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GeorgiaHDTV's HDTV Primer (Updated 01.24.2006) |
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Note: The following is a work-in-progress HDTV primer, based on questions
I've attempted to answer for folks over the past few years via email. This is
coming off the top of my head, so please bear with me and shoot me a
line with error corrections. |
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1. HDTV Introduction 2. HDTV Receivers (a.k.a. STBs-- set-top-boxes) 3. HDTVs 4. HDTV Antennas 5. Recording HD 6. Why Doesn't XYZ in HD Look Good? ---------------- 1.) HDTV Introduction As you may have read, HD (High Definition) is the greatest television achievement since color was introduced in the 50's. HD programming has up to four or five times the resolution as an SD (Standard Definition) television transmission. Basically, SD is the television resolution we've pretty much used for the last 50 years, having anywhere from 240 to 480 horizontal scan lines. This is known as the NTSC standard. The number of horizontal scan lines is referred to as "resolution." The resolution will be followed by a letter-- either "i" or "p." "I" means "interlaced." When broadcasters first sent television content over the airwaves, the content was split into two interlaced frames. The first frame would carry the odd-numbered lines. The second frame would carry the even-numbered lines. This happens fast enough that our eyes can't see two separate images. For reference, VHS tapes have around 240i lines of resolution. Cable tv has around 390i lines of resolution. DVDs have 480i lines of resolution. In the late 90s, as DVD players became mainstream entertainment devices, a new scanning rate was utilized. Most dvd players now are capable of a scanning rate of 480p. The "p" means "progressive." Rather than interlacing the odd and even lines in two separate frames, progressive scanning displays all scan lines at once. This leads to a much more crisp picture-- especially in scenes where there is movement. Notice that there are still 480 lines, but now they're scanned all at the same time. Ok, let's backtrack for a second... In the late 80s, engineers started playing with the new ATSC television standard. Over the years, ATSC standards gave birth to HDTV (High Definition Television). HDTV is pretty much any resolution between 480p and 1080p (the holy grail). However, the two main resolutions are 720p and 1080i. Most broadcasters are leaning towards 1080i (including HBO, Showtime, NBC, CBS, and HDNet). The current 720p supporters are ABC and ESPN (both owned by the same company). Some people say that 720p is better suited for sports as movement is more fluid when progressively scanned. FOX is not yet on either list, as they broadcast in 480p which is not technically HD. It's actually called EDTV (Enhanced Definition TV). FOX will move to HD this year (2004) and will choose 720p. While the numbers may not look like a totally new tomato, the difference between 480p and 720p (and 480p and 1080i) is just as incredible as the difference between black-and-white and color television. It's something you have to see to believe. To make the television experience more "theater-like", HDTV is shot in a widescreen format with Dolby Digital as the default sound format (either stereo or full 5.1). The HD standards also include guide information, station information, and a few more "less important" details. ---------------- 2.) HDTV Receivers An HD receiver is a device for receiving High Definition television programming. It pretty much looks like a satellite or cable receiver. There are several different types of HD receivers:
Cable HDTV receivers, operate pretty much the same as satellite receivers, except most of the time you lease the STB from the cable company. Cable operates on a QAM stream, which allows compression of multiple channels into a single feed. Cable HD stations do not suffer from the same weather-related dropouts as satellite dishes or OTA antennas, but they as just as prone to dropouts as any other HD source. In the Atlanta area, Comcast and Charter currently offer cable HDTV receivers for lease. Comcast offers a dual-tuner DVR from Motorola, while Charter offers Scientific-Atlanta equipment. Both are similar to TiVo. As of April 1, 2004, all cable companies *must* offer an HD cable box with working firewire. OTA HD Receivers are capable of receiving the HDTV that local tv stations send out. They do not decode satellite and usually don't decode cable. Most of them include a typical NTSC tuner, just like the one you will find included in any tv (think: "channel scan feature" on your tv's menu). The most common way to output HD from an HD receiver is the use of component video connections (the red, green, and blue jacks, often labeled "Y-Pb-Pr"). You cannot send HD over s-video or composite (that lone yellow jack), as those types of connections cannot handle the enormous bandwidth of HDTV. Most satellite receivers include DVI or HDMI (DVI + 5.1 audio), which are also capable of sending out HD content. To enjoy the 5.1 surround sound of HDTV, you'll use the optical or digital coaxial (orange or black colored) jacks to connect to your A/V receiver (the thing that connects to your speakers). ---------------- 3.) HDTVs Now, just because you have an HD receiver, that doesn't mean you're completely ready for HDTV. In addition to the HD receiver, your tv needs to be HD-capable, HD-ready, or HD-integrated. The tv will need either component video inputs ("Y-Pb-Pr" described above) or some digital interface like DVI, HDMI, or firewire. If you see "HDTV monitor", "HD-ready", "HDTV" or anything along those lines somewhere on the frame of your tv, you're set. Some tvs have component inputs that are not HD-ready. In these situations, the component inputs will accept 480i or 480p only. There should be labels above these connections on the rear of the tv detailing which resolution that input will accept. ---------------- 4.) HDTV antennas Let's be frank here for a second-- any television antenna will receive HDTV. Don't be fooled by anything marketed as an "HDTV antenna." The only thing different about those HDTV antennas is the higher price that some poor fool would pay. They are all the same thing. They all receive the same UHF and VHF spectrum. Don't let any salesman tell you differently. Ok, enough of that rant. ---------------- 5.) Recording HD Hollywood is very, very afraid of people recording HD content. You cannot record HDTV over component connections. There is one VCR (W-VHS standard) made in Japan that records via component in 1125i if you don't mind paying $6000 and only recording the stereo sound. HD-DVRs and firewire-equipped devices are the only transports available for HD recording. Firewire can be encrypted to allow freely, allow once, or disallow copying entirely. As mentioned earlier, HD cable boxes must have working firewire ports. When these receivers are connected to a firewire-equipped VCR (like the JVC DH-HM30000u) via its firewire connection, they are capable of recording full bandwidth HD content and 5.1 surround sound without any degradation. In Atlanta and other parts of the country, Comcast is offering a Motorola 6412 series HD STB which includes firewire outputs. This move was prompted by a Congressional ruling requiring all cable companies to provide a firewire-equipped STB by April 1, 2004. HD-DVRs are becoming readily available at this time. Sony offers a standalone OTA-only HD-PVR. Dish Network and JVC offer a dual tuner satellite and OTA HD-PVR. Hughes (Directv) released its much-anticipated HD-TiVo in 2005. ---------------- 6.) Why Doesn't XYZ in HD Look Good? Not all HDTV is created equal. Sometimes a program on an HD channel will look either washed out or overly soft. There's a simple explanation for this-- the program is being upconverted to HD from an inferior source. Let's take ESPN as an example. As you've most likely noticed, ESPN-HD is an exact mirror of the plain Jane ESPN. Unfortunately, *some* of the time, the quality of the HD channel isn't exactly leaps and bounds over the SD channel. ESPN quite simply doesn't have the equipment to shoot every event in HD. When this happens, they have to take their regular 480i content and upconvert it to high definition (720p in this case). Their 480i tapes obviously don't have 720 horizontal lines but they fill that lagging space all the same. This "filling" is the upconverting process. The end result is a "soft" or "washed out" picture. Sometimes, ESPN-HD is also stretched to fill a 16x9 screen-- adding to the poor picture quality-- but that's a subject for another time. When ESPN-HD does broadcast in true HDTV, the picture is as outstanding as some of Discovery HD's programming. This little scenario also carries over the HBO-HD and Showtime-HD. A great deal of both companies' original programming is shot in true HDTV. Both channels will *usually* broadcast premier blockbusters in true HDTV, as well. At the same time, a great deal of their older programming is merely upconverted from standard definition sources. HBO does a fairly good job of announcing true HDTV on their online schedules-- as they often do their own remastering in-house. Look for the "True HDTV" moniker on their website. Now, let's contrast ESPN-HD to HDNet, who only broadcasts true HDTV. Ever noticed a washed out picture on HDNet? I didn't think so. HDNet's source material is always a true 1080i video or a "master tape" that has been painstakingly mastered (or remastered, as the case may be) in High Definition. |
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