What is the reason for the goroutine that reads incoming RTCP packets?

[mstyer]

I'm looking at the code for several of the examples, e.g. reflect, and I see the following code (e.g. lines 96-106 in reflect/main.go):

	// Read incoming RTCP packets
	// Before these packets are returned they are processed by interceptors. For things
	// like NACK this needs to be called.
	go func() {
		rtcpBuf := make([]byte, 1500)
		for {
			if _, _, rtcpErr := rtpSender.Read(rtcpBuf); rtcpErr != nil {
				return
			}
		}
	}()

What is the reason for this? I'm trying to find any docs that would help explain what this is doing and why it's needed, but I'm coming up empty.

My follow-on question is, if I have multiple tracks with mutiple rtpSender objects, I assume I need to do this for all tracks separately. Is that correct?