HFC:Duplicate Detector Match error

Technical support and discussion of Newsbin Version 6 series.

HFC:Duplicate Detector Match error

Postby oberron » Tue Dec 06, 2011 9:29 am

Hello,
I keep having a Duplicate Match Error, when I'm attempting to download something. I'm certain I've never downloaded those specific files before. It only seems to happen when an Iso file is involved, as I have tried other files and it seems to work o.k. I'm using the latest version of Newbin, but I did do an upgrade from version 5. Is this a bug or I'm I missing something? This did not occur with the previous version I was using. So far this is the only issue I seem to be having, otherwise it works great! Any help would be appreciated. Thx!
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Re: HFC:Duplicate Detector Match error

Postby Quade » Tue Dec 06, 2011 9:32 am

There's probably some common prefix that's the same on this ISO as on some other ISO. You can disable the signature checking or queue the files with Ctrl-Y to bypass the filters for these files.
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Re: HFC:Duplicate Detector Match error

Postby oberron » Tue Dec 06, 2011 9:47 am

Thanks for getting back with me so quickly. I will try that and see if that helps. Btw, when this is occurring I've been using an NZB file. Don't know if that is related? Also, I'm not sure what you mean by a common prefix? Could you possibly explain that a bit further? Also, Is there something that has changed from version 5 to 6, that would cause this behavior? Thx again!
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Re: HFC:Duplicate Detector Match error

Postby Quade » Tue Dec 06, 2011 10:09 am

Signature filtering comes from back in the days of dialup connection speeds. People depend on them so, I can't really change how it works.

Newsbin just checks the first 23K of the file against the first 23K of any other file it's downloaded. That means if you downloaded a file in the past and the first 23K are identical to the first 23K of a new file, the new file is considered a match and rejected. That's the "common prefix". With file sizes being what they are these days. I consider 23K to be insufficient but, it is what it is. Most of the time the first 23K seems to be unique but, apparently in this case it's not.
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Re: HFC:Duplicate Detector Match error

Postby oberron » Tue Dec 06, 2011 10:29 am

I disabled the signature checking and that took care of the problem. In version 5, I always had it checked and it worked fine. I would like to avoid downloading something in the future I had forgotten about, but I guess you can't have it both ways. Do you have any idea why this would occur in version 6 but not 5? Just trying to make sense of it, as it was never a problem before. I hope I'm not being a pest. Thanks for your help!!
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Re: HFC:Duplicate Detector Match error

Postby itimpi » Tue Dec 06, 2011 10:32 am

The signature match algorithm is identical in the two releases, so unless there is some other factor involved that is not obvious then v5 would also have rejected the file as a duplicate.

As Quade said only the first 23KB of the file is used to generate the 'signature' so it is possible to get false positives. This was probably just one of those cases.

There is also always the possibility that you HAVE downloaded the file before - possibly with a different name. The signature check process ignores file name and works off file content.
Last edited by itimpi on Tue Dec 06, 2011 11:15 am, edited 2 times in total.
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Re: HFC:Duplicate Detector Match error

Postby Quade » Tue Dec 06, 2011 10:33 am

In version 5, I always had it checked and it worked fine.


It works exactly the same as version 5. You simply hadn't run into this case before. It has nothing to do with V5 or V6. it's a function of what you happened to download.
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Re: HFC:Duplicate Detector Match error

Postby oberron » Tue Dec 06, 2011 10:42 am

O.K. guys, thank you for your help, I appreciate it!!
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