Sidtool

Convert Commodore 64 SID music in the form of .sid files into other formats!

Basically, it's a massive hack made for fun and no profit. The vision, though, is to extract the actual information from .sid files, which are files storing music for the Commodore 64.

.sid files contain actual Commodore 64 machine code that writes to registers corresponding to the Commodore 64 sound chip, the SID (Sound Interface Device). Which means that in order to play back a .sid file like it would sound on an actual Commodore 64, you will have to simulate both the processor and the sound chip.

This project does not attempt to produce an authentic playback of the sounds - lots of those players already exist - but instead lets you export a Commodore 64 song into a format that lets you edit and experiment with the song. Want to change the instruments? Go ahead. Want to take out parts of the song and use in other projects? You can do that. Want to just listen to your favourite Commodore 64 song played back by a piano? Definitely do that!

Supported Output Formats

Ruby

You can get a simple Ruby file which defines a list of synths to play at certain points in time. This can be used to play back the music in Sonic Pi (see below), or you can write a Ruby script to do your own post-processing.

Midi

If you just want to listen to a .sid file, the easiest way is to export to midi file format and open the file in a player such as VLC. However, if you want to further edit the result, import the file in a music editor such as GarageBand on a Mac. Then you can use all of the tools provided by your music editor to change instruments and rearrange the song.

Limitations

Only a subset of the so-called PSID format is supported (a few .sid files use the RSID format which requires a more complete Commodore 64 environment to run), and maybe not all shortcomings of the support is handled well.

Only PAL (50 frames per second) is supported. No CIA timers or other fanciness is supported.

The conversion runs a specified number of frames (default is 1500 - this can be changed on the command line). Ideally it should be able to run until the song finishes.

For these and other limitations, please consult the issues.

Installation

gem install sidtool

Usage

You can find lots of .sid files (and a super nice list of players for a wide range of platforms) at the High Voltage SID Collection homepage.

Show information, like the author and number of songs in a file:

$ sidtool --info <input file>

Convert the default song from a .sid file to a midi file:

$ sidtool --out <output file> --format midi <input file>

Convert the default song from a file to a Ruby list (--format ruby is the default):

$ sidtool --out <output file> <input file>

The Ruby output can then be used to play back the music, for example in Sonic Pi:

load '<path to your output file from before>'

previous_frame = 0
::SYNTHS.each do |synth|
  current_frame = synth[0]
  frames_to_sleep = current_frame - previous_frame
  previous_frame = current_frame
  sleep frames_to_sleep/50.0 if frames_to_sleep > 0
  
  in_thread do
    use_synth synth[2]
    played_synth = play synth[1], attack: synth[3], decay: synth[4], sustain: synth[5], release: synth[6]
    
    this_frame = current_frame
    controls = synth[7]
    controls.each do |c|
      sleep (c[0] - this_frame) / 50.0
      this_frame = c[0]
      control played_synth, note: c[1]
    end
  end
end

It's a bit hacky, I know. Part of the issue is that Sonic Pi has a limit on the size of the edit buffer, so paste the above into the buffer and edit the first line so it loads the (probably rather large) output file from sidtool.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/olefriis/sidtool.

License

The gem is available as open source under the terms of the MIT License.