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When I am watching DBS on my 52X92 screen, there are obvious picture quality differences between the various SD channels. The PPV channels are best, followed by the premiums, then the locals and superstations, finally unwatchables like Bravo, IFC, TCM, etc.


If the DBS companies are playing with the quality (compression?) levels with SD stations, what makes us believe that they aren't doing the same thing with HBOHD and SHOHD ? This is supposed to be a 19.2 Mbps Mpeg2 compressed signal. Is there any way to measure the received horizontal resolution since they don't transmit test patterns, and the content quality (transfer, etc) varies anyway ?


I just don't trust the DBS or cable companies to pass us true HD, when they can't even do SD well. The marketing arms of these outfits will eventually water HD down to the lowest common denominator, 27" TVs, just to claim they are broadcasting HD.
 

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I wonder the same thing myself. Recently, I installed the 8VSB card for my Dish 6000 receiver and I can say that the OTA HDTV picture from WHYY in Phila. is far superior to anything I have seen on HBOHD over the past 5 months. I've also noticed that the Dish Network HDTV demo channel also looks better than HBOHD.
 

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That's how they've accommodated any signal since they started compressing eh. broadcasting. I'm talking about DirecTV since I use to subscribe to them.


I always thought that when HDTV became widespead that DirecTV would be forced to carry an unaltered signal as delivered from the source to its subscribers but I'm not so sure anymore. HBOHD I've read is bandwidth limited to under 14Mbps when it should be at a minimum 19.2Mbps. What's the deal with that?


What will happen with DirecTV remains to be seen. Is it unreasonable to assume that once the North American TV viewer gets introduced to HDTV, will they settle for seriously compressed TV or even bandwidth limited HDTV from the likes of DirecTV and digital cable? The answer to that question will be significant for the current HDTV format.

 

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I believe there is some degree of compression on both U.S. DBS services' HD programming - but no where nearly as much as used on their SD programming. Also keep in mind that some of what goes out on HBO and Showtime HD is merely upconverted SD source.
 

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Quote:
Originally posted by wagnerjc:
Can anyone give me compression data from both DirecTV and Dish for HBO? I have basically been kicking myself since signing for DirecTV instead of Dish. Also does anyone know about "real" HDTV expansion timelines for either of the DSS providers? Thanks.

This has all been discussed at length before. There is no compression of the HD data stream by either DirecTV or DISH. It is a bit for bit pass through, likewise with ExpressVU, as well. The 19 megbit ideal is best for live programming while the region of 14 megbit is thought to be adequate for film. While this is arguable, the fact remains that HBO and Showtime determine their actual data rate not DirecTV or Dish. CBS transmits at about 19 megbit.


My experience with display devices has been that 19-21" computer monitors with typically a dot pitch of .25-.28mm render better detail than the typical direct view CRT HD monitor (which are typically .75.-.80mm dot pitch)and most rear screen projectors using 7"inch tubes. I have a Sampo 32" direct view HD monitor, a 7" CRT front projection system, and a 19" computer monitor I use for reference purposes. The computer monitor yields the best detail, albeit it from a smaller image.


Unfortunately, the 1080i digital standard does have some limitations/tradeoffs. The original non-MUSE Japanese NHK 1125/60 system was far better in yielding a consistent "looking out an open window" effect...but not viable commercially. Still, 1080i/720P are better than no HD at all!

 

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Quote:
Originally posted by wagnerjc:
Can anyone give me compression data from both DirecTV and Dish for HBO? I have basically been kicking myself since signing for DirecTV instead of Dish. Also does anyone know about "real" HDTV expansion timelines for either of the DSS providers? Thanks.
I can't give you compression data, but I can tell you that Dish doesn't do any additional compression of the HD channels. If you look at the layout of use for the 61.5 bird, you can see that all four of the HDTV channels have been given their own transponder:

http://www.lyngsat.com/dig/dish3.shtml


Also,

Showtime-HD is excellent, so I won't stop you from kicking yourself :)

 

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tm22721

It's not that the DBS can't do SD well, it's that they can't do it well on all channels so they choose to compress some more than others to fit even more channels into their lineup. This is the part where you can't "trust" them to do what's technically possible to yield best PQ. However, as cwood points out, for HD they just pass on whatever they are provided. Given that this is variable in PQ, it might seem as though the DBS folks vary what they do to it.


cwood

I assume you mean non-digital MUSE Japanese system and it was indeed terrific (at least when I saw an NHK demo in , yes, 1989!) but subject to the same interferences any analog system suffers.

I think for detail resolution comparisons you should really take the viewing angle into consideration : if you're looking at your computer monitor from , say 2 feet, you'd need to step back from the Samsung quite a lot to get the same apparent screen size and you might have to knock a hole in the wall to stand far enough back from your 7incher. Then the comparison would be a fair one - alternatively, look at your computer monitor from a few inches!


imws, The 19.2 Mbps is the maximum available at this time and it is more than enough for some material, so adding an SD channel into the stream has little effect. For some material with lots of detail and fast action, the same SD could affect the HD by using some key bandwidth


Jason, You got it right - there is considerable variation in the transfer quality of HD programming (think cheap photoprocessing at the supermarket versus professional printing of photos and you begin to get the idea!) since a large part originates on film. Some directors and producers also like to soften the detail of HDcam originated material to make it "look like film"!!!


AJ
 

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Quote:
Originally posted by Ray H:
I believe there is some degree of compression on both U.S. DBS services' HD programming - but no where nearly as much as used on their SD programming. Also keep in mind that some of what goes out on HBO and Showtime HD is merely upconverted SD source.
This issue has been discussed ad nauseam in numerous threads. Why do you believe compression is used on the DBS services? I don't know about DirecTV, but Dish does NOT use any compression for the HD channels.


