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docs: slim CLAUDE.md down to rules, file map, and non-obvious internals

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Drop class-by-class architecture listings that are derivable from the
code; keep only constraints a model cannot infer (status.json coupling,
header injection, read-only mount, shutdown deadline, dsnoop/ipc).
Add webui.html to the file map.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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jonathan
2026-06-10 11:50:09 +02:00
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# CLAUDE.md # CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository. Guidance for Claude Code when working in this repository.
## Rules ## Rules
- **Always update `README.md`** whenever user-facing behaviour changes (new flags, new endpoints, changed Docker setup, new features). The README is the primary external reference; CLAUDE.md documents internals. - **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.
- **Always commit `README.md`** in the same commit as the code changes it documents — never let the README fall behind. - Run `python -m pytest tests/` after changing `isr.py` (tests cover the recorder only).
## Project Overview ## Files
ISR is a Python audio recording application that captures from multiple simultaneous sources (Icecast/HTTP streams and ALSA soundcard devices) with time-based file splitting. All application code is in two files: `isr.py` (recorder) and `web.py` (archive browser UI). | 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 ## Commands
```bash ```bash
# Run the recorder python isr.py [config.ini] # recorder; --list-devices to list ALSA inputs
python isr.py # uses config.ini python web.py # web UI on :8080 (--dir, --port, --threshold, --min-gap, --analyses-dir)
python isr.py myconfig.ini # custom config file python -m pytest tests/ # test suite
python isr.py --list-devices # list available ALSA devices docker compose up -d / down # web UI mapped to host port 8050
# Run the web UI
python web.py # http://localhost:8080
python web.py --dir recordings # custom recordings directory
python web.py --port 8888 # custom port
python web.py --threshold 0.03 # loudness threshold (0-1, default 0.05)
# Stop: Ctrl+C (or docker compose down)
# Install dependencies
pip install requests # for stream recording
pip install numpy soundfile # for FLAC output and web waveform analysis (optional)
# Docker
docker compose up -d
docker compose logs -f
docker compose down
``` ```
## Architecture Dependencies: `requests` (streams), `numpy` + `soundfile` (FLAC output and FLAC/waveform analysis — both optional, code degrades gracefully).
### Audio Backend System ## Non-obvious internals
- **AudioDevice** — Dataclass: id, name, channels, sample_rate, backend type
- **AudioBackend** (ABC) — Abstract base for audio capture backends
- **ALSABackend** — Native ALSA support via `arecord` subprocess (the only backend)
- **ALSAStream** — Context manager that wraps an `arecord` subprocess and reads PCM in a thread
- **AudioSystem** — Discovers available backends, lists devices, resolves device specs
### Recorder Classes - **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.
- **BaseRecorder** (ABC) — Common settings, `get_next_split_time()`, `generate_filename()`, `record()` interface - **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.
- **StreamRecorder(BaseRecorder)** — Records HTTP/Icecast streams with format auto-detection and OGG/FLAC header injection - **Split timing:** files split at clock-aligned boundaries (`get_next_split_time()`), e.g. `split_minutes = 60` → on the hour.
- **SoundcardRecorder(BaseRecorder)** — Records from ALSA devices; outputs WAV or FLAC via `_AudioFileWriter` - **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`).
- **_AudioFileWriter** — Unified write/close interface for wave (WAV) and soundfile (FLAC) - **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`.
- **RecorderManager** — Loads config, creates recorders, manages threads, handles shutdown - **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.
- **Path safety:** every file parameter in `web.py` goes through `_safe_path()`, which resolves and verifies the path stays inside the recordings dir.
### Key Implementation Details - **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).
- ALSA backend spawns `arecord` as a subprocess; raw PCM is read in 100 ms chunks via a reader thread
- Device selection: `default`, `monitor` (loopback), partial name match, or exact `hw:X,Y` ID
- Thread-safe audio buffering with `threading.Lock()`
- OGG/Opus/FLAC headers captured from first ~16 KB of stream and prepended to each split file
- File splits aligned to time period boundaries (`get_next_split_time()`)
- SIGTERM handled in `main()` so Docker `docker compose down` shuts down cleanly
- `RecorderManager._write_status()` atomically writes `recordings/status.json` every 2 s while running; deleted on clean shutdown so the web UI shows no stale active-recording badges
### Web UI (web.py)
- **`GET /`** — Single-page archive table; lists all recordings sorted newest first
- **`GET /api/files`** — JSON list of file metadata (name, size, date, duration, ext, recording flag)
- **`GET /api/analyze?file=<path>`** — RMS loudness analysis for WAV and FLAC files; returns waveform data, loud sections, and duration. Requires `numpy` and `soundfile` for FLAC.
- **`GET /api/status`** — Returns `{"active": [...]}` from `status.json`; used by the UI to animate the REC badge on in-progress files (polled every 5 s)
- **`GET /stream/<path>`** — Serves audio for inline `<audio>` playback with full HTTP Range support (seekable). Responds 206 Partial Content for range requests. Files are served with `Content-Disposition: inline`.
- **`GET /download/<path>`** — Serves audio as a file download (`Content-Disposition: attachment`)
- All paths are validated against the recordings directory to prevent path traversal.
## Configuration
Copy `config.example.ini` to `config.ini`. Each section defines a recording source:
- `type = stream` — HTTP/Icecast stream recording
- `type = soundcard` — ALSA device recording
The `output_directory` value is used as-is: a relative path like `recordings` resolves to `recordings/` next to `isr.py`. No Docker-specific config change is needed — the docker-compose.yml mounts `./recordings` at `/app/recordings` to match this default.
## Docker
Two services share a `./recordings` bind mount:
- `recorder` — runs `isr.py`; volume at `/app/recordings`; mounts `asound.conf` as `/etc/asound.conf`; maps `/dev/snd`; `ipc: host` for dsnoop shared memory; `stop_grace_period: 30s`
- `web` — runs `web.py`; same `./recordings` read-only at `/recordings`; exposes port 8080 internally (mapped to 8050 on the host)
**Sharing the soundcard with darkice (or any other ALSA app):**
ALSA `hw:` devices are exclusive. `asound.conf` defines a `dsnoop` virtual device `shared_mic` that both processes use instead:
1. `sudo cp asound.conf /etc/asound.conf` on the host
2. Change darkice config to `device = shared_mic`
3. Set `device = shared_mic` in `config.ini`
4. `ipc: host` in `docker-compose.yml` is already set — required for dsnoop shared memory to cross the container boundary