Hi @suaji,
Might I suggest using a <canvas> tag and using the window.innerWidth and window.innerHeight properties to auto fit the window? So it would essentially autofit any size without the need to hardcode.
Something similar to what's suggested in this video:
You could also put the <video> inside the <canvas> tag and do the needful from there. I don't know if that's how you've arranged the page as the red box had blocked the upper and lower tags.