gzdoom-gles/dumb/docs/modplug.txt

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 * modplug.txt - Our official position regarding      / / \  \
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********************
*** Introduction ***
********************

ModPlug Tracker is a very popular tracker for Windows. Its popularity is due
to the intuitive interface and its many advanced features. The author has
done a good job with this piece of software, but sadly in doing so he has
desecrated the IT file format.

I am not against ModPlug Tracker being used to write music modules. As
already stated, it has some very advanced and convenient features; I use it
myself. However, I believe its users should be aware of the entire situation
before using it for any serious work.

   ModPlug Tracker - http://www.modplug.com/


*************************
*** Incompatibilities ***
*************************

There are a few situations in which ModPlug Tracker misinterprets the
original module formats. I shall list the five I am most aware of, from least
to most annoying:

5. Create a multisample instrument, for example a piano. Play a low note.
   Then go up the scale, but in the pattern data, make sure the instrument
   column is blank; put in only the notes. Play this with ModPlug Tracker,
   and play it with Impulse Tracker. Impulse Tracker changes sample as you go
   up the scale; ModPlug Tracker does not.

4. Arpeggio and Retrigger Note effects behave badly when combined with
   Portamento, which can appear in the volume column. While Retrigger Note
   isn't too bad, Arpeggio sounds completely wrong. Try it and see what
   happens. Then repeat the experiment in Impulse Tracker.

3. The filter algorithm is incorrect, in more ways than one. When Jeffrey Lim
   programmed the low-pass resonant filters into Impulse Tracker, he used a
   standard filter algorithm with a slight modification to achieve greater
   resonance. ModPlug Tracker does not incorporate this modification.
   Furthermore, ModPlug Tracker uses integer arithmetic with nowhere near
   enough precision; the wave output is really poor in some cases. I don't
   doubt it damages the acoustic properties of the filters in subtle ways.

2. When looping, ModPlug Tracker resets all variables. The original trackers
   do not do this.

1. Worst of all, ModPlug Tracker has no regard for playback volume, and
   generally has a much lower output level than the original trackers.

Cases 3, 2 and 1 lead people to write IT files that play badly in the
original trackers. If some of these problems could be fixed, I'd be all for
it - but these problems have been reported to the author and he had no
motivation to fix them. ModPlug Tracker has been around long enough that
fixing 3, 2 and 1 would be detrimental to too many people's music.


******************
*** Extensions ***
******************

Worse than the incompatibilities are the extensions ModPlug Tracker makes,
mostly to the IT format. DUMB currently supports one of these extensions,
namely stereo samples, but supporting the others is not high on my list of
priorities.

Other extensions ModPlug Tracker has provided mostly take the form of extra
effects. For instance, S98 and S99 can be used to enable or disable reverb. I
believe the latest versions of ModPlug Tracker offer alternative types of
filter, such as high-pass and band-pass. As soon as an IT file uses any of
these features, it will play incorrectly with Impulse Tracker.

By far the most evil extension provided by ModPlug Tracker is the effect
plug-ins. These enable IT files to use VST effects. I recently downloaded an
IT file that uses some effects from a collection named "DirectX Media Audio
Effects". When can we expect these effects to be ported to Linux?


******************
*** Conclusion ***
******************

ModPlug Tracker is trying to be two things at once. It wants to be an editor
for the existing formats, but at the same time it wants to be proprietary,
with all its own features and extensions. Unfortunately it is succeeding;
there are many IT files out there that only play right in ModPlug Tracker. In
my opinion, ModPlug Tracker should have come out with its own file format, in
which all these extensions would have found a home.

If you are going to use ModPlug Tracker's extensions, I recommend you
ultimately convert your music to a streamed format such as Ogg Vorbis. (If
you were thinking of using MP3, then don't - consider using Ogg Vorbis
instead.) If you release IT files that use ModPlug Tracker's extensions,
please state prominently that the files are designed to be played with
ModPlug Tracker. Finally, don't ask me to support ModPlug Tracker's
extensions; ModPlug Tracker's playback code is available for use in your
games, so use that instead.

   Ogg Vorbis - http://www.vorbis.com/

Despite all the above problems, don't forget that ModPlug Tracker does have a
lot of very useful features for editing files. These include a function for
removing unused patterns, samples and instruments, drag-and-drop sample and
instrument ripping, drop-down menus for selecting the effects by name without
having to memorise the codes or refer to help, and lots of other nice things.
I do recommend it as an editor, provided you make sure you are aware of the
situation and do not use ModPlug Tracker's extensions or incompatibilities
inadvertently.

Oh, and by the way, save your final version with Impulse Tracker. Then the
samples will be compressed for you!


Ben Davis
entheh@users.sf.net
IRC EFnet #dumb
See readme.txt for details on using IRC.