"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
Inverted Video
Started by ●September 20, 2007
Reply by ●September 20, 20072007-09-20
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 >
Reply by ●September 20, 20072007-09-20
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�
Reply by ●September 20, 20072007-09-20
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
Reply by ●September 21, 20072007-09-21
<stratus46@yahoo.com> wrote in message news:1190340231.709119.264430@y27g2000pre.googlegroups.com... On Sep 20, 7:19 am, Ren� <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� 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.
Reply by ●September 22, 20072007-09-22
<stratus46@yahoo.com> wrote in message news:1190340231.709119.264430@y27g2000pre.googlegroups.com... On Sep 20, 7:19 am, Ren� <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� 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
Reply by ●September 22, 20072007-09-22
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� <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
Reply by ●September 23, 20072007-09-23
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� <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� > >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.
Reply by ●September 24, 20072007-09-24
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
Reply by ●September 24, 20072007-09-24
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.ppsxI 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
