Packet mumcord watch

Part of the Plugin data protocol. Flow: Flow-Watch-Party.

Packet mumcord.watch

Purpose. A YouTube watch party in the user's channel. Every participant plays the video in their own embedded player; only playback commands and the shared playlist travel.

dataID	mumcord.watch
Encoding	JSON object
Version sent / accepted	2 / 1 and higher
Sent to	Mumcord users in the sender's own channel who announced watch-party
Defined in	crates/engine/src/watch_party.rs, watch_party/playlist.rs

Receivers ignore messages from anyone who is not in their own channel, and commands and playlist edits from people who have not joined.

Message types

JSON object with v and a type t. Positions are milliseconds into the video. Video ids must be exactly 11 characters of A-Z, a-z, 0-9, - and _ (a YouTube video id); anything else is dropped.

t	Fields	Meaning
start	video	The sender started a party for this video, paused at the start.
join	none	The sender joined the party.
leave	none	The sender left the party.
cmd	cmd: {"kind":"play"|"pause"|"seek","position_ms":<u32>}	A playback command.
state	video, playing, pos, starter, members, last, cur, skip	The full party, for someone who came into the channel later. Sent twice, about 3 seconds apart.
pl	ops: array of playlist edits	Playlist edits, bundled (version 2).
next	from, id, video, skip	The sender went on from entry from to entry id playing video; skip is true when skipped instead of ended (version 2).

state fields: video (id), playing (boolean), pos (u32 ms), starter (session), members (sessions that joined, at most 32 are tracked and the list is checked against the people in the channel), last (optional {"by":<session>,"cmd":{...}}, who did what last), cur (entry id of the current video, 0 for the video the party started with; version 2), skip (optional session of who skipped to it; version 2).

Playlist edits

o is the operation, c a Lamport clock, k a sort key; entries are ordered by k, ties broken by id.

o	Fields	Meaning
add	id, v (video id), k, c, optional by	Adds an entry. by names who added it when that is not the sender.
rm	id	Removes an entry for good; a later add or move of that id is ignored.
mv	id, k, c	Moves an entry; of two moves the higher c wins.

Examples

{"v":2,"t":"start","video":"abcDEF12345"}
{"v":2,"t":"cmd","cmd":{"kind":"pause","position_ms":61500}}
{"v":2,"t":"state","video":"abcDEF12345","playing":true,"pos":61500,"starter":12,"members":[12,15],"last":{"by":15,"cmd":{"kind":"play","position_ms":61500}},"cur":0}
{"v":2,"t":"pl","ops":[{"o":"add","id":3141592,"v":"ghiJKL67890","k":1.0,"c":4}]}
{"v":2,"t":"next","from":0,"id":3141592,"video":"ghiJKL67890","skip":false}

Version and limits

• Version 1 clients drop pl and next (unknown t) and ignore the new state fields.
• The playlist holds at most 50 entries (MAX_ENTRIES). Edits are bundled, split to fit 1000 bytes, and sent at most once per second (FLUSH_INTERVAL).
• At most 32 participants are tracked (MAX_PARTICIPANTS).

Privacy

Shows which video the channel watches and who joined. Only video ids travel; Mumcord never puts anything but a validated id into a player URL.

Used in

Flow-Watch-Party, announced via Packet-mumcord-hello.