Root cause (verified via code reading + Oracle design review):
- webrtc_paused IS correctly initialized to true in StatePortal::new()
- encode_cpu_frame DOES respect paused via early return
- BUT encode_thread_loop unconditionally sent timing on every Ok(()),
causing stats.record_encode_thread to tick encoded_frames even for
paused-dropped frames -> phantom encoded_fps=29.7 during idle
- Real waste: handle_pw_frame imports DMA-BUF + VAAPI scale + NV12 clone
+ crossbeam send at 60fps even when no WebRTC client is connected
Fix (Option B - surgical bugfix):
- Add EncodeOutcome enum (Encoded/SkippedPaused/SkippedDisconnected/
SkippedDuplicate) to encode_cpu_frame return type
- encode_thread_loop only reports timing on Ok(Encoded), not on skips
-> encoded_fps naturally stays at 0 during idle (also helps #20)
- handle_pw_frame entry: early return on paused, skipping ALL frame
processing (DMA-BUF import, VAAPI scale, NV12 clone, channel send)
- MP4 mode unchanged (webrtc_paused is None, gate is no-op)
- Side benefit: last_fillable_frame stays None during initial idle,
so maybe_send_filler_frame also early-returns -> no filler waste
during the pre-connect idle window (partial mitigation for #18)
Out of scope (TODO comment added at state_portal.rs:178):
- Encoder still initializes on first PipeWire frame (one-time ~50ms
SwEncEncode::new_webrtc cost). Full deferral (Option A) requires
splitting WebRTC signaling lifecycle from media lifecycle - deferred
until startup cost becomes user-perceptible
- Bitrate formula unchanged (5*W*H*fps/100) - tracked by #21
Verification (34s idle + 60s connected session):
- 0 'skipping duplicate frame' events during idle (was ~30/sec before)
- 0 BWE bitrate updates during idle
- 0 IDR production during idle (was 180 frames into the void)
- First IDR produced 178ms after connect (ForceKeyframe -> IDR in 10ms)
- cargo test transform/fps_limit/backend_detect: 34 passed
- SAFETY comments preserved verbatim
encode_thread_loop hardcoded sws_us=0 and output_bytes=0, making the
stats dashboard show zeros for those columns. The previous encode_us
was measured around the entire encode_cpu_frame call, mixing sws +
encode work into one bucket.
Add SwEncodeTiming { sws_us, encode_us, output_bytes } to SwEncEncode.
- drain_encoder returns Result<usize> (total encoded bytes), accumulated
before the Muxer/Channel match so branch duplication and multi-packet
drain are both handled correctly. output_bytes = bytes produced by
libavcodec even if downstream delivery drops them.
- encode_cpu_frame resets last_timing to Default at entry (so early
returns from disconnect/pause/dedup never report stale prior values),
measures sws_us around sws_scale, measures encode_us around
avcodec_send_frame + drain, then stores the complete snapshot.
- take_timing() uses mem::take to return and clear in one step.
- flush() ignores the byte count from drain_encoder.
- state_portal encode_thread_loop calls take_timing() for real values.
WebRTC client bandwidth estimate now drives both encoder bitrate and
resolution tier selection, replacing the previous static-target encoder.
- webrtc.rs: enable str0m BWE (seeded at 5 Mbps), surface
EgressBitrateEstimate + KeyframeRequest events, expose
get_bwe_estimate() / set_need_keyframe()
- state_portal.rs: wire bitrate/resolution channels between the WebRTC
thread and the encode thread; tier ladder [1440p, 1080p, 720p] with
downscale at 60% budget and upscale hysteresis (120% sustained 10s)
- avhw.rs: SwEncImport::poll_resolution_commands() rebuilds the import
filter graph on UpdateResolution; SwEncEncode::recreate_encoder()
rebuilds sws/enc_video/yuv_frame atomically; hash_sampled_y_plane()
skips duplicate frames; VBV x264opts cap IDR bursts; H.264 level 4.0
(muxer) / 4.2 (WebRTC)
- state.rs: sync wlr-screencopy GOP to fps*2 max 20 for parity
- fix: drain bitrate_rx + resolution_rx BEFORE the stride check in
encode_cpu_frame() so the new (smaller-stride) frame produced after
a resolution change does not hit the stale (larger) enc_width and
crash the encode thread
- WebRTC GOP widened to fps*2 max 20 (was fps/2 max 10)
- Move WebRTC send to dedicated wl-webrtc-webrtc thread (was inline in main loop)
- Reduce frame_rx 16→1, input_tx 2→1 (drop-on-full), webrtc_tx 32→2
- Recv_timeout 10ms→2ms to reduce pipeline latency
- Fix sent_gap_p95 stats bug: compute gap at actual send time in WebRTC
thread instead of batch-draining at snapshot time (was always 0.0ms)
- High profile via AVCodecContext.profile, veryfast preset, 5x bitrate
- Stats drain via sent_gap channel with record_send_from_thread()
- Shutdown: drop input_tx → join encode → drop webrtc_tx → join webrtc
shutdown() calls enc.flush() → drain_encoder() → tx.send() on a
crossbeam bounded(32) channel. If the channel is full and the
receiver (webrtc_rx) is alive but not being drained, send() blocks
forever — a self-deadlock since both ends belong to the same struct.
