Full live investigation of the persistent 503 "deviceBusy" on main-stream ISAPI
snapshots (10.0.10.13): ruled out config (byte-identical to a working sibling
model), ruled out firmware age (reproduced on both the original V5.8.11 and
current V5.11.0 builds, ~15 months apart), and ruled out real resource
contention (a full channel-ID sweep shows every ID fails identically except
the one hardcoded working value, including nonexistent channels) — pointing
at a broken/incomplete ISAPI snapshot handler that mislabels itself as
"busy," not a real encoder ceiling.
RTSP main-stream frame-grab was confirmed as a working route around it, but
given the bug and the sub-stream's real-world plate-read accuracy problems,
the owner decided to replace the DS-2CD1047G3H-LIU units rather than carry
an ffmpeg/RTSP dependency to work around vendor firmware. Ingested the
vendor datasheet as a source page along the way.
Claude-Session: https://claude.ai/code/session_01FWncR69HgGPuei1dLrW3cU
Vendor spec sheet (raw/DS-2CD1047G3H-LIU.md) for the DS-2CD1047G3H-LIU — the exit-lane
camera at 10.0.10.13 (park-buzi) already covered extensively in lpr-camera for its
persistent main-stream ISAPI 503 (deviceBusy) and its 2026-06-27 config-DB-corruption incident.
This is the first vendor-sourced spec data for the model; everything before it was field-derived.
Key takeaways
4 MP, max resolution 2560×1440 (ColorVu 3.0 — color night imaging, not IR-only).
Main stream: H.265+/H.265/H.264+/H.264 only — no MJPEG option.Sub-stream: H.265/H.264/
MJPEG (MJPEG is sub-only). This is a concrete, spec-level asymmetry that plausibly explains
why the ISAPI on-demand JPEG snapshot is reliable on sub but structurally broken on main: sub
can serve a snapshot natively, main has to transcode out of H.264/H.265 on demand. Consistent
with — and a likely root cause for — the persistent deviceBusy behavior already logged in
lpr-camera.
Bit rate range 32 Kbps–16 Mbps. The site's main-stream config (6144–12288 Kbps, confirmed
live 2026-08-23) is well inside spec — rules out "misconfigured over the camera's own ceiling"
as a cause, confirming what live testing already showed.
ROI: 1 fixed region for main stream — another main-only constraint/asymmetry vs. sub.
API: ONVIF (Profile S, Profile G), ISAPI, SDK. ISAPI is fully in-spec for this model — the
503 is a real firmware/hardware limitation, not a case of using an unsupported API.
Protocols include RTSP (alongside HTTP/ONVIF/etc.) — confirms RTSP is a documented, supported
surface on this model, not a workaround outside its design.
Simultaneous live view: up to 6 channels. Available in -LIU/-LIUF/-LIUF/SL/-LIUF/SRB
variants at 2.8mm/4mm focal lengths; the deployed unit is the base -LIU.
How this changes the picture
Confirms rather than overturns lpr-camera's existing conclusion (sub-stream-only for ISAPI
snapshots on this model) — but gives it a concrete mechanical explanation (main has no MJPEG path)
instead of just an empirically-observed limitation. See lpr-camera § "Main-stream ISAPI
snapshot 503 vs. RTSP" for the 2026-08-23 live comparison against a DS-2CD1043G2-LIU sibling
(main-stream ISAPI snapshot works fine there) and the confirmed RTSP frame-grab workaround.
julian
3a176c5cc8