New big screen TVs: are compression artifacts normally visible?

A friend and neighbor just bought a 46" Samsung LCD TV with all the bells & whistles. We have been trying out all the options – it reads MPG files from a flashdrive, displays super VGA direct from a laptop, accepts HDMI, component and composite input, etc. and the picture from most sources is pretty amazing. DVDs look great, Roku is pretty good; haven’t tried Blu-Ray.

But the picture from the cable TV source (Charter) is less than acceptable, at least to someone as picky as me. I observe what are best described as “compression artifacts,” similar to what you see on badly compressed JPG images, most noticeable around text or at boundaries with sharply-defined objects. It gets worse with more motion, but is always present in some amount.

We observe this with both HD and all standard-def channels.

The video quality is the same whether we connect the TV directly to the cable coax or go thru the charter-supplied digital converter box, although we can’t get the hi-def channels without the converter box, of course. From the converter box to the TV, we have tried HDMI or component cabling with the same results.

A Charter tech came by and verified the signal strength was acceptable. He said he could see the signal quality deterioration on the screen, but could not explain or fix it.

A short ways down the street is another neighbor with a similar, big-screen TV, and his signal does not show this degradation. My video across the street, although I only have a 19" CRT screen, seems to have a clean signal. All of us are on the same fiber cable feed.

So I’m wondering what the problem is. Are cable signals so poor and I am so picky, or is there some adjustment somewhere? I have no experience with satellite TV, but would it be better or worse?

BTW, the video degradation is not related to aspect ratios, nor caused by stretching or shrinking images to fit on the screen.

One last thought. When we were buying the new TV, the salesmen were touting the refresh rate – higher, the better. Is there any possibility that the refresh rate is a contributing factor and this TV is just too low?

cable operators compress the hell out of HD for any number of reasons. There’s nothing to be done other than bitch at the cable company.

ETA: it doesn’t help that they’re using MPEG2 compression which isn’t that great at higher resolutions, and in theory they have ~19 Mbit/s to play with but in practice I’ve seen “HD” cable content as low as 9 or 10 Mbit/s.

if you connect using component video instead of HDMI, the image will probably “soften” a bit and the artifacts might not be as noticeable.

According to Charter, the ratios they use are fixed for each channel, but the sports channels get a lower number. 6:1 is typical, but some channels go up to 12:1. PEG (local public-access, standard def) is at 14:1.

However, that applies to all customers from a hub, and our hub feeds at least an entire county. I really don’t know if 12:1 can be seen by a good set of eyes, but I don’t see why one person’s TV should look much different from another’s if they get the same signal and have similar specs.

I don’t know the bit rate they are using. I will try to find out tomorrow, but everyone gets the same rate.

I noticed the artifacts on both, but didn’t try an A/B comparision.

Yea, I’ve seen some friends’ big screen TVs and the HD channels that have fast-moving action (like football) look just TERRIBLE. Artifacts everywhere. I usually don’t mention it because I don’t think they notice.

More static scenes look nice, but once things start moving quickly it goes south fast.

It’s one of the reason I don’t buy cable TV.

Does the big screen down the street use the same cable company and the same cable box as your friend?

Based on this, the best conclusion is that the problem lies on the side of the cable company or the cabling itself, not the TV.

If DVDs look good, then standard def TV ought to look good, too.

Some of the motion artifacts may be the TV (LCD or LED, right?). LCD TVs, whether backlit via LEDs or a regular bulb do have some problems with very fast motion. The higher refresh rate is supposed to compensate somewhat for this. Though, unless you are uber-sensitive to the motion artifacts, it shouldn’t really be a problem. Some, of course, may be the cable company compressing the signal itself.

That said, you’re not really going to see much improvement from a refresh rate greater than 120 Hz. If the salesman was pushing the 240s, that’s mainly because they cost more, not from any significant improvement in quality.

The general compression artifacts aren’t the TV - that’s the signal from the cable company or problems in the wall/outside cabling.

Having a good quality DVD image means it’s not the TV.

Having a good Roku signal means you’re getting sufficient network bandwidth via the cable internet (I assume the internet connection is also cable? If not, signal quality may really be the culprit).

Signal strength is a good thing to measure, but it’s not enough. If the signal is noisy, it can still be strong. Noise can come from a lot of places. For example, if there’s a signal booster on the cable, the signal may be strong, but the booster itself will also boost any noise on the line.

Also, “good” signal strength doesn’t always mean “enough”. The signal may be strong enough according to the meter, but if there’s a splitter in the house (to run cable to multiple rooms), the quality at each outlet may degrade.

