Digital TV, cable hookup, why ghosting in image?

Factual Questions
1

I’m going over to a friend’s house soon to see if I can help with a problem he has with his very new, big-screen digital TV. He claims to be observing ghosting on some (maybe all) channels. I’m wondering just how that can happen on an all-digital hookup.

The coax cable is coming from the street (<150ft), where it’s fiber back to the head end. The coax from house to street was replaced by Charter about 2 years ago and they verified the levels were OK then. It is connected to a 3-way splitter supplied by the cable company (Charter), so I’m pretty sure it’s rated OK. One of the splits goes directly to the TV’s cable input, the other to another TV, and to the Internet cable modem. None of the cables are very long and it’s not a big house with long, snaky runs.

So where is the ghosting being picked up? I can’t blame the master feed from Charter, as I live just two houses away and I don’t see it on my digital TV, although it’s possible I am on a different distribution box.

Where would I check first, or should I just give up and call the Charter techs?

2

Is his tv a cable card device? If not he might be tuning to analog channels. His cable carrier should be transmitting afew unencrypted digital channels. Make sure he is tuning to those. Other than using a cable card device like a TiVo or home theater pc the only way to get a full digital lineup is through the crappy cable boxes his carrier will happily rent him.

3

Does it happen with other sources, or only cable?
If other sources, then is it a projection TV? It could be a convergence issue.

But it’s this line that concerns me…

Unless your friend has a CableCARD compatible TV (very unlikely), then he’s running an analog signal to the TV. Is he using a cable box? If he’s got coaxial cable going from the cable box to the TV, that’s an analog connection.

Get him an HDMI connection, and the problem will disappear.

4

A slight clarification to the above post. It possible that his tv has a built in QAM tuner that will tune to unencrypted digital channels. It’s almost always a very limited lineup though.

5

He is able to see digital channels like 9-9 and other numbers greater than 100. This is a modern digital TV, so no digital converter box is needed to view those channels, although the numbering scheme does not coincide with the official Charter numbers.

Other sources, like a MPG file from a flash drive, do not exhibit ghosting at all.

This is not a projection TV, but a flat screen (LED?), thin-box unit.

If we were to use a HDMI cable, what would that cable run from/to? He’s already direct from outside cable to TV, so to use HDMI, we’d have to impose something between.

6

Ok, let me (kinda) start over…

TV has a digital and analog tuner.
Digital Tuner may be ATSC (what’s used in Over-the-Air (abbreviated OTA) digital broadcasting)
Digital Tuner may be QAM (what cable companies use)
It may be both.

With respect to cable-only channels:
Regardless, no TV is going to be able to tune any encrypted cable channels; and nowadays, that’s nearly every non-OTA channel. If your friend is paying for cable channels other than the very basic OTA channels, then he won’t be able to tune them.

With respect to ghosting:
Cable companies are required to carry the OTA channels. Theoretically, they could be carrying the digital channels by decoding them and rebroadcasting them in analog. I don’t know if your cable company does this. They probably carry a mix of digital and analog channels. I’d check to see if ghosting occurs on the (supposedly) digital channels. If so, I’d fumble through the TV menus to see if that channel were really digital, or if the TV were receiving an analog signal. You’ll have to hunt down where the signal is analog and where the ghosting is being introduced.

Still, the easiest and best solution is to get some variety of set-top box that can decode the encrypted QAM channels that your friend is likely paying for, and then going from that box to the TV via HDMI.

7

I’m trying to find out the model of the TV to see if it has a QAM tuner.

None of the channels he has or wants are encrypted, AFAIK. He claims to be able to get some HD channels, so those would have to be digital and not encrypted.

I will be going over to his house later and I’ll get a better idea what is going on and what the images look like.

Charter charges $5/month for their converter box, which complicates the setup, so we don’t want to use or pay for that unless it’s absolutely necessary.

8

If there is ghosting in the digital channels (if it exists in the few HD channels he gets - probably his local 4 or so), then something may be wrong with his tuner, or perhaps the image is being overly processed by some sort of image filter. Check the settings for stuff like compression or noise reduction. I know these things can make the image look very soft and unclear… though I wouldn’t call it ghosting.

9

I don’t mean to insult your intelligence but they do make very thin projection TV’s. They’re about double the thickness of a regular flat screen.

I second the question about other input sources of video. What does a DVD look like?

10

He’s (probably) also paying for 100+ channels that he isn’t able to watch. While I’m not certain of this, I’m confident that there isn’t a single cable provider in the US that offers its digital cable channels, completely unencrypted (aka ClearQAM).

It really sounds to me like he’s got the following:
[ul]
[li]Digital OTA channels (ATSC tuner) w/ no ghosting[/li][li]Analog OTA channels (NTSC tuner)[/li][li]Some “basic” cable channels still being transmitted via NTSC / analog (NTSC tuner)[/li][/ul]

The ghosting could be anywhere, but these analog channels are not a priority for the cable companies. You could complain. They could fix it, but unless they nail it in 1 or 2 visits, they probably won’t do anything.

I’m really baffled about why he won’t introduce a cable box. Without it, he’s losing out on channels that he’s probably subscribed to and superior picture quality. I say this as someone who decided to do exactly that… ditch the cable box. I ditched cable too. I put up a small, basic antenna, plugged right into the TV.

11

A cheap home theater PC might be another way to go (small form factor, ATOM processor on a mini-ATX mobo). Though cable card tuners won’t be plentiful and cheap until later this year. Might also keep you off the grid as it were until then by giving you stuff like HULU and netflix.

Definitely make sure he’s not paying for more than their basic cable package if he is dead set on not using a cable box.

12

OK, I’ve returned from the suspect site, and here’s the scoop:

My friend has a Samsung 670 series digital, 46" screen TV.

He cannot receive any channels above 100, although many channels that Charter assigns in the 900 range can be viewed on other, under-100 numbers, such as 83-6.

A channel I know is originally sent out digital, 9-9, looks exactly the same as its twin, analog 97.

Playing a known-quality MPG file thru a flashdrive provides a signal that is nearly perfect and much better than the cable signals. I was able to compare the same file from these two sources (because I program that particular channel for the TV stations and have the source file).

The “ghosts” he was seeing are a combination of true analog ghosts, digitally-induced compression artifacts, and other signal degradation from various sources.

He is obviously not viewing any HD signals. The quality of the image varies considerably from channel to channel. Many compression artifacts are observable on some channels; other channels look pretty good. The aspect ratio is 4:3 or 16:9 depending on the channel.

He has decided to get Charter (cable) to install a digital converter box, check to make sure he is getting the channels he wants, and while a tech is around, to check on the signal level at all of his TVs, because it looks like there are more splitters all over the house that I did not know about, feeding other TVs.

Almost forgot – the Charter cable bill is absolutely inscrutable and incomprehensible.

I will report back to this thread after the Charter tech’s visit on Friday.

13

Some TV stations aren’t broadcast over the air. The local station I program for is not carried on satellite, either; just on cable. If you want hyper-local programming, the cable provider is the only way to go.

One reason to not use a cable converter box is the extra complexity it introduces in the signal chain. It seems puzzling why this extra component, dating from 20-30 years ago, is still needed today. It delays channel changing and renders some remote devices useless. Charter charges $5 per month for a 20yo gadget (they don’t supply new ones, just used) that shouldn’t be needed, but seem to be desirable, all things considered.

Just fine.

14

I knew I should’ve been more careful when I said “baffled.” I can think of a few good reasons (including those you mentioned) to forgo a STB. We’re in this mess because of DRM.