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IDProjectCategoryView StatusLast Update
0001666OpenMPTPlayback Compatibilitypublic2023-02-15 21:01
Reportermrbumpy409 Assigned ToSaga Musix  
Status resolvedResolutionfixed 
Platformx86 / x64OSWineOS Version(version plz)
Product VersionOpenMPT / libopenmpt 0.6.8 (upgrade first) 
Target VersionOpenMPT / libopenmpt 0.7.0 (upgrade first)Fixed in VersionOpenMPT / libopenmpt 0.7.0 (upgrade first) 
Summary0001666: volume slide ramping too smooth in Interference demo soundtrack

In the famous soundtrack for Sanity's Interference demo, Virgill uses the volume slide command to essentially create a sawtooth-wave amplitude LFO over the samples. On the Amiga, the return to full volume happens quickly, creating a percussive sound. In OpenMPT, however, this return to full volume is ramped, creating a notably softer effect.

You can download the MOD from here:

The issue takes place in pattern 30, all channels. Virgill is using the technique described in this video, starting at the 4-minute mark:

I have attached audio of pattern 30 played in both OpenMPT and Amiga for comparison.

TagsNo tags attached.
Has the bug occurred in previous versions?yes
Tested code revision (in case you know it)




2023-02-14 17:59

reporter   ~0005553

audio files for comparison



2023-02-14 18:20

reporter   ~0005554

The same technique is used at the beginning of Fury Forest by Moby ( I have attached audio comparisons for this one as well. The effect on Amiga is once again much more percussive. IMO, OpenMPT should still have a tiny amount of ramping to avoid the clicks you hear here, but I would argue that OpenMPT's current amount of ramping in this context is too smooth.

Note that on-the-fly sample swapping needs to be enabled in compatibility settings for proper playback of this module.

Saga Musix

Saga Musix

2023-02-15 20:54

administrator   ~0005555

Last edited: 2023-02-15 21:01

Indeed, when using instrument numbers + volume slides the volume was ramped over a whole tick. This didn't happen when instead using set volume + volume slide (a combination that's not possible in the MOD format but is for example possible in XM, S3M and IT). The behaviour has now been made consistent between those two possible ways of the gating effect. While it's a small change in code, it is a big change in practice affecting potentially many modules out there. Hence I'm not quite comfortable in backporting it to older OpenMPT or libopenmpt versions (yet), and will keep the fix from r18739 in the upcoming major update (OpenMPT 1.31) only.

Issue History

Date Modified Username Field Change
2023-02-14 17:57 mrbumpy409 New Issue
2023-02-14 17:59 mrbumpy409 Note Added: 0005553
2023-02-14 17:59 mrbumpy409 File Added: Interference pattern
2023-02-14 18:20 mrbumpy409 Note Added: 0005554
2023-02-14 18:20 mrbumpy409 File Added: Moby - Fury Forest audio
2023-02-15 20:50 Saga Musix Assigned To => Saga Musix
2023-02-15 20:50 Saga Musix Status new => assigned
2023-02-15 20:54 Saga Musix Note Added: 0005555
2023-02-15 20:54 Saga Musix Status assigned => resolved
2023-02-15 20:54 Saga Musix Resolution open => fixed
2023-02-15 20:54 Saga Musix Fixed in Version => OpenMPT / libopenmpt 0.7.0 (upgrade first)
2023-02-15 20:54 Saga Musix Target Version => OpenMPT / libopenmpt 0.7.0 (upgrade first)
2023-02-15 21:01 Saga Musix Note Edited: 0005555