I am new to HDTV and have a quick question. Right now I have TWC's HD service. Some of the HD channels look great while other HD channels look not so good. By reading this forum, I realize that not all HD channels are created equal and some will look better than others. However, how about if we consider the same HD channels transmitted by different sources. In my case, would there be any major difference between one of my current TWC HD channels, and the same channel transmitted via satellite?

TWC is likely using MPEG-2 encoding at a higher bitrate while satellite will tend to use MPEG-4 at a lower bitrate. For locals, the cable company can just pass along data stream from the station while satellite would have to re-encode for MPEG-4.

A cable company squeezed for bandwidth may try rate-shaping to get more streams per QAM channel, in which would mean re-encoding the MPEG-2 stream to a lower net bandwidth.

if at all possible your best bet for quality comparison is to hook up a UHF antenna and pick up a local over the air HD channel. Compare that to the HD channel from TW...

Thanks guys. A more specific question:

Is it possible the TWC would could reduce a full screen HD picture to a 4:3 picture, or is that controlled from the source? For example, I noticed the "Biggest Loser" was allegedly supposed to be in HD, but it was a low quality (to me) 4:3 picture. I am assuming thats how it is broadcast and not controlled by TWC--- right?

Thanks guys. A more specific question:

Is it possible the TWC would could reduce a full screen HD picture to a 4:3 picture, or is that controlled from the source? For example, I noticed the "Biggest Loser" was allegedly supposed to be in HD, but it was a low quality (to me) 4:3 picture. I am assuming thats how it is broadcast and not controlled by TWC--- right?

Most reality TV shows like that one are not in HD, they are 4:3 SD that the local station upconverts on their HD channel with sidebars usually. Only some programs are true HD, mostly the filmed drama and comedy shows. Its the network and stations, not the cable system.

If you see a modern film or TV show in 4:3 with black (or other coloured) bars each side, it is almost certainly a show made in 4:3 SD which has been upconverted to 16:9 OR if the show is definitely being made in HD then it is possible that the station you are watching has taken their SD network feed and upconverted it rather than the HD network feed (either by mistake or because they need to add a graphic overlay or similar which they can only do in SD) On some relatively rare occasions old films (and TV series) shot on film in 4:3 are transferred to HD in their original aspect ratio - and these are about the only time you will see an HD programme with pillarbox bars either side.

However just because a show is 16:9 doesn't absolutely guarantee it is made in HD - some shows are shot 16:9 SD and upconverted (some networks do this more than others. It is more common on Fox and PBS than NBC, ABC and CBS AIUI)

Similarly some overseas (and occasional US) sporting events are shot in 16:9 SD (or occasionally the feeds taken by American broadcasters are 16:9 SD from an HD production) and on some occasions these are upconverted to 16:9 HD rather than being cropped to 4:3 SD and upconverted.

(Sometimes sporting events - particularly golf - shot in HD still use some SD cameras - so you may notice picture quality changing on a shot by shot basis)

As to your quality question - just like SD - there is a range of picture / production quality in HD, and different broadcasters broadcast their HD at different qualities (the higher the data rate the better the quality usually), and different rebroadcasters (satellite and cable outlets) can also offer different qualities if they decode and recode (satellite broadcasters often reduce the horizontal resolution to save space) or rateshape (reduce the data rate without recoding by removing high frequency content)

I am new to HDTV and have a quick question. Right now I have TWC's HD service. Some of the HD channels look great while other HD channels look not so good. By reading this forum, I realize that not all HD channels are created equal and some will look better than others. However, how about if we consider the same HD channels transmitted by different sources. In my case, would there be any major difference between one of my current TWC HD channels, and the same channel transmitted via satellite?
Also used TWC for HD, since mid-2000, sometimes comparing OTA stations with cable--but not DBS delivered. (Differences with CBS were minor, but more recent mutlicasting by stations (not CBS locally) may have widened the PQ gap.) Only recently has DBS begun local station delivery using MPEG-4, which ideally--not actually yet, it appears--only requires about half the bit rate of MPEG-2.

On my 64" 1080i CRT RPTV screen, the biggest PQ difference between HD channels is usually live 1080i, the sharpest, and those delivering older movies, with varying degrees of 1080i image softness. Live 720p is usually less crisp than live 1080i when you start comparing backgrounds in wide shots such as sports crowd scenes. But then 720p may have half the format/spatial and effective resolution (http://archive2.avsforum.com/avs-vb/showthread.php?p=5667245&&#post5667245) (resolvable detail) of 1080i. Differences between the two HD formats narrows with 24p productions, generally dramas, since these inherently provide lower effective resolution (see quotes/sublinks (http://www.avsforum.com/avs-vb/showthread.php?p=9314235&&#post9314235)). The extra camera filtering (http://archive2.avsforum.com/avs-vb/showthread.php?p=7904193&&#post7904193) in 24p-drama production is a key factor. And some live 720p versus 1080i sports seems similar resolution-wise--here at least--when newer 1080/60p cameras are used to cover events delivered, say, on weekdays from a 720p network and weekends from a 1080i network. Downconversion from 1080/60p to 720/60p within the cameras boosts 720p's PQ. Most 720p 24p-captured dramas are also downconverted from 1080/24p master tapes.

Qualified my 720p versus 1080i viewing above because testing (http://www.avsforum.com/avs-vb/showthread.php?postid=5175424#post5175424) with HDNet's Saturday 6:30 am ET test patterns shows my cable STB and/or head end only delivered 1290 lines of effective resolution. Assuming that limitation applies to other channels, that means resolvable details between ~1290 and ~1700 lines (1080's limiting resolution) couldn't be seen even if delivered from program sources. Other AVSers report similar resolution limitations, with a few on smaller cable systems reporting closer to the full 1920X1080 resolution with 1080p displays. DirecTV's MPEG-2-based HD Lite, which reformats 1080i to 1280X1080i, obviously has a similar limitation.

Besides all the source and distribution variables above, displays and seating distance during comparisons plays a role. Some tests by Gary Merson showed that many fixed-pixel displays may halve vertical resolution because of a deinterlacing technique (see sublinked three articles (http://archive2.avsforum.com/avs-vb/showthread.php?p=9178202#post9178202)), and some 1080p displays didn't deliver full test pattern resolution (http://hdguru.com/?p=187). While programs don't (for now) match maximum test pattern resolutions in equivalent resolvable details, if your display can't resolve them you may not notice potential PQ enhancements. -- John

Thanks for the responses, guys. As a Noob I have a lot to learn and experience. Just today, I found the program "Cops" at full screen HD with a pretty good PQ and not the 4:3 "HD" crappy PQ that it was broadcast at a week ago.

W

Thanks for the responses, guys. As a Noob I have a lot to learn and experience. Just today, I found the program "Cops" at full screen HD with a pretty good PQ and not the 4:3 "HD" crappy PQ that it was broadcast at a week ago.

W

Actually if I'm not mistaken, "Cops" on Fox is widescreen upconverted SD...better than 4:3 SD, but not true HD.

It sure wasn't as good as HD Theater!