Always-on capture

For a study that runs for months---a year in one room---recording raw ambisonic audio is impractical (terabytes) and a privacy hazard (speech). The capture daemon (v0.11, optional [capture] extra) extracts features continuously on a small always-on computer and keeps only those.

pip install "ambiscape[capture]"
ambiscape capture --list-devices          # find your 4-channel interface
ambiscape capture /data/room --device 2 --block-seconds 3600

It captures each block (hourly by default) to a short-lived WAV, runs it through the same tested extractor as analyze, saves a feature .npz, and then deletes the audio. Audio exists only one block at a time---robust (a crash leaves the block on disk to reprocess) and privacy-preserving. At each midnight the day is rolled up into a catalog- and longitudinal-ready summary.json (plus a non-identifying deposit unless --no-deposit):

/data/room/2024-03-21/features/100000.npz   # one per block
/data/room/2024-03-21/analysis/summary.json # rolled up at day end

A year is then 365 daily scenes; point ambiscape longitudinal /data/room at the root to see trend and season. --keep-audio retains the block WAVs (for ground truth); Ctrl-C/SIGTERM stops gracefully and rolls up the day in progress.

Soundfield (A-format) microphones

A soundfield mic that outputs A-format (four raw capsules) needs converting to B-format (AmbiX W/Y/Z/X) before extraction. In the library:

from ambiscape.capture import CaptureDaemon, aformat_to_bformat
CaptureDaemon("/data/room", aformat_matrix=my_mic_matrix).run()

The 4×4 matrix comes from the microphone maker's calibration. A mic that already outputs B-format needs no matrix; pass --order fuma if it is FuMa rather than AmbiX.

Running it for real

The daemon is a plain long-running process; on a Raspberry Pi run it under systemd for auto-start, restart-on-failure, and clean shutdown, log to an SSD (not the SD card), and keep the clock true with NTP. A complete hardware-and-setup guide for a year-long room logger (with an optional light sensor) lives in the companion ambient-pi repository.