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Our security camera writes new AVI files every 20 minutes and overwrites itself every 3 hours, and when it starts overwriting it removes the earliest 20 minute AVI file (so that there is still enough space left on the SD card for more than 20 minutes, it is never "Full").

We're trying to retrieve the first and maybe second file that was "overwritten", and Photorec managed to find quite a few AVI files but only 1 of them is readable. We suspect the earliest AVI files aren't really "overwritten" as there is still enough spare space on the SD card for over 30 mins of footage. Also it recovered some big .gz files It plays for about 5 minutes even though it is supposed to be 20 minutes. It seems like the AVI files are recovered in a different pieces, so that only the beginning of the AVI file is playable and the rest are not as they lack some information? Also when it is in the process of recovering, it looks like there is an AVI file being recovered but then after a while the AVI files disappears. We are not tech experts by any means, so apologies in advance if we don't understand technical language! How can we recover playable AVI files? Would Testdisk be better?

Thanks for your advice

nadsnads wrote: 25 Feb 2021, 17:36 Our security camera writes new AVI files every 20 minutes and overwrites itself every 3 hours, and when it starts overwriting it removes the earliest 20 minute AVI file (so that there is still enough space left on the SD card for more than 20 minutes, it is never "Full").

We're trying to retrieve the first and maybe second file that was "overwritten",

You won't recover overwritten files, maybe deleted ones.

and Photorec managed to find quite a few AVI files but only 1 of them is readable. We suspect the earliest AVI files aren't really "overwritten" as there is still enough spare space on the SD card for over 30 mins of footage. Also it recovered some big .gz files It plays for about 5 minutes even though it is supposed to be 20 minutes. It seems like the AVI files are recovered in a different pieces, so that only the beginning of the AVI file is playable and the rest are not as they lack some information? Also when it is in the process of recovering, it looks like there is an AVI file being recovered but then after a while the AVI files disappears. We are not tech experts by any means, so apologies in advance if we don't understand technical language! How can we recover playable AVI files? Would Testdisk be better?

You can try Testdisk but you should check out if your file system is supported by Testdisk here:
https://www.cgsecurity.org/

Some AVI files are recovered, but only 1 in 4 are playable. The AVI files were originally around 3.2gb each, but now the recovered ones are only 980mb each.

Somehow the AVI files are smaller and the ones that are playable stop playing when they are less than 50% through.

It looks like the unplayable files need to be joined to the playable ones somehow? Any ideas? Thank you!