[Android Central Question]

I apologise for reposting the same question, however, I do not have an account here and I had details to add, please read to the end.

I've had a Samsung Galaxy S5 since May 2014. Up until just over a year ago I've been using a 2GB SanDisk SD card in it, but the storage was full, and so I changed it to a 16GB Samsung EVO SD card, moved everything from my phone onto it, then put the old card back and moved everything from there back onto the phone, all with no problems. A few weeks ago, the 16GB and the phone storage were both full, so I removed the SD card and put a new 16GB Samsung EVO plus into the phone. I then moved all of the videos, some 200, stored on the phone onto the new SD card. However, all except the GIF files didn't want to play on any video player player. I moved one video back to the source folder on the phone, but it still wouldn't play. I continued using the new card for a week, then I removed it and put my old card back. The video that I moved back to the phone still isn't playing. My old SD card is still full, but my phone has 1GB free now. I haven't used the new SD card again.

Is there a way of recovering these videos without having access to a PC, as I don't have one? What caused the problem? How do I prevent it in future?

Additional details- I haven't updated the software on the phone since I got it, so I've been using KitKat 4.4. However, a few days after putting in the new SD card and while It was still in, I accidentally updated the software to KitKat 4.4.2. It was after this that I removed the new card.
Also, I do not have any cloud backups of any of my data because I do not have enough monthly Internet data to upload it.

[B. Diddy]

Welcome to Android Central! It's worth creating an account here so that you can actually carry on a discussion within the thread you created, since this probably won't be a simple one-post answer. https://forums.androidcentral.com/as...ml#post3754828

SD cards have never been a completely reliable way of storing or transferring data on Android devices. For one thing, SD cards themselves are inherently unreliable, using memory chips that are bottom of the barrel (according to a friend in the industry), which makes them prone to data corruption or failure. In addition, counterfeit cards continue to be a problem (i.e., someone taking a smaller card and programming it to report as a larger card -- which means that if you try to save more data than it can really hold, that data can become corrupted or lost).

The implementation of SD support can also vary in reliability. Samsung was notorious for this in the days of the S4, which I believe had firmware that would increase the risk for SD card corruption. And don't get me started on Adoptable Storage.

Another common problem is removing a card without first Unmounting it in Settings>Storage. Doing so is like removing an SD card from a PC without first Ejecting it -- it can lead to data corruption if the device was in the middle of a read/write operation at the time of removal.

The bottom line is that it's difficult to say exactly why your videos aren't working. Using a PC would be your best bet, first to see if the files play normally on the computer. If they don't, you can use chkdsk to look for bad sectors: http://forums.androidcentral.com/amb...d-sd-card.html

[Rukbat]

Recovering a deleted file is possible, "recovering" a corrupted file, if you don't have the original uncorrupted version, isn't. The computer can't guess what was in the parts of the file that aren't there. It might be possible, if you open the "bad" files in a hex editor, and if you know what the layout of the file should be, and if it's the header of the file that's bad, you can fix it manually.

That's why moving files is a bad idea. You copy the files, check the copies and, if they're good, you delete the originals. If a copy becomes corrupted you still have the original to make another copy from.