Embed Video in pattern (??) in svg. Is it possible and how?

Question

css

you need to insert letters into the background in the SVG video .. it’s not very clear how .. are there any experts in this field?))

Answer 1

For example like this:
Google "SVG mask video"

Answer 2

Unfortunately, that's not it .. here the video is in the background and the svg is simply superimposed with a mask.
I have a slightly different one .. there is a block in the background of which there is a video, in the center of the block there is a letter, inside which (in a pattern) there is another video clip) ..