Home

The two most common files on a camera memory chip are JPEGs and AVI files. Typically, memory chips do not get fragmented, but if the chip is full, or individual files have been deleted, then fragmentation can occur. As long as the FAT file system remains intact, there is not problem. If the chip is deleted, or formatted, then all details of file fragments is lost.

Using signature analysis, many files will be recovered, but the fragmented ones will be lost.  An AVI file has a very strict structure, and it does rely on the final 16 bytes of the file being intact, and in the correct location.  In other words, a 99% complete AVI file will not read - although a repair would be possible.

Once the CnW software has done a recovery of all files on a memory chip, the files are tested to see if valid.  At this point, it will try and reconstruct non valid AVI files.  The AVI recovery process has two possible approaches, probably unique to CnW Recovery software

Approach 1 AVI recovery

The first approach to recovery of fragmented AVI files is to search the disk for the index section of the file (idx1) stored at the end of the file.  Once this has been located, a list of each file chunk is known, along with it's size and location.  It is then possible to test possible clusters of data to ensure they fit with the index. By working this way, it is extremely unlike to get a false positive match for a AVI cluster

Approach 2 for AVI recovery

Not every disk will contain a full AVI file, as some fragments may have been overwritten.  In this case, if it is not possible to recover the complete index, a new one will be created based on the amount of the sequential avi data that can be read.  The file will not be complete, but it can be viewed.

For more details, see the section on Fragmented JPEGs. and ensure that the Process Fragments is enabled.