CISO Plus

Converting PSP ISO file to compressed CSO format

The code is mainly based on two projects:
phyber/ciso
barneygale/iso9660

But, I made some modifications and added extra features of what CisoPlus has:

1. Threshold: Only the blocks of which compression ratio is below the specific threshold will be compressed.
2. Do not compress multimedia files: Leave PMF and AT3 files alone.
3. Vaccum files for system upgrading: Fill these files with blank data (the iso file is untouched), so it can save even more space.