Fixing broken ADPCM samples
In most Wolfteam games, the ADPCM samples are broken by the loader program.
This results in the low tom tom being almost silent.
Affected games are:
- Arcus Odyssey
- Choutouryuu Retsuden Dino Land
- FZ Senki Axis
- Niko^2
- Ryu: Naki no Ryu yori
Granada uses a different sound driver for FM music and doesn't suffer from the issue.
Fixing the bug:
- Download the Wolfteam X68000 Sample Fix Tool
- extract the sound driver loader from the disk image
The file is called MDRV.X or M_DRV.X and usually located on disk 1. - fix the loader program using the tool above
- copy the file back into the disk image
The bug is caused by the game doing some invalid sound driver calls when starting AXIS.X on disk 3.
It ends up calling the "sound channel enable" function in a way that disables the FM3 channel.
Thanks to GTheGuardian for helping me to find the cause of the bug.
Looking at the disassembly, I assume they wanted to write to memory address $EB000A and somehow used the wrong macro name.
The fix is rather simple:
- Open the image of disk 3 in a hex-editor
- search for these bytes: 303C FFEB 323C 000A 3403 4E41
- replace the 4E41 (TRAP #1 instruction) with 4E71 (NOP)