Renders the current frame as a base64 JPEG, or null when none is available.
The frame cadence the track negotiated, in ms (the caller clamps it to its floor).
The id of the latest state change — read at capture time to tag the frame.
The sink frames are written to, creating it if needed; null when there is none (no session/client yet).
Whether the session has an established inbound video track — without one the pump is inert.
OptionalIsWhether exposure policy currently lets this channel show the model pixels. Optional: absent means
permitted. While false the pump captures and sends nothing and drops any pending settle.
Logs a problem; the pump never throws into a timer or an unawaited promise.
Reports a frame the sink took (for Events$, diagnostics, tests). A refused frame is not reported.
Sends the "do not narrate your own change" note after a confirmation frame the sink took.
How the pump reaches the channel and the session.