I was in a "warehouse" store recently where there were a few dozen TV sets on display, fed in banks from three different canned feeds. All suffered from ghost images and the ghosts from any one feed seemed identical. Can there be digital ghosts? If yes, how? Were the ghosts originally analog, then digitized? If yes, do producers of TV demos typically do it so sloppily? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
OT Digital TV
Started by ●January 3, 2008
Reply by ●January 3, 20082008-01-03
Jerry Avins wrote:> I was in a "warehouse" store recently where there were a few dozen TV > sets on display, fed in banks from three different canned feeds. All > suffered from ghost images and the ghosts from any one feed seemed > identical.Perhaps the TVs are fed by the composite analog video signal. They simply connected all cables in the parallel. No wonder there is a reflection.> Can there be digital ghosts? If yes, how? Were the ghosts > originally analog, then digitized? If yes, do producers of TV demos > typically do it so sloppily?"If you give me $1000, I will do it much better" (tm) VLV
Reply by ●January 3, 20082008-01-03
Jerry Avins <jya@ieee.org> writes:> I was in a "warehouse" store recently where there were a few dozen TV > sets on display, fed in banks from three different canned feeds. All > suffered from ghost images and the ghosts from any one feed seemed > identical. Can there be digital ghosts? If yes, how? Were the ghosts > originally analog, then digitized? If yes, do producers of TV demos > typically do it so sloppily?What makes you think the inputs were digital? To answer your last question, I'd say no. I've seen lots of very high quality displays in the last couple of years at Best Buy, Walmart, BJ's, etc. --Randy PS: Did you know you can buy a grand piano at BJ's? ISYN. Incredible. -- % Randy Yates % "I met someone who looks alot like you, %% Fuquay-Varina, NC % she does the things you do, %%% 919-577-9882 % but she is an IBM." %%%% <yates@ieee.org> % 'Yours Truly, 2095', *Time*, ELO http://www.digitalsignallabs.com
Reply by ●January 3, 20082008-01-03
Randy Yates wrote:> Jerry Avins <jya@ieee.org> writes: > >> I was in a "warehouse" store recently where there were a few dozen TV >> sets on display, fed in banks from three different canned feeds. All >> suffered from ghost images and the ghosts from any one feed seemed >> identical. Can there be digital ghosts? If yes, how? Were the ghosts >> originally analog, then digitized? If yes, do producers of TV demos >> typically do it so sloppily? > > What makes you think the inputs were digital? > > To answer your last question, I'd say no. I've seen lots of very high > quality displays in the last couple of years at Best Buy, Walmart, BJ's, > etc.The detail in the pictures would (I estimated) have required about a 20MB unencoded channel. to repeat, the ghosts were the same in intensity and pixel spacing on all the displays.> > PS: Did you know you can buy a grand piano at BJ's? ISYN. Incredible.Please translate ISYN. BTW, it was BJ's. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●January 3, 20082008-01-03
On Jan 4, 5:27 am, Jerry Avins <j...@ieee.org> wrote:> I was in a "warehouse" store recently where there were a few dozen TV > sets on display, fed in banks from three different canned feeds. All > suffered from ghost images and the ghosts from any one feed seemed > identical. Can there be digital ghosts? If yes, how? Were the ghosts > originally analog, then digitized? If yes, do producers of TV demos > typically do it so sloppily? > > Jerry > -- > Engineering is the art of making what you want from things you can get. > �����������������������������������������������������������������������Multi-path doesn't care whether you transmit analog or digital. There are some digital systems that pretend to have fixed the problem but as you see it is still a major problem. OFDM is supposed to have it fixed but I hear that isn't true either. Hardy
Reply by ●January 3, 20082008-01-03
HardySpicer wrote:> On Jan 4, 5:27 am, Jerry Avins <j...@ieee.org> wrote: > >>I was in a "warehouse" store recently where there were a few dozen TV >>sets on display, fed in banks from three different canned feeds. All >>suffered from ghost images and the ghosts from any one feed seemed >>identical. Can there be digital ghosts? If yes, how? Were the ghosts >>originally analog, then digitized? If yes, do producers of TV demos >>typically do it so sloppily? >> >>Jerry >>-- >>Engineering is the art of making what you want from things you can get. >>����������������������������������������������������������������������� > > > Multi-path doesn't care whether you transmit analog or digital. There > are some digital systems that pretend to have fixed the problem but as > you see it is still a major problem. OFDM is supposed to have it fixed > but I hear that isn't true either. > > > HardyDoes that imply that digital TV is no _more_ susceptible to multipath related problems than analog. That is, currently having an acceptable picture, will I have an acceptable picture without upgrading my antenna?
