How does NACK works in webrtc?

Question

I would like to ask how does NACK work in webrtc. I know that we can receive NACK packets. But I don't know if we need to resend rtp packets manually or it done automatically by webrtc and we just need to enable or disable NACK. Also i don't know if it's enabled from the beginning. From sdp I see that there is something like

a=rtcp-fb:96 nack

a=rtcp-fb:96 nack pli

I'm not sure but from these lines I understand that NACK is enabled. So if yes, do I need to resend rtp packets manually or it done automatically by webrtc? Thank you for any help.

Answer 1

It depends on whether you are writing a WebRTC native client or simply using the WebRTC Javascript API within a web browser. Most use cases are the latter, and in these cases the browser’s WebRTC implementation handles NACKs for you — you don’t need to worry about it.

If you’re writing a native client, then it would help to implement NACKs as the quality will improve, but it’s not strictly necessary.