Gotracker

What is it?

It's a tracked music player written in Go.

Why does this exist?

Heucuva needed to learn Go forever ago and figured this was a good way to do it.

What does it play?

Files from/of the following formats/trackers:

• S3M - ScreamTracker 3
• MOD - Protracker/Fasttracker/Startrekker (internally up-converted to S3M)
• XM - Fasttracker II

What systems does it work on?

• Windows (Windows 2000 or newer)
  • Sound Card
    • WinMM (WAVE_MAPPER device)
    • DirectSound (via optional build flag: directsound)
    • PulseAudio (via optional build flag: pulseaudio) - NOTE: Not recommended except for WSL (Linux) builds!
  • File
    • Wave/RIFF file (built-in)
    • Flac (via optional build flag: flac)
• Linux
  • Sound Card
    • PulseAudio
  • File
    • Wave/RIFF file (built-in)
    • Flac (via optional build flag: flac)

How do I build this thing?

What you need

For a Windows build, we recommend the following:

• Windows 2000 (or newer) - we used Windows 10 Pro (Windows 10 Version 20H2)
• Visual Studio Code
  • Go extension for VSCode v0.19.0 (or newer)
  • Go v1.15.2 (though it will probably compile with Go v1.05 or newer)

For a non-Windows (e.g.: Linux) build, we recommend the following:

• Ubuntu 20.04 (or newer) - we used Ubuntu 20.04.1 LTS running in WSL2
• Go v1.15.2 (or newer)

How to build (on Windows)

1. First, load the project folder in VSCode. If this is the first time you've ever opened a Go project, VSCode will splash up a thousand alerts asking to install various things for Go. Allow it to install them before continuing on.
2. Next, open a Terminal for powershell.
3. Enter the following command

   go build

   When the command completes, you should now have the gotracker.exe file. Drag an .S3M file on top of it!

How to build (on Linux)

1. Build the player with the following command

   go build

NOTE: In order to use PulseAudio, you must have your PULSE_SERVER connection string environment variable configured:

• e.g.:

  PULSE_SERVER=tcp:127.0.0.1:4713

  (Take note that there are bugs associated with TCP connection strings; see bugs section below) For more information about the PULSE_SERVER environment variable, please see the PulseAudio documentation.

How does it work?

Not well, but it's good enough to play some moderately complex stuff.

Bugs

Known bugs

Tags	Notes
player	Unknown/unhandled commands (effects) will cause a panic. There aren't many left, but there are still some laying around.
player	The rendering system is fairly bad - it originally was designed only to work with S3M, but we decided to rework some of it to be more flexible. We managed to pull most of the mixing functionality out into somewhat generic structures/algorithms, but it still needs a lot of work.
loader	Attempting to load a corrupted tracker file may cause the deserializer to panic or go running off into the weeds indefinitely.
mod	MOD file support is buggy, at best.
mod loader	MOD files are up-converted to S3M internally and the S3M player uses NTSC-based lookup tables, so with a PAL-based MOD, the period values produced will end up being very slightly divergent from what is expected, as the S3M format converts note information to key-octave pairs, opting to look up the period information at time of need instead.
xm	XM file support is in a somewhat nascent state. Don't expect your favorite song to play in it well.
s3m opl2	Attempting to play an S3M file with Adlib/OPL2 instruments does not produce the expected output. The OPL2 code has something wrong with it - it sounds pretty bad, though steps have been taken to remedy its strange output.
mod s3m	Amiga Paula/"LED" low-pass filter support is available, but the filter itself is a very lazy (and very over-optimized) Butterworth implementation. It will not produce the expected output.
xm opl2	Attempting to play an XM file with Adlib/OPL2 instruments does not work. Most of the code for playback is there, but there's none for loading OPL2 instruments from file, so there's no way for the instruments to make it to the playback code.
windows winmm	Setting the number of channels to more than 2 may cause WinMM and/or Gotracker to do unusual things. You might be able to get a hardware 4-channel capable card (such as the Aureal Vortex 2 AU8830) to work, but driver inconsistencies and weirdnesses in WinMM will undoubtedly cause needless strife.
player	Channel readouts are lazily attempted to match the layout from the tracker the song file came from. As a result, there are probably strange artifacts presented in it by the attempted simulation.
player mixing	The mixer still uses some simple saturation mixing techniques, but it's a lot better than it used to be.
pulseaudio	PulseAudio support is offered through a Pure Go interface originally created by Johann Freymuth, called jfreymuth/pulse. While it seems to work pretty well, it does have some inconsistencies when compared to the FreeDesktop supported C interface. If you see an error about there being a "missing port in address" specifically when using a TCP connection string, make sure to append the default port specifier of :4713 to the end of the PULSE_SERVER environment variable.
windows directsound	DirectSound integration is not great code. It works well enough after recent code changes fixing event support, but it's still pretty ugly.
flac	Flac encoding is still very beta.
xm	Linear Frequency Slide support uses an in-situ floating point power-of-2 calculation, which may be very slow on some hardware. Additionally, it is not going to match what Fasttracker II does internally - using a pre-calculated lookup table - so the output may sound slightly different from expectation.

Unknown bugs

• There are many, we're sure.

Further reading

Take a look at the fmoddoc2 documentation that the folks at FireLight studios released forever ago - it has great info how how to make a mod player, upgrade it to an s3m player, and then dork around with the internals a bit.