10ms-30ms of latency in most cases. One frame time at 60fps is 16ms,
so if you wait for each picture to be completely scanned in over HDMI
before you start scanning it out to the glass then that's going to set
your minimum latency. And obviously if the input frame rate is less
than 60fps it's possible that the latency may go up.
We had an arcade game at MAGFest (Music and Gaming fest with a computer
museum room in the greater DC area) that used dual LCD TVs from a hdmi
splitter. The players complained that the one side was too laggy. Friend
put a LCD latency test unit on the displays, and sure enough one screen
was about 30ms behind the other. Playing with the test widget (it's a box
with a hdmi cable, box goes against screen and detects the flashing) the
top of the screen and bottom of screen is definitely off a chunk of time
as the rows are scanned in order across the panel (at least on TVs we
had.) We swapped it out.
The LED video wall stuff I play with scans the image in every 8 lines, but
it's much slower than a TV.
I don't know how humans do it, but on some of the music rhythm arcade
games that use LCDs it's desired to have the original LCD over any
replacement since the timing of the game is meant for it. People have made
hacked DLLs that allow adjustment of timing windows but it's never as good
as the original, which is why the original LCDs sometimes go for $5000.
These games are imported from Japan.
How does a human do this? You hit the button as the line comes to the
bottom of the screen where the solid line is across the bottom. This is
why the timing is important:
https://www.youtube.com/watch?v=Oy2h2yDKYyY
https://www.youtube.com/watch?v=0nGhSAoQqcA
(Those aren't really on fast, the games go quite a bit faster than that
even)
- Ethan
--
: Ethan O'Toole
