Evidently s is a GoPro format called Superview
Also see section "Video Settings – Diving Deeper" on this page
RES: Video Resolution – Explained
The GoPro has a lot of settings so this is an important topic to understand. 1080 means the file is 1920 x 1080 pixels – this is the classic widescreen size of your HDTV. If the resolution is 1440 it means it’s the same width as 1080 but taller (1920 x 1440 pixels). It’s a 4:3 aspect like an old non-widescreen TV. It provides more vertical view above and below compared against 1080. The HERO3+ Black edition has a few resolutions above 1080 which will simply provide more detail than 1080 (2.7K and 4K). If you want to go lower, the camera can go down to standard definition as well. Lastly if the resolution has an “S” on the end, it’s in Superview mode. This is explained in more detail below.
S: Superview – Explained
Superview automatically captures the visual information from one of the tall modes (1440 or 960) and dynamically stretches it to fit a 16:9 aspect ratio (1080 or 720). It doesn’t just stretch it down, everything would look fat, but pinches the center so anything in the center of the frame looks good, while it stretches out the outsides. I explain this and how to do it manually in great detail in this post. Superview has the potential for great results as well as some pretty funky looking video. Basically anything POV without a ton of important visual items in the edges of the frame will look good – examples are motocross from the head, downhill mountain biking from the head or chest, skiing on the head or chest, surfing from the nose of the board, etc. Anything where you start interacting with people or holding it in your hand will end up with some stretchy looking figures. Bottom line for this mode is the more view you have in any of your sports the more immersive and smooth your video will be – try it out and see how you like it.