Rene KievitsandClaude Opus 5
7529a60650
Captures the TV's audio and sends it out over several transports. The
primary one is HyperHDR: RTP/L16 to a host-side loopback device, since
HyperHDR has no network audio input of its own. A second route renders
the spectrum on the TV and sends FlatBuffers images to port 19400
instead, for setups where touching the host's sound config is not an
option.
native/ the service: capture backends (PulseAudio, ALSA, exec,
test tone, all dlopen-based), DSP, and one file per sink
frontend/ D-pad driven UI at a fixed 1920x1080
servicefiles/ native service manifest plus the boot script
host/ RTP receiver and the loopback installer for the HyperHDR
machine
tools/ build/package, asset generation, Homebrew Channel
manifest, on-TV probe
test/ host-side suites: FlatBuffers and RTP verified against
real decoders, the engine end to end, the page in jsdom
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
223 lines
7.6 KiB
Markdown
223 lines
7.6 KiB
Markdown
# Configuration and the Luna API
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Everything the UI does goes through the service's Luna API, so anything the UI
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can do you can also do from an ssh session with `luna-send`.
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## Where the settings live
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```text
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/var/lib/webosbrew/audiocap/config.json when the service can write there
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/tmp/audiocap-config.json fallback, lost on reboot
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$AUDIOCAP_CONFIG overrides both
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```
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The service falls back to `/tmp` when it is not running as root, and the UI says
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so under *System → Settings file*. Settings written there survive the session
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but not the TV.
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Edits are merged, not replaced: sending `{"hyperhdr":{"port":5005}}` changes the
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port and leaves everything else alone. Writes are atomic — a temporary file,
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`fsync`, `rename` — so a power cut during a save cannot leave a truncated
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config behind.
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## Settings
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### Top level
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| Key | Default | Meaning |
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| --- | --- | --- |
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| `autoStart` | `false` | start capturing as soon as the service starts |
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| `logLevel` | `"info"` | `error`, `warn`, `info` or `debug` |
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| `sinks` | `["hyperhdr"]` | which outputs to open |
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`autoStart` only matters if something starts the service at boot — that is what
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the *Start on boot* toggle installs, a script in `/var/lib/webosbrew/init.d/`
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that pokes the service so the Homebrew Channel launches it.
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### `capture`
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| Key | Default | Meaning |
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| --- | --- | --- |
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| `backend` | `"auto"` | `auto`, `pulse`, `alsa`, `exec` or `tone` |
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| `device` | `""` | PulseAudio source, or an ALSA PCM like `hw:0,0` |
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| `server` | `""` | PulseAudio server address; blank autodetects |
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| `command` | `""` | for the `exec` backend |
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| `rate` | `48000` | 44100 or 48000 |
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| `channels` | `2` | 1 or 2 |
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`auto` tries PulseAudio, then ALSA. It never tries `exec` — that one needs a
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command only you can supply.
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The backends:
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| id | Name | Notes |
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| --- | --- | --- |
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| `pulse` | PulseAudio monitor | records the monitor source of the active sink; `libpulse.so.0` is `dlopen`ed at run time, so a TV without it simply reports the backend unavailable |
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| `alsa` | ALSA PCM | same arrangement with `libasound.so.2` |
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| `exec` | External command | runs a command and reads raw interleaved S16LE from its stdout, e.g. `arecord -D hw:0,0 -f S16_LE -r 48000 -c 2 -t raw` |
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| `tone` | Test tone | a sweep; proves the network path without touching the TV's audio at all |
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### `dsp`
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| Key | Default | Meaning |
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| --- | --- | --- |
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| `attack` | `0.6` | seconds for the reported level to catch a rise |
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| `release` | `0.12` | seconds for it to fall away |
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These shape the numbers in the status document and the on-TV visualiser. They do
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not touch the audio sent to any sink.
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### `hyperhdr` — RTP/L16 audio
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| Key | Default | Meaning |
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| --- | --- | --- |
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| `host` | `""` | the receiving machine |
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| `port` | `5004` | UDP port |
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| `multicast` | `false` | send to a group instead of a host |
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| `multicastTtl` | `4` | hop limit when multicasting |
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| `sapAnnounce` | `true` | announce over SAP so PulseAudio can find the stream |
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Payload type 96, 16-bit big-endian PCM, packets kept under 1400 bytes of
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payload so nothing fragments on a normal Ethernet MTU.
