How to make a layer with a transparent "hole" inside?

Question

css

Good day!
Please tell me how to implement such a layer with a "keyhole", through which the background video is visible? prntscr.com/9qbu7b
As far as I understand, you need to use svg, can you throw off an example of such an implementation or an approximate algorithm for solving the problem?
Thank you!

Answer 1

codepen.io/fixcl/pen/CHgrn
codepen.io/SahAssar/pen/YPWxWX

Answer 2

1. Open photoshop
2. Create a square/rectangular white picture (video size)
3. Cut a hole in it in the center of the desired shape
4. Save as png with transparency
5. In HTML, insert a div as a layer above the video.
6. Use this picture as background for this diva
7. Profit!