: Pixellation / Macroblocking


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FrankM
2005-10-01, 09:49 AM
Anyone notice more pixelation again lately?

I was watching Smallville in HD and had a lot of pixelation going on...

Lots on sportsnetwork too (the spinning logo, etc).

/sigh

SpinalTap
2005-10-03, 02:36 PM
I was just going to post a question on this as well....

I am seeing a TONNE of pixelation lately. I just bought a new LG 50PX10 plasma display, and I was worried it was the TV. DVD quality is excellent, so I am thinking/hoping that it is the 9200 receiver.

My signal strength seems good to me (94% for 91 and 74% for 82). I was going to try switching my HDI cable to composite to see how that works.

Could I have a defective receiver? What other things can I look at to resolve this issue?

Thanks.

57
2005-10-03, 03:04 PM
Be aware that there is a difference between pixellation and macroblocking. See the Digital Home FAQ on "Acronyms & Definitions". Macroblocking occurs on fast moving scenes due to the limits of MPEG.

http://digitalhomecanada.com/forum/forumdisplay.php?f=30

skypilot
2005-10-03, 03:57 PM
Anyone notice more pixelation again lately? /sigh
Yes, I have noticed more pixelation as of late. I have a 9200 and live in southwestern Ontario, near London. Home from work today and noticed more than usual :(

I must say that I find I see more of it on TMN, both HD and SD, although I watch more HD. Rome and Stargate Atlantis, etc. This bugs me since I'm paying for a premium service here, although I'd rather it didn't happen on any channel.

Thanks to 57's direction about differentiating between macroblocking and pixelation; I definitely have been seeing more pixelation.

57
2005-10-03, 04:00 PM
I've been recording Rome and it's been pristine for the past few weeks. I didn't watch last night's yet. (Rogers, SA8300HD)

had0ken
2005-10-03, 04:23 PM
i have noticed that pixelation that occured during smallville priemere too. it was during fast scenes or explosions. also noticed it on csi , anyone know why it happens? is it because my signal is low? only about 69-70% on both

poncho@home
2005-10-03, 04:30 PM
I was just about to post about this as well. After looking at a sample image of macroblocking, that's what I got a lot more regalular then before. What can I/we do?

Obviously EV is compressing way too much, a buddy on Videotron never gets this, so how do we go about getting this corrected? Can it be my receiver? I noticed that after a powerfailure once that my receiver had a hard time starting up and ever since, the On screen guide is very slow. Also my receiver often does not have guide information available...

Should I call EV?

57
2005-10-03, 04:38 PM
Macroblocking is due to compression. There are two sources of compression.

First there is MPEG2, which compresses the original 1+ Gb/sec stream to 19.4 (or so) Mb/sec. This is a compresson factor of more than 50. When there is too much movement on screen, you'll see macroblocking because the compression can't keep up. There is nothing you can do about this - it's a limitation of the current technology

Secondly, there is the compression that the service providers do. Some don't to any further compression (Rogers Ontario for example). Some do further compression - Satellite due to bandwidth limitations and some channels on some Cable Service providers, depending.

You can complain to BEV (for all the good that'll do...), or you can consider another service provider, but check carefully before switching, it could be worse....

SpinalTap
2005-10-03, 10:36 PM
Well, I switched my DVI cable for composite and I can no longer see any pixellation - or at least it is 99% better than it was with DVI. Can anybody explain why this might happen?

tdti1
2005-10-03, 11:16 PM
Over compression, the more channels they add the worst the PQ will get, for the best HD and SD you can get a big dish:
http://satellitetheater.com/C-Band%20World.htm

Or try to fix the crap bell is feeding you look into something like this:
http://www.algolith.com/index.php?id=mosquito_hdmi
http://www.algolith.com/index.php?id=dragonfly

Jeffy
2005-10-04, 08:20 AM
"...switched my DVI cable for composite and I can no longer see any pixellation..."

LOL. This proves my theory about the difference in the definition of picture quality. Composite is destroying the picture quality that you no longer see the details (including MPEG artifacts).

Yeah, my car looks perfect from 100 feet away too. Same thing.