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### `hyperhdrViz` — Flatbuffers images
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| Key | Default | Meaning |
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| --- | --- | --- |
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| `host` | `""` | HyperHDR's address |
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| `port` | `19400` | Flatbuffers port |
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| `priority` | `150` | HyperHDR priority; lower wins |
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| `width` / `height` | `64` / `36` | image size |
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| `fps` | `30` | frames per second |
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| `mode` | `"spectrum"` | `spectrum`, `level` or `pulse` |
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| `saturation` | `1.0` | colour intensity |
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| `minBrightness` | `0.02` | floor so the lights never go fully black |
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### `udp`, `tcp`, `http`
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| Key | Default | Meaning |
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| --- | --- | --- |
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| `udp.host` | `""` | destination; a host, a multicast group, or `255.255.255.255` |
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| `udp.port` | `4010` | |
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| `udp.multicastTtl` | `4` | |
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| `tcp.port` | `4011` | the TV listens on this |
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| `tcp.maxClients` | `4` | |
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| `http.port` | `4012` | `/audio.wav` and `/audio.raw` |
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| `http.maxClients` | `4` | |
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All three carry interleaved S16**LE** — little-endian, unlike the RTP sink,
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because that is what everything reading a raw pipe expects.
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---
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## The Luna API
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Service name `org.webosbrew.audiocap.service`, all methods on `/`.
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```sh
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luna-send -n 1 -f luna://org.webosbrew.audiocap.service/getStatus '{}'
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```
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| Method | Payload | Reply |
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| --- | --- | --- |
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| `start` | optional settings patch, applied and saved first | the status document |
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| `stop` | `{}` | the status document |
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| `getStatus` | `{"subscribe":true}` for a feed every 100 ms | the status document |
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| `isRunning` | `{}` | `{isRunning, state}` |
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| `getConfig` | `{}` | `{path, persistent, settings}` |
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| `setConfig` | a patch, bare or under `settings` | `{saved, restartRequired, settings}` |
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| `resetConfig` | `{}` | `{saved, settings}` |
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| `listBackends` | `{}` | `{backends:[{id,name,description,available}]}` |
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| `listSinks` | `{}` | `{sinks:[{id,name,description}]}` |
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| `getDiagnostics` | `{}` | `{backends, system}` — see below |
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| `getLogs` | `{"clear":true}` optional | `{logs}` |
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| `quit` | `{}` | ends the process; the next call starts a new one |
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`setConfig` reports `restartRequired: true` when the capture is running, because
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most settings are read when a run starts.
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### The status document
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```json
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{
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"returnValue": true,
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"state": "running",
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"running": true,
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"error": null,
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"capture": {
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"backend": "pulse",
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"backendName": "PulseAudio monitor",
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"device": "…monitor",
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"rate": 48000,
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"channels": 2,
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"frames": 4915200,
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"blocks": 9600,
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"timeouts": 0,
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"uptimeMs": 102400
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},
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"levels": {
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"peak": 0.42, "rms": 0.19,
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"peakDb": -7.5, "rmsDb": -14.4,
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"clipping": false,
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"bands": [0.0, "…16 values…"]
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},
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"sinks": [
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{ "id": "hyperhdr", "ok": true, "name": "HyperHDR audio (RTP)",
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"error": null, "target": "192.168.1.50", "port": 5004,
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"packetsSent": 12345, "bytesSent": 4321000, "sendErrors": 0 }
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],
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"configPath": "/var/lib/webosbrew/audiocap/config.json",
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"configPersistent": true
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}
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```
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`state` is `stopped`, `starting`, `running` or `error`. A sink that failed to
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open reports `ok: false` and an `error`, and the run continues without it — one
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broken output does not take the others down.
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Each sink adds its own fields. `packetsSent`/`bytesSent`/`sendErrors` for the
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datagram sinks, `clients`/`droppedBytes` for the stream servers,
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`connected`/`registered`/`framesSent`/`connectFailures`/`lastError` for the
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visualiser.
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### Diagnostics
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```json
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{
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"backends": [{ "id": "pulse", "name": "…", "available": false }],
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"system": {
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"root": true,
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"uid": 0,
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"libraries": { "libpulse.so.0": "/usr/lib/libpulse.so.0",
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"libasound.so.2": null },
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"binaries": { "parec": false, "pactl": true },
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"pulseSockets": ["/var/run/pulse/native"],
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"pactlSources": "…",
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"alsaCards": ["0 [Loopback]: …"],
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"alsaCapturePcms": ["00-01: …"]
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}
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}
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```
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This is the fastest way to find out why a backend reports itself unavailable.
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`tools/tv-probe.sh` collects the same picture from a shell, plus a few things
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the service does not look at.
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## Doing it from a shell
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```sh
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# change settings and start in one call (the patch is saved, like setConfig)
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luna-send -n 1 -f luna://org.webosbrew.audiocap.service/start \
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'{"capture":{"backend":"tone"},"sinks":["http"]}'
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# point the RTP sink somewhere else and keep it
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luna-send -n 1 -f luna://org.webosbrew.audiocap.service/setConfig \
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'{"settings":{"hyperhdr":{"host":"192.168.1.50"}}}'
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# watch the level
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luna-send -i -f luna://org.webosbrew.audiocap.service/getStatus '{"subscribe":true}'
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# what went wrong
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luna-send -n 1 -f luna://org.webosbrew.audiocap.service/getLogs '{}'
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```
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