Sega/Mega CD headers have incorrect serials

[hizzlekizzle]

As discussed in this reddit thread: https://www.reddit.com/r/RetroArch/comments/17860mt/comment/k52yvgo/?context=3

It appears Sega CD games semi-frequently have the wrong serial number in their headers, leading to incorrect matching when we scan them. Some examples:

Tomcat Alley (USA) - Appears as Wonder Dog (Europe)
Sol-Feace (USA) - Appears as Wolfchild (Europe)
Silpheed (USA) - Appears as Double Switch (USA)
Prize Fighter (USA) (Disc 1) - Appears as Prize Fighter (Europe) (Disc 1)

In each of these cases, the actual game's header includes the serial of the "appears as" game, and the "appears as" game also has that same serial in its header. This unfortunately indicates that checking headers is unreliable, at least for these games.

Would it be possible to have a list of games where we "if X serial, do a manual checksum to verify"?

I believe this issue started following this still-excellent and much-appreciated PR: libretro/RetroArch#11719

If that's indeed the case, would it make sense to revert Sega/Mega CD back to the old method?

[RobLoach]

Wonder Dog: http://redump.org/disc/53290/
Tomcat Alley: http://redump.org/disc/24405/

Looks like the serials are brought into the .dat files correctly. Something definitely is up.

[9p6]

What about the games without a serial like Snatcher (USA)? I've noticed they're being filtered out entirely from rdb

https://github.com/libretro/libretro-database/blob/master/metadat/redump/Sega%20-%20Mega-CD%20-%20Sega%20CD.dat#L3219

[RobLoach]

Without a serial there is no way to identify them against the DB. Best way to handle that is the manual scan.

[9p6]

Maybe a redump entry can be edited to add serial field since it's visible in the header dump below. I'll try to register account there.

[RobLoach]

The redump forums are active. Definitely post it up in the Additions and Fixes section.