Galaxy S6 - taking stills from within a video?

[AC Question]

Hi! Just jumped from the S4 to the S6, and I (mostly) LOVE it! One thing that I used a LOT was the option to grab still from within a video. A little camera icon appeared, and you could then snap a few quick shots while taking or viewing video. I am still able to capture a photo while I am TAKING the video - it's the viewing thing that I have not discovered how to do. I have tried in both "Video Player" and "Photos" option for opening the file, with no joy either time.

I found instructions for enabling this feature on the S5, but not for the S6. Any help would be fantastic!