HDTV - High Definition Television

What is HDTV?

HDTV is a new digital standard for television, one with a higher resolution picture and a wider aspect ratio (the ratio of width to height of the screen).

I have used this page as a way to keep notes on what I'd learned while figuring out what system to buy. I did finally buy the Toshiba 34" 16x9 HDTV-ready set, and the matching Set-Top Box. It had gotten uniformly good reviews and in fact I'm happy with it. Now that I have bought one, the emphasis on this page will shift more to using an HDTV and the content available, and less on the different models available.

So Why Bother With HDTV?

A wider aspect ratio (the ratio of width to height) is a better match for movies. The normal American TV standard, called NTSC (National Television Standards Committee), uses a 4:3 (=1.33 to 1) aspect ratio, while HDTV provides for 16:9 (=1.78 to 1). Actual feature films vary in their aspect ratios but can be 2:1 or even higher. To show these on TV, they either have to be cropped or letterboxed or distorted, or some combination of these. A wider aspect ratio on the TV side makes the required modifications less severe.

The higher resolution of HDTV gives a more detailed and realistic picture. Regular analog TV today is made up of 480 (may be up to 486) visible horizontal scan lines, interlaced. Interlaced means that the odd numbered lines (a total of 240) are shown and then the even numbered lines are shown. These fields happen every 60th of second, in sync with the frequency of the power lines, so that 30 full frames are shown per second. Persistance of vision blends these into a smooth moving image. The shorthand for this system is 480i (i for interlaced). Real 480 line resolution is known as 480p (for progressive), 480p draws 480 lines 60 times a second (sometimes reduced to 30 or 24 times to match the frame rate of film). Some people say that 480i is perfectly swell, while others say they see flickering and that 480p is better. Most digital sets convert 480i into 480p using a line doubler.

DTV (Digital Television) is actually a whole collection of formats, including 480i, so that it is backwards compatible with regular TV. All the 480 line formats are considered to be Standard TV (SDTV), while the 720 line and 1080 line formats are HDTV. There are 18 modes altogether in HDTV of these ATSC (Advanced Television Systems Committee) formats. Most DVDs are still 480i, although they may be widescreen.

Also, being digital, HDTV will have no snow or ghosts if you can get it at all. Home Theatre Magazine's tests of HDTV antennas showed that they could get digital TV clearly when they could not get a good analog signal over the air. With digital TV, you get CD quality sound, too - Dolby AC-3, also known as Dolby Digital 5.1. The two formats for DVD are Dolby AC-3(Dolby Digital 5.1) and DTS(Digital Theater System), which adds one more speaker.

The 18 ATSC Digital TV Formats

What Kind of Content is Available for HDTV?

There's no point to having an HDTV if there's nothing to watch. Here are sources for HDTV content:

• Over the air (OTA). TV stations are broadcasting HDTV versions of some of their shows at the same time as the regular NTSC version goes out, using different channels assigned to them by the FCC. These channels are mostly UHF channels and you'll need an antenna to get them. Antennas work up to 30 or 40 miles from the broadcasting tower. Probably rabbit ears would work if you're right near the tower, else you'll need a proper outdoor antenna. CBS, NBC and PBS use 1080i for HDTV, while ABC and FOX use 720p. Some HDTV shows on now: The Tonight Show with Jay Leno, Family Law, 60 Minutes, Judging Amy, Yes Dear, King of Queens, Friends, Will and Grace, Touched by an Angel, Young and the Restless. Rose Bowl and Rose Parade are NOT in HD. Sometimes the Superbowl is broadcast in HDTV and sometimes not. All broadcasters are supposed to switch to digital TV by 2006. I say digital TV rather than HDTV because you can have digital 480i, like today's NTSC sets.
• Satellite.

  Voom is a satellite service that offers 30 channels of HDTV, plus a bunch of regular channels. Worth checking out if you're into HD.