Quality differences relate to video vs film transfer, quality of the HD transfer, pan and scanning a Panavision 2.35 movie, as HBO does, etc.
 

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Quote:
Originally posted by AJSJones:
tm22721

cwood

I assume you mean non-digital MUSE Japanese system and it was indeed terrific (at least when I saw an NHK demo in , yes, 1989!) but subject to the same interferences any analog system suffers.

I think for detail resolution comparisons you should really take the viewing angle into consideration : if you're looking at your computer monitor from , say 2 feet, you'd need to step back from the Samsung quite a lot to get the same apparent screen size and you might have to knock a hole in the wall to stand far enough back from your 7incher. Then the comparison would be a fair one - alternatively, look at your computer monitor from a few inches!



AJ
Actually, the term MUSE is sometimes mis-used. MUSE compression technolgy was never particularly effective. I'm referring to the full 30 meg bandwidth analog system, no compression. As you noted, also subject to all of the problems of analog but as a studio or field production system, as opposed to a transmission system, it was superb.


As for viewing distance, I take that into field of vision, distance, screen height multiples, etc...the computer monitor still wins! Oh for a front projector with 9" tubes!!
 

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The veterans on this thread are correct that this topic has been discussed many times before. Do a search and read some history on it. A couple of points I would like to emphasize is that all dBS TV is compressed. Most all digital recording is compressed. D1 which is rarely ever used for air masters is an uncompressed digital recording format.

The point is that the artifacts you see that vary from program to program and from channel to channel are mostly due to source media, not varying degrees of compression at DBS. These DBS engineers will increase compression based on the source but generally try to avoid compression that will be detrimental to the picture quality on the source. This means that stations like CNN will be compressed far less than stations like TNN, where they have been known to air whole programs sourced from VHS air masters, the bottom of the heap for video quality. And, TNN is not at the bottom of technical quality either when putting them in the mix of all the networks on DBS. I just happen to know what they will air.

AFAIK- the DTV HDTV channels are not restricted on bandwidth and present the full bandwidth of the source signal. I have been told that as more HDTV channels get added they may restrict the HDTV bandwidth to that which will allow two channels per transponder. Currently this is not being done. A restriction like this could reduce the H res to that of HDCAM spec but would reduce D5 spec resolution to that of HDCAM or 1280 H pixels. Considering that very few receivers and monitors are viewing that detail between HDCAM and D5 quality, I doubt anyone would seriously miss this using present day receiving technology. It appears to me that there is far more quality spresd due to transfer technique including film source prints than we will see by the squeeze of 2 HDTV channels per transponder. Consider that nearly all source video is at HDCAM quality anyway, we should embrace this slight restriction in favor of increased programming. That's my opinion!


Another area of observation that many lay consumers will mistaken for compression artifacts is chroma noise. Much of this is generated at your receiver end. I know it is here. I have 3 receivers and rate them for Chroma noise as follows:


1. DTC-100

2. Dish 6000

3. Dish 5000 w HDTV mod.

4. DST50 off the air

5. DST50 from Dish 5000


I consider the 6000 and the DTC-100 near equal and the DTC-100 off the air signal close to the DTC DBS signal.


This means that my recordings I have off the DST-50/PVHD1000 are equal in noise content to the #5 which is a shame. I would expect that using a 169Time mod to the DTC-100 would produce better recordings due to receiver being a lower noise device but I don't have anyway to test that now. The #4 and 5 is not bad but the others are just a bit better for chroma noise.


------------------

Don Landis

Home Theater Pics at: www.scubatech.com Last updated 3/25/01
 

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I have had limited experience in evaluating HBO-HD as my Directv satellite installation and Sony HD-100 receiver are new. But, clearly, there is a difference in picture clarity and detail on HBO-HD, depending on the movies or program. IMHO many films appear no better than their DVD counterparts while others (like last nights' Adam Sandler film) are just outstanding and what I would consider "true" HD. I am anxiously awaiting Springsteen's concert this evening which I believe was filmed in high definition. So far, I have not been disappointed in this investment - quite the contrary.
 

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Quote:
Originally posted by Don Landis:
These DBS engineers will increase compression based on the source but generally try to avoid compression that will be detrimental to the picture quality on the source. This means that stations like CNN will be compressed far less than stations like TNN, where they have been known to air whole programs sourced from VHS air masters, the bottom of the heap for video quality
The above statement could not be further from the truth. It's really starting to bother me that people will defend mediocre PQ as delivered by digital cable systems and small dish DBS and instead blame the source station instead of the CATV Co., or DBS Co., whoever is providing the digital feed.


Maybe I'm being naive but I find it very hard to believe that TNN would use VHS sourced tapes for some of their programs and that DirecTV would be so cognizant of this that they would reduce their bandwidth appropriately.


Ridiculous!.


My digital cable TV feed of TNN looks like crap, a colleague has an all analog system (cable TV) that also carries TNN. It looks wonderful on the analog system. I watched the same show and same episode on TNN on both systems and the analog system wins in terms of PQ.


If Mr. Landis truly believes that DirecTV will compress only to a degree, then what he is saying is that a DirecTV station will look about the same as that same station received via analog means (low tech TNN included). Now anyone who has lived with small dish DBS will surely see the fallacy in that. What about it Don? Or should we blame not the source station, not DirecTV, but the Colorado firm that digitizes everything for every service provider out there that wants to transmit a DTV signal.


The problem with this board is that there are far too many technical experts and too few business experts. Did you hear about Survivor III being in HDTV, yeah man they can do it with a $4000 Terabyte RAID system and still meet their budget.



[This message has been edited by imws (edited 04-07-2001).]


[This message has been edited by imws (edited 04-07-2001).]
 
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