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Pixelation in HD content: The signal or the television?

by dgden / December 12, 2007 2:41 AM PST

I have a Sony XBR4 LCD HDTV and noticed that in some HD content there is visible pixelation especially in faster motion when I see pixely squares appear.

It is fairly minor and appears to be noticeable in some HD programming but not the other. Was watching Victoria Secret Fashion Show in HD, darn those girls look great in high def :), and noticed a bit of pixelation when models walked down the runway.

I have not noticed it so much in other shows though, take Smallville in HD or Leno or Letterman (not much motion in talk shows though). I don't recall seeing it in a bunch of others as well.

This is actually one artifact that I really dislike and would like to know if this would be an issue with the content such as loss of some information in the signal, or is it the TV that is not able to keep up with the processing?

Is it something I would see on any HDTV or would it not be a problem say on the Plasma VS LCD?

Could I still see the pixely squares when wantching Blue Ray or HD DVD (I don't own either one)?

Thanks for the input!

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ok well it not the broadcaster signal.
by gabereyes / December 12, 2007 3:25 AM PST

I also watched Victoria Secret Fashion Show in HD on my HD CRT TV and I didnt see any pixelation, and I had it recorded on my DVR so I went back a few times to check. lol

Anyways if you dont see any pixelation on still or none motion pictures the picture settings on the TV should be fine, this maybe a LCD thing, you might try playing with the 120hz setting in the menu and see if it helps by turning it off or on.

As for HD channels the only one I seem to have a problem with is A&E channel and TBS channel and it not pixelation its just crappy color and sharpness.

hope this helps
good luck
gabe

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What is your source Antenna or actual Cable?
by dgden / December 12, 2007 4:35 AM PST

Question for you:

Do you get your HD through the air broadcast signal or was it through a digital cable box?

My TV is plugged in directly to the cable (no digital cable box) and the HD channels I pick up are the regural air broadcast HD, using the reciever built in to the TV.

In addition, I don't have a dedicated antenna plugged in, it just uses the cable itself as an antenna (hope this makes sense) and I actually don't even pick up all the HD availible in the area because of that.

What's your connectivity like?

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All of the above
by gabereyes / December 12, 2007 8:16 AM PST

I have Dish network as a full time service, but sence I have cable internet I hooked up basic cable straight to the TV, plus an off air antenna hooked throught the dish box for local HD channels.

I live in the midwest and with all the ice storms, I never know if one is working or not, so I figured if I have three types of service one is bound to work. lol

I did also have a cable box a couple of months ago, I just switched to dish so I did see it through a cable box too, but I dont see any diffrents from the box and going straight to the TV.

gabe

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intermitten pixelation delay on a plasma hdtv
by ekeeley / February 10, 2013 1:55 PM PST

I have noticed since I have had three majot boards replaced that I would see a delay in pixel refresh on my plasma hdtv. what could be causing this, is it the signal coming in or something going on with myh hdtv

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pixelation in HD
by magilla414 / December 12, 2007 6:02 AM PST

this problem is what has been keeping me from buying a new TV. Through all my browsing I noticed it on all LCD's and a slightly lesser extent on plasma's-in all price ranges. I have been told that this problem is only visible if you are sitting too close to the screen and is more apparent in the store. I'm glad someone mentioned having the problem in a home setting. I mostly watch sports, so it would drive me crazy to see constant pixelation during the action. Please let me know if you still see this effect (i heard it called the screen door effect) when sitting further away of if you find another solution. Thanks.

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Screen door effect is a different thing...
by dgden / December 12, 2007 6:51 AM PST
In reply to: pixelation in HD

Pixelation is sometimes referred to as blocking, I believe. Screen door effect is something entirely different and is present (really) only on rear projection HDTVs.

My brother owns a Rear Projection LCD and I have an LCD HDTV. Now I know what people are talking about exactly when they say screen door effect. It's a percieved texture of a rear projection LCD screen (maybe DLP as well) which makes it look like you're watching a TV through a barely visible mosquito net, because the space between pixels is more apperent than on other technologies.

It's not nearly as bad as some people see it but it is a matter of perception.

A good example of a pixelation, on the other hand, would be a low resolution DivX movie, where you see the image starts to look like a jigsaw puzzle in fast motion.