Reply by ●January 3, 20082008-01-03
On Thu, 03 Jan 2008 13:00:39 -0500, Jerry Avins <jya@ieee.org> wrote:>Randy Yates wrote: >> Jerry Avins <jya@ieee.org> writes: >> >>> I was in a "warehouse" store recently where there were a few dozen TV >>> sets on display, fed in banks from three different canned feeds. All >>> suffered from ghost images and the ghosts from any one feed seemed >>> identical. Can there be digital ghosts? If yes, how? Were the ghosts >>> originally analog, then digitized? If yes, do producers of TV demos >>> typically do it so sloppily? >> >> What makes you think the inputs were digital? >> >> To answer your last question, I'd say no. I've seen lots of very high >> quality displays in the last couple of years at Best Buy, Walmart, BJ's, >> etc. > >The detail in the pictures would (I estimated) have required about a >20MB unencoded channel. to repeat, the ghosts were the same in intensity >and pixel spacing on all the displays.As mentioned, I suspect that if you looked at the feeds they were actually distributing the signal in analog form via the composite or cable feeds. An impedance mismatch at the splitter input (or a number of things) would result in the same ghost at all displays. Some of those retail displays are still set up for showing analog TVs, so the signal distribution may still be NTSC. The guys that put those displays together are usually not paid enough or not knowledgable enough to know or care how to fix it, IMHO, if they even noticed.>> PS: Did you know you can buy a grand piano at BJ's? ISYN. Incredible. > >Please translate ISYN. BTW, it was BJ's. > >JerryEric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Reply by ●January 3, 20082008-01-03
On Thu, 3 Jan 2008 10:17:54 -0800 (PST), HardySpicer <gyansorova@gmail.com> wrote:>On Jan 4, 5:27 am, Jerry Avins <j...@ieee.org> wrote: >> I was in a "warehouse" store recently where there were a few dozen TV >> sets on display, fed in banks from three different canned feeds. All >> suffered from ghost images and the ghosts from any one feed seemed >> identical. Can there be digital ghosts? If yes, how? Were the ghosts >> originally analog, then digitized? If yes, do producers of TV demos >> typically do it so sloppily? >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> ����������������������������������������������������������������������� > >Multi-path doesn't care whether you transmit analog or digital. There >are some digital systems that pretend to have fixed the problem but as >you see it is still a major problem. OFDM is supposed to have it fixed >but I hear that isn't true either. > >HardyFor digital transmission, though, multipath doesn't result in the "ghosting" that Jerry is describing. That's a tell-tale sign of multipath for an analog signal, but is inexplicable for digital transmission without a display error. Having the same display error on an array of different makes an models makes no sense at all with digital transmission, hence Jerry's questions. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Reply by ●January 3, 20082008-01-03
Jerry Avins <jya@ieee.org> writes:> Randy Yates wrote: >> PS: Did you know you can buy a grand piano at BJ's? >> ISYN. Incredible. > > Please translate ISYN.I Shit You Not. -- % 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
Reply by ●January 3, 20082008-01-03
HardySpicer wrote:> On Jan 4, 5:27 am, Jerry Avins <j...@ieee.org> wrote: >> I was in a "warehouse" store recently where there were a few dozen TV >> sets on display, fed in banks from three different canned feeds. All >> suffered from ghost images and the ghosts from any one feed seemed >> identical. Can there be digital ghosts? If yes, how? Were the ghosts >> originally analog, then digitized? If yes, do producers of TV demos >> typically do it so sloppily? >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> ����������������������������������������������������������������������� > > Multi-path doesn't care whether you transmit analog or digital. There > are some digital systems that pretend to have fixed the problem but as > you see it is still a major problem. OFDM is supposed to have it fixed > but I hear that isn't true either.How can you produce a ghost of a number? You can add two analog signals and see the images superposed. Adding two bitstreams should make junk. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
