The webcam's frame rate is checked against 15 frames a second. While you move, under 12 or a freeze longer than 300 ms reads as stutter; those are starting values.
- Audio delay warns at 120 ms, near the ITU-R BT.1359-1 detectability point for sound after picture, and fails at 250 ms, our own line.
- Connection delay is read against ITU-T G.114, and jitter above 50 ms warns; the jitter line is ours.
- Every line is printed from the code that applies it. Lines marked as ours or as starting values have not yet been calibrated on a set of real devices.
The short answer
For a video call, SystemCheck's profile runs these checks: browser and system, webcam, microphone, speakers, audio delay, internet, browser settings. Each turns a measurement into pass, warn or fail using a fixed line. Where a published standard gives a line, the check uses it and names it; where none does, the line is ours and the page says so.
Webcam
The browser is asked for the camera's picture, and its size and frame rate are read against 640 by 480 at 15 frames a second. A camera that delivers its rate while still can drop frames when you move, because many lower their rate in poor light, so the check also asks you to wave. Under 12 frames a second, or a gap longer than 300 ms, reads as stutter to the person watching. Those two are starting values, to be calibrated on real webcams.
Audio delay
The audio check plays clicks and you tap along, which measures the delay you actually hear, including Bluetooth. It warns at 120 ms, near where ITU-R BT.1359-1 puts the point at which people notice sound arriving after the picture, and fails at 250 ms, our line, past that standard's acceptability point and where standard Bluetooth audio commonly lands.
Connection
Upload and download are measured, along with delay and jitter. A measured round trip is halved and read against ITU-T G.114's one-way lines. Jitter, how much the delay varies, warns above 50 ms; that line is ours, a little above what voice planning guides commonly use, because video calls buffer slightly more.
Terms used here
Questions
- What frame rate should a webcam have for video calls?
- SystemCheck checks for at least 15 frames a second at 640 by 480, and for smooth delivery while you move. Many calling apps send less than the camera can capture when the connection is slow, so a good camera alone does not guarantee a smooth picture at the other end.
- Why does my webcam's frame rate drop in a dark room?
- Many webcams lengthen each frame's exposure in low light to gather more of it, which lowers the frame rate. More light on your face is the usual fix.