Recover deleted and fragmented AVCHD video files
Many video recorders use FAT32 as a file system. This means when a file is deleted all details of any fragmentation is lost. As AVCHD files (the .mts stream) can be large, the chance of fragmentation is also increased. Recovery by a simple undelete, or data carving will only produce partial results. The start of the file may be seen, but not all of the data. In this process, many fragments may be recovered, but the sequence largely lost.
The chance of fragmentation has been increased on some cameras by the way other meta data files are handled. On at least one JVC camera, the .CPI file is written before the final stage of the .MTS file has been saved. This means that .MTS files are always fragmented, and so the final section of video would be lost on a simple carving reconstruction. The second issue with JVC camera is that the delete process clears down all 32 bit of the cluster pointer stored in the FAT. On most PCs, only the upper 16 bits of the cluster pointer are cleared which makes recovery initially easier (even though it has not affect on fragmentation).
CnW Recovery have developed routines to recover, when possible, all of the video files. The process starts with standard data carving, but with the option to process fragments enabled. At the end of carving, the user is given the option to process the fragments. The next stage can be slow, but the results can be impressive. Each fragment is examined and then the following fragment is searched for. This way, the original .MTS file is reconstructed in a way that can be viewed, as originally filmed.
For straight memory chips the best solution is to use the AVCHD wizard function. This scans and mapped the whole memory chip and joins fragments together using a very accurate process. The result is a small number of continuous fragments - competing software will often produce a very large number of very short fragments.
For technical reasons, this defragmentation is not viewable on the demo download.
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