REMB (Receiver Estimated Maximum Bitrate) is an older WebRTC congestion-control signal in which the receiver estimates how much bandwidth the path can carry and tells the sender, via an RTCP feedback message, to stay under that ceiling. The sender then adapts its encoder bitrate to avoid overflowing the link, which for audio mostly means it gives way to video under contention since voice needs little. REMB was the original bandwidth-estimation approach in libWebRTC and is now largely superseded by transport-wide congestion control (transport-cc), which moves the estimation to the sender for finer, faster reaction. You still encounter REMB in older stacks and as a fallback.
