All HDTV is not created equal!

Wondering why blu-ray looks so much better than satellite HD?

Here is a very interesting article:
http://blogs.zdnet.com/Ou/?p=962

Especially if you are looking at Dish, FIOS and Comcast.

 

I have OpenBand, so I know what junky HD looks like.

 

I have been voicing my concerns with this for about 2 years now and it all goes back to the original issues that many of us have commented on - the pixelized images that we so often see with our HD programs on Openband. You can really see this with full motion images and real-time programming - not some .jpg on a computer.

Openband is compressing the signals (my opinion) but that is the only reason crap like this would be happening. And since it is happening and seen by multiple people, it is not because of one person's set-up.

The most important element that we should care about from Openband (or any provider) is at what bit rate we are receiving the signal. The more compression, the lower the bits and thus, the lower the quality. An HD signal that has too much compression will show these artifacts at some point on everyone's TV.

And the other thing that really gets my frustration going (in case you are asking) is the other issue that is commonly referred to as "macroblocking". You will see this as if you can see small squares as part of the image around or next to changes in the image, like someone's eye during a close-up. Wow, that drives me nuts because here I am thinking that - hey this is an HD channel, and is supposed to be a movie in HD but I get a better image on my DVD???? ummm yea, that is probably right. And if Openband is getting their signal from DirecTV (I think they are for some) then unfortunately, DTV is the worst for this practice (signal bit rate compression) too.... but they are getting better.

Anyway... don't get me started... sorry.

 

Sorry - I apologize to myself and others... but this is a complicated "picture" and is not something that can be addressed in a few quick comments but Providers (like Openband) are also unable to control some of the problems.

There are limits to how much bitrate can be given to any given length of time due to memory buffers and bandwidth constraints. Openband, Verizon or Comcast can't fix picture quality problems that originate elsewhere, and content owners (such as MHD, HDMovies) can't give all the programs the 40 mbit/s or so they would need to be able to peak so that they do not block up on strobe effects or motion. Every time the light flashes and then goes dark or if there are explosions, the content on screen changes so much that it really needs to be encoded as an I frame. However, I frames take like 3x the space of P frames, and 10x the space of B frames. 18mbit/s is just barely enough to sustain a "block-free" image for 1080i video (which is the best most of us have), and when you get to lots of scene changes in a small amount of time, there's just no avoiding blocking.

We can complain about it, but at the end of the day, it won't change anything. Multipass encoding with uncapped variable bitrate distribution isn't an option for a fixed system such as ATSC because there are specified standards for transmission and decoding buffers that can't be exceeded.

Even some regular DVDs suffer from blocking, and I would imagine that for HD cams that record in MPEG2 format that there would be blocking in that too, although not as bad since they would usually be recording at a higher rate.

When a clear case can be made for provider-specific over-compression (which is what I am trying to claim), then I think we have a valid issue. I can not prove this to be the case but food for thought, is to start asking. Why would Openband (or any provider) care to provide top quality HD when they can get by with less. As long as the number of subscribers they gain by having more channels is greater than the number of subscribers they lose due to PQ complaints, they have no reason to change. And with Openband, it is even worse... we HAVE to stay a customer!

But to be fair, there's really no point in complaining to Openband or Verizon about PQ issues because of the source material, they can't do anything. Content providers material is being sent to numerous different system operators who send to their customers at different rates via different methods. Providers have to provide a feed that will work for the largest number of systems serving the largest number of subscribers. They can't arbitrarily decide to start feeding at 45mbit/s and requiring the individual system operators like Openband or Verizon to reencode their stream like a network affiliate. That would be extremely expensive and not worth the hassle or money.

I know, stop.... but just wait until I get Steve started, he loves this stuff too, I think even more than I do!!!

 

Dave thanks for the info. And keep it coming.


I love movies, but I know nothing about the mechanics of it on how it arrives to the TV and why the quality can vary so much. You have been explaining it so even I can understand a little bit.

So keep up the great explanations.

We used to get pixel problem with comcast. But after they finally sent an tech out that know what he was doing it all has disappeared on all out TVs. He said like I think you did, it was an signal strength problem. He ajusted something at the main box inside. The had another tech come out and did something to the street box and it has been perfect since.

 

I've always wondered how the quality of HD broadcasts works.... I'm wondering if the local affiliates to the networks get a MPEG2 stream in, or some uncompressed stream which they can then do overlays on and then compress into MPEG2 for OTA. But if the network feed comes in as lossy MPEG2 and then they do an overlay/logo, I'm assuming the whole image would have to be re-encoded, and not just the area of the logo, thus taking the image quality down.

Then you have MPEG4 like Directv/E* (and I'm assuming some cable companies are using using)... are they taking a MPEG2 input signal and transcoding it/downrezzing it? which is liking recompressing a JPG... krapp. Cable companies could have had a foot up on Satellite if they only dumped analog channels (prolly 80% of their bandwidth) and went to mpeg4.

I have Directv and it would be nice if they decommed all the mpeg2 stuff and went to mpeg4.... that would allow for less compression of the signal all around. sigh. mpeg4 hd on directv is pretty good, though. I'd like someone to see what the resolution and bitrates are really.

Basically I want 200 channels of lossless 4K (4096x3112) resolution now Now if only I could stop my eyes from deteriorating! =)

 

Yea Steve that is true... a really good video encoder can make all the difference. Yes you can get one for your house but as you correctly also point out... which average Joe is going to pay in the thousands of dollars for one of these... in addition to the $15k for a good home theatre.

