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fix(desktop): enable PulseAudio loopback flag so screen share starts on Linux

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Chromium gates the PulseAudio loopback path behind the
PulseaudioLoopbackForScreenShare feature flag. Without it, returning
audio: 'loopback' from setDisplayMediaRequestHandler rejects the whole
getDisplayMedia request, so screen share never starts when the user has
"Share system audio" enabled. Also surface a clear warning toast on
loopback failure (PipeWire-only without pulse compat, macOS without
Catap) instead of failing silently — no auto-retry, since the picker
selection is already consumed.
This commit is contained in:
Jannis Braun
2026-04-29 23:43:44 +02:00
parent e0861597bc
commit f538f1d92e
3 changed files with 38 additions and 3 deletions
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docs/systems/voice.md
+14 -1
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@@ -206,7 +206,7 @@ ScreenShareConfig {
fps: number, // 30-120
mode: 'gaming' | 'text', // Affects bitrate & content hint
customBitrateKbps: number | null, // Admin override (if allowed)
shareAudio: boolean // System audio (disabled in Electron)
shareAudio: boolean // System audio loopback (see Platform Support below)
}
```
@@ -234,6 +234,19 @@ ScreenShareConfig {
- `allowCustomBitrate` toggle
- `bitrateMatrixOverrides` (JSON sparse overrides)
### System Audio Loopback (`shareAudio`)
The "Share system audio" toggle in `ScreenSharePicker` adds an audio track to the screen-share publication. In the browser it maps to `getDisplayMedia({ audio: true })`. In Electron, the `setDisplayMediaRequestHandler` callback (`packages/desktop/src/main.ts`) returns `audio: 'loopback'` to opt into Chromium's system-audio loopback path.
| Platform | Mechanism | Notes |
|----------|-----------|-------|
| Browser (Chrome/Edge) | `getDisplayMedia({ audio: true })` | Tab/window/system audio per the user's pick |
| Electron / Windows | Chromium native loopback | Works out of the box |
| Electron / macOS 13+ | CoreAudio Tap (Catap) | Requires `NSAudioCaptureUsageDescription` (set by `electron-builder.yml#mac.extendInfo`) |
| Electron / Linux | PulseAudio loopback | **Requires** the `PulseaudioLoopbackForScreenShare` Chromium feature flag — enabled at startup in `main.ts` for Linux. Works on PulseAudio and on PipeWire systems with the `pipewire-pulse` compat layer. PipeWire-only systems without pulse compat will fail. |
**Failure handling.** When loopback is not supported, Chromium rejects the entire `getDisplayMedia` request — the source-picker selection has already been consumed, so silently retrying without audio would re-prompt the picker. `startScreenShare` (`utils/screenShare.ts`) instead surfaces a warning toast directing the user to disable "Share system audio" if their system does not support loopback. We do **not** auto-mutate the user's `shareAudio` preference.
---
## Voice Fullscreen