Understanding the Stats Overlay

Every punktfunk client has an in-stream stats overlay. All clients use the same vocabulary, the same measurement points, and the same math, so a number on your phone means exactly what the same number means on your desktop.

The four measurement points

Every latency figure is the time between two of these four points in a video frame's life:

1. capture — the host grabs the frame from the (virtual) display. Stamped on the host's clock and carried with the frame.
2. received — your client has fully received and reassembled the frame from the network (after any FEC recovery), before decoding.
3. decoded — the video decoder has produced the picture.
4. displayed — the picture is handed to the screen (as close to "photons" as the platform lets us measure).

Reading the overlay

1920×1080@120 · 119 fps · 38.2 Mb/s · HEVC 10-bit HDR · GPU decode
end-to-end 14.2 ms p50 · 19.8 p95 · capture→on-glass
= host 3.1 + network 6.7 + decode 2.1 + display 2.3
lost 3 (0.1%) · skipped 1 · FEC 12

• Line 1 — the stream. Resolution@refresh, frames received per second, and the received video bitrate (goodput — FEC overhead not counted), plus codec details.

• Line 2 — the headline. end-to-end is the directly measured time from host capture to the endpoint named at the end of the line (capture→on-glass here). p50 = the typical frame (median), p95 = the slow outliers. This is the one number that summarizes your stream.

• Line 3 — where the time goes. The stages tile the end-to-end interval — each starts where the previous one ends, so they add up to the headline:

  • host — capture → sent: the host's own share (capture read, encode, error coding, the paced send), reported by the host itself once per frame.
  • network — sent → received: the network flight plus reassembly on your device.
  • decode — received → decoded, on your device.
  • display — decoded → displayed: waiting for the right screen refresh, rendering, and vsync.

  Against an older host that doesn't report its share yet, the first two terms merge into a single host+network number — same total, one split fewer.

  (Stage values are per-stage medians, so they sum only approximately to the headline median — percentiles aren't perfectly additive. The headline is measured directly, never computed as a sum.)

• Line 4 — reliability (only shown when something is nonzero). lost = frames the network dropped beyond FEC's ability to recover; skipped = frames your client chose not to display because a newer one had already arrived; FEC = packet shards the error correction recovered this second (loss that you didn't feel).

All values refresh once per second over the last second of frames.

Clocks, and the (same-host clock) tag

end-to-end and host+network span two machines, so they need the two clocks to agree: at connect, the client runs an NTP-style handshake with the host and corrects for the measured clock offset. If that handshake wasn't possible, the overlay appends (same-host clock) — the numbers are then only trustworthy when client and host run on the same machine. decode and display are single-machine measurements and are always exact.

What each platform can measure

Not every platform exposes a true "displayed" instant, so the headline's endpoint is always spelled out rather than pretending:

A shorter chain means the number is smaller because it measures less — check the endpoint before comparing two devices.

Comparing with Moonlight / Sunshine

Moonlight's overlay and punktfunk's measure different slices of the pipeline, and the single biggest difference is:

Moonlight has no end-to-end number. Its overlay shows separate client-side segments (decode time, queue delay, render time) and — on Sunshine hosts — a host-side number. Nothing in Moonlight measures capture-to-glass, and nothing measures the network flight of video frames. punktfunk's end-to-end line has no Moonlight counterpart — never compare it against any single Moonlight line.

To compare fairly, reconstruct an approximate end-to-end from Moonlight's lines:

Moonlight ≈ host processing latency (avg)
          + ½ × average network latency
          + average decoding time
          + average frame queue delay
          + average rendering time

…and compare that against punktfunk's end-to-end. (It's still approximate: Moonlight's segments are averages over a slightly different window, and the ½·RTT term stands in for a one-way frame flight that Moonlight doesn't measure.)

Line-by-line matrix

Other differences worth knowing when squinting at both overlays side by side:

• Averages vs percentiles. Moonlight's time values are means; punktfunk shows medians (p50) with a p95 for the headline. Under jitter, a mean sits above the median — Moonlight's numbers read slightly "worse" than an equivalent p50.
• Windows. Both refresh about once per second; Moonlight over a ~1–2 s sliding window, punktfunk over the last full second.
• Host frame rate. Moonlight's headline FPS estimates what the host produced (received + lost). punktfunk shows what your client actually received, and reports loss separately.