www.ice-graphics.com

[Sonic The Hedgehog]

Repairing files fails with "Matrix calculations failed", if the source blocks 3, 49 and 238 are damaged, and the recovery blocks 2, 3 and 5 are used to repair.

it looks like ICE ECC uses the exact same algorithm for creating recovery data in ecc files, as QuickPar and MultiPar uses for Par2 files.

QuickPar also fails with a calculation error if source blocks 3, 49 and 238 are damaged, and the recovery blocks 2, 3 and 5 are used for recovery.

MultiPar however, succeeds to repair the files.

This is a rare case, but very annoying if it happens.
Other combinations might result in the same error.

[ICE Graphics]

ICE ECC use the same matrix for generating codes, like QuickPar.
But there is the difference. If there is additional block (when 3 block damages and there are 4 recovery blocks) ICE ECC always recover. But QuickPar or MultiPar will fail.

[Sonic The Hedgehog]

I've done some more testing, here are the results:

3 damaged blocks (3, 49, 238) and 3 recovery blocks (2, 3, 5):

QuickPar: fail
MultiPar 1.2.8.7: fail
MultiPar 1.2.4.3: success
ICE ECC: fail

3 damaged blocks (3, 49, 238) and 4 recovery blocks (2, 3, 5, 6):

QuickPar: fail
MultiPar 1.2.8.7: fail
MultiPar 1.2.4.3: success
ICE ECC: success

So, MultiPar 1.2.4.3 can recover the files in both cases, ICE ECC can't.

[ICE Graphics]

It's very very very rare case. And it's easy to fix if there is at least one additional recovery block. So practically, due to always there are additional blocks this is never happened.