MPT 1.28.02 effects documentation

[TheRealByteraver]

Hello everybody, I'm new to the forums. Modplug's Effect reference is a real goldmine for somebody like myself that wants to write their own replay routines, so I use it (and the wiki) as a reference. My question is:
- Is the effect reference a reference as to how Modplug plays in native mode or in compatible (XM/S3M/IT/MOD) mode? I ask because I noticed that in the .MOD effect reference the arpeggio command supposedly uses effect memory. I believe this to be wrong, as there would be no way to distinguish between "no effect" and "arpeggio", since it's effect number is zero, in a "real" .MOD that is.

Thank you in advance for pointing me in the right direction

- Erland

[Saga Musix]

Welcome to our forums.
Generally the effect reference assumes the default (i.e. compatible playback mode), unless noted otherwise. The reference does not claim to be complete in any way, there can be mistakes like the one you just found (it has been fixed in the meantime), and in particular it does not mention the edge cases that are differnet depending on compatible playback being enabled or disabled (at least most of the time).
Textual specifications of module effect commands tend to be incomplete and omit edge cases, so don't expect to be able to write a fully compatible player based on them (neither the OpenMPT manual, nor the FastTracker manual or any other).

However, what might be more useful for you is the Development category on the wiki, in particular the test case pages. There I have documented many playback quirks for MOD, XM, S3M and IT and when they were fixed in OpenMPT, all with reproducable example files.

[TheRealByteraver]

Hi, thank you for the fast reply and for clearing that up. I noticed the development category on the wiki page before, you people have done some amazing work. Seeing just how many incompatibilities there are between mod/s3m/xm was a real eye opener for me. I tinkered around with the .xm format before (and even contacted Fredrik Huss back then to "complain" about the not-so complete xm.txt documentation ) and I had no idea FT2 had so many problems. Their implementation of the pattern loop effect... I lol'ed when I read MPT's help file.

Anyway, I am aware of the issue tracker, but the arpeggio thing mentioned before is not a bug in MPT, only a typo in the documentation. Should I inquire about such issues here or still in the issue tracker?

Best Regards
- Erland

[Saga Musix]

The issue tracker should only be used for reporting actual bugs in the program. Mistakes on the documentation, like the one you found, can either be discussed in the forum (like you did) or you can directly fix them yourself (the wiki is free for anyone to edit).

[TheRealByteraver]

Fair enough, I feel more comfortable mentioning it here rather than editing the wiki directly so  that's what I'll do for now.

Other question: I found an interesting discussion on https://github.com/schismtracker/schismtracker/wiki/Player-abuse-tests. Unfortunately the player-abuse-tests.zip file is no longer available for download. Are these issues all covered on https://wiki.openmpt.org/Development:_Test_Cases/IT ? Or is there no real link between both lists? It seems an interesting resource.

Best Regards

[Saga Musix]

The player abuse tests are kind of the birth of my own player tests; that's where it all started. As such, there is only little overlap between them and my tests.
You can find the contents of the missing archive here: https://resources.openmpt.org/player_tests/it/player-abuse-tests/

[TheRealByteraver]

Fantastic, thanks!

[TheRealByteraver]

Two more questions about the effect documentation (wiki page https://wiki.openmpt.org/Manual:_Effect_Reference):
1) The MOD Pattern delay effect has the following remark: "If multiple EEx commands are found on the same row, only the leftmost is considered.". However, MPT handles this effect the same way in Protracker 1/2 compatibility mode as it does for FT2 compatibility mode, meaning that the rightmost EEx command defines the length of the pattern delay (Also effect EE0 is not ignored in either mode but cancels an earlier pattern delay effect). I suppose this is an error in the wiki/manual and not in MPT's replay routine.

2) Small typo on the page https://wiki.openmpt.org/Manual:_Compatible_Playback in the section "S3M compatibility settings" it says at the bottom (last sentence, about sample offset effect):
    "Similarly to the MOD format, this setting causes notes with an instrument number to use the same sample offset as the previous note."
This should probably read:
    "Similarly to the MOD format, this setting causes notes without an instrument number to use the same sample offset as the previous note."

Shall I update the documentation accordingly?

[Saga Musix]

Thanks for noticing, both sentences have been corrected. The former was most likely a copy&paste mistake, the XM and MOD format should behave identically.