Two quality improvements:
Preset: ultrafast -> veryfast. Unlocks Main profile with CABAC
entropy coding, hexagonal motion search, 3 reference frames, and
adaptive quantization — typically 30-40% better quality at the same
bitrate. The desktop handles the extra encoding cost trivially
(150+ fps at 1080p).
Downscaling: the receiver now advertises its display resolution in
the signaling answer (display_width/display_height, 0 = unknown).
When the capture exceeds the display (e.g. 2256x1504 source on a
1920x1080 receiver), the sender scales down preserving aspect ratio
before encoding — the same sws_scale pass that already converts the
pixel format also handles the resolution change, so there is no
extra step. This concentrates the entire bitrate into pixels the
display actually shows (~2.7x more bits per visible pixel at
4000 kbps when going from 2256x1504 to 1620x1080).
The renderer caches the display size during window creation
(native monitor resolution in fullscreen/KMSDRM; window size
otherwise). The receiver includes it in every signaling answer; the
sender pipeline computes aspect-preserving, even-rounded scaled
dimensions when the display is smaller than the capture.
meson test 5/5 in both configurations, valgrind clean.
A gtkmm-4.0 control panel (behind -Dgui=true, default off): refresh
shows discovered receivers (grouped and preference-sorted), a bitrate
scale, and start/stop that runs the whole session on a worker thread
so the interactive portal picker never blocks the UI. The CLI and the
GUI now share the new sc_app_core static library holding the
pipelines, session orchestration (negotiation + PLI feedback), and a
state store.
The sender pipeline publishes its state to
$XDG_RUNTIME_DIR/screencast/sender.json (session id, receiver,
bitrate, pid, start time; stale files detected by pid liveness) and
persists the last session for one-click restarts. The new
'screencast waybar' subcommand prints a waybar module line and its
--toggle flag stops a running sender gracefully or spawns a detached
restart of the last receiver.
Waybar on the dev machine is wired: custom/screencast module with
click-to-toggle and right-click panel, plus styles, with a timestamped
backup of both config files. Both binaries are installed to
/usr/local/bin.
Validated: waybar output (idle and streaming states with a synthetic
state file), GUI launches on the desktop (window observed via
hyprctl), meson test 5/5 in both build configurations, formatting
clean.
Loss recovery for the streaming path:
- PLI over signaling: the depacketizer now reports damaged frames
(DepacketizeResult) and the receiver asks the sender for a keyframe
(SessionPli, rate-limited to one per 500 ms). The sender keeps the
signaling channel open during the session and honors PLIs through
the new thread-safe SenderPipeline::request_keyframe(). Recovery
takes one frame time instead of waiting out the GOP.
- RtpJitterBuffer: reorders RTP packets by sequence number (16 packets
/ 60 ms) before the in-order depacketizer, so Wi-Fi reordering is
not misread as loss; in-order streams release immediately, and a
straggler older than the delivered sequence is discarded.
- Hardware H.264 decode probe: DecoderFactory tries h264_v4l2m2m (the
VideoCore path on the Pi) with an automatic software fallback and a
clear journal line for the chosen path; --swdecode opts out.
Validated: PLI end-to-end with a probe that drops a mid-keyframe
packet over real UDP (receiver logged the damaged frame and the PLI
arrived with the session id); hardware probe fails cleanly and falls
back on this desktop; jitter reordering covered by unit tests.
meson test 5/5 in both build configurations, valgrind clean.
The receiver does not need the sender's PipeWire/xdg-desktop-portal
capture stack, which small ARM boards neither have nor want. Add a
-Dsender=false meson option that skips the capture backend and the
sender pipeline (SC_HAS_SENDER guards in main.cpp/pipelines.cpp);
receiver-only builds refuse --send with a clear message while
--receive and --discover work unchanged.
scripts/install-receiver.sh targets such boards (e.g. Raspberry Pi
Zero 2 W): installs build and runtime dependencies via apt, checks the
compiler for C++20 <format> support before the long build (GCC 13+,
i.e. Raspberry Pi OS Trixie), builds SDL3 from source when the distro
does not package it, compiles a receiver-only binary, runs the test
suite, installs to /usr/local/bin, and enables avahi-daemon.
Also refresh the stale README (phases, dependencies, current
roadmap, Pi receiver section).
