm (happens at very end of Pattern 1) That requires refreshing the page to fix, so pretty bad.

bryc commented 5 years ago

Looking into this more: The issue comes from E0x effect (Amiga filter). That shouldn't even work in FT2 XM mode (just backwards compatibility for MODs), and according to some documentation, should only work in .MOD when x = 1. Those example files all use "E00" (x = 0) which actually should turn the filter off!

Edit: I got E00/E01 backwards. Even after checking correct documentation. Embarrassing. Guess I was too convinced that the reason E00 was there was for it to be off. Sorry for confusion!

steffest commented 5 years ago

It's the other way around actually: E00 turns the filter on, E01 turns it off (see e.g. docs on https://github.com/cmatsuoka/tracker-history/blob/master/reference/amiga/protracker/Protracker_v2.0a/PTEffects.txt but I also just checked this on a real amiga to be sure) But you are right that XM files should ignore it: even Digibooster on the amiga - which can read and write xm files - ignores it. It's updated now.