`pulsesrc` with no `device=` reads PulseAudio's default source —
which is the user's microphone, not system audio output. The stream
was technically working but the laptop was hearing the desktop's
mic (or silence on systems without one) instead of system audio.
At host startup, shell out to `pactl get-default-sink` to discover
the current default sink, then pass `device=<sink>.monitor` to
pulsesrc. Resolving at session-start covers users who switch outputs
(speakers vs headset vs HDMI) between sessions. pactl added to the
host's required-binary list.
Verified cross-machine: audio came through clearly with the prior
~1s latency floor preserved.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Symptom: cross-machine streams drifted ~6-9 seconds per minute. mpv
showed continuous "Audio device underrun detected" with video packets
piling up in its demuxer queue while audio queue stayed at 0.
Root causes:
- pipewiresrc captured at the host monitor's refresh rate (180Hz),
not at the configured framerate. The encoder + mux produced 6x more
frames per wallclock second than mpv could consume at realtime,
burying audio packet density in mpv's demuxer queue.
- `--profile=low-latency` sets `audio-buffer=0`, which is too
aggressive — any sub-millisecond network jitter immediately
starves the audio device. Underruns slowed mpv's audio clock, and
with `video-sync=audio` (also from low-latency profile) video
followed.
Fixes:
- `videorate ! video/x-raw,framerate=<fps>/1` after pipewiresrc to
cap input to the requested rate deterministically.
- mpv command grows `--audio-buffer=0.2 --demuxer-max-bytes=2M
--demuxer-readahead-secs=0.5`: small audio buffer to absorb network
jitter, demuxer cap to prevent runaway buildup.
A leaky-queues attempt landed and was reverted in the same commit —
it removed backpressure without addressing the root cause and made
things worse.
Verified cross-machine 6m51s: drift held at ~1s floor, zero audio
underruns, perfect A-V sync.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
The old tokio::select! tore down the whole bridge when EITHER
direction's io::copy finished. For a one-way streaming workload the
reverse direction carries only the initial HTTP GET; once mpv stops
sending and the read half EOFs, the data direction got killed mid-
stream and the host logged "bridge closed cleanly" while the user's
video disappeared.
Spawn the reverse direction as a detached task and `.await` only
the data direction. When the data direction ends naturally, abort
the reverse task. The function gains Send + 'static bounds on T,
which TcpStream satisfies.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
The previous ffmpeg-as-HTTP-server pipeline shape held back two
improvements at once. ffmpeg as the runtime server lost a one-shot
`-listen 1` accept to a probe-and-discard health check, and forced
us to size analyze/probe budgets carefully so ffmpeg would serve
before our deadline. Replacing it with a small tokio task that
accepts once, drains the HTTP request, writes a fixed 200 OK, then
`tokio::io::copy`s gst stdout to the socket removes all of that.
VAAPI H.264 (vah264enc) drops CPU encode from ~50% of a core to
single-digit %. An earlier attempt at vaav1enc had to be abandoned:
libavformat cannot demux AV1-in-MPEG-TS with the custom mapping
even with a 20MB probe budget — mpv reports video=eof. H.264 keeps
the hardware win on the well-trodden demuxer path.
scripts/smoke-pipeline.sh mirrors the runtime pipeline with
videotestsrc/audiotestsrc into a file and asserts that mpv reports
`video=playing` (not video=eof). The naive --frames=10 check was
a false positive when no video stream is recognized; the verbose
grep is the real gate.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Moves the full capture+encode+mux pipeline into gst-launch, leaving
ffmpeg as a thin HTTP server. Verified end-to-end on KDE Plasma 6
Wayland: screencast portal → mpv mirror-tunnel rendering in real time.
