Why the GoPro or DJI camera can lose files
There are many reasons that files can be lost on a GoPro, DJI, or any camera. Most reasons are operator error, or a accident with a camera. Fortunately, actual camera errors are rare. The memory chip can fail, but the most common chip related issue is a fake memory chip.
Accidental deletion or formatting
This probably the most common problem. If you think everything has been copied then files may be deleted, or chip formatted. If the file copy failed for any reason, eg output drive run out of space, then once the chip has been formatted, neither the original or copied files will exist. Fortunately, GPR software is extremely good at recovering these files as long as nothing has been
to the memory chip. As you may have read elsewhere on this website, GoPros do not save files sequentially, but typically interleaved high and low resolution. When a video is deleted, the location of each fragment is also lost, so 'undelete' will not work. For this reason, most other recovery programs fail. They find the file start but then read 'rubbish'.
Occasionally, memory chips can just become corrupted. It could be a power on glitch, or error while inserting the chip. GPR actually typically ignores the file system on the memory chip. This if the chip header has been deleted, or FAT corrupted, this can be handled. A chip that cannot be read logically in a computer will be handled by GPR. Recovery is normally very good.
The GoPro / DJI camera are incedibly robust cameras, but there are limitaions. Sometimes a serious accident can cause the camera to stop recording before the video has been finalised. The process of finalising is when the moov atom is created and added to the video file. The moov atom contains the location of every frame (video and audio). In order to recover the video all this meta data has to be created from scratch. The forensic version of GPR will often do this. Sometimes, though for very critical videos it is necessary for CnW to do some manual tweaking. Please contact us if this required.
One question is how much video until the point an accident is recoverable? The answer is not precise, and depends how much of the camera memory has been written to the memory chip at the critical point. Typically it appears that a few final seconds may be lost. Other times it may record a crash but only stop when the camera hits something. GPR will recover what ever has been written to the memory chip. As ever, it is absolutely critical that nothing is written to the memory chip - this includes any other data recovery program that may claim to 'undelete'
Fake memory chips
One problem sometimes encountered with any video camera are fake memory chips. These are sD cards that are labelled say 64GB, but only have 8GB of memory. The card has been modified so the computer thinks it is a 64GB chip. However, when the first 8GB has been written, the rest is lost. Because the directory is typically stored at the start of the chip, the camera thinks everything is OK. Only when it comes to replay is the error detected. As the data has never been saved, no recovery is possible. The first 8GB will be OK. To help detect this error GPR looks for duplicate clusters and these are counted and displayed on the main screen. An error message is also displayed. There can be false positives so one should always verify the results. The best way to avoid this problem is to buy branded cards and avoid cheap cards. Also, test the chip. The simplest test is to do a recording, of maybe a clock, and make sure that all videos can be viewed.