feat(scene): broadcast sources play in sync on the publisher's timestamps

README.md

@@ -153,6 +153,17 @@ failover replaces the first relay's copy once that copy ends. It plays the
 best video and audio its catalog lists, switches when the catalog changes, and
 comes back on its own when the publisher restarts.
 
+A broadcast source, a guest's included, plays on its publisher's timestamps,
+so its sound and picture stay in sync through network jitter and stalls. Its
+audio plays as far behind what arrives as the network's jitter needs, measured
+as it goes, the same delay `moq play --delay auto` holds, up to 2 s. Each
+picture waits for the sound stamped with it, and the canvas shows the last one
+meanwhile. A sound stall longer than that delay pauses the picture too and
+starts both again together; a picture stall leaves the sound playing. A burst
+after a stall skips ahead to the delay. Without audio, the
+picture plays 100 ms behind. Sources shows how far behind each broadcast
+plays.
+
 ### Audio mixes
 
 Audio from every source is mixed whether or not its scene is live. A
@@ -174,7 +185,9 @@ studio remembers for you rather than in the scene file. Use headphones: a
 microphone that hears the speakers feeds the mix back into itself.
 
 A source's **delay** holds it back in every mix, up to 2 s, so a microphone
-lines up with a camera that lags it.
+lines up with a camera that lags it. A broadcast's picture already follows its
+sound, so its delay holds the sound back from its own picture: use it only for
+a publisher whose sound leads their picture.
 
 Each mix is advanced on the program clock, and each output reads its mix on
 its own, so an output that falls behind skips ahead in its own audio rather

quest/m0/README.md

@@ -91,7 +91,6 @@ repository.
 - [Studio on macOS with capture granted](/quest/m0/app-macos.md) - camera, screen, and audio capture run on a Mac, not only Linux
 - [Studio on Windows](/quest/m0/app-windows.md) - the studio runs on Windows, not only Linux
 - [Audio source tracks](/quest/m0/audio-source-tracks.md) - microphones and system audio get their own tracks, for isolated recording and replay
-- [Broadcast sources play in sync](/quest/m0/broadcast-sync.md) - subscribed broadcasts and guests play audio and video on the publisher's timestamps, with `moq play`'s delay
 - [Wayland display and window sources](/quest/m0/wayland-sources.md) - portal-picked sources that reopen without the picker
 - [Keyframes](/quest/m0/animation.md) - keyframed item properties with easing, starting when their scene goes on program
 - [Media file source](/quest/m0/media-file.md) - a local video or audio file plays as a source, looping or from the start on demand

quest/m0/sync-clap.md

@@ -22,7 +22,3 @@ The studio sees a source's audio only through its strip's level meter, read
 once a frame, which is too coarse to time a clap. Timing it needs the
 source's samples, or an onset, with their position on the bus clock, which is
 moq-audio work: land it there first and pin it.
-
-## Related
-
-- [Broadcast sources play in sync](/quest/m0/broadcast-sync.md) - broadcast sources align on the publisher's timestamps instead

rs/moq-scene/src/lib.rs

@@ -37,6 +37,7 @@ mod edit;
 mod effect;
 mod lut;
 mod overlay;
+mod playout;
 pub mod publish;
 pub mod replay;
 mod scale;