  DirecTV and DISH Network offer some limited HDTV (or DTV). Some set-top boxes, such as the RCA DTC100 and the Panasonic TU-HDS20, include DirecTV decoding circuitry. The DTC-100 has only a 15pin VGA output for HD, the Dish 6000 in addition to the VGA has also HD component output. Satellite DTV is quite compressed compared to over-the-air HDTV and users report being bothered by digital artifacts. Before you spend big bucks for satellite HDTV, be sure to check on exactly what content is available in high definition. You may be surprised at how little is available. The reason for this is that the bandwidth required for one HD channel could support many standard channels and so it really doesn't pay for the satellite folks to offer much HDTV. Local channels are not available in HDTV via DirecTV - you would have to get them over-the-air.
  Bob Wetherill writes: Within DirecTv, channel 509 is the HD station that HBO provides. Channel 199 is a demo channel directly from DirecTv called HD Net, and broadcasts various things from some hockey games to lacrosse games to documentaries of different countries and animals in the wild. Sometimes HBO 509 broadcasts shows like "Sex in the City" and "The Sopranos", but as the show starts there is a statement that the show is not available in HDTV. These are the only HDTV stations within DirecTv.
  Joe Graff has more.

• DVD = Digital Video Disc, or Digital Versatile Disc. Regular DVDs are almost all 480i, but some "progressive DVDs" exist at 480p. Most DVDs are widescreen and work best with a 16:9 monitor. For best results, you'll probably want a progressive scan DVD player. Nearly everyone with an HDTV setup has a DVD player; they both use the 16:9 aspect ratio. For an excellent in-depth explanation of how progressive scan DVD players work, and a comparison of some current DVD players, check out this Home Theater and High Fidelity review. (Thanks to John Stevenson for the link.)
  The big news these days is that there are now two competing HD DVD formats. Sony and others back one called Blu-Ray and Microsoft and others back one called HD-DVD. As everyone and their uncle has already written, it's like Beta and VHS all over again. No one knows which will win in the end, but we're all pretty sure one will and those who bought the other will be stuck with a white elephant. Some players may come out that will handle both formats.
• Cable. HDTV signals take up too much bandwidth and the cable companies don't want to waste a bunch of bandwidth on one HDTV signal that not many people will use anyway. However, things are changing. Our local cable system now offers a limited selection of HDTV content. There is an additional fee and you have to use their special set-top box. Call your provider and ask.
• Videotape. The D-VHS video tape format can record and play SDTV digital TV signals directly. The High Speed (HS) mode of D-VHS can record and play HDTV signals. VCRs that support D-VHS are starting to appear in stores. Some movies are now available in this format from HDNet.
• Digital Video Recorder. Some DVRs for HDTV are finally starting to be available, such as the DishPlayer DVR 921 and DirectTV's HD-DVR250. JVC and LG also have models. These are like Tivo or ReplayTV, only they do HD.

Anamorphic DVDs

Here is a definition that I got from the newsgroup alt.video.digital-tv, from messages posted by Scott Regener, Glen Jarboe and Charlie Pearce.

A widescreen movie is in a different aspect ratio than that of a conventional television set. Therefore, part of the picture space is "black bars" which contain no useful information. Rather than encode the movie with black space, as normal "widescreen" DVDs and VHS tapes do, the picture is "stretched" up and down to fill the 4:3 frame of your conventional television. (Except, an anamorphic image will not necessarily fill a 4:3 frame - if its aspect ratio is wider than 16:9 it will still contain black bars top and bottom.) The widescreen television then takes this stretched picture and stretches it the other way (wide) to make it appear normal. When viewed on a conventional set, an anamorphic widescreen picture will make everyone look *way* too thin and tall. The advantage of doing this is that no horizontal resolution is lost (because the frame is exactly as wide as it was initially) but vertical resolution is increased because the amount of information vertically is higher. The disadvantage is that a DVD player has to convert an anamorphic DVD back to the original shape to display it on conventional televisions. If the DVD player's conversion logic is poor, the picture may actually look worse on conventional sets.

HDTV Digicams

These are just now starting to come out. The first is the JVC GR-HD1, which costs $3,500 and records 720p (30/s), 480p (60/s) or standard DV. It uses regular one hour DV casettes.

Some Basic Geometry

HDTV-Ready Sets

The term "HDTV-ready" means a higher resolution monitor with one or two built-in NTSC tuners, but without a digital set-top box. It will work as-is with regular television, VCRs and DVDs, even progressive ones. It will require a set-top box to decode 720p or 1080i digital HDTV signals.

