Lag measurement

[c0pperdragon]

Lag measurement

[c0pperdragon]

For lag measurement to this precision at also makes a difference on which part of the screen the measurement is done.
The original analog signal (lets only consider PAL here) has a line frequency of 15625.
A standard digital 1920x1080x50 signal has a line frequency of 56250 which means it will show 14062 inputs lines per second (when quadrupling the lines). So the digital signal will have an added lag of 7us on every scan line further down.
So the lag should be about 1.8ms higher if measured on the bottom of the screen than when measured at the top of the screen.
For different output resolutions this would also vary a bit.

You can easily make the comparision by creating a very slim blinking rectangle either at the top or at the bottom.