Get game audio into the browser via PulseAudio + a WebSocket bridge

VNC/noVNC only ever streams video, so game sound needed a completely
separate path. Adds pulseaudio/pulseaudio-utils/libasound2-plugins and
routes ALSA's default device through Pulse (/etc/asound.conf), so
dosbox/scummvm need zero special config. server.sh starts one
PulseAudio daemon and one pcm_ws_bridge.py (from docker-common) for the
container's whole lifetime, capturing Pulse's single default sink via
parec.

Audio is a single shared mix, not per-game - considered and dropped a
per-slot-isolated design (mirroring the video architecture) as
unnecessary complexity per direction. Every running game's audio just
mixes into the one default sink; every /screen/<name> page connects to
the same AUDIO_PORT.

setup_server.py gains GET /screen/<name> (an iframe onto the game's
noVNC screen plus an Enable Sound button - browsers require a user
gesture before audio can start) and GET /pcm-worklet.js. The "Open
Screen" link simplifies from a client-side-JS-built cross-port link to
a plain same-origin relative link, since /screen/<name> now reads the
real host server-side from the request's own Host header.

Found and fixed a real bug along the way: parec --device=@DEFAULT_SINK@.monitor
looks correct but fails with "Stream error: Invalid argument" - the
actual PulseAudio macro is the single token @DEFAULT_MONITOR@.

Verified end-to-end with real audio, not just plumbing: confirmed via
`pactl list sink-inputs` that dosbox connects to Pulse correctly
(unmuted, uncorked), then used xdotool to advance stuntcar past its
silent title screen and captured real audible game audio (RMS ~9292)
through the WebSocket bridge with a raw Python client.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NiNnj78HGx1KWyCCo39HSz

This commit is contained in:

jens

2026-07-28 16:27:10 +02:00

co-authored by

Claude Sonnet 5

parent c1942f5ec4

commit 301503a276

8 changed files with 284 additions and 36 deletions

									
										scripts/server.sh
									
		+7
		-1
	
												View File
												
				@@ -2,5 +2,11 @@

				set -x

				SETUP_PORT=70${DISPLAY_NUM}

				AUDIO_PORT=71${DISPLAY_NUM}

				SETUP_PORT=${SETUP_PORT} exec ${SCRIPTS_HOME}/setup_server.py

				pulseaudio --start --exit-idle-time=-1 --log-target=stderr >/var/log/pulseaudio.log 2>&1

				${SCRIPTS_HOME}/pcm_ws_bridge.py ${AUDIO_PORT} \

				    parec --device=@DEFAULT_MONITOR@ --format=s16le --rate=48000 --channels=2 --raw --latency-msec=20 &

				SETUP_PORT=${SETUP_PORT} AUDIO_PORT=${AUDIO_PORT} exec ${SCRIPTS_HOME}/setup_server.py