The AVI video format is very popular with cameras. If a camera FAT32 memory chip is deleted, then the locations of any fragmented AVI is lost. As AVIs tend to be large files, 20-30MB a minutes, the chance of fragmentation is high.

CnW Recovery has a routine that will help process fragmented AVI files. It is part of the Data carving function, when the Process fragments option is enabled. There are two modes that the routine will work in, as follows.

Defragmenting by carving.

This mode operates by finding the start of an AVI file - it has a signature of RIFF - and then finding the ‘idx1’ section of the file. This section of the files indicates where each element is stored. By having the idx1, it is then possible to search the disk for clusters that match the idx1 pointers. By using this technique the chance of a false match is almost zero.

Recovery by recreating the idx1

The prefered method described above will have a very high chance of producing a working file, but is does rely on all data clusters still remaining on the disk. Sometimes cluster can be overwritten, and so it is impossible to recover the complete original AVI file. In these instances, the program will make use of what it has, and reconstruct the idx1 section of the file. This will give a shortened AVI file, but one which will be viewable. The length of the file does depend on how it was fragmented and so in the worst case, it could be just one cluster long, or 99% complete