RAR Archive Repair ?

Heofz

Heofz

Heofz

Soldato
Joined
20 Oct 2002
Posts
3,469
Location
London, UK
I have a question for you guys:

Lets say I were to create a RAR archive, which was, say, 1GB in size, which itself was split into 10 parts, each 100MB.

Now lets say that I've sent all but one of these parts to a friend successfully, but for one reason or another, that missing part has since been deleted from my hard drive, and thus gone forever.

Now I still have the original files that was rar'ed. Is there any chance I could generate the missing part again from my files? Just re-creating the rar archive with the same settings, and picking out the missing part does not work, as it has to be a perfect CRC32 match.

So for example, if part 6 out of 10 was missing, but I still had all the other parts, is there a program that could look at part 5, look at part 7, look at the original files I archived, and generate the missing part 6 in its original glorious form?

Otherwise I'll have to send the whole lot to my friend again, which would be a real pain :(

I've tried a couple of rar repair tools by searching on google, and none of them are anywhere near as sophisticated enough to do the above task.

Does anyone know if this can be done?
 
The normal repair method for RAR files is to use PAR2 parity files to recreate the missing parts but this relies on having extra recovery blocks rather than the original files. I doubt you'll find something that will recover the rar files based on the contents - why would anyone create such a thing when you can simply recreate the archive from the original files?
 
rpstewart said:
why would anyone create such a thing when you can simply recreate the archive from the original files?
Click to expand...
for the situation as described in the OP :p (in the case of there being no recovery blocks or PAR files). Nevermind though, seems to be too much hassle anyway, would probably be easier to send the whole bunch again.

Thanks anyway peeps :)
 
Grr... its happened again!!

Right, this is getting annoying... I want to try something but run it past you guys beforehand in case there's anything I should know first. Please bear with me, I'm sure its a complicated & confusing question so I've used colours to help illustrate what I mean.

Let's say I've extracted the majority of a file from a multi-part RAR archive using WinRAR, and ticked the "Keep Broken Files" option. Let's call it Vodka.mkv; red font for this file, green font for my original file.

So now I have the extracted Vodka.mkv sitting here, with correct filesize, but I know a segment of data inside the file is corrupt, while other parts are perfectly intact. *(see footnote)

Now here's the question: If I still have the original Vodka.mkv file perfectly intact somewhere else, and I roughly knew whereabouts inside Vodka.mkv the corrupted segment lies, would I be able to repair my Vodka.mkv by creating PAR2 files from my Vodka.mkv and using those files in combination with Vodka.mkv to produce a perfect copy of Vodka.mkv?

*Footnote: I'm making the assumption that when making multi-part RAR archives, WinRAR breaks the file up in a completely linear fashion. This is a *big* assumption and if this is not the case then I guess I'm screwed :o
 
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