Edit: guessed it would have helped to add a link https://www.facebook.com/BigBendWeather/
This was more of an experiment switching from a static image to a video on Facebook. After thousands of FB nag screen about why I should update my cover images, I caved and decided to try it out. It's too bad FB does not have a single, authoritative source for specifications, and after searching, you it's all very vague. Well, not all of it but most. Facebook states the video should be 20 - 90 seconds, should be an MP4 and the pixel dimension (aspect ratio) should be 820 x 312, which is 2.63:1. (wider than any HD, 2K, 4K or even any 8K aspect ratios.
Then, you keep reading and find that FB recommends that the pixel dimensions should be 820 x 462, which is1.77:1 (commonly known as 16:9), which is regular old 1080i or 1080p, and is the format of most Hi Def TV's and Monitors. It is also the format of virtually all consumer HD video devices and of many professional video cameras (AFAIK).
So, when FB stated they recommend the video should be 820 x 462, I assumed this standard "window" would be what appears on the cover video. This is also important as I am a stickler for putting my copyright noticed on everything. There are still folks that think because it is so easy to steal digital content, it is OK to do so and as much as I hate adding a notice, it is something I simply have to do.
Now that I had the specs in hand, I grabbed 10 stills, cropped them to a 1.77:1 (16:9) format, dragged them onto a timeline, spliced in a short time lapse segment and then added a couple of Pan and Zoom, Ken Burns effects and a couple of spins and called it good for the editing, Then a simple title overlay for the copyright info, down in the lower right corner. I exported it to a QuickTime Reference movie, opened it in Adobe Media Encoder and created a standard MP4 file.
Some critical info they might have offered is the maximum file size you can use and or possibly the bitrate? They state if it does not meet their criteria, you will receive an eror. However, they only error I received was the dang FB upload thingy went on for over an hour. After a few tweaks, I got it to upload and from what I experienced, it the upload is over 100MB, it will fail, but somewhere just under 100 megs, it succeeded.
All seemed well until I had a noticed to position the video, huh? I created it exactly as they suggested so why would this be necessary. After utilizing the ruler tool in Firefox, I figured out the video was cropped back to the original, non recommended aspect ratio. In essence, FB single handedly cropped out my copyright notice. That was not acceptable so I went back and adjusted the position of my © notice and rendered the thing again and uploaded it. Now it appears as expected on the FB cover. But...if you click the video and it opens up in a new page, you see the original 16:9 crop, but the copyright notice is now way up high where it is really obnoxious.
The problem is, you can easily change resolution in video editing applications, but changing the aspect ratio is something you don't do - unless you are willing to see black bars or distort the image. If the Facebook designers had a grip on video, they would understand that most businesses would like to create a video and be able to use it in numerous social media outlets and not have to create a completely different edit for each provider.
Anyway, I hope you enjoy it - it is still a little rough and maybe in another 7 years, re-edit it and replace it all over again.