Having CRC problems in multi-part RAR video files?

Here is the predicament that will probably seem familiar to you:

You are downloading <insert someone’s name here>’s <insert an activity name here> recordings, however since it is a HUGE file; it is compressed in multi-part form to make it suitable for file sharing sites.

You start downloading it by getting all parts; one by one. You start extracting it; you call your friends/family to watch it together only to see that the CRC check has failed on the last part! 😦 (or any other, but for purposes of demonstration, assume that it is some part close to the last one)

CRC(Cyclic Redundancy Check) is an Error Correction Code. If the CRC check fails on a file, it means that during the transmission of that particular file; some bits were corrupted causing the CRC check to fail.

repairArchive.

You could, of course, try to repair it by opening the faulty part and selecting “Repair archive” from the Tools menu as shown on the bottom, and trying to extract it again.

 

 

 

But what if that also fails?

You’ve waited a long time(assuming your internet connection isn’t super-duper fast) to see this, but you won’t be able to see anything?

Well, one solution is to just re-download the part that the CRC check has failed,(there is no guarantee that this will solve the problem, but it is worth a try)

But since you don’t want people to wait any longer, you decide to go on with the second option.

winrar_rcm

Then you could right click your file, and from the WinRAR context menu select “Extract files…”  to select extraction options for this particular extraction.

 

 

winrar_extract_options

 

 

You will see some options here in this screen; but what we are interested in is the “Keep broken files” option.

 

 

 

 

 

What it basically does is to not delete the extracted sections of the multi-part RAR file if and when an error occurs. So, say you’ve got an 8-part file and only the last part is corrupted during download, and that the whole video file is around 800 MBs. You will get approximately 700 MBs of it; and will be able to watch it! (Actually, if the extraction process does not end whilst encountering an error; –which I have observed that it does on some occasions(e.g. if there is an unexpected end of archive error)- you will be able to get the whole file!)

In some video formats, you may not be able to control the slider to get the video to move forward.(Such that you will always have to watch it from the beginning)

But hey, it is better than nothing right? What if the corrupted part was no longer downloadable because the link is now broken? You will still be able to watch it!

What if you kept these compressed files on a CD-ROM and it degraded with age such that the video file is corrupted? Won’t you be able to see the video?

You will!

What if you downloaded only half of the parts but want to take a quick look?

You can!

Are you on a *nix environment? Just use the unrar command with the Keep Broken Files switch to tell him to keep the partial/broken file.

e.g. unrar x -kb filename.part1.rar

Nothing works? Is it FUBAR? Well, as a last resort, you may need to have to download it all again. 😦

You may also be having memory problems, check your RAM with a software.

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4 Comments

  1. Mike said,

    March 9, 2009 at 6:54 pm

    Enjoy reading your blog.Btw, this is first time I visit to your blog 🙂

    ________________________
    Why pay $1000’s for solar or wind power when you can build your ownprofessional system for less than $200?! (in your own backyard)

  2. Ozan said,

    March 10, 2009 at 11:24 am

    Glad to hear that! Hope your visits won’t cease 😉

  3. g said,

    September 5, 2010 at 10:21 am

    hohoho… I got different story but very funny.
    I have 5 parts of rar (compressed movie file).

    And once I extracted using WinRar, it stop at the 5th file (CRC Error).
    Gosh!

    What I do is just follow ur steps.
    Put those 1st – 5th files in a same folder. Then extract them using Keep Broken Files. 😀 and, it’s okay.
    The movie could be watched until the end of the story!

    Nice man… 😀
    thanks!

  4. Rohit said,

    October 21, 2010 at 12:00 am

    WOW! I tried the Keep Broken Files option…and it worked! Fantastic.

    I have been facing this problem for so long, I used to hate RAR files. Now I know the solution to at least partly open the parts which are not corrupted.

    Ozan, you are a STAR! Many thanks.


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