And Boomer, here is a little more on how this works... I found this as part of an article I was reading and thought it was good data:

Cable companies have anywhere from 110 to 135 slots, depending on the particular system. Each analog channel consumes one slot, and many cable companies still have 70-80 analog channels (including Openband).

That leaves 30-55 slots to do all digital SD and HD. Using QAM256 modulation, cable companies have 38.8Mbps available per slot (same space as one analog channel). Most cable providers squeeze 12-14 digital SD channels per 38.8Mbps; to help do that, they often down-convert their SD from 704x480 resolution to 544x480 or 528x480.

A few providers like Verizon FiOS passthrough the original 704x480 resolution, but even they stick 7-9 SD channels per 38.8Mbps QAM channel.

Quote:
FiOS HD bitrates as of Dec 23.

Channel Resolution Average Bitrate Peak Bitrate

TNT 1920x1080 17.8 19.4
ESPN 1280x720 18.1 20.0
ESPN2 1280x720 17.8 20.0
NFL Network 1920x1080 16.8 17.0
CSN MidAtlantic 1920x1080 16.6 17.7
HD Net 1920x1080 17.3 19.2
HD Net Movies 1920x1080 17.2 18.7
Universal 1920x1080 10.5 ?
HD Theater 1920x1080 17.2 18.2
Wealth TV 1920x1080 13.3 14.0
National Geo. 1280x720 13.3
MHD 1920x1080 17.0 18.1
Food Network 1920x1080 14.2 15.0
HGTV 1920x1080 14.0 ?
A&E 1280x720 18.0 18.2

Numbers are based on the average of several recordings from each channel.

FiOS SD bitrates as of Dec 8.

Channel Resolution Average Bitrate
USA 50 704x480 5.05
TBS 52 704x480 3.25
FX 53 528x480 2.51
CNN 80 704x480 3.10
CNBC 83 704x480 4.97
Disc 100 528x480 4.87
TNT 101 704x480 4.92
SciFi 160 704x480 2.42
TCM 200 704x480 2.63
AMC 201 704x480 3.64
Starz 340 704x480 3.56
Showtime 361 704x480 2.75

Average bitrates on some of these channels will vary by up to 20% depending on content.

Compare that to 720x480 @ 8+Mbps for DVD.

 

Also, Boomer about the MPEG4 and DTV:

The SD quality on DirecTV is not good relative to Comcast, as they down-convert all SD to 480x480. That said, DirecTV's new MPEG-4 HD channels are good, and with all the HD channels they have, you may not watch much SD.

Be aware that DirecTV has not moved their older HD channels -- including ESPN-HD, ESPN2-HD, Discovery Theater HD, Universal HD, HBO-HD East, and SHO-HD East -- over to MPEG-4 yet. Those HD channels will be a significant downgrade over Comcast until DirecTV replaces them with MPEG-4 versions (expected later this year).

Comcast has traditionally had excellent HD PQ -- the best you could get outside of FiOS -- but recently, Comcast management decided to apply extra compression, degrade their existing HD to make room for new channels. In several articles, Comcast notes that to remain competitive, they are no longer going to cater to "golden eye" customers with larger screens. Comcast is now applying this added compression when (or just before) they add new channels such as CNN HD, USA HD, SciFi HD, Food HD, Animal Planet HD, etc. This is partly what I am worried about with Openband.

With Comcast degrading their HD, I don't see any reason to stick with them, especially after DirecTV moves ESPN-HD, ESPN2-HD, Discovery Theater HD, and Universal HD to MPEG-4 in 3-6 months.

 

Yea Steve, very well said. I got lost in making simple points, and I am only trying to make high-level comparisons at this point (I mean for my own personal experience with Openband) and my suspicion that they are doing more compression these days to fit the extra HD channels... and I am not excited about more HD channels that look bad, it defeats the purpose in some cases.

 

there are a lot of really useless hd channels. I'd rather have fewer higher quality channels then a lot of ones that suck

 

yea, you mean like the HD channel of the guy flying his RC helicopter in a school field!!!

 

yeah that's one of them.

What about the PBS channel that likes to play the Joy of painting on the hd channel all day. The picture quality on that show was sub par in the 70's lol. Oh how I like to look at the happy little trees in hd. Upscaled it looks so much worse. I like PBS but I don't need 4 PBS channels in HD. (I'm kinda being sarcastic. I do actually find Bob Ross fun to watch but not in HD)

 

For the broadcast networks, over the air is the way to go. With a HDTivo and a multistream cablecard from Openband along with an OTA antenna, I've been much happier. Maybe it's just me, but I think the HD broadcast network feeds on Openband have the worst picture quality

 

I agree that the broadcast network feeds are awful.

 

Yeah, DirecTV SD channels are krapp... I heard they are 'optimized' for a 27" TV ... but now with bigger TVs, it's time to ditch everything for MPEG4 HD and downconvert if necessary IMHO =)

Does anyone know about what I was wondering about earlier with how local affils overlay graphics on a signal and if that brings the PQ down a step? Because if it does, then if you have National network feed (not sure if this is MPEG2 or some lossless format hopefully) -> affiliate (adds logo, blah, etc) -> uplink to directv which then lossy converts it to MPEG4 ..... ugh! =)

Not to take this in a different direction, but I'd also like to state my hatred for the overlays and logos and promos in the corners that it seems most people have grown to accept. I remember when I think I first saw Fox do it in the late 80s or early 90s... it's gotten so much worse since then =) I know what channel I'm watching, and if I don't, I'll press info... it seems this is leftover from the analog age and needs to go away =) Or at least put into some separate metadata stream..

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