What I have seen on my HDTV, is no where near as pronounced as on a low quality digital video. What is important to me, however, is a clear understanding on whether this is a limitation of a television set or a problem with the signal quality.

If you're a streaming a video through internet connection and some packets are lost, you will likely experience blocking of the image until the stream quality is restored.

I have seen opinions on the web claiming that this is a limitation of the video compression combined with a signal quality while other claim it's the TV.

Is this is a signal quality issue, it's not a problem as it will be improved as the TV world moves towards digital and HDTV. If this is a TV problem and I will see the pixelation even when watching Blue Ray, well that really sucks.

Technical knowledge on this anyone?

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pixelizingscreen door effect,stair stepping,blocking
by dinox64 / December 12, 2007 9:54 AM PST

I have a Plasma and never once had that problem. Of everything I read and have read,never came across that happening on Plasmas. Now at work today, I did hear some guys talking about how Tv's today have built in boosters to bump up the low signals they receive,and that it sometimes gets shot back to the box and shows as noise on the screen. But that has nothing to do with the pixelating you're seen. That is the technology that goes with LCD and manufacturers can't get the refresh rate fast enough to correct it. They may sometime soon. It's just like the problems associated with Plasma when it first came out. Now burn in, too hot, bright rooms and short life are no longer factors. But it never had a pixelating problem,it's always been smooth and soft on the edges of its image.

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I am not convinced...
by dgden / December 13, 2007 2:56 AM PST

Since my purchase of LCD HDTV I've read quiet a bit of stuff, some technical and some not.

In my understanding, that most of the HDTVs including Plasma and LCD have a refresh rate of 60Hz (except the new 120Hz LCDs). Please correct me if I am wrong.

My LCD is actually 120Hz (Sony XBR4), which means it actually refreshes twice as fast as other HDTVs on the market be it plasma or regular LCD, so I do not believe the refresh rate is an issue here.

I've also seen posts when people said that pixelation is a signal issue and can be seen on both Plasma and LCD.

Once again, I don't know if that's true or not that's why I am hoping for more accounts and maybe a more professional explanation of why pixelation maybe seen.

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1 millisecond (1 ms) is the cycle time for frequency 1 kHz .
by gabereyes / December 13, 2007 1:26 PM PST
In reply to: I am not convinced...

The TV can do 120hz that equals 120 milliseconds.

But the LCD panel can only do 8ms response time, so the panel is getting sent 120hz but it cant keep up.
Meanwhile, plasma display's pixel response time is virtually instantaneous, limited only by the speed of the video processing
engine.

this is what might be causing the pixalation.

check out this link.
http://www.phctoys.com/Fujitsu_White_Paper_2005.pdf
I just found it, while I was looking for an answer for you.

good luck
gabe

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Good info but still wrong :)
by dgden / December 13, 2007 3:41 PM PST

There was this really good post (too bad I didn't bookmark it) about the whole 120Hz and response times, but I understood. Here's a quote from the PDF you sent:

Many of today's larger LCD screens spec out at respose times that sometimes exceed 25ms - long enough to smear motion. Any response longer than 16 2/3 ms will smear TV's 60 fields-per-second video.

This only proves that response times of current LCDs are sufficient for the video signal and the math is consistent with the post I read. So 8ms response time is way plenty for a 60Hz refresh rate, actually twice faster than the required minimum of 16 2/3.

For 120Hz the required time would half of that which is 16.66666/2 is approx 8.33 which comes very close to the 8ms response time but is still sufficient.

So your argument is incorrect. And by the way, plasmas do suffer from phosphor lag, which has been reported by many video gamers. But let's not get into the whole Plasma VS LCD. I am just intersted in the pixelation side of things.

By the way, pixelation is not the same as motion blur.

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I haven't seen any of those horribly slow refresh rate LCDs.
by NM_Bill / December 14, 2007 12:19 PM PST

You seem very well informed yet you haven't nailed your pixelation problem. I got a rear projector, not Sony specifically because it had a picture that blended together well with no sign of pixelation whatsoever, that I objected to in typical plasmas at that time, four years ago.

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ok sorry I didnt do the math.
by gabereyes / December 15, 2007 4:25 AM PST

Math gives me a head ache.

Im not sure what causes the pixelation, It could be signal and/or TV processing, maybe it has something to do with digital all together.

