For archiving CHD-Files in less than the original

Hi all,

I think I have found a way to create all the changes to chd files via database from an existing database.

To create this database I need all the CRC32 / MD5 / SHA-1 data of every chd file which has ever been changed.
So from the first version to the last. If you can help me put these together (or maybe you have an online database
where these versions are shown), I would try to write a patcher that will make the needed one out of each
predecessor version. This would require less data to back up than putting each version somewhere as a CHD file online.

For archiving, I think the best alternative.
For example, I have already successfully created a 0.158 CHD from a 0.203 CHD file.
The patch for this was only 25 KB. Also, the conversion of the same 0.158 CHD file back to the 0.203 version was also
only 25 KB in size.

Even though the changes from one version are very large, the size of the patch file is not larger than the source CHD file.

Thanks and cheers

Which CHD was that? Because I'm impressed that the difference is so small.

CHDs are individually compressed and I expected a much bigger difference.

Sorry, the Patch File is not 27K! It is 272K.

The CHD is savage\savage.chd

---------------------------------------------------------
Rollback Patch of: Savage Quest, 1999, Interactive Light

This Patch creates a Rollback CHD for MAME/FBMAME/HBMAME
and other arcade emulators. For best archiving the oldest
versions of arcade DISK/CD dumps.

---------------------------------------------------------
You need the file: savquest\savquest.chd from MAME v0.203
---------------------------------------------------------
CRC32: A1339D2D
MD5  : E6D7C497C0837D259D4F622D6ECD0205
SHA-1: E501492F2C3EF86A431328DBD631D38A81922A92

IMPORTANT: The SHA-1 code in MAME203.dat is the inner SHA-1
code from the file savquest.chd and not the SHA-1 code from
the real file.

---------------------------------------------------------
Rollforth Patch of: Savage Quest, 1999, Interactive Light

This Patch creates a Rollforth CHD for MAME/FBMAME/HBMAME
and other arcade emulators. For best archiving the newest
versions of arcade DISK/CD dumps.

---------------------------------------------------------
You need the file: savquest\savquest.chd from MAME v0.149
---------------------------------------------------------
CRC32: 1979E206
MD5  : D9A3D7CA9D69784C915B42C62B7A562C
SHA-1: EDEE2E9C42D294F5CB5A16805041522194C44BB9

IMPORTANT: The SHA-1 code in MAME149.dat is the inner SHA-1
code from the file savquest.chd and not the SHA-1 code from
the real file.

Cheers