Two-layer fix:
- avhw.rs: replace tx.send() with tx.try_send(); handle Full (drop
frame) and Disconnected (set flag) separately.
- state_portal.rs: drop webrtc_rx before flushing in shutdown() so
try_send returns Disconnected immediately.
Regression tests added for the channel semantics.
- Replace 'let _ = tx.send()' with proper error handling: log warning,
set webrtc_disconnected flag, and break drain loop on SendError
- Add Arc<AtomicBool> webrtc_paused shared between State/StatePortal
and SwEncState, synced from wrtc.is_connected() in poll_webrtc()
- Skip encoding in encode_filtered_frame() when paused or disconnected
- Drain and discard stale channel frames on disconnect
- Resume encoding automatically on WebRTC reconnection
- Add src/webrtc.rs: HTTP signaling server + str0m Sans-IO WebRTC transport
with H.264 Annex-B → RTP packetization and key-frame request handling
- avhw: introduce FrameOutput enum (Muxer | Channel) so SwEncState can
output to either MP4 muxer or crossbeam channel for WebRTC
- cap_portal: support portal session restore tokens (PersistMode::ExplicitlyRevoked)
to skip re-authorization dialog; add --no-persist flag to force fresh dialog
- args: make --output optional when --port is used for WebRTC mode
- state_portal: integrate WebRTC pipeline (encoder channel → RTP forwarding)
with shorter GOP for WebRTC (fps/2, min 10)
- main: redirect tracing to stderr; validate --output or --port required
- Add dependencies: str0m 0.20, serde_json 1, dirs 6
BUG-2 (HIGH): SHM Buffer event caused permanent hang
In the ZwlrScreencopyFrameV1 dispatcher, receiving a SHM Buffer event
left in_flight_surface stuck at AllocQueued forever, preventing
queue_alloc_frame() from requesting new frames.
Fix: treat Buffer as a metadata offer (v3 protocol), wait for
BufferDone to decide failure, and add AllocQueued state guard to
LinuxDmabuf handler.
BUG-3 (MEDIUM): Portal backend picked wrong GPU on multi-GPU systems
state_portal.rs hardcoded /dev/dri/renderD128 then renderD129, which
selects the wrong GPU when PipeWire uses a different device.
Fix: extract find_drm_render_nodes() as shared utility; defer DRM
device selection to first PipeWire frame; test each candidate with
av_hwframe_transfer_data to find the GPU that can actually import
the DMA-BUF frame.
BUG-4 (LOW): VAAPI device context created twice unnecessarily
try_finalize_output() created an AvHwDevCtx stored in EverythingButFmt,
but negotiate_format() discarded it (_hw_device_ctx) and EncState::new
created a new one.
Fix: thread the existing hw_device_ctx through negotiate_format() and
create_encoder() to EncState::new() which reuses it when provided.
Add a second capture backend for compositors without wlr-screencopy
(KWin, GNOME, etc.) using the xdg-desktop-portal ScreenCast interface
and PipeWire DMA-BUF streaming.
New files:
- src/backend_detect.rs: auto-detect wlr-screencopy vs portal backend
- src/cap_portal.rs: Portal session setup + PipeWire DMA-BUF thread
- src/state_portal.rs: StatePortal encoder pipeline (DMA-BUF → VAAPI)
Changes:
- Cargo.toml: add ashpd 0.13, tokio 1, pipewire 0.9, libspa 0.9,
crossbeam-channel 0.5
- src/args.rs: add --backend CLI flag
- src/avhw.rs: extract create_encoder() from inline State code
- src/main.rs: route to portal or wlr-screencopy based on backend
- src/state.rs: fix params.destroy() on dup failure, cleanup
in_flight_surface on copy fail, use create_encoder()
- tests/integration_test.rs: add --backend flag tests
scale_vaapi defaults to the input sw_format (RGBZ) when no output format
is specified. h264_vaapi encoder only supports NV12/YUV formats.
Adding format=nv12 ensures the filter outputs the correct color format
for hardware encoding.
- registry_queue_init consumes registry events during its internal
roundtrip without forwarding them to Dispatch<WlRegistry>. Added
bind_initial_globals() to manually iterate GlobalList and bind all
initial globals (wl_output, xdg_output_manager, dmabuf, screencopy,
wlr_output_manager) at State::new time.
- Fix av_freep segfault in build_filter_graph: av_buffersrc_parameters_alloc
returns a plain pointer, use av_free instead of av_freep (which expects
pointer-to-pointer).
- Fix filter graph format negotiation: remove software format filter that
broke scale_vaapi hardware pipeline. Chain is now src -> scale -> sink.
- Downgrade repeat_pps error to warning (not available in FFmpeg 6.x).
dailz