How to extract corrupted RAR files

Question

I try to extract a file from set of .RAR parts. I always get the following error:

Corrupted

so I tried many programs to extract the corrupted RAR files. I have 10 parts, each one 400MB big. The last progam I used was Recovery toolbox for RAR.

It gave me the following message:

Severity:!High
Message:Recovery error for file XXXX with message set file
pointer error.

The program extracted 2GB of data, but it should extract 4GB.

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Is there any way to extract the content or am I supposed to download the files again from another server?

Solution 1

Short Answer

No, you are doomed, redownload is your best option.

Long Answer

You can start fiddling around with a hex editor and try to fix bad values in the RAR file, if you know how to define bad and how RAR works. But that's for sure a very hard route to take.

Solution 2

No, you don't have to download (all) the files again. That's precisely one of the reasons to split an archive into volumes.

If you use the actual WinRAR, it won't give you some cryptic "corrupted" message, but tell you exactly what's going on.

For example, if it reports

!   C:\archive.part05.rar: Packed data CRC failed in filename. The volume is corrupt
!   C:\archive.part10.rar: CRC failed in filename. The file is corrupt

In this case, the only corrupt volume is archive.part05.rar. Redownload that one and try again.

Solution 3

When I find myself in a situation like this where I have what looks like a corrupted file (of any kind) that is too large to just up and re-download, what I do is to find a way to download just the bad pieces.

There are two common ways to do this: the eDonkey network and the BitTorrent network.

What you need to do is to search for the corrupted file either using a torrent search engine or an eDonkey client like eMule. If you manage to find that specific file, then you can begin the download just enough to make sure that the program has all the information needed to verify the file (metadata for torrents and a full .met for donkey files).

At this point, you can import or replace the new file that will be downloaded with the original corrupt one (or better yet, a copy of the corrupt one), and re-hash the file.

That way, eMule/µTorrent/etc. will be able to see (hopefully) most of the file is already downloaded and only re-download the bad pieces/chunks, thus saving you a lot of bandwidth (at the cost of a lot of time depending on the file in question and its current popularity).

Comments

[Synetech]

I take it that the archive had no recovery record?

[Anyname Donotcare]

ohhh god,i should re-download 4gb again , and no guarantee not to face the same problem..

[Oliver Salzburg]

A broken RAR file implies missing data. If the recovery data in the RAR file is not enough to reconstruct this data, you will not be able to regenerate it out of thin air. Not with a hex editor, not with some magical software.