Feature: start server-to-client audio muted by default, re-enableable from client UI

[jsapede]

Feature request: start server-to-client audio muted by default, re-enableable from the client UI

Context

On LinuxServer.io Selkies-based containers (e.g. linuxserver/firefox), I would like the remote session to start with server-to-client audio muted, but let the user enable it later from the existing audio toggle in the web client sidebar.

This is a common pattern for shared/remote browsers: no surprise audio on connect, but audio available on demand.

Current behavior

There are only two possible states today:

1. SELKIES_AUDIO_ENABLED=true (default): audio pipeline can start; whether sound plays depends on browser autoplay policy / user gesture.
2. SELKIES_AUDIO_ENABLED=false: audio is hard-disabled server-side. When the client clicks the audio button and sends START_AUDIO, the server refuses it:

INFO:data_websocket:Received START_AUDIO command from client for server-to-client audio.
INFO:data_websocket:START_AUDIO: Starting pcmflux audio pipeline.
INFO:data_websocket:Server-to-client audio is disabled by server settings. Not starting pipeline.

The UI toggle stays visible (unless also locked via |locked), but clicking it does nothing — it is effectively a dead control.

What is missing

A middle-ground setting, something like:

• SELKIES_AUDIO_START_MUTED=true — server starts with the pcmflux capture pipeline not running (audio_enabled stays true so START_AUDIO is honored), client UI shows the audio button in muted state; clicking it sends START_AUDIO and the server starts the pipeline.

From reading the source (selkies/settings.py, selkies.py::_start_pcmflux_pipeline, selkies.py::START_AUDIO handler), this looks straightforward:

• Keep audio_enabled=True.
• Add a new boolean setting, e.g. audio_start_muted (default false).
• In _start_pcmflux_pipeline() / session init: if audio_start_muted is set, skip auto-start of the pcmflux pipeline.
• The existing START_AUDIO handler already supports starting the pipeline on demand (await self._start_pcmflux_pipeline()), so the click path already exists.
• Send the new flag in the server_settings payload so the client renders the toggle in "muted" state initially.

Environment

• Container: lscr.io/linuxserver/firefox:latest (baseimage-selkies)
• Mode: default websockets mode
• Verified on image pulled 2026-08-25

Happy to test a patch or beta image if useful. Thanks!

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[junkerderprovinz]

This wanted to live upstream rather than in the baseimage, since the decision happens in the client boot path: selkies-project/selkies#322 adds SELKIES_AUDIO_START_MUTED (default false). In the websockets mode these images run, the client then simply never sends its initial audio request; the sidebar audio button starts it, and a user's choice in a running session wins over the default. If that lands and the baseimages later pick up a release carrying it, enabling it here should come down to setting that env on the container. Thanks for the clear write-up of the use case.