Optionalcodec?: "vp8" | "h264" | "vp9" | "av1" | "h265"OptionalpreviousTrackId?: stringtrackId this receiver's pipeline was previously set up for, set when a transceiver gets reused for a new track. Lets the worker find the cryptor that still owns the (already transferred) encoded streams and re-point it, rather than creating a fresh cryptor with no pipeline at all.
undefined for audio tracks