Discord's media relay negotiates H264 forwarding from the SDP fmtp. The
hand-built answer in handleProtocolAck emitted a=rtpmap:101 H264/90000 +
RTX fmtp + rtcp-fb but NO a=fmtp:101 ...;packetization-mode=1;profile-level-id=42e01f.
Our encoder emits baseline slices up to 8KB (>RTP MTU), so the packetizer
fragments them into FU-A units (RFC 6184). Without packetization-mode=1 the
relay drops every FU-A slice while passing SPS/PPS (small single NALs) and
Opus audio (no fragmentation) — result: black/broken video, working voice.
Matches @dank074's original fmtp and the native offer (which already had it).
asepharyana
db01117afa