SHEET 04 · Systems & Hardware
BirdNET at 8,000 ft
14 security-camera microphones turned into a bird survey — 228,926 detections and 98 species at ≥0.75 confidence in 20 days, each bird on a Slack card within a median 9.9 s of singing
228,926 detections98 species ≥0.759.9 s to Slack6,532 camera-hours2026localSystems & Hardware
About
The building's cameras have microphones. Their 48 kHz Opus tracks come off go2rtc into 40-second Ogg segments, and BirdNET runs in-process on the open segment every 10 seconds, row-identical to the batch tool. Detections go to a SQLite ledger; gated clips and spectrograms go to a Slack channel. Before any clip is cut, a speech gate — Silero VAD, with YAMNet in the grey zone — withholds anything with a voice in it: 7,278 of 32,290 so far. Cameras at private spots are excluded in the registry.
The idea was measured before it was built. Two independent spectral captures showed the archive path brick-walled at 8 kHz where the live path reached 11 kHz, and moving to the live path recovered an entire genus: hummingbirds went from zero in 189 camera-hours to 1.7 an hour. Validation is written down: pinned model version, a range filter for the site and week, 150 clips reviewed by ear with 12 confirmed false, night hours as an unsupervised false-positive monitor, and two enthusiastic wrong conclusions retracted in place.
Key features
- 0114 of 19 cameras enabled; privacy exclusions coded in the registry, not remembered
- 02ffmpeg RTSP → Ogg/Opus segments, PCM-identical to FLAC at a fifth the size; a truncated-on-shutdown bug measured and fixed to exactly 40.0 s
- 03In-process BirdNET-Analyzer 2.4.0 every 10 s; libsndfile decode so live and batch agree to the last decimal
- 04Speech gate before any clip or card: Silero VAD, YAMNet in the grey zone; 7,278 withheld
- 05Slack cards with spectrogram, species and count: median 9.9 s, p90 14.4 s from the bird
- 069.8 GB/day for 14 streams; 4,018 segments, 0 bad, 0 restarts in the first three days; retention by timer
- 07Validation: 150 gated clips reviewed by ear, per-species caveat lists, a not-here list, night hours as the false-positive monitor
- 08An acoustic-adjacency map of the building from 108 same-species co-detections within ±3 s
- 09Eight-view D3 dashboard rebuilt from the ledger: dawn chorus clock, hourly heatmap, field guide, birds × weather
Gallery
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