Hi, I finished the tool.
You can download it from http://gamefileformats.the-underdogs...grisc-0.1a.zip
I still consider it an "alpha" version since I didn't test it thouroughly but it did it's job.
Instead of playing the videos it now saves each frame as PNG file and the soundtrack to a Wave file.
The parameter is simply the name of the SNM file. The files will be created in the current directory.
This shouldn't drop any frames anymore, too.