Obico polling could freeze the live camera stream within seconds of opening
the viewer. Cause: when the buffer-reuse path in obico_detection._capture_frame
saw an empty _last_frames[printer_id] entry (stream startup before the first
JPEG lands, or upstream mid-reconnect after a 30s read timeout), it fell
through to capture_camera_frame_bytes() and opened a second RTSP socket. On
firmwares that allow only one camera connection, that second socket forced
the printer to drop the live fan-out connection - the viewer's ffmpeg then
hit its own 30s timeout, looped through 30 reconnects at 0.2s, all racing
the next Obico poll, and the broadcaster pump exited.
Widen the gate from "do we have a buffered frame?" to "is any fan-out stream
registered for this printer?". New is_stream_active() helper checks
_active_streams / _active_chamber_streams independently of buffer state.
_capture_frame consults it first: if a viewer is attached, it returns the
buffered frame when available or None (skip this poll cycle) when not. Never
opens a competing socket while a viewer is connected.
Cost: at most one missed Obico detection cycle per viewer-attach (~10s lag).
Benefit: zero competing-socket events while any viewer is connected.
try_get_active_buffered_frame() refactored to delegate to is_stream_active()
so the two helpers stay in lockstep. The /camera/snapshot caller is unchanged
behaviorally (snapshot is a user-initiated single-shot; falling through to
fresh capture on an empty buffer is the desired behavior there).
maziggy
ce5f4e5f1a