Here is what I have seen, any TV that is 100% digital, meaning the signal passes all the way to the image in digital form, I can always see some type of pixelation this is mostly on LCD, DLP, and micro projections sets.

as for any phosphor based TV like CRT, Plasma, and CRT projo, I dont see it in most cases.
and on my HD CRT tv I almost never see any pixalation, I would try getting an DVE calibration disc, and go through the moving test paterns to see if you get any pixelation, that should answer this tuff question.

I once heard that most phospher based TV's turn the digital HD signal back to analog RGB internally before processing and displaying the image, if this is true this could be the answer, but I dont know how much of this is true or not.

but it makes sence, its like a reciever taking a dolby digital sound track and tranfering the digital to analog using a DAC, this works very well for sound, why not video too.

P.S. if you find out if its the TV or the Signal please let me know.
gabe

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Whoa there, Hoss!
by Dr. Planarian / December 14, 2007 8:26 PM PST

The item to which this is a reply is a very disinformative post.

120 Hz is NOT a 120 ms framing rate! 120 Hz comes out to an 8.3 ms refresh time. An LCD screen like the Sony XBR4's with a 4 ms latency can easily handle this. As far as I know, no commercially available television has a refresh rate faster than 120 ms.

This, however, has nothing to do with pixellation. Only a few of the most recently released television sets refresh this rapidly.

Television signals are sent at a rate of 30 frames per second. It doesn't matter what the source of the TV signals might be, whether over the air, through a cable, from a satellite provider, whatever. NTSC television pictures run at 30 fps. Always.

The advantage of 120 Hz is that it can also handle content from sources like Blu-Ray players capable of transmitting movies at their native 24 fps. The number 120 is evenly divisible by both 24 and 30, so no movie frames need to be repeated as each fifth one must be when shown on a regular 60 Hz television.

But none of this relates to pixellation in any way whatsoever.

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Oops
by Dr. Planarian / December 14, 2007 8:27 PM PST
In reply to: Whoa there, Hoss!

I meant to say, "As far as I know, no commercially available television has a refresh rate faster than 120 Hz (not ms).

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Pixelation
by rsbruner / December 14, 2007 11:31 AM PST
In reply to: I am not convinced...

I have a SONY XBrR 1 and Panasonic Plasma TV. The only time I have ever experienced pixelation on either TV is through the OTA antenna. We have DISH Network, and the only time I have ever seen pixelation is when something was recorded on the DVR during a terrible storm - about 2 times a year. My parents have cable and a Sony rear projection LCos tv like myself and have no pixelation issues except for a dirty DVD. So it is not related to the TV technology - we also have had a Philips LCD TV that had no pixelation.

We have had screen door effect issues playing video games on the Plasma, but not as much on the LCD and not at all on the rear projection LCoS TV.

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Help with shutter delay
by sdowling73 / December 17, 2007 5:03 AM PST
In reply to: pixelation in HD

Which digital point and shoot camera, preferably one of the small ones that fit in purse and has a large LCD screen has the shortest shutter lag (at least i think that's what you call it for the hesitant time between pressing the button to snap picture and when it actually captures it. This delay is frustrating when you have a young child or animal in your viewfinder and by the time the pic has snapped they have looked away. I tried the Casio EX-Z77 and it seemes to have a rapid response????????? got any other suggestions. the other important factor is how long the batteries last?

texasgal

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Reply to Signal or TV
by wahmof2boys / December 14, 2007 3:37 PM PST

It seems pretty clear from the responses so far that no one knows what causes your problem with pixelation. Each person seems to have his or her own opinions and experiences. Well ..... I will add mine.

I have cable HD in an apartment I live in. I was experiencing pixelation, and sometimes sound interference along with it.

At first, the cable folks said it was my TV. (Did we expect anything else?) After they sent two sets of repair folks out, they finally decided to test the signal coming into my apartment. They found out that the signal was, in fact, not as strong as it should be on the HD channels.

After some thought and experimenting, I suggested that the signal coming into the apartment building (150+ units) might be split too many times (and maybe needlessly so) before it reached my apartment (on the top floor). They checked the efficiency in their use of splitters, did some rewiring, and now I get HD with no pixelation.

My comments may not be applicable to your situation at all, but one more thought among the many might just be the one you need.

