Why won't my video play?

[Android Central Question]

I recorded a video today and afterwards, after recording it, as I tried to play it it displayed: Failed to play video - An unknown error has occurred. It's done this to all of my videos since I got an SD card put in. I believe the SD card is screwing it up, but I don't know how to fix it. I tried transferring it to my device, using third-party mp4 fixing software, and now i'm stuck. The video took ages to make and I really wouldn't want to permanently lose it. Please help.

 

[B. Diddy]

Welcome to Android Central! Which phone? Are you using the stock Camera app? Can you clarify -- is the video saved to the SD card? If so, Unmount the card (in Settings>Storage), take it out and insert it into your computer. Copy the video file to your computer, and see if it can be played there.