Almost all HDTV systems take a component approach, with the monitor and digital tuner separate items to buy. This is because the tuner part (also called a set-top box) is more likely to change, whereas the monitor is more standardized. In fact, the monitors are much like computer monitors and you can sometimes use them for computers, or use computer monitors for HDTV. My Toshiba lets me choose from five inputs, which I have set to: regular cable, ReplayTV box, spare (unused), DVD player and HDTV set-top box.

Monitors come in the following different forms:

• Direct view. This is a regular CRT picture tube like you're used to seeing, only it will probably be 16:9 aspect ratio. Some true HDTV monitors are 4:3, however. They must be capable of showing a 16:9 image with full HDTV resolution (letterboxed, of course). My interest is in 16:9 monitors, which I will concentrate on here.
• Plasma Flat Panel. Many are only standard definition (480p) - make sure yours is "HD Ready". Questions to ask: how many standard NTSC tuners are included (1 or 2)? Does it include an HD tuner also? In Hi-Def mode, what is the resolution? It's just like computer monitors, with 1024 x 768 being the low end.
• Rear Projection - RPTV. These are the "home theater" models, usually 56" and up. Great big things - too big, in my case, for where I want the set.
• Front Projection. Now this is getting fancy. You hang a video projector from the ceiling and project the image on a movie screen that comes down when you press a button. Again, this takes up lots of room.

I've decided to discontinue my listing of HDTV sets, because I have quit updating it since I bought my own set (a Toshiba CW34X92 and matching STB, the DST3000). Here's where you can find reviews.

• HomeTheaterReview.com
• Digital Connection
• Widescreen Review
• Epinions.com

Set-Top Boxes = Digital Tuners

In addition to an HDTV-ready set, you will have to buy a set-top box, also known as a digital tuner, in order to receive true HDTV. The HDTV-ready set by itself is only capable of tuning analog signals, and (in combination with a DVD player) showing DVDs.

Many digital tuners can receive both over-the-air HDTV and satellite HDTV signals. For satellite you will of course need a dish and an account with a satellite TV provider. For over-the-air you just need an antenna (see next section).

It is usually best to buy your set top box from the same manufacturer as your HDTV-ready set, to insure compatibility. I hear that only about ten percent of the people who buy an HDTV-ready set also buy a set-top box. That 90% won't be getting true HDTV. Many of the same places that sell HDTV-ready sets also sell set-top boxes. The cable companies offer something they call digital cable, but this is not high definition, and buying their box won't get you true HDTV. However, I have heard of late that some cable companies are supplying digital set-top boxes that can do true HDTV, which could save you the cost of a digital tuner. Just make sure it's HD, and not SD digital.

HDTV Antennas

What is an antenna? We wouldn't have had to address this question years ago when all TV was over-the-air and every roof had an antenna, but now that cable is ubiquitious, it's an issue. A TV antenna is not the same thing as a satellite dish (which technically is a kind of antenna, but let's not confuse things). An antenna is not the same thing as a set-top box or digital tuner. An antenna is usually mounted on your roof and it's an assemblage of wires and rods that captures over-the-air signals. A cable connects the antenna to your digital tuner and another cable connects that to your HDTV-ready TV. If you live in an urban area quite close to the TV transmitter you may be able to get away with indoor "rabbit ears" but if you are out in the suburbs, you will need an outdoor antenna.

Antennas were reviewed in the January 2000 issue of Home Theatre magazine. Here in the Seattle area all the digital TV channels are UHF (some areas have VHF digital channels - see the DTV channel plan). Seems like any UHF antenna would work, and a regular beam seems best. Terk and others make special HDTV antennas, too - but they are probably not specially useful for HDTV. Radio Shack makes UHF-only antennas that would do fine.

Folks around here seem to use ChannelMaster antennas. Height matters - adding ten feet to your antenna mast could fix your problems. A company called Antiference in the UK makes an indoor yagi antenna that might be interesting to try.

You don't have to worry anymore about private Covenants Conditions and Restrictions (CC&R) such as apply to the deeds of houses in many developments. The Federal Telecommunications Act of 1996, Section 207, specifically overides restrictions that impair the viewer's ability to receive over-the-air television broadcast signals or direct broadcast satellites. [more..]

More information on antennas is available at Antenna Web. Stark Electronics sells TV antennas at a discount.

HDTV Message Boards

• AV Science Forum (the best info is here)
• Newsgroup alt.video.digital-tv
• DTV Forum