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#35 RMPS support
Did anybody consider adding support for RMPS tags in images? Sometimes the only remaining copy is an old backup disc which can only be used alongside with BlindWrite or Alcohol emulation. I know that CDEmu supports emulating disc topology using .BWA or .MDS but there is no support for RMPS tags, probably because there is no information available about its format. I think it would be worth investigating such possibility.
Hmm, I have never really looked into RMPS - if I recall correctly that's the approach that allowed you to make a physical copy of disc and also store its metadata (presumably topology) on the copy. And then the emulation software created a virtual drive / overlay that effectively presented this modified disc as the original one (presumably by applying the topology emulation).
Depending on where and how the metadata is stored, I am not sure where it would fit in CDEmu, because it would require us to analyze the contents of the disc (filesystem/subchannel/wherever the data is stored), which is something I would rather avoid. Because RMPS-enabled backup copy could be stored as any (raw) image format, this does not belong in the parser level. But perhaps, it could be optionally done as a common post-processing step after the parser does its job and before the disc object is returned...
(And if we had a MDS or a B6T image writer, we could create an "unpack" utility for RMPS disc images...)
I'll think about it, and when I have a bit more time, perhaps try to create some RMPS-enabled discs to see what the format is like.
The metadata are stored as an embedded sectors in main image data which are otherwise zeroed, i.e. in .MDF or .BWI/.B5I/.B6I file. This happens on the fly during writing it to disc. If the correct driver is loaded it could then hide these sectors from copy protection engine, though it didn't in earlier versions. I've found a US 20070047393A1 patent with a vague description of the whole process, apparently filed by Alcohol employees, but it didn't describe the actual data format, unfortunately. I was unable to find any other description on the net, so experimenting is probably the only option left.
To make things even more complicated there are several versions of these formats, e.g. Blindwrite 4.5, Blindwrite 6, Alcohol's RMPS v1 and v2. I've experimented with BlindWrite 4.5 a bit and I think that there is a structure similar to that of .BWA but in compressed format, perhaps using some form of delta compression of the hyperbolic curve's points. Also, there seems to exist some reverse conversion code inside BlindWrite 5-7 executable, but I didn't find a way to execute it. OTOH, decompiling would be too time consuming.
There are some image writers out there, e.g. Disc Image Chef. But there is no support for RMPS either, apparently due to a lack of standard. And the only users who have some incentive are archivists as it seems. This is a chicken and egg problem.