Stereoscopic 360 video player in Unity?

Would i be able to create custom interfaces in the sample?
Also, would i be able to put a video file with an image on top and at the bottom like i mentioned earlier, or the sample just requires one .mp4 file and there's no option for messing around with it?

It will probably be easier to noodle with the interface in Unity, but you can make a custom interface in C++ for the Oculus360VideosSDK sample. See VideoMenu.cpp.

Alright, i'll check it out.
Could you please just answer my question about the video/images combination in the sample file?

You could do it like I described for Unity or native. Either make separate meshes with the static textures on them or copy the static images into a larger atlas texture each frame, such as with glBlitFramebuffer.

Since i'm not that familiar with Unity i guess i can't fully understand it, but i will look into it.

To sum it all up though - there is a way to render out a 360 stereo video from unity, where (for example) the middle part is video and the upper and lower parts are static textures. 
This, as opposed to rendering the whole thing as a video, would reduce the file size.

Is that correct? 

Mostly correct. If you just include the static textures in your video, the size increase should not be major. Video codecs like H.264 will encode the still images in one "I frame" and be done with them.

You meant "the size decrease"?
Because if i include textures in the video i should get a smaller size than if it were all 100% video, no?

Sure. It's only slightly more expensive to store a static image as a video file than as an image file.

Okay I'll try all of that out.
Many thanks for your support and quick responses!