🚀 go-pugleaf

> OK, so I'm a finicky purist, but the black level is NOT 0.33V when the video
> signal is inverted - it is 0.3V when the "right way up".  In your inverted
> world,  the black level should be at about 0.7V.

Sorry, Mike, but you're not a particularly exact purist! :-)

Assuming RS-343A signal levels, black is nominally 54 mV above blank, which
is the reference; if you insist on considering the sync tips as 0, then
blank would *nominally* be at 0.286V + 0.054V, or 0.340V up from the sync
tip - so the original answer was at least closer to correct.

Actually, there's quite a large tolerance on the location of the "black"
level with respect to "blank" - this difference usually being referred to
as the "setup", and speced (as I recall) as 7.5 +/- 5 IRE.  And the good ol' 
RS-170C standard - which is what many are using when talking about "NTSC" 
video, although the mapping between the two isn't that clean - uses a 1.4 V 
p-p signal, with 1.0V from blank to white and 0.4V from blank to sync.

And, as always, your mileage in the PAL/SECAM world may vary.  I'm not
up on the current practices in non-NTSC consumer equipment.


Bob Myers  KC0EW   Hewlett-Packard Co.      |Opinions expressed here are not
                   User Interface Tech. Div.|those of my employer or any other
myers@fc.hp.com    Fort Collins, Colorado   |sentient life-form on this planet.