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Pixellation
by Dr. Planarian / December 14, 2007 8:08 PM PST

Pixellation occurs when the bandwidth cannot keep up with the amount of data it is expected to carry. This is most frequently a signal compression issue rather than a television problem. I first began to notice it on my old ANALOG TV when my cable provider changed over to digital signals.

You may have noticed it most severely in that fashion show because of all the flash photography. Most scenes, even those containing fairly rapid motion, have large areas that don't change as the picture goes from frame to frame. The areas that keep the same color and luminosity are amenable to high compression ratios. When you get a lot of flashbulbs popping, however, you need to rapidly refresh EVERY SINGLE PIXEL on the whole screen, and this requires much more data to be transmitted, more than the system can handle. So they deal with this by making the "pixels" bigger, and thus the pixellation.

You have a Sony XBR4 -- so do I. It is NOT your TV. I don't get any such effect even under extreme conditions on HD content played on either my Blu-Ray or HD-DVD player, which are connected via HDMI cables. I have enough bandwidth there.

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yep, it's the compression (and maybe the p's & i's)
by travinta / December 15, 2007 2:13 AM PST
In reply to: Pixellation

In my local market (Denver), the NBC affiliate splits its signal to allow for their "NBC Weather Plus" channel. No big deal for most broadcasts, but for football I get lots of pixellation. Switch over to Fox or CBS or ESPN: little to no pixellation.

Fox seems to have the best signal for sports, which I attribute to 720p broadcast signal -- is it accurate to say that 720 has less info (as far as lines of resolution) but displayed more completely (720 "new" lines at a time vs. only 540 with 1080i)? -- I remember reading somewhere that 720p was superior to 1080i in broadcast signals due to the bandwidth limitations with broadcast TV.

But I only have a Sony rear-projection 3-LCD (not even an XBR), but who can beat it when your wife wins it on a grocery store scratch ticket, eh? Hard for me to complain about the occasional pixel box!

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Excellent insight, thanks
by dgden / December 15, 2007 7:30 AM PST
In reply to: Pixellation

Thanks Dr. Planarian. Your feedback especially considering that you have the XBR4 and Blue Ray/HD DVD is possibly the best prove that it is not the TV.

I also read a number of online posts that mentioned compression as one of the culprits and it makes perfect sense. I was really hoping for some feedback from someone who uses Blue Ray with HDTV LCD.

In addition, I never see any pixelation on my upconverting 1080p DVD player, but of course it is not the same as a true 1080i/p content.

I am going to get a Comcast digital box soon and see if experience any blocking on their HD On Demand content.

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Comcast On Demand pixellation
by travinta / December 15, 2007 8:20 AM PST

Let me know what you find out after you watch an HD On Demand movie. Anytime I've watched HD content with Comcast On Demand has shown HUGE blocking problems. I've always wondered if it was the compression, or if there was something wrong with my box. Since I don't get as much pixellation with other HD content, I think it's the compression.

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Yes!
by 3rdalbum / December 16, 2007 5:38 PM PST
In reply to: Pixellation

Dr Planarium has it exactly correct. Modern video compression is "temporal", meaning that it mostly only transmits the differences between each frame, and occasionally sends a whole frame (the "keyframe"). When the whole picture is changing (for instance, if you see a shot of ripples on a body of water), the transmitter is basically sending continuous keyframes, and has to resort to "spacial" compression (removing image data frame-by-frame) to try to keep the bitrate down. The transmitter might also drop frames, making the motion jerkier.

If you have low signal strength, these periods of high bitrate can look worse. Do us a favour and use your TV's settings to check the signal strength. If it's under 60%, you should upgrade your aerial; but before you do that, simply change the RF cables from the wall to the TV. Often when people buy a new digital TV, they just keep using the worn-out, brittle, corroded RF cables that they used for 15 years, and you can imagine what that does to the signal. Replace the cabling and see if that makes an improvement.

If it does, then you've fixed the problem. If it doesn't, then upgrade the aerial and put some sort of filtering device in the signal path. Many surge protector boards from electrical retailers have RF plugs to protect against surges, and these can also resolve interference problems (if you have high signal strength).

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HD Pixellation
by sdowling73 / December 17, 2007 5:25 AM PST
In reply to: Yes!

