[jochenkirstaetter]

Summary

Part 4 of 6 for Linux desktop support (stacked on #41 / linux-3-input and #38 / linux-2-basics).

Adds Linux audio capture/render, media session (MPRIS) integration, screen capture, hardware/software H.264 video pipeline, MP4 muxer, and virtual camera (v4l2loopback) support:

• Audio (desktop/app/src/linux/audio.rs, voice.rs):
  • PipeWire / PulseAudio (pw-cat / parec / pacat) PCM audio capture and playback workers with automatic backend selection and fallback.
  • Voice input streaming and hotkey recording integration.
• Media Sessions & SMTC (desktop/app/src/linux/media_sessions.rs, smtc.rs):
  • In-process D-Bus (zbus) MPRIS (org.mpris.MediaPlayer2.Player) discovery, metadata polling, and transport controls (Play, Pause, Next, Previous, Seek), with playerctl CLI fallback so the 2s polling loop does not fork subprocesses.
  • Outbound MPRIS target (org.mpris.MediaPlayer2.nectarlink) exported over zbus on /org/mpris/MediaPlayer2 with PropertiesChanged emission alongside mpris-state.json.
• Video, Screen Capture, MP4 & Virtual Camera (desktop/app/src/linux/video.rs, screen_capture.rs, mp4_muxer.rs, vcam.rs):
  • ffmpeg / gstreamer H.264 decoder/encoder and MP4 muxer backends.
  • PipeWire / X11 / Wayland screen capture stream integration.
  • v4l2loopback virtual camera frame output (desktop/app/src/linux/vcam.rs and desktop/vcam/).

Verification

• cargo fmt --all --check
• cargo xtask strings --check
• cargo clippy --locked -p nectarlink-desktop -p nectarlink-vcam -p s1-qt-rust --all-targets -- -D warnings
• cargo test --locked -p nectarlink-desktop -p nectarlink-vcam (302 + 6 unit tests pass)

[thtbee]

Thanks for opening this. Our notes from testing are all in one place on #38 (comment), with a section for this part; I checked them against 355c08b again just now. The ones I'd look at first:

• pc_audio_stream.rs: the pw-record fallback has no target, so it records the default source, which is the microphone. It needs -P stream.capture.sink=true (and the sink as --target).
• recordings.rs: convert_audio passes -- before the output file, which ffmpeg rejects, so conversion always fails.
• linux/h264.rs: no libavcodec.so.62 (FFmpeg 8, Ubuntu 26.04).

Happy to look again whenever you push.

[jochenkirstaetter]

Updated with linux-3-input and integrated @thtbee's Part 4 review fixes from linux-review-fixes (cf7ab65, c9f5b10 — PipeWire ScreenCast portal pod builder, 64-bit SPA_TYPE_Fd, vcam/vmic/mp4/camera hardening), plus libopenh264-dev in CI and runtime OpenH264 v2.0/v2.3 SLayerBSInfo ABI detection so pc_mirror unit tests pass across Debian/Ubuntu libopenh264-7 and upstream libopenh264.so.8. Huge thanks @thtbee for the collaborative effort!

[thtbee]

Reviewed on the final branch (0b37495) along with the rest of the series: all findings addressed, and Linux and Windows checks, the FUSE end-to-end run and the package builds pass. Thank you.

[thtbee]

Re-approving after #38 and #41 merged.