Manually fixing CRC Errors

[guitarboy]

I keep getting CRC errors, despite following the various bits of advice in this thread: http://forums.sabnzbd.org/index.php?topic=3409.0 Usually repeating the download fixes the problem, but that's a waste of bandwidth.  So I started experimenting with manually fixing the failed download, and so far have been able to fix every RAR set that's failed in SABnzbd.

Here are the steps:

1. Re-download the PAR files. NZBMatrix makes this easy (don't know about other index sites) - just click on the name of the NZB file, select the NZB File Details tab, scroll to the bottom, click the PARs checkbox, then click the Download Selected as NZB button.  Note - you can ignore the "Repair failed" message on the downloaded PAR files.
2. Copy the PAR files to the same folder as the RAR files from the failed download.
3. Open the .par file with QuickPar - you can download QuickPar from http://www.quickpar.org.uk/
4. When QuickPar is finished repairing the file, run an unrar utility.  I've been using command line unrar, but it looks like RARZilla is worth a try: http://www.philipp-winterberg.com/softw ... _unrar.php

Of course, it would be much easier if SABnzbd would just allow a retry after a CRC error.  It's a mystery to me why the error occurs with SABnzbd, but not when I manually repair and unpack.  I understand that SABnzbd 6 will offer a retry feature.

[shypike]

 I understand that SABnzbd 6 will offer a retry feature.

It will.
What kind of CRC errors do you get?
In articles or when unpacking the RAR files?

[guitarboy]

The errors usually occur during unpack.  E.g.

Repair:
[mydownload] Quick Check OK
Unpack:
[mydownload] ERROR: CRC failed in "mydownload.mkv"

[shypike]

Can you send me an example of an NZB that shows this behaviour?
bugs at sabnzbd.org
So far the only thing I can think of is that SABnzbd gets a corrupted par2 file
and doesn't notice this and therefore approves a set that should not be approved.

The easy way around this it to disable QuickCheck and rely on par2.
However, I hope you can help to uncover an possible QuickCheck bug.

[pobox]

There should be no mystery about a CRC error and no need for a retry feature.  Was a QuickCheck bug found or was this a wasted opportunity?

[shypike]

There have been some reports suggesting a QuickCheck problem.
However, no usable evidence was ever produced.
So far I have no reason to assume that there is a problem.