Skip to content

capture(wayland): fix black screen and pts timing on gst-launch #9

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
domenkozar wants to merge 1 commit into
base: main
Choose a base branch
from
Open

capture(wayland): fix black screen and pts timing on gst-launch #9

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
36 changes: 22 additions & 14 deletions internal/airplay/capture.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -87,20 +87,25 @@ func startWaylandCapture(ctx context.Context, cfg CaptureConfig) (*ScreenCapture

encoderParts := detectGstEncoder(cfg)

// Single GStreamer pipeline: capture from PipeWire portal and encode to H.264.
// Keep the pipeline simple — pipewiresrc ! videoconvert handles DMA-BUF to
// system memory conversion automatically. The stream is encoded at the portal's
// native resolution; we do not rescale to a configured size because the captured
// surface size is whatever the compositor hands us (Wayland surfaces are not
// pixel-perfect to any requested size). The actual encoded dimensions are read
// back from the H.264 SPS downstream.
// videorate drop-only=true passes frames through without duplicating during
// idle periods (avoids wasting bandwidth on static screens). skip-to-first
// avoids buffering before the first frame.
// Single GStreamer pipeline: capture from the PipeWire portal and encode to
// H.264.
// - vapostproc imports the portal's DMA-BUF via VA-API (plain videoconvert
// fails to negotiate DMA-BUF on many drivers, giving a black screen).
// - format=I420 forces 4:2:0 — RGB screens otherwise make x264enc emit
// "High 4:4:4 Predictive", which most receiver decoders reject (black).
// - videorate re-stamps buffers onto a regular fps timeline: the portal can
// deliver pts=0, which confuses encoder/muxer timing. drop-only=true never
// duplicates frames during idle periods (no wasted bandwidth on a static
// screen); skip-to-first avoids buffering before the first frame.
// The stream is encoded at the portal's native resolution; we do not rescale
// because the captured surface size is whatever the compositor hands us. The
// actual encoded dimensions are read back from the H.264 SPS downstream.
const pwFdNum = 3
gstArgs := []string{
"--quiet",
"pipewiresrc", fmt.Sprintf("fd=%d", pwFdNum), fmt.Sprintf("path=%d", nodeID), "do-timestamp=true",
"!", "vapostproc",
"!", "video/x-raw,format=I420",
"!", "videoconvert",
"!", "videorate", "drop-only=true", "skip-to-first=true",
"!", fmt.Sprintf("video/x-raw,framerate=%d/1", fps),
Expand All @@ -125,13 +130,15 @@ func startWaylandCapture(ctx context.Context, cfg CaptureConfig) (*ScreenCapture
if err != nil {
cancel()
pwFd.Close()
dbusConn.Close()
return nil, fmt.Errorf("gst stdout pipe: %w", err)
}
stderr, _ := cmd.StderrPipe()

if err := cmd.Start(); err != nil {
cancel()
pwFd.Close()
dbusConn.Close()
return nil, fmt.Errorf("start gst-launch: %w", err)
}
pwFd.Close() // child inherited it
Expand Down Expand Up @@ -258,30 +265,31 @@ func (sc *ScreenCapture) Read(buf []byte) (int, error) {
}

func (sc *ScreenCapture) Stop() {
if sc.stopped || sc.cmd == nil {
if sc.stopped {
return
}
sc.stopped = true
if sc.cancel != nil {
sc.cancel()
}

// Close stdout to unblock any pending Read() call
// Close stdout to unblock any pending Read() call.
if sc.stdout != nil {
sc.stdout.Close()
}

if sc.dbusConn != nil {
sc.dbusConn.Close()
}
if sc.cmd.Process != nil {

if sc.cmd != nil && sc.cmd.Process != nil {
_ = sc.cmd.Process.Signal(os.Interrupt)
}

select {
case <-sc.waitCh:
case <-time.After(2 * time.Second):
if sc.cmd.Process != nil {
if sc.cmd != nil && sc.cmd.Process != nil {
_ = sc.cmd.Process.Kill()
}
<-sc.waitCh
Expand Down
Loading