3–5 fps downscaled on Jetson, not 15 fps from camera
Context
Section titled “Context”The v1.9 plan specified ingesting the Amcrest/Dahua sub-stream at 640×480 / 15 fps for inference. After spec’ing the full Phase I pipeline:
- Cycle duration at sewing workstations is 10–90 seconds. Detecting “person enters ROI” → “person leaves ROI” with reasonable hysteresis does not require fine temporal resolution.
- 15 fps × 2 cameras × YOLOv8n + TensorRT on Orin Nano Super is feasible but pushes thermal limits in a passively-cooled enclosure (relevant given ADR pending on fan + enclosure).
- 15 fps × 24-hour recording at 4 Mbps per stream produces ~43 GB/cam/day. Two cameras over 120 days = ~10 TB — exceeds the 4 TB NVMe even before SQLite and OS overhead.
Decision
Section titled “Decision”Run inference at 3–5 fps, downscaled on the Jetson from the ingested sub-stream. Recording cadence to be specified separately (likely matches inference rate for Phase I; main-stream higher-fps recording deferred to Phase II).
Why:
- Sufficient temporal resolution for cycle-counting at 10-90 s cycles (5–25 frames per cycle even at 3 fps).
- Compute headroom — Jetson stays well below thermal throttling under sustained load.
- Storage — drops NVMe write load proportionally; 120-day buffer fits comfortably in 4 TB.
Consequences
Section titled “Consequences”- Phase II behavioral monitoring may need higher fps. Phone-use detection, fast hand motion, gesture recognition typically want ≥10 fps. Re-evaluate when Phase II workload is defined.
- Sub-stream resolution is not the actual ingest resolution. Amcrest sub-stream presets are 704×480 / 352×240 / CIF / QCIF — note that 640×480 is not a Dahua/Amcrest sub-stream preset. Ingest the closest preset and downscale on the Jetson to 640×480 if the model expects it.
- Recording fps and inference fps may diverge later. Phase II may want to record main-stream 1080p separately from inference fps for forensic playback and training data. Phase I keeps them coupled.
References
Section titled “References”- Memory: “Pipeline: 3–5 fps and downscaled on the Jetson (revised down from earlier 15 fps plan on 2026-05-11 — collapses Phase I compute & TBW concerns to non-issues)”