RTMP

moq import rtmp accepts pushes from OBS, FFmpeg, and hardware encoders; moq export rtmp serves plays to VLC, ffplay, and mpv, or pushes to a remote RTMP server such as Twitch. Both legacy RTMP (H.264 + AAC) and enhanced RTMP (HEVC, AV1, VP9, Opus, AC-3, multitrack) work in each direction.

# Accept an OBS push and publish it to a relay.
# In OBS: server rtmp://host:1935/live, any stream key.
moq --connect https://relay.example.com/anon --broadcast live.hang import rtmp --listen '[::]:1935'

# Serve the broadcast to RTMP players
moq --connect https://relay.example.com/anon --broadcast live.hang export rtmp --listen '[::]:1935'
ffplay rtmp://localhost:1935/live

# Restream to Twitch
moq --connect https://relay.example.com/anon --broadcast live.hang export rtmp --connect 'rtmp://live.twitch.tv/app/<key>'

A listener bridges exactly one --broadcast and ignores the RTMP app and stream key, so multi-tenant routing by key belongs in your own program using the moq-rtmp library, which hands you each publish or play request to accept, map to a path, or reject. The CLI listener is unauthenticated; firewall it.

Each push is its own broadcast. Import publishes the encoder's own timestamps and anchors the catalog clock on the first frame, so it names the wall time the push arrived. A group starting before the previous group's start, such as an encoder restarting its timestamps mid-push, ends that push with an error.

A player that advertises enhanced-RTMP multitrack receives every rendition. Any other player receives one video rendition: the largest picture (then highest bitrate) in a codec it advertised. A push carries the largest one.

Implemented in pure Rust (no librtmp). The CLI speaks plaintext rtmp:// only. The library adds RTMPS on the same port when the embedder supplies a TLS config, and by default still accepts plaintext rtmp:// there, so stream keys can arrive unencrypted. The embedder can set plaintext to false to serve rtmps:// only: a plaintext client is refused at its first byte and the refusal is logged with the peer address. Refusing plaintext without a TLS config fails at startup. FLAC and MP3 enhanced-audio payloads are dropped because hang has no catalog codec for them.

Incoming chunk streams are reassembled independently, including interleaved control, audio, and video messages. Each connection retains at most 256 chunk stream IDs, including completed streams' header history needed by compressed headers. Reusing an ID does not consume another slot; the connection releases all slots on teardown. A 257th distinct ID is refused, even if its numeric ID is small. The limit counts streams rather than constraining their numeric IDs.

Incomplete messages reserve their declared payload lengths against a 64 MiB connection budget before allocation. Completion or an RTMP Abort releases that reservation; malformed input or exhaustion closes the connection and releases its parser state. The 24-bit RTMP message length still allows a payload up to 16 MiB minus one byte. Four maximal payloads fit, with exactly four bytes remaining.

These internal limits leave room for the gateway's five chunk-stream roles and FFmpeg's fixed control/audio/video channels as well as OBS's control and media channels. They bound retained state independently of chunk size and retain support for large keyframes. Undecoded input has a separate 64 MiB buffer limit. Connections exceeding these limits are unsupported.

Run just rs bench-rtmp to compare decoding one active stream while 1, 16, 64, or 256 streams retain state, across 128-byte, 4 KiB, and 64 KiB messages with 128-byte and 4 KiB chunks. The benchmark smoke runs nightly.