Missing and/or broken OpenMPT test modules.

Several test modules from the OpenMPT regression tests are not played correctly:

• mod/PortaSmpChange.mod: the new sample is never applied. Both behaviors are tested as of #785
• it/extreme-filter-1.it: the output clips at the end of the envelope for the first two filter notes.
• it/extreme-filter-2.it: note timbre sounds weak/empty. This one currently isn't tested, but I checked it due to the prior being wrong.
• it/s7xinsnum.it: instrument NNA note cut cancels all three notes playing in channel 1, but it should only cut the most recent/current note.

I am sure this list is in no way complete, these are just the ones I noticed while fixing tests for #496.

edit: all unimplemented OpenMPT IT tests updated list of all unimplemented OpenMPT modules as of 2024-11-14:

MOD:

• InstrDelay.mod
• InstrSwapRetrigger.mod #785
• NoteDelay-NextRow.mod
• PTInstrSwap.mod #785
• PTInstrVolume.mod #785
• PTRetrigger.mod
• PTStoppedSwap.mod #785
• PTSwapEmpty.mod #785
• PTSwapNoLoop.mod #785
• PatLoop-Break.mod
• PatternDelaysRetrig.mod
• PortaSwapPT.mod #785
• TempoChange.mod

S3M:

• AdlibZeroVolumeNote.s3m
• LoopReset.s3m
• NOP.s3m
• NoCombinedSlidesOnFirstTick-Fast.s3m
• NoCombinedSlidesOnFirstTick-Normal.s3m
• OffsetLoopWraparound.s3m
• OffsetPastSampleEnd.s3m
• OxxMemory.s3m
• OxxMemoryWithRetrig.s3m
• PatternDelays.s3m
• PeriodLimitUpper.s3m
• PortaAfterArp.s3m
• RetrigAfterNoteCut.s3m
• RetrigSlide.s3m
• TonePortamentoWithAdlibNote.s3m
• VibratoTypeChange.s3m
• weirdloop.s3m

XM:

• ArpSlide.xm
• ArpeggioClamp.xm
• AutoVibratoSweepKeyOff.xm
• BidiPrecision.xm
• DelayVolume.xm
• Finetune-Precision.xm
• FreqWraparound.xm
• FT2PanLaw.xm
• GlobalVolume.xm
• NoteOffFadeNoEnv.xm (2025-12-07: broken)
• NoteOffInstrChange.xm (2025-12-07: OK)
• Off-Porta.xm (2025-12-07: OK)
• PanSlideZero.xm
• PanSustainRelease.xm
• PatLoop-Infinite.xm
• PatLoop-Jumps.xm
• PatLoop-Nested.xm
• PatLoop-Overflow.xm
• PatLoop-Various.xm
• PatternDelay-NoteDelay.xm
• Porta-LinkMem.xm #817
• PortaDelay.xm
• PortaJustStoppedNote.xm
• PortaResetDirection.xm
• RetrigFade.xm
• RetrigTick0.xm
• SampleChange.xm
• SamplePortaInInstrument.xm
• TremoloVibrato.xm
• VibratoCombinations.xm
• VibratoDouble.xm
• VolColDelay.xm
• lowest.xm
• porta-delay.xm
• retrig.xm

IT:

• BidiPrecision.it
• DNA-NoInstr.it
• DoubleSlide.it
• DoubleSlideCompatGxx.it
• FilterPortaSmpChange-InsMode.it
• FilterPortaSmpChange.it
• FilterResetPatDelay.it
• GlobalVolFirstTick.it
• GlobalVolume-Macro.it
• InitialNoteMemory.it
• InitialNoteMemoryInstrMode.it
• InstrAfterMultisamplePorta.it
• JxxTicks.it
• LoopBreak.it
• LoopStartAfterPatternEnd.it
• NoMapEffects.it
• NoSlide.it
• NoteFade-InsMode.it
• NoteFade-SmpMode.it
• OffsetWithInstr.it
• PanResetInstr.it
• PanbrelloHold.it
• PatternDelay-NoteDelay.it
• PatternDelays.it
• PatternDelaysRetrig.it
• PitchPanReset.it
• PortaCutCompat.it
• PortaResetAfterRetrigger.it
• RandomPan.it
• RandomWaveform.it
• ResetEnvNoteOffOldFx.it
• ResetEnvNoteOffOldFx2.it
• SampleSustainAfterPorta.it
• SampleSustainAfterPortaCompatGxx.it
• SampleSustainAfterPortaInstrMode.it
• SlideDelay.it
• SwapNNA.it
• VibratoDouble.it
• VibratoSweep0.it
• dct_smp_note_test.it
• empty_sample_offset.it
• env-flt-max.it
• extreme-filter-test-2.it
• filter-reset-envelope.it
• ins-oc.it
• ins-ox.it
• ins-xc.it
• ins-xx.it
• noteoff3.it (seems to vary somewhat from IT)
• sbx-priority.it
• surround-pan.it
• swing1.it
• swing2.it
• swing3.it
• swing4.it
• swing5.it
• tickdelay.it
• tremolo.it
• vibrato-oldfx.it
• vibrato.it
• weirdloop.it

Start by reproducing one of the listed OpenMPT regression modules, such as it/extreme-filter-1.it or it/s7xinsnum.it, and compare the observed playback with the behavior described in the issue. Review the existing OpenMPT regression-test setup; done means resolving a selected discrepancy and confirming the module behaves correctly in the relevant test coverage.