We have a lot of pixellation and some sound drops in houston, tx with dish network. they have been out multifple times and i think i am on my fourth new receiver. personally, i think they are clueless as to why it happens, but i would definitely think long and hard before going to hd until they get some resolutions. it is very frustrating to have the whole picture pixellate we also lose our signal for no apparent reason - - no bad weather. also we will have short sound drops. i'm almost ready to go back. in fact i do whatch the non-HD locals for clear pic. anybody got any ideas. i have a 46" samsung dlp

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Poor reception
by ..ben / December 17, 2007 5:30 AM PST
In reply to: HD Pixellation

Those are classic symptoms of a weak signal. How far away are the stations from you? What kind of antenna are you using?

Best,
Ben

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...
by ..ben / December 17, 2007 4:23 AM PST

Opposite end of the spectrum here...

I have a cheapo LCD, and I notice much more pixelation on the TV channels (via a Sammy ext. tuner) than on Blu-ray.

I'm inclined to blame it on the TV stations.

best,
Ben

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Corrupted HD signal
by a300cow / February 5, 2008 1:09 AM PST

I have been dealing with this pixelation problem since Feb 07 and after having my HD set replaced and then dealing with Comcast for 6 months I then switched to Direct TV only to find that Comcast was telling the truth. Comcast acknowledged that it was a problem and could not believe that so few people were complaining about it. They gave me a video credit back to Feb 07 but said they could not do anymore for me because it was not in the cable system but the incoming feed to them. My conclusion...everything is routed through satellites and I believe there is too much being compressed as they are required to also transmit analog signals until Feb 09. For those of you who did not have an HDTV until after 06 you would not know what true HD is supposed to look like. You will not read about this in the news paper as it would slow down HDTV sales.
Rick

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Tv
by gretzkyv99 / February 5, 2008 11:47 PM PST
In reply to: Corrupted HD signal

Regardless of your Hdtv, if you are watching regular tv or HDtv you will see pixelation. Even in the vaunted 120hz tv's. I see it less on my plasmas, but when running BlueRays on both LCd's or plasmas, you see little if any pixelation on either. I dont know how many calls I take every week pertaining to the xbr4's and 5's about them being pixelated, I ask them is it in the Vivid setting and is the Motion Enhancer turned up to high and 100% of the time it is which leads to the tv looking pixelated and giving you a unnatural picture.

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HD signal
by a300cow / February 6, 2008 1:25 AM PST
In reply to: Tv

I disagree. I set my Sony to lower than vivid settings and the pixelation still causes an out of focus picture from a distance. A plasma or lcd hides it well but still does not have the HD detail it should have. The Comcast techs could clearly see the problem from their office on a 15 inch Panasonic lcd. In 2006 my Sony could be set on vivid with a WOW effect...true hd with no pixelation. I now have a Sony 55A2020 and the only fault this set has is the ability to show 6.2 million pixels and thereby show a corrupted signal that much easier. Turning off CineMotion, Adv Iris or decreasing sharpness is of no help. Something happened to the main signal feeds between the end of 06 and the beginning of 07. Comcast, Direct TV and all the rest are left to sell HD that is nowhere near 1080 quality.
Rick

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Blocking
by froasier / February 12, 2008 6:13 PM PST

This is not pixelization--it is what is known as blocking, and occurs because of video compression used in the broadcast (transmission) or storage medium. Your TV shouldn't be the culprit here. Blu-ray and HD-DVD should give you flawless picture.

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Blocking
by a300cow / February 13, 2008 2:25 PM PST
In reply to: Blocking

Digital blocking is caused by a weak signal. Pixelation is caused by too much compression of the digital data. I can go to any local sports bar and see the same problem that I have, only not as pronounced because the lcd sets they use do not show as much detail as the Sony I have. In 2006 Sony sets had about the best picture in HDTV out there but now they are so good they also show the lousy HD signal that has been available since around late 06 or early 07. C/C would not have replaced my set if they suspected it was Comcast, but they did as every tech sent to my house could see the problem. Keep in mind that Comcast after working this problem for months acknowledged the problem and could see it at their office on a 15 inch lcd and they said they cannot believe more people are not complaining about this. They told me that it was not the cable system but the feed coming to them. So I switched to Direct TV which I am happy with for many other reasons but they have the same issues with pixelation and well...Comcast was being honest with their conclusion. My point is, we who are paying for HD programing are getting a lousy picture, only most people would not realize it unless they saw what it was really supposed to look like.
Rick

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