On a printer with an external camera, watching the live view while a print
ran meant the layer timelapse recorded almost nothing and the finish photo
went out with no image. The reporter measured 0 of 87 layer captures on one
print and 0 of 105 on another, both watched throughout. A USB camera allows
one V4L2 handle, so a capture during a live view fails outright.
The built-in camera has had this rule since #1348 and #1271: reuse the
viewer's buffered frame rather than opening a second connection. It was
never extended to the external paths, and it could not have been -- the
buffer it depends on was only ever populated by the built-in paths.
generate_mjpeg_stream yields multipart-wrapped chunks, so the route layer
could not recover the JPEG, and a guarded caller would have found an empty
buffer and skipped every time.
So the stream now publishes each raw frame through a new on_frame callback
(parallel to on_process from #2675), and the six one-shot consumers reuse
it: layer timelapse, the finish-photo moment and its background fallback,
the notification snapshot, Obico polling, and the plate check. A viewer
attached with nothing buffered yet skips that one attempt rather than
competing -- kicking the viewer off is worse than missing a frame.
on_frame exceptions are logged and swallowed, like iter_subscriber's
on_unsubscribe: buffering is a side effect and must never be able to take
the live stream down with it. The external stream's teardown now releases
the buffered frame too, ownership-checked so a concurrent viewer of the
same printer keeps its own.
Two side effects on paths not touched here, both improvements: the snapshot
endpoint and the finish-photo fallback chain consult get_buffered_frame and
can now serve an external camera's live frame. plate_detection's docstring
already claimed this behaviour while implementing it only for the built-in
fallback; that drift is resolved.
go2rtc and several IP cameras still emit a warm-up / black frame on every
fresh MJPEG connection — even with the v0.2.4b2 warm-up-skip fix it
slipped through intermittently for @nkm8's setup. His own bisect named
the clean solution: go2rtc exposes /api/frame.jpeg as a dedicated
single-frame endpoint that never returns the encoder's stale keyframe.
Adds an optional external_camera_snapshot_url column on printers. When
set, every single-frame capture path (snapshot endpoint, [SNAPSHOT]
notification thumbnails, [PHOTO-BG] finish photo, layer timelapse,
Obico ML, plate-detect / calibrate-plate) routes through _capture_snapshot
on the override URL via plain HTTP GET, bypassing the warm-up dance.
Live view stays on the configured stream URL — only single-frame
captures use the override. Override is camera-type-agnostic. SSRF guard
applies (existing _sanitize_camera_url allowlist). Empty string treated
as unset.
Settings UI: new "Snapshot URL (optional)" input + Test button under
External Cameras, hidden for camera_type=snapshot since the live URL is
already a single-frame source. en + de fully translated; 6 other locales
seeded with English copy.
5 backend tests pin the routing contract; 3 frontend tests pin the
input + debounced PATCH. Documented in
bambuddy-wiki/docs/features/camera.md with the go2rtc example.
Camera snapshot, test, and plate detection endpoints created temporary
JPEG files with default 0644 permissions. Switch from NamedTemporaryFile
to mkstemp with explicit 0600 permissions.
- Path traversal: Convert device number to integer to break taint chain,
use strict /dev/videoN validation with range limit
- SSRF: Add documentation explaining intentional SSRF for user-configured
external camera URLs, add lgtm suppression comments
- Info exposure: Don't expose exception messages in plate calibration
errors, only expose error type name
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Automatically detect if objects are on the build plate before printing
and pause the print immediately if detected.
Features:
- Per-printer toggle to enable/disable plate detection
- Multi-reference calibration: store up to 5 reference images per printer
for different plate types (textured, smooth, high-temp, etc.)
- Automatic print pause when objects detected at print start
- Push notification and WebSocket alert when print is paused
- ROI (Region of Interest) calibration UI with sliders to adjust
detection area
- Reference management: view thumbnails, add labels, delete references
- Works with both built-in and external cameras
- Uses buffered camera frames when stream is active (no blocking)
- Split button UI: main button opens modal, chevron toggles on/off
- Green visual indicator when plate detection is enabled
- Included in backup/restore
maziggy