"Jim Lesurf" wrote in message
...
In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...


With a CRT in principle all you have to do is allow the CRT to switch scan
width. No need for any 'pan and scan' or 'letterbox' processing by either
source or display.

In principle yes, I'm talking about what actually happens, not what is
possible. Since the end of 405-line transmissions TV sets (as opposed to
computer monitors) have never had switching for horizontal scan frequency or
width. Quite a lot can switch the vertical frequency between 50 and 60Hz and
a few have a vertical scan amplitude switching for letterbox presentation of
widescreen material.


I had thought we had been discussing lip synch delays caused by
*displays*.
For fairly obvious reasons, if a source like a DVD player or tuner has to
have a process delay for the image it can easily then apply a similar
delay
to the sound. This just requires the designer to know what they are doing.
However when the display has a vision delay, the designer may have no
control over the sound path from an external source feeding video to the
display.


Well we were, I just made the point that just because you are watching on a
CRT that doesn't mean there isn't any "faffing about". Widscreen CRT TV's
all have digital processing to cope with various aspect ratios etc.

But it isn't the faffing about needed to convert the pixel number/layout
(which is in effect standards conversion) that causes the long delays that
cause lip-sync problems, rather that is due to more fundamental aspects of
the way flat-screen displays work.

David.