One thing you can try is going to the point inside the house where the cable signal is split into different rooms. See how many splits there are, and if there’s a booster. Try reducing the number of connections to the bare minimum (maybe just a direct connection between the outside box and the new TV). It could be a matter of the splitter/booster creating tons of noise.

Also, try hooking up a video source output (like a DVD player) at the internal junction point (letting the signal travel through the walls) and use the direct wall coax connection on the TV. If the signal looks bad, it’s the internal house cabling.

If the internal house wiring is to blame, satellite sure isn’t going to fix the problem. It’s possible the external cabling has a lot of interference noise of some sort (power lines?). If so, that could affect signal quality. In this case, a satellite connection would improve matters, if only because there’s no interference on the signal.

but with digital transmission, a noisy or weak signal won’t cause image degradation in the way it will on analog. If digital goes wonky, you’ll get picture freezes and big blocks of just the wrong information.

like this:

As suggested above try the component video input instead of the HDMI (or whatever it is) input. When I got cable it was before the big screen TV (as I had no reason to have a big screen TV b4 :smiley: ), the cable guy left both cables and said that the HDMI cable is nice as it is small, but sometimes the picture is better with the component.

I have the both connected, but usually have it on component because the HDMI setting takes a moment to show a picture and the component seems a bit better picture wise, but not much but enough to have me use component. Score two analog! :slight_smile:

I know what you mean, but this signal is bad enough with little or no motion, then it gets worse.

But is satellite TV any better?

If you check my post #1, “All of us are on the same fiber cable feed.” In fact, about 5000 customers or more share the same hub, according to a Charter supervisor.

Cable company: should affect all customers. Cabling itself: not unless you can show how one end of the cable compresses the signal and the other end deompresses it. That’s not how this system works. I agree that it is most likely not the TV (another TV in the same house shows a similar degraded video signal).

I’m sure some are (see my previous post). I know motion is harder to compress without losing something, but would the TV be introducing additional compression & artifacts on top of the cable signal? I’m assuming not, so please set me straight if you know this is wrong.

Good to know, thanks.

Roku can’t be expected to be the highest quality at today’s technology, no matter what the Internet speed. Netflix uses some proprietary compression schemes and in my professional opinion, is one tiny step below DVD right now. It, too, has some problems with motion.

The Internet connect is 10Mb/sec down, cable. That’s good enough for almost anything we can throw at it.

See my previous posts. Charter says the signal is adequate and low-noise.

But Charter tested the signal strength at this particular outlet, and found it adequate (“very acceptable” is what he said). Charter has also supplied all the wiring and spitters to their specs and has tested the signal strength at all outlets in the past and pronounced them acceptable.

Don’t think that’s the problem, see above.

If it was, Charter would detect it with their fancy-schmancy analyzer, and they say there’s no problem. Besides, even if the sig was noisy, how does it get compressed before the TV? Noise doesn’t do that.

If the digital signal arriving at the converter box or TV were poor due to noise, the kind of data recovery used would be closer to the sample jz78817 linked to; blockyness, image freezes and pixelation. That is NOT what we are seeing.

See above. I don’t think this applies much to digital. But if satellite signals were compressed differently, it’s possible the end product would be improved (or degraded).

And that’s exactly NOT what we are seeing. Compression artifacts are quite different (at least to someone who works with TV every day as I do).

I am not at a place where I can post pix right now, but late tonight I will show two JPG images to illustrate what I mean, just in case you are uncertain what it looks like. Meanwhile, just think of a highly-compressed JPG image, where the edges of objects are all wobbly.

Meanwhile, look at the samples here. Especially notice the “bubbles” around the text “Text Caption” under the second picture. That’s what I mean.

In my post #1, I said, “… we have tried HDMI or component cabling with the same results.”

When you compare the compression artifacts between channels, does it seem to match the compression ratios that Charter gave you? It doesn’t matter if the guy down the street doesn’t see them, this proves that the underlying problem really is compression.

I assume you have cable boxes to decode or at least decompress the signal. Are you all using the same make and model of cable box?

Charter hasn’t given me exact ratios by channel – that’s probably somewhat restricted, proprietary info. All they said was that sports channels had less compression and PEG channels, the most (6:1 or less to 12:1 or more). That’s not much to go on – if you have more motion but less compression, what is the end result, more distortion or less?

