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ICE ECC Bug - Matrix calculations failed

 
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Sonic The Hedgehog



Joined: 25 May 2016
Posts: 2

PostPosted: Wed May 25, 2016 3:00 pm    Post subject: ICE ECC Bug - Matrix calculations failed Reply with quote

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.
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ICE Graphics
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Joined: 31 Mar 2003
Posts: 430

PostPosted: Thu May 26, 2016 7:46 am    Post subject: Re: ICE ECC Bug - Matrix calculations failed Reply with quote

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.
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Sonic The Hedgehog



Joined: 25 May 2016
Posts: 2

PostPosted: Thu May 26, 2016 5:43 pm    Post subject: Reply with quote

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.
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ICE Graphics
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Joined: 31 Mar 2003
Posts: 430

PostPosted: Fri May 27, 2016 8:45 am    Post subject: Reply with quote

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.
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