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IDProjectCategoryView StatusLast Update
0000291OpenMPTPlayback Compatibilitypublic2013-04-27 13:11
Reportermrbumpy409 Assigned ToSaga Musix  
Status resolvedResolutionfixed 
Platformx86OSWindowsOS VersionXP
Product VersionOpenMPT (upgrade first) 
Target VersionOpenMPT (upgrade first)Fixed in VersionOpenMPT (upgrade first) 
Summary0000291: ramping sounds different between live playback and rendered audio (linear/no interpolation only)

When playing a song using either linear or no interpolation, the ramping sounds very different compared to cubic spline and polyphase interpolation. In fact, it sounds as though the volume isn't ramping as smoothly. To summarize:

Live Playback:

  • No Interpolation: non-smooth ramping
  • Linear Interpolation: non-smooth ramping
  • Cubic Spline Interpolation: smooth ramping
  • Polyphase Interpolation: smooth ramping

Rendered Audio File:

  • No/Linear/Cubic Spline/Polyphase Interpolation: smooth ramping

Here is a zip file containing some comparisons using "Building Up and Down" by DRAX, and also including the original XM file:

Steps To Reproduce
  1. Load "Building Up and Down" by DRAX (see above link for zip file)
  2. Set both ramp in and ramp out to 10.
  3. Set the interpolation to polyphase.
  4. Play the song and listen closely to the sound of the first instrument you hear.
  5. Switch the interpolation type to either linear or no interpolation.
  6. Play the song again and notice how each note sounds as though it is cutting out with a muffled "pop".
Additional Information

The "live playback" recordings in the zip file linked above all have a glitch at the beginning where the first note is partially cut off. Please ignore this as this is not a fault of OpenMPT.

TagsNo tags attached.
Has the bug occurred in previous versions?at least some previous versions, but that's as far as I know
Tested code revision (in case you know it)


Saga Musix

Saga Musix

2012-08-10 09:21

administrator   ~0000858

I'll get back at this when I'm back from Evoke, but indeed there are several parts in the code which distinguish between rendered/live playback and even do different things depending on the CPU load.

Saga Musix

Saga Musix

2013-04-26 20:48

administrator   ~0001194

Cause has finally been identified and fixed. Please test:



2013-04-27 04:57

reporter   ~0001196

The mptrack.exe file you linked does indeed seem to fix this bug. However, clicking the "Play from start" button only plays the first pattern of a song (tested with only a few .XM files).

Saga Musix

Saga Musix

2013-04-27 13:11

administrator   ~0001201

Oops, there's a silly bug that I introduced last night that would truncate all but the first order item. Should be fixed now, simply re-download the executable.

Issue History

Date Modified Username Field Change
2012-08-10 05:42 mrbumpy409 New Issue
2012-08-10 09:21 Saga Musix Note Added: 0000858
2013-04-26 17:35 Saga Musix Assigned To => Saga Musix
2013-04-26 17:35 Saga Musix Status new => assigned
2013-04-26 20:48 Saga Musix Note Added: 0001194
2013-04-26 20:48 Saga Musix Status assigned => feedback
2013-04-27 04:57 mrbumpy409 Note Added: 0001196
2013-04-27 04:57 mrbumpy409 Status feedback => assigned
2013-04-27 13:11 Saga Musix Note Added: 0001201
2013-04-27 13:11 Saga Musix Status assigned => resolved
2013-04-27 13:11 Saga Musix Resolution open => fixed
2013-04-27 13:11 Saga Musix Fixed in Version => OpenMPT (upgrade first)
2013-04-27 13:11 Saga Musix Target Version => OpenMPT (upgrade first)