Pipeline:
pipewiresrc(do-timestamp) → videoconvert → x264enc (zerolatency
ultrafast) → h264parse(config-interval=-1) → byte-stream caps →
mpegtsmux ← (aacparse ← avenc_aac ← audioconvert ← pulsesrc) →
fdsink fd=1
ffmpeg -fflags nobuffer+discardcorrupt+genpts -flags low_delay
-analyzeduration 0 -probesize 32 -f mpegts -i pipe:0 -c copy
-f mpegts -listen 1 http://127.0.0.1:N
Why each piece is load-bearing (do not relitigate without cause):
- x264enc + h264parse + byte-stream caps: raw video over a pipe hits
stride/format negotiation problems (green screens with mis-aligned
rows). Encoding inside gst sidesteps that entirely.
- mpegtsmux inside gst: H.264 Annex B carries no timestamps. Without
a container, ffmpeg sees "Timestamps are unset" and downstream
muxing breaks. mpegts in gst preserves pipewiresrc's clock.
- byte-stream + alignment=au caps: h264parse defaults to AVC format
(length-prefixed NALUs) for some downstreams; ffmpeg's mpegts
demuxer needs Annex B start codes.
- audio in gst (pulsesrc + avenc_aac): keeping ffmpeg as a pure
passthrough (`-c copy`) avoids ffmpeg's audio-input dependency
delaying HTTP serving until both inputs are ready.
- `-analyzeduration 0 -probesize 32`: stop ffmpeg from buffering 5MB
/ 5s of input before deciding it understands the stream.
- Also fixes a separate one-shot bug from earlier: the previous
health-probe in wait_for_listener consumed ffmpeg's single
`-listen 1` accept slot, so the actual bridge connect hit
Connection refused. Replaced with connect_to_capture which
returns the bridge socket.
Adds dep checks for pipewiresrc, x264enc, h264parse, mpegtsmux,
pulsesrc, avenc_aac, aacparse with per-distro install hints.
Known gap: VLC currently shows a green screen against the stream
even though mpv works fine. Likely VLC-specific demuxer/latency
settings, not a pipeline correctness issue — to investigate as a
follow-up. mpv is the recommended client either way.
`gst-launch-1.0` and `pipewiresrc` ship in separate packages on most
distros (Arch: `gst-plugin-pipewire`, Debian: `gstreamer1.0-pipewire`,
Fedora/openSUSE: `pipewire-gstreamer`). Having the gst binary present
was no guarantee the Wayland capture pipeline would actually work —
without the plugin gst would bail at runtime with `no element
"pipewiresrc"`, which then cascaded into ffmpeg seeing EOF on its
stdin and exiting before its HTTP listener bound, then the host
hitting "Connection refused" against its own port. Confusing.
Now `deps::check_host_binaries` probes `gst-inspect-1.0 --exists
pipewiresrc` on Wayland and fails early with a per-distro install
hint pointing at the right package.
Implements the Wayland host pipeline from plan §4.5:
ashpd ScreenCast portal
-> CreateSession + SelectSources + Start + OpenPipeWireRemote
-> (pipewire fd, node_id, width, height)
gst-launch-1.0 pipewiresrc fd=N path=NODE_ID ! videoconvert
! video/x-raw,format=NV12 ! fdsink fd=1
ffmpeg
-f rawvideo -pix_fmt nv12 -video_size WxH -i pipe:0
-f pulse -i default
-c:v libx264 -preset ultrafast -tune zerolatency
-c:a aac -f mpegts -listen 1 http://127.0.0.1:<rand>
Phase 1 ships software x264 per plan §7; VAAPI is Phase 2.
src/host/wayland.rs is the new module. capture.rs becomes a thin
dispatcher with a CaptureHandle enum (Wayland today, X11 next).
host/mod.rs swaps the 150ms sleep for a poll-until-listener-ready
helper, and calls handle.shutdown().await for an orderly SIGTERM /
1s grace / SIGKILL teardown. The Drop impl is the panic backstop.
The pipewire fd handoff clears CLOEXEC before gst-launch spawn and
closes the parent's copy of the raw fd after the child has it.
Also deletes the empty src/host/tunnel.rs and src/viewer/tunnel.rs
placeholder files — the generic bridge in common/tunnel.rs is doing
the work, and there's no host- or viewer-specific tunnel concern
worth a module yet.
mollusk