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It seems like everyone is buying a new HDTV this year. The conversation around the water cooler is full of tech buzzwords. When the HDTV standard in the US was created by the ATSC (Advanced Television Systems Committee), they defined eighteen different standards, but not all standards are in common use.

The standards you should be familiar with for HDTV (High Definition TV) are 720p, 1080i, and more recently 1080p. The number in the format (eg “720”) is the vertical lines of screen resolution and the letter in the format (eg “p”) represents the display technique. The letter “p” stands for “progressive” scan and the letter “i” stands for “interlaced”.

HDTV (720p, 1080i, and 1080p) has a 16: 9 widescreen aspect ratio (width: height). EDTV (Enhanced Definition) is a standard definition television (SDTV is the pre-HDTV format), but with some “interpolation” software. EDTV offers a superior picture than SDTV, but not as sharp as HDTV. EDTV uses progressive scan. EDTV sometimes has a 16: 9 aspect ratio (widescreen).

For reference, standard definition television (SDTV, the pre-HDTV format) has 480 lines of vertical resolution and a 4: 3 aspect ratio. The SDTV signal in the US has historically been an interlaced signal. This means that your TV draws each frame in two passes: one for the even horizontal lines and a second pass for the odd lines. The specification is a maximum resolution for the technology, but signal sources are often less than the maximum. For example, VHS tape has approximately 240 lines of vertical resolution, SDTV over-the-air has approximately 330 lines of vertical resolution, and DVD SDTV has approximately 480 lines of vertical resolution.

The televisions of Europe and Japan have been (and are) of progressive format. A progressive format makes a single pass for all lines. Progressive images look a bit smoother than an interlaced image, especially when there is a lot of movement on the screen, such as sports.

To add to the confusion, BluRay DVDs do it, and satellite TV companies will broadcast in 1080p later this year. This standard has both the highest number of lines of vertical resolution and the preferred progressive format. Dish Network will begin broadcasting via satellite in 1080p in August 2008 with 150 HDTV channels, and DirecTV will begin broadcasting both via satellite and over the Internet in late 2008, with about 130 channels of HDTV programming. Satellite companies compress their signal with MPEG-4 techniques, reducing the bandwidth required for transmission. Currently, the only source material for 1080p is movies, especially movies originally created for IMAX. None of the major networks (ABC, ESPN, etc.) have announced support for 1080p yet. Also, Sony PlayStation 3 and Xbox 360 have 1080p games.

HDTV video format: 720p, 1080i and 1080p, the higher the number the better, right? Although 1080i technically has a higher resolution, it is not the obvious choice. 1080i has 1080 vertical lines of resolution and 1920 horizontal lines of resolution. 720p has 720 lines of vertical resolution and 1280 lines of horizontal resolution. But the 720p system is progressively scanned. This compensates for the lower level of resolution. The 1080p signal is the best of both worlds, plus picture information in a progressive format.

If your received signal, for example for a satellite receiver, is mostly standard definition, a 1080p TV will not significantly improve your picture compared to a 720p TV. Image quality is primarily limited by the source signal (480 lines of vertical resolution). Similarly, if your signal has a 720 source, then the 1080 TV will not enhance your picture. All high definition sports broadcasts from Fox, ESPN and ABC are broadcast in 720p.

Some networks have opted for the 1080i format because it provides more image information, while ABC, Fox, ESPN and the National Geographic Channel have chosen the smoother 720p images. HDTV programming on CBS, NBC, and other networks is broadcast in 1080i. The newer 1080i or 1080p HDTVs will likely make this type of programming somewhat sharper than it would appear on a 720p television. This becomes more important because as the TV screen gets larger, the visible difference in detail between the 720p and 1080i and 1080p displays becomes more apparent. Because of this, most HDTVs over 50 inches are 1080p or 1080i.

1080p HDTV System Capabilities:

A 1080p HDTV displays all input signals at 1080p, because this is the normal resolution for the unit. If the system is lower than 1080i or 1080p, then a special purpose chip in your HDTV scales the signal. It will be interpolated, as EDTV does with an SDTV signal. If the signal is 1080i, the system will combine the odd and even interlaced frames and display the entire signal as 1080p. The resulting performance should be similar to that of a true 1080p video source.

HDTV cable:

More than 100 million American households can receive HDTV from their cable system, and all of the nation’s top 100 cable markets have HDTV programming available. Unfortunately, most cable providers only have a few of the 50+ HDTV networks available.

HDTV satellite:

While the selection of local HDTV channels is generally better over cable than satellite, the major satellite companies offer more national HDTV channels than almost all cable providers. Both DirecTV and Dish Network have committed to offering more than 130 HDTV channels by the end of the year. “Satellites will be limited not so much by the number of channels they can transmit but by the number of channels they can get,” Bob Scherman, Satellite Business News.

  • By 2010, 60% of US households will use a satellite signal, up from 15% in 2002.
  • Summary:

    The screen resolution for HDTV has become comparable to the clock speed of the microprocessor for personal computers. Although clock speed is not necessarily a perfect indication of overall system performance, it is often viewed that way by the consumer.

    Interestingly, when a group of experts, the SMPTE (Society of Film and Television Engineers), recently ranked the importance of the resolution, it came in fourth place. SMPTE ranked contrast ratio, color saturation, color temperature, and grayscale ahead of resolution in importance. The Imaging Science Foundation came to a similar conclusion. However, most HDTV manufacturers combine quality features like an improved contrast ratio with higher screen resolutions on their top-of-the-line HDTVs. So if you buy a PC with a top-of-the-line screen resolution, you will most likely receive the top of the manufacturer’s product line for other important screen criteria.

    Prices have fallen significantly in the last two years, but it appears that the rate of price reduction has slowed significantly recently. “Television buyers visiting large stores may be more concerned about getting a low price and may not seek expert advice. However, television buyers should be aware that the lower prices they find at Large retailers are mainly due to the fact that these stores tend to carry second-brand televisions, rather than large brands such as Sony or Panasonic. When comparing the prices of a specific television model in each type of retailer, the prices are strikingly similar, “said JD Power’s Larry Wu.

    And on a final note, be sure to consider the audio side of your system. George Lucas (Star Wars) once said that audio is half the experience of watching movies. It is also true for a good football or basketball game.


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