In article <%5sSj.15851$E77.5569@[EMAIL PROTECTED]
> "WGD" <wgd.roaming@[EMAIL PROTECTED]
>
writes:
>Alan:
>
>When one talks 720p, aren't they really talking about the ACTIVE lines?
>Thus a screen marketed by firm 'A' at 720p and by firm 'B' at768p, are
>really one in the same, the difference being the retrace time? Like NTSC
>displays 480 active lines in a 512 line period.
Yes, they are talking about displayed lines.
The 720 line displays (generally older DLP sets), or 768 lines (some
plasma
and some LCD sets) generally show all those lines. The retrace has
nothing to
do with it, and doesn't even exist for some of the display technologies.
The
sets are not really the same, as they differ by 48 lines, for example.
NTSC has 483 active picture lines, but sometimes some might not be sent,
if the source was digital with 480 lines. Many NTSC sets have 5-10%
overscan
so 24 to 48 of those lines are not visible on the screen. The actual
ratio of
frame to line rates is 525, not 512.
>Pumping 1080i (active - really 1125) lines in 720 active lines is really
a
>good down-conversion, compression trick. Yes?
Depends on the set. Some do a good conversion, some do a poorer one.
Alan
|
