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Rene KievitsandClaude Opus 5 7529a60650 Audio capture and streaming app for webOS 5/6

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>

2026-08-26 10:21:00 +02:00

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LG TV Audio Cap

Captures the audio playing on an LG webOS 5 or 6 TV and streams it off the set. The reason it exists is HyperHDR: ambient lighting that reacts to what the TV is actually playing, without a microphone in the room or an audio splitter behind the telly.

It installs through the Homebrew Channel and runs as a native background service with a remote-friendly UI in front of it.

┌────────────────────── LG webOS TV ──────────────────────┐
│  PulseAudio / ALSA / a command                          │
│              │                                          │
│         capture ─► level + 16-band analysis             │
│              │                                          │
│              ├─► RTP/L16 ──────────────► HyperHDR host  │  ← the main path
│              ├─► Flatbuffers images ───► HyperHDR       │
│              ├─► raw PCM over UDP                       │
│              ├─► raw PCM over TCP                       │
│              └─► WAV over HTTP                          │
└─────────────────────────────────────────────────────────┘

Why it works this way

HyperHDR has no network audio input. Its sound-reactive effects read a local capture device. So the main path here does not try to talk to HyperHDR at all: it sends the TV's audio to the HyperHDR machine as RTP/L16, and a small receiver there turns it into a normal sound device that HyperHDR can select. That is host/lgtv-audiocap-receiver.py, and host/install-loopback.sh sets up the loopback for it.

If you would rather not run anything on the HyperHDR machine, there is a second path: the TV does the frequency analysis itself and sends finished images to HyperHDR's Flatbuffers port. Fewer moving parts, but the lights react to the TV's idea of the spectrum rather than to real audio.

See docs/hyperhdr.md for both, step by step.

Requirements

An LG TV on webOS 5 or 6, rooted, with the Homebrew Channel installed.
Root for the service. The TV's audio devices are not readable otherwise; the app has a Grant root access button that calls the Homebrew Channel's elevate-service for you.
For the main HyperHDR path: a Linux machine running HyperHDR with either snd-aloop or PulseAudio/PipeWire available.

Installing

From the Homebrew Channel. Open the Homebrew Channel on the TV, find Audio Cap, install, launch.

From an ipk. Copy the ipk to the TV and install it with the Homebrew Channel's Install from file, or from a workstation:

ares-install --device tv out/org.webosbrew.audiocap_1.0.0_all.ipk

From source. See docs/development.md.

First run

Launch Audio Cap on the TV.
System → Root access: press Grant root access if it says the service is not root. It restarts itself.
Capture → Backend: leave it on Automatic to begin with. If nothing is captured, run tools/tv-probe.sh on the TV to see what your firmware actually offers, then pick a backend by hand.
Outputs → HyperHDR audio (RTP/L16): turn it on and enter the address of the machine running HyperHDR.
On that machine: sudo ./host/install-loopback.sh --install-service, then point HyperHDR's sound capture at the device it prints.
Press Start on the TV. The level meter should move.

Nothing captured, no idea why? docs/troubleshooting.md.

The other outputs

Each can run at the same time as the others.

Output	What it is	Use it for
HyperHDR audio	RTP/L16, port 5004	the main path; also readable by PulseAudio's `module-rtp-recv` with no custom software
HyperHDR visualiser	Flatbuffers images, port 19400	HyperHDR with nothing installed on the host
Raw PCM over UDP	S16LE datagrams, port 4010	your own scripts; lowest latency
Raw PCM over TCP	S16LE stream, port 4011	anything that would rather connect than listen
HTTP WAV	`http://tv:4012/audio.wav`	opening the TV's audio in VLC

Layout

native/        the webOS service: capture, DSP, sinks, Luna API (C)
frontend/      the on-TV app (plain HTML/CSS/JS, no framework)
servicefiles/  services.json, package.json and the boot script
host/          the receiver and loopback setup for the HyperHDR machine
tools/         build, packaging, asset generation, on-TV probe
test/          host-side tests: wire formats, the capture pipeline, the UI
docs/          the longer explanations

Documentation

docs/hyperhdr.md — connecting it to HyperHDR, both ways
docs/configuration.md — every setting, and the Luna API
docs/development.md — building, testing, packaging, publishing
docs/troubleshooting.md — when it does not work

License

MIT.

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