If you want to support every meeting platform, you can’t really make any assumptions about the data format.
To my knowledge, Zoom’s web client uses a custom codec delivered inside a WASM blob. How would you capture that video data to forward it to your recording system? How do you decode it later?
Even if the incoming streams are in a standard format, compositing the meeting as a post-processing operation from raw recorded tracks isn’t simple. Video call participants have gaps and network issues and layer changes, you can’t assume much anything about the samples as you would with typical video files. (Coincidentally this is exactly what I’m working on right now at my job.)
At some point, I'd hope the result of zooms code quickly becomes something that can be hardware decoded. Otherwise the CPU, battery consumption, and energy usage are going to be through the roof.