What I normally do to send a video, I think the phone limits the size to 1MB, since my phone is not in front of me I am cannot double check.
I open the stock message application.
-Add the recipient
-Click on the the paper clip below
-Choose Capture video
-Film one (at the bottom of the screen you'll see the size progress bar at the bottom, and I think it times out at 1 minute(again no phone in front of me to check))
-Then click save it
Then is will add it to the message, all my family with iOs/android device receive them fine.
Hope this helps.