ISR/CLAUDE.md

CLAUDE.md

Guidance for Claude Code when working in this repository.

Rules

• Always update README.md when user-facing behaviour changes (flags, endpoints, Docker setup, features), and commit it in the same commit as the code change. README is the external reference; CLAUDE.md documents internals.
• Run python -m pytest tests/ after changing isr.py (tests cover the recorder only).

Files

File	Purpose
isr.py	Recorder: streams (Icecast/HTTP) + ALSA soundcards, time-aligned file splits
web.py	Archive browser: HTTP server, file listing, RMS loudness analysis, cut/delete
webui.html	Single-page UI (HTML/CSS/JS), loaded by web.py at startup — must sit next to web.py and be copied in the Dockerfile
config.ini	Recording sources; copy from config.example.ini. [general] gives defaults, every other section is a source (type = stream or type = soundcard)
asound.conf	dsnoop device shared_mic so ISR and other ALSA apps can share a soundcard

Commands

python isr.py [config.ini]        # recorder; --list-devices to list ALSA inputs
python web.py                     # web UI on :8080 (--dir, --port, --threshold, --min-gap, --analyses-dir)
python -m pytest tests/           # test suite
docker compose up -d / down       # web UI mapped to host port 8050

Dependencies: requests (streams), numpy + soundfile (FLAC output and FLAC/waveform analysis — both optional, code degrades gracefully).

Non-obvious internals

• Recorder/web coupling is one file: RecorderManager atomically writes recordings/status.json every 2 s listing in-progress files; deleted on clean shutdown. web.py reads it to show REC badges and to refuse analyse/cut/delete on active files. In-progress WAV/FLAC headers are unfinalized, so durations are not read for active files.
• Stream splits: OGG/Opus/FLAC codec headers are extracted from the first ~16 KB of each connection and prepended to every split file so each file plays standalone. A new file is always opened on reconnect (gap in stream). MP3/AAC need no headers.
• Split timing: files split at clock-aligned boundaries (get_next_split_time()), e.g. split_minutes = 60 → on the hour.
• ALSA: capture spawns arecord as a subprocess, raw PCM read in 100 ms chunks by a thread. Device spec resolution: default → exact hw:X,Y → partial name → fallback to any literal ALSA PCM name (so shared_mic from asound.conf works without appearing in arecord -l).
• Shutdown: SIGTERM is converted to KeyboardInterrupt in main(); RecorderManager.stop() joins all threads against a single shared 25 s deadline to stay inside Docker's stop_grace_period: 30s.
• Analysis cache: results stored as <analyses-dir>/<file>.analysis.json keyed by threshold+min_gap; orphans pruned at web startup. In Docker the recordings mount is read-only for the web container, so the cache uses a separate ./analyses bind mount. The threshold and min_gap keys MUST stay first in the cache JSON — _cached_analysis_params() reads only the first 256 bytes to avoid parsing the large embedded result.
• Analyze responses: /api/analyze returns rms_display (~800 points), never the full per-window RMS list — the UI doesn't use it and it is ~45x larger.
• HTTP/1.1 keep-alive: _Handler.protocol_version = 'HTTP/1.1'; every response path must set an accurate Content-Length. _copy_to_response() force-closes the connection if it under-delivers (file truncated mid-serve).
• Live playback: for files listed in status.json, /stream/ patches the header on the fly so the browser sees the duration recorded so far and can seek; responses get Cache-Control: no-store. WAV: _live_wav_header derives sizes from the byte count. FLAC: _live_flac_header parses the sample count out of the last frame header in the file tail (CRC-8-verified to reject false sync matches) and rewrites STREAMINFO total_samples — duration is NOT derivable from byte size for FLAC.
• Path safety: every file parameter in web.py goes through _safe_path(), which resolves and verifies the path stays inside the recordings dir.
• dsnoop in Docker: sharing the soundcard requires asound.conf on the host and ipc: host in docker-compose (dsnoop uses shared memory across the container boundary).