An off-the-shelf GPU can encode / decode thousands of channels of video and audio in real-time.

There are some cloud providers that offer this as a service, allowing you to have the end-points of, e.g., video calls to use different audio and video codecs.

This is quite useful, e.g., when some people join the call only using audio via a cell phone in a different country using a different audio standard (or a land line, etc.). Or when somebody joins the video call from laptop tethering from a phone on a train. Or for switching video codecs depending on whether somebody is sharing their desktop or using a webcam to record their face.

The client can picks the codecs that are the best fit for the current situation (content, bandwidth, latency, etc.) and a could server transcodes the video from everyone else in the meeting to their clients format.