Ticket 4482, 09:42
Reported fault: cursor feels half a beat behind. Dragging a chart, the line arrives after the hand. Writing on a PDF, the ink trails the stylus. Video is fine.That last sentence is the useful one. Video fine plus dragging wrong points to latency, not bandwidth.
Method
Camera at 240 frames per second, filming the laptop screen and the panel in the same field of view, then counting frames between click and pixel change.187 milliseconds.
Reference points: below 100 ms most people call it instant. Between 100 and 150 it feels heavy but usable. Above 150, dragging and handwriting fall apart because the hand and the eye stop agreeing.
Where the time went
Capture, encode, transport, decode, render. Capture and render are cheap now, ten to twenty milliseconds together.Encoding is expensive: software H.264 on a low-end chip takes sixty to eighty milliseconds, H.265 with hardware support closer to forty.
Transport was the surprise. The dongle was on 2.4 GHz in a room with three access points, a wireless keyboard and a Bluetooth speaker. Every retry added tens of milliseconds, and the retries were constant.
Three changes, one afternoon
Dongle to 5 GHz: 94 ms.A dedicated access point for the panel instead of the shared office network: stopped evening traffic competing with a morning board meeting.
Dongle firmware update, which fixed a buffering bug on 1080p content. Final measurement 70 ms. The client said it felt normal, then asked why we had not mentioned this earlier. We had, in the proposal, on page four.
The rule for installers
If the meeting involves live annotation on a drawing, or video that must stay in sync with audio, use the cable. Wired is under ten milliseconds and always will be.Wireless is for sharing a deck. No amount of tuning changes that, and a panel that connects in two seconds but buffers on the third laptop is worse than one that takes five seconds to pair and never stutters.