Forums

Inverted Video

Started by Unknown September 20, 2007
"Simon S Aysdie"  wrote
> Why is video inverted for transmission?
So that the peaks of sync pulses are transmitted at +100% modulation, which allows TV receivers to show the most stable picture in the presence of noise (eg, fringes of the coverage area of the TV station). RF RCA Broadcast Field Engineer, retired
And, black dots due to noise spikes in a bright picture annoy much less 
than white spots in a night-scene.

Rich.Fry1@gmail.com wrote:
> "Simon S Aysdie" wrote >> Why is video inverted for transmission? > > So that the peaks of sync pulses are transmitted at +100% modulation, > which allows TV receivers to show the most stable picture in the > presence of noise (eg, fringes of the coverage area of the TV > station). > > RF > RCA Broadcast Field Engineer, retired >
On Thu, 20 Sep 2007 05:31:20 -0700, Rich.Fry1@gmail.com wrote:

>"Simon S Aysdie" wrote >> Why is video inverted for transmission? > >So that the peaks of sync pulses are transmitted at +100% modulation, >which allows TV receivers to show the most stable picture in the >presence of noise (eg, fringes of the coverage area of the TV >station). > >RF >RCA Broadcast Field Engineer, retired
..and the mean power output of the TX is lower -- - Ren�
 On Sep 20, 7:19 am, Ren=E9 <rjz~nosp...@xs4all.nl> wrote:
 > On Thu, 20 Sep 2007 05:31:20 -0700, Rich.F...@gmail.com wrote:
 > >"Simon S Aysdie"  wrote
 > >> Why is video inverted for transmission?
 >
 > >So that the peaks of sync pulses are transmitted at +100%
modulation,
 > >which allows TV receivers to show the most stable picture in the
 > >presence of noise (eg, fringes of the coverage area of the TV
 > >station).
 >
 > >RF
 > >RCA Broadcast Field Engineer, retired
 >
 > ..and the mean power output of the TX is lower
 >
 > --
 >  - Ren=E9

So, the transmitter is max power at black but the CRT receiver is max
power at white. At some number of viewers the power company should see
a constant load. Right?

GG

<stratus46@yahoo.com> wrote in message 
news:1190340231.709119.264430@y27g2000pre.googlegroups.com...
On Sep 20, 7:19 am, Ren&#2013265929; <rjz~nosp...@xs4all.nl> wrote:
 > On Thu, 20 Sep 2007 05:31:20 -0700, Rich.F...@gmail.com wrote:
 > >"Simon S Aysdie"  wrote
 > >> Why is video inverted for transmission?
 >
 > >So that the peaks of sync pulses are transmitted at +100%
modulation,
 > >which allows TV receivers to show the most stable picture in the
 > >presence of noise (eg, fringes of the coverage area of the TV
 > >station).
 >
 > >RF
 > >RCA Broadcast Field Engineer, retired
 >
 > ..and the mean power output of the TX is lower
 >
 > --
 >  - Ren&#2013265929;

So, the transmitter is max power at black but the CRT receiver is max
power at white. At some number of viewers the power company should see
a constant load. Right?

Riiiiiight.

But then consider that LCDs use maximum power when displaying
all black (because they have to turn on ALL the pixels to block the
backlight. 


<stratus46@yahoo.com> wrote in message 
news:1190340231.709119.264430@y27g2000pre.googlegroups.com...
On Sep 20, 7:19 am, Ren&#2013265929; <rjz~nosp...@xs4all.nl> wrote:
 > On Thu, 20 Sep 2007 05:31:20 -0700, Rich.F...@gmail.com wrote:
 > >"Simon S Aysdie"  wrote
 > >> Why is video inverted for transmission?
 >
 > >So that the peaks of sync pulses are transmitted at +100%
modulation,
 > >which allows TV receivers to show the most stable picture in the
 > >presence of noise (eg, fringes of the coverage area of the TV
 > >station).
 >
 > >RF
 > >RCA Broadcast Field Engineer, retired
 >
 > ..and the mean power output of the TX is lower
 >
 > --
 >  - Ren&#2013265929;

So, the transmitter is max power at black but the CRT receiver is max
power at white. At some number of viewers the power company should see
a constant load. Right?

GG

Good point. I found that the power drawn from some CRT based sets can double 
from full black to full white.