Validated in both configurations: meson test 5/5 each; the
receiver-only build has no PipeWire/portal references, refuses --send
cleanly, and --discover works headlessly.
Add mDNS/DNS-SD discovery and JSON session negotiation so two peers on
a LAN connect without hard-coded addresses.
- Discovery (Avahi threaded-poll client): the receiver announces
_screencast._tcp with its signaling port; senders browse and resolve
peers. Strict lock ordering (poll lock before state mutex) keeps the
callbacks deadlock-free; name collisions rename via
avahi_alternative_service_name.
- Signaling: one JSON object per newline-terminated TCP line. The
receiver hosts a server (port 5005) and answers session offers with
its RTP port; senders connect, offer, and stream to the negotiated
endpoint. WebSocket was deferred: no WS library is installed, the
skill permits plain TCP, and the wire format is transport-agnostic.
- Dual-stack transports: this machine resolves its own services over
IPv6, so getaddrinfo now runs AF_UNSPEC and listeners bind IPv6 with
IPV6_V6ONLY=0 (IPv4 fallback), covering UDP and TCP alike. The
signaling client shutdown now uses shutdown() so a reader blocked in
recv() cannot hang the join (a plain close() does not wake it).
- CLI: --discover lists receivers (deduped to one entry per host);
--send auto-disovers when exactly one receiver is found; --peer
targets a receiver directly; --signaling-port overrides the default.
Validation: meson test 5/5 (new signaling round-trip test), valgrind
clean. End-to-end over loopback: --discover finds the announced
receiver, a probe negotiated a session and streamed 60 frames over
both IPv4 and IPv6, and the receiver reported stream started. mDNS
resolution was verified against avahi-browse as an independent
reference.
The receiver window never appeared on Wayland. Two causes:
- The window was created on the main thread while event pumping and
presenting ran on the render thread. SDL's Wayland backend requires a
window's creation, event processing, drawing, and destruction to
happen on one thread; a cross-thread surface simply never maps, with
no error reported. The renderer now lives entirely on the render
thread, with a condition-variable handshake so ReceiverPipeline::
start() still reports renderer failures and timeouts.
- On Wayland a window is invisible until the first render commit, so
even a healthy receiver showed nothing while waiting for a stream.
The renderer presents one blank frame at init: the window is visible
immediately, black until video arrives.
Also log 'stream started (WxH)' when the first frame decodes and the
first rendering failure, which is what made the remaining debugging
observable.
Validated headlessly end-to-end: a synthetic solid-color RTP feed drove
the real receiver over localhost UDP; the window mapped, reported
'stream started (320x240)', and a grim screenshot of the window region
showed the fed color (V=198, SATAVG=74 during the red feed). Phase 5
marked complete in docs/PHASES.md; current phase is now Phase 6.
Wire the first end-to-end pipeline: capture -> encode -> packetize ->
UDP -> depacketize -> decode -> render.
- UdpRtpTransport: raw POSIX UDP sockets (IPv4 via getaddrinfo), a
receive jthread woken by socket close on stop; port 0 skips binding
so the sender uses an OS-assigned source port. ASIO stays deferred
to the signaling phase per ARCHITECTURE.md.
- SdlRenderer: SDL3 window/renderer with RGBA texture upload; the
texture is recreated on resolution change. RendererFactory now
returns RendererResult so SDL init failures carry a message,
mirroring the codec/capture error patterns.
- screencast binary: parse_cli plus SenderPipeline/ReceiverPipeline
per the app scaffolds; the sender creates its encoder once capture
reports real dimensions, the receiver keeps a bounded 3-frame queue
to hold latency down and renders on its own thread until the window
closes. cli argv signature fixed to 'const char* const*' so main's
argv converts implicitly.
- Encoder: drop AV_CODEC_FLAG_GLOBAL_HEADER so libx264 repeats SPS/PPS
in-band at each keyframe -- the receiver decodes from the bitstream
alone, which also makes mid-stream joins and later PLI recovery
work without out-of-band parameter negotiation. The round-trip test
now exercises exactly that path.
- tests: new udp-loopback integration test pushes synthetic frames
through a real localhost socket and decodes 10/10 frames with the
right dimensions; valgrind clean (loopback + codec). meson test 4/4.
Manual validation on the desktop (receiver window shows the captured
desktop) is documented in docs/RUNBOOK.md.
fegger