Restoring Damaged .AVI files

[ReggieB]

Hi All!

I've had a look at the other forum threads on this topic, but having tried many of the suggestions I thought it would be best to ask for advice on my specific problem.

I had a number of .avi files deleted by Windows which I managed to recover using data recovery software. A few files play normally, but lots do not.

The files appear to contain the actual data (file size over 1Gb) but are missing the header information. Tried splitting the corrupt file and replacing the first file with the first file from an identical working .avi file as suggested in another thread, but now I get the error "Error 39 you have reached the end of the file".

Tried to fix using DivFix to rebuild the index but this also returns error messages "corrupted data found at frame 2, error offset".

If anyone has any ideas I would be very grateful!

Many thanks

ReggieB

[johnmeyer]

My experience with this, unfortunately, is not positive. A lot of the freeware recovery tools do a lousy job with large files and don't actually recover them correctly. As a result, you may not have as much of the original video as you think. Therefore, reconstruction may not be possible.

[JVRaines]

I once repaired a DV-AVI file by copying in known-good DV headers, manually fixing up chunk pointers in a hex editor (tedious!), and finally rebuilding the indexes with AVI Repair.

[ReggieB]

I've used a paid-for app called iCare Data Recovery, as I had a feeling the free apps would be a bit dodgy! The only manual repair I have attempted so far is to split the corrupt file into 2Mb sections and the same with a working file which is almost identical. Then I replaced the first file of the corrupt file with the first file of the working file, and joined them, however whilst it can be opened in an .avi repair app, it still returns multiple errors Is there an obvious floor in this process that I have missed?

Are there any other ways of replacing the header information which appears to be missing?

Thanks for the replies!

[ReggieB]

This is a screenprint of the results in GSpot if this reveals anything useful?

[JVRaines]

By joining arbitrary 2 MB sections you have created Frankenstein's monster. No wonder it lurches around and falls down. You need to transplant only the main and stream headers. To do so, open the good file in a hex editor and search for movi. Back up a few bytes and you will see the string LIST. Everything before the "L" of LIST is the header.

[ReggieB]

That's great thank you! Just needed someone with a technical eye to see where I was going wrong!

I've opened the good file and located movi and the string LIST just prior to it. (Screenshot attached).

Is it just a case of copying everything before the "L" into the bad file?

[jagabo]

I've opened the good file and located movi and the string LIST just prior to it. (Screenshot attached).

Is it just a case of copying everything before the "L" into the bad file?

Yes. But that's just the start. In my experience with undeleted files, if the header is bad the rest of the file is likely to be bad too.

[JVRaines]

Is it just a case of copying everything before the "L" into the bad file?

Yes, but first repeat the search in the bad file to identify its header, which is the only part of that file you will replace.

In my experience with undeleted files, if the header is bad the rest of the file is likely to be bad too.

It depends on the capabilities of your AVI recovery software. Some programs will scan for chunks and fix up the size values, while others will simply choke. In the latter case, it's necessary to identify and count byte ranges, then replace size bytes with the correct values, respecting little-endian byte ordering.

[ReggieB]

Ok so I've transplanted the header into the bad file, and tried to open in VirtualDub to repair it, however I get the error "Invalid AVI file: The main 'movi' block is missing". When I open in DivFix it returns the error "I/O error 131".

Like you say, maybe this is just the beginning! Still staying positive tho!

[JVRaines]

Does your bad file even have a movi chunk? If not, then you are probably out luck unless you can find a good heuristic program to work on it. Otherwise, the problem is likely to be incorrect chunk size values as I explained above.

[ReggieB]

I've looked at the bad file and you are right there is no movi chunk. Not looking good for this file! I've looked at another and there appears to be a movi chunk but it is located halfway through the file and there is no header (screenshot attached). Is there hope for this file? Looks like it may be jumbled.

Thanks

[johnmeyer]

BTW, if you haven't written anything else to the hard drive on which these deleted AVI files reside, you might simply try using another file recovery tool.