pub fn render_answer(answer: &SdpAnswer) -> StringExpand description
Serialize an SDP answer for the application/sdp response body.
str0m can emit a rejected media line (port 0) with an EMPTY format list,
e.g. m=audio 0 UDP/TLS/RTP/SAVPF . This happens when we restrict the
CodecConfig (see crate::session::rtc_config_with_codecs) and the peer’s offer
carries a codec the broadcast can’t egress – the classic case being AAC
audio over WHEP, which we can’t carry, so the audio m-line comes back
rejected with no payload. An m-line with no <fmt> violates RFC 4566, and a
browser rejects the WHOLE answer in setRemoteDescription, killing playback
of the media (e.g. video) that WAS negotiated. So we give any such line a
placeholder static payload; the media stays rejected (port 0), so the
placeholder is never used.