Ym2Mym

Description

The Oric computers are equiped with a AY-3-8912 sound chip.

This component can be found in multiple variants in many other systems such as the MSX, Amstrad CPC, Atari ST, some of the Sinclair Spectrum machines, among other.

It is an unfortunate fact that only very few Oric games had music back in the 80ies, but this can be fortunately fixed today thanks to the huge catalog of available musics on the other machines!

YM Files

The YM file format was originally designed by Arnaud Carré as a way to record Atari ST musics to make them replayable on a PC.

Technically a YM file is simply a register dump of the music: A program captured 50 times per second the content of the values sent to the YM chip. With 14 registers to record, 50 times per second, it means that one second of music takes 700 bytes, so roughly 42kbytes per minute of music.

The chosen solution was to store the data sorted by register number, and then compress the whole file with the LHA compressor, which typically reduces the music files to less than 10kb even for very long musics.

Unfortunatelly this means that the music file must be entirelly decompressed before it can be used, which makes it unusable on 8bit machines. That's where the MYM format comes in.

MYM Files

The MYM files are basically YM files that have been uncompressed and recompressed in a way that allows for partial decompression over time. The efficiency is not as good, but at least it works.

Ym2MYm can be used to perform this conversion. It will work only on YM files that do not use special timer effects such as digidrums or sid.

Utilisation

To transform a binary file as a texte file:

%OSDK%\bin\Ym2Mym [switches] source.ym destination.mym [load adress] [header name]

Switches


History

Version 1.5

Version 1.4

Version 1.3 (Broken!)

Version 1.2 (Broken!)

Version 1.1

Version 1.0

Version 0.2

Version 0.1