Obviously, modern TVs should have an adjustment for fuzziness. Heck, it could probably be made automatic knowing the size of the MPEG blocks. Detect FFT peak at MPEG block frequency and apply low pass filtering. Trivial.

Tonino71
2005-10-04, 08:52 AM
Hi, I have a sony 46wt520 with a bell 3100 reciever. I find that if I use the
coax out, i get no pixelation or fuzziness, but when I use the s-video or
rca outs, I do get pixelation, only being able to view in pro mode.

Has anyone else noticed this?

Is this normal with bell?

any sugestions or recomendations?

57
2005-10-04, 09:29 AM
Well, I switched my DVI cable for composite and I can no longer see any pixellation - or at least it is 99% better than it was with DVI. Can anybody explain why this might happen?
Do you mean component video or composite.

Composite has about 400 lines maximum vertical and horizontal resolution (you can test it with a setup DVD). HD connections have 5 X the overall resolution (at least twice the amount in vertical and horizontal). Therefore, any imperfections on the screen are more visible.

S-video has 480 lines maximum resolution and again, the lower resolution of composite or RF-coax may "appear" to make the image "smoother", but you're probably just missing details.

Battscrew
2005-10-04, 10:04 AM
I am using DVI on my 6100 and it is very rare that i have an issue. Maybe every couple of months?

SpinalTap
2005-10-04, 04:43 PM
Sorry 57, I meant component video (with the seperate red, green and blue cables).

So are you saying the max resolution on component is only 400 lines? So an HD signal coming from the receiver is getting paired down, so I am just not seeing the imperfections now? Is DVI always better?

You also referred to HD connections. Which ones are those?

Sorry for all the questions, somewhat of a newbie and still concerned that I may have to return my tv.

57
2005-10-04, 11:51 PM
So are you saying the max resolution on component is only 400 lines? No, I said composite and that's what I meant.

Component video, DVI and HDMI are all "HD capable" connections. See the Digital Home FAQ on "Cables & connections".

I have no idea why the macroblocking would be less on component video, I can certainly see it just fine when it occurs using my component video connection...

Perhaps it's due to the way your inputs are (not) calibrated - see the Digital Home FAQ "DVI/HDMI Information" which discusses the fact that different inputs have different calibration. If DVI gives you a "sharper" image, that would excacerbate any macroblocking.

See also the Digital Home FAQ "What you need to do to your new HDTV", as a proper setup can minimize macroblocking.

http://digitalhomecanada.com/forum/forumdisplay.php?f=30

Glen68
2005-12-31, 01:47 AM
Over compression, the more channels they add the worst the PQ will get, for the best HD and SD you can get a big dish:
http://satellitetheater.com/C-Band%20World.htm

Or try to fix the crap bell is feeding you look into something like this:
http://www.algolith.com/index.php?id=mosquito_hdmi
http://www.algolith.com/index.php?id=dragonfly


Has anyone tried these products

57
2005-12-31, 01:58 AM
BUDs certainly work, but not many people have the room. There's a fair bit to learn regarding BUD equipment, subscriptions, etc. but yeah, they work. BUDs themselves are almost free these days.

The other "crap fixers" are $3k. Doubt many people have them.

s21477
2005-12-31, 10:07 AM
Interesting stuff.....

Just one question about this pixelation. If the signal we're getting is digital, shouldn't the picture be either perfect (relatively) or not there at all unlike an analogue signal that would have various stages of degradation?

Sorta like a digital cell phone vs analogue? The digital phone has either full reception or it cuts out completely, whereas an analogue phone has lots of static.

So back to pixelation, if my above statements are true, the signal strength wouldn't affect this pixelation, and that it would be the source data and not the quality of transmission?

AndreH
2005-12-31, 10:38 AM
Being digital, it will end up partially there in a different way. Only what is received can be decoded, which results in a garbled blocky image.

On a cell phone, you will hear a garbled sound too.

What I notice with my decoders is that when I record an HD program with the PVR, I almost always get the first few seconds garbled when I play it back. Not a big deal since it only lasts 2-3 seconds, but it's fairly consistent.