Re: how can I recover a deleted video on my samsung galaxy tablet
1) The tablet has to be rooted.
2) You have to install an app that recovers deleted files. (Most of the ones that actually work aren't free.)
3) By writing to the tablet's storage, which rooting and installing apps does, you risk overwriting the very file you're trying to recover. If you think you may delete a file you don't want to delete, and don't want to make sure everything is backed up, root and install an app before the problem occurs.
4) If the file was on the external SD card, turn the tablet off, remove the card, putt it into a USB adapter and plug it into your computer. Then download
PhotoRec (it's free, but it's worth a king's ransom), burn it to a disk (CD or DVD) and use it to boot the computer. Tell it to recover files from the SD card and save them to your hard drive. If there's a block of data on the SD card that looks like a video file, PhotoRec will recover it and save it as the type of file it is. (It will probably find a lot of stuff you forgot you once had on the card.)
And no, PhotoRec probably won't work on the internal storage of the tablet. (It won't cause any damage if you try it, though.)