That’s a good point; I haven’t compared the models, and all are supplied by Charter. However, in post #1, I said “The video quality is the same [poor] whether we connect the TV directly to the cable coax or go thru the charter-supplied digital converter box…” (except we couldn’t get VOD or HD channels).

If the cable signal is good all the way to the coax jack (according to the cable tech), and the TV shows pictures appropriately in other circumstances (accoding to you), there aren’t that many other elements. This leaves the coax cable from the jack to cable box, the cable box itself, and the connection to your TV.

  1. Swap out the Coax from wall to cable box.

  2. Try different input output methods such as component video (already suggested by some).

  3. You may have a bad cable box. Electronics don’t always end up in the fully alive/fully dead states, they may just give degraded service (particularly if they are too hot, does the box feel warmer than you expected?). You can probably have the box switched out to see if that is the source of the problem. I find it hard to believe that the technician did not try that.

An example of #2 is my router at home. If my internet gets very slow, I go see if my router is hotter than normal. For some reason it frequently gets hot and then starts dropping packets which makes my internet really slow. If the decompression portion of the cable box is only receiving 90% of the information it needs, then it uses the error correcting codes to fill in the missing as best as possible. Result: Blockly looking pictures.

Well, your reply to J Cubed may make my reply less relavent.

Thanks, anyway! But remember that the technician has tested the coax from end to end – up to the TV or converter box input, and declared it clean and perfect using what looked like a very expensive tester. Hard to argue bad cables after that.

  1. Have you tried moving your 19" TV over and plugging it into your neighbors cable, so that you can compare how it looks at your house vs. at his? You might as well drag along your cable box as well.

We got our first flat panel about 3 months ago. Went from a 25" CRT to a 52" LED-LCD. What had looked like a prefectly acceptable signal suddenly became unbearably pixellated/plagued by compression artifacts. Blowing the image up by that much had emphasised the flaws.

  1. Also, as noted below, I’d suggest going out and looking at each of the splitters. In our last house, the previous owner had bought a bunch of cheap splitters, probably at Radio Shack or some such place. A cable tech came out and gave us some upgraded splitters and it made the difference between being able to get a connection and not being able to make a connection.

  2. All cable techs are not made equal. Ask for another one to be sent out. Some do a great job, some are worse than my 15 yr old nephew. Like the phone/DSL guy who forgot to plug a cord back in, in the box on the outside of my house, and the 2 guys after him who obviously didn’t bother to open the box because they also missed it.

All excellent points, Tastes of Chocolate.

We have a 2nd-tier tech dude coming early tomorrow morning, which should be quite int…ter…est…ing… If that doesn’t resolve anything, schlepping my TV across the street is one option, but in the cold and snow, lugging a 75 lb, 19" CRT 200 ft or into/out of a car in the snow isn’t my idea of a fun winter afternoon. :slight_smile:

Taking my cable box across the street…this might or might not work. Each box is serialized, and there could be a problem with my serial number on my neighbor’s cable feed (depends on exactly how that is implemented).

As far as cheap splitters, you are right, but I learned my lesson with Charter, and since they supply all the splitters customers need free, I’m willing to let them do that. In this case, they have supplied them and blessed them with holy Charter water already. Remember, the cable supplier says everything at this address works perfectly according to their instruments, but they also say they see the bad picture with their eyes. That’s where we are at right now.

So what what was the outcome when you expanded your TV and noticed the artifacts that weren’t visible before? Did that get fixed, and how? That seems pretty similar to our situation.

I’d bet $5 it’s a setting you don’t have correct within the cable box menu system. Is there a 480/720/1080 switch/toggle on the back? Have you found a “System Info” or “System Options” in the menus to switch to high def?

$5, eh? Get yer beer ready!

I didn’t set up the box, tech #1 did. I don’t recall such a switch on the back. If such an option is available by menu, I would expect the tech to know about it. Wouldn’t that be a hoot if that was the problem, and he didn’t know how to set it up?

Since we get HD OK otherwise, it seems unlikely. And I’m at a loss to explain how the resolution setting (which I am quite familiar with) affects the compression.

Tomorrow will be quite informational.

HD channels will come through even if you don’t have the correct setting set - they just won’t be in HD.

We just bought a 60" Samsung this weekend. The store (HHGregg) was displaying a DirecTV signal on their sets that was, to my eyes, horrible. At my request, a BluRay signal was used on each set I considered. That is a true test of what the set is capable of.

Once home, my FiOS signal was far superior to the DirecTV image used at the store. Pretty darn close to BluRay on many channels.

I would also caution against comparing a 19" set to a 46" set. Smaller images generally appear sharper.