When the standards were developed many decades ago, I doubt power usage at 
the receiver end was considered. Noise and picture stability were more 
important. Transmitter power was probably a consideration as well.
John 


In article <5li9sfF83c16U1@mid.individual.net>, rcrowley@xp7rt.net 
says...
> > <stratus46@yahoo.com> wrote in message > news:1190340231.709119.264430@y27g2000pre.googlegroups.com... > On Sep 20, 7:19 am, Ren&#2013265929; <rjz~nosp...@xs4all.nl> wrote:
<snip>
> So, the transmitter is max power at black but the CRT receiver is max > power at white. At some number of viewers the power company should see > a constant load. Right? > > Riiiiiight. > > But then consider that LCDs use maximum power when displaying > all black (because they have to turn on ALL the pixels to block the > backlight.
No, they're just twisted a different direction; same power. -- Keith
On Fri, 21 Sep 2007 09:29:58 -0700, "Richard Crowley"
<rcrowley@xp7rt.net> wrote:

> ><stratus46@yahoo.com> wrote in message >news:1190340231.709119.264430@y27g2000pre.googlegroups.com... >On Sep 20, 7:19 am, Ren&#2013265929; <rjz~nosp...@xs4all.nl> wrote: > > On Thu, 20 Sep 2007 05:31:20 -0700, Rich.F...@gmail.com wrote: > > >"Simon S Aysdie" wrote > > >> Why is video inverted for transmission? > > > > >So that the peaks of sync pulses are transmitted at +100% >modulation, > > >which allows TV receivers to show the most stable picture in the > > >presence of noise (eg, fringes of the coverage area of the TV > > >station). > > > > >RF > > >RCA Broadcast Field Engineer, retired > > > > ..and the mean power output of the TX is lower > > > > -- > > - Ren&#2013265929; > >So, the transmitter is max power at black but the CRT receiver is max >power at white. At some number of viewers the power company should see >a constant load. Right? > >Riiiiiight. > >But then consider that LCDs use maximum power when displaying >all black (because they have to turn on ALL the pixels to block the >backlight. >
At least until OLED screens get in the channel. Not additive color mixing schema there.
On Thu, 20 Sep 2007 14:42:21 +0200, Andre Lodwig <a.lodwig@lrz.tum.de>
wrote:

>And, black dots due to noise spikes in a bright picture annoy much less >than white spots in a night-scene. > >Rich.Fry1@gmail.com wrote: >> "Simon S Aysdie" wrote >>> Why is video inverted for transmission? >> >> So that the peaks of sync pulses are transmitted at +100% modulation, >> which allows TV receivers to show the most stable picture in the >> presence of noise (eg, fringes of the coverage area of the TV >> station). >> >> RF >> RCA Broadcast Field Engineer, retired >>
I've written a very short piece about analogue ( VSB AM) TV and why it is broadcast with sync upwards - ie inverted. It has nothing to do with noise performance but is entirely a system matter. TV will not work non-inverted. http://81.174.169.10/odds/analoguetv.ppsx d -- Pearce Consulting http://www.pearce.uk.com
nospam@nospam.com (Don Pearce) writes:

> On Thu, 20 Sep 2007 14:42:21 +0200, Andre Lodwig <a.lodwig@lrz.tum.de> > wrote: > >>And, black dots due to noise spikes in a bright picture annoy much less >>than white spots in a night-scene. >> >>Rich.Fry1@gmail.com wrote: >>> "Simon S Aysdie" wrote >>>> Why is video inverted for transmission? >>> >>> So that the peaks of sync pulses are transmitted at +100% modulation, >>> which allows TV receivers to show the most stable picture in the >>> presence of noise (eg, fringes of the coverage area of the TV >>> station). >>> >>> RF >>> RCA Broadcast Field Engineer, retired >>> > > I've written a very short piece about analogue ( VSB AM) TV and why it > is broadcast with sync upwards - ie inverted. It has nothing to do > with noise performance but is entirely a system matter. TV will not > work non-inverted. > > http://81.174.169.10/odds/analoguetv.ppsx
I cannot read a "ppsx" file. Can you post it in something more standard, like pdf? -- % Randy Yates % "The dreamer, the unwoken fool - %% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..." %%% 919-577-9882 % %%%% <yates@ieee.org> % 'Eldorado Overture', *Eldorado*, ELO http://www.digitalsignallabs.com