Is there any information on how well HD is broadcast via the various possibilities. I assume the best HD is with CBS over-the-air, since the local CBS stations have only one signal. Compression it would assume be a minimum. Next in line may be the over-the-air stations with multiple sub-channels. It would seem there must be some loss in fidelity. But what about cable and the satellite services of Dish and DirecTV. So how do all these services compare. Is there any data out there.

It gets exceptionally complex regarding PQ, as you're aware from just those factors. MPEG-2 maximum bit rate (OTA signals) isn't necessarily a deciding factor since the encoder's efficiency needs to be considered. And DBS delivered in MPEG-4-like formats might match or exceed MPEG-2 with far fewer bits. Lack of blocking and other artifacts with adequate bit rates is an obvious PQ factor, but defining PQ/fidelity after that gets ambiguous. Searching this forum will show an earlier thread with a table by member bfdtv that compares some measured bit rates between Comcast and Verizon's FIOS. Edit: Here's a Verizon table (http://www.avsforum.com/avs-vb/showpost.php?p=12689065&postcount=16).

High definition deals with greater resolutions, and some of the earliest test results (http://archive.avsforum.com/avs-vb/showthread.php?postid=326565#post326565) (mid-90s) for OTA-type ATSC signals showed maximum effective resolutions (http://archive2.avsforum.com/avs-vb/showthread.php?p=5667245&&#post5667245) (resolvable detail) from test patterns for B&W and color (720p and 1080i), although 720p derived from 1080 downconversion can deliver effective resolutions closer to the 1280X720 format resolution. An intro resolution paragraph in an advisory technical report (http://rhopkins.us/drbob.tv/documents/tsreport.pdf) to the FCC outlines anticipated resolutions for HD formats and a later table compares measured results (table 2.3). The test results link just above shows another, simplified, version of this table.



Sampled video (e.g.,cameras, telecines), apparently used for these early ATSC tests, differs from non-sampled test patterns (computer or pattern-generator signals) since sampling requires reconstruction filtering that reduces resolvable details. But far more additional (optional) filtering is involved with dramas where cameras often have filters for artistic intent and lenses are often focused to blur details. For most dramas, then, maximum horizontal effective resolution typically falls below the fidelity (resolution-wise) seen with documentaries or travelogue shows. Some measured resolutions for movies are outlined here (http://www.avsforum.com/avs-vb/showthread.php?p=9314235&&#post9314235) (see sublinks). Blu-ray discs can potentially deliver higher effective resolutions than OTA/cable/DBS, although the resolutions measured for movies a while back were obtained from pro HD-D5 master tapes using far higher bit rates than Blu-ray discs. -- John

Over-the-air Digital TV stations with no subchannels would rank at the top, along with all of Verizon FiOS, and Comcast's retransmission of local OTA Digital TV stations. None of these are reduced in HD image quality.

DirecTV, Dish Network, AT&T U-verse, and most every cableco in the country all reduce HD image quality (to different degrees) on pretty much all HD channels. I'm sure there are exceptions, for example other cableco's may also pass local HD intact from the source like Comcast, I just don't have direct knowledge of this.

Based on my own observations, and general forum feedback, I'd say for overall HD quality here is a guide:

1)
OTA DTV
Verizon FiOS
Comcast local HD

2)
DirecTV
Various local cable
Dish Network

3)
Various local cable
AT&T U-verse


The problem with further specificity, is that local cable varies widely in HD image quality, even among systems of the same company in service different areas. For details on your area, see the HDTV Locals Forum, which has local topics for pretty much every TV market in the US, some markets with multiple cable & OTA specific topics.