What is HDTV

Today in my class when we were simply chatting there was a talk about high definition and none of us were clear about it so I did a bit of googling found some information.

HDTV offers consumers much higher resolution and better picture color and clarity when compared to standard analog televisions.A standard television is able to display 480 lines of pixels. Each line takes 1/60 of a second to draw. The line drawing is done by having the odd lines drawn first followed by the even lines, which is commonly called interlaced scanning.Until recently, consumers wanting large-screen televisions had to rely on CRT technology. Now large screen televisions are available that use digital display technology. Instead of relying on interlacing, digital displays create their images using a fixed grid of tiny, individually controlled pixels and offers 720 lines of pixels up to 1080 and uses progressive scanning where the entire picture moves at one time every 1/60 of a second.

While many use the terms Digital Television (DTV) and High-definition Television (HDTV) interchangeably, they are, in fact, two very different things. DTV refers to the actual TV signal being transmitted digitally (instead of as an analog signal). DTV offers several broadcast options, which two are considered to be HDTV formats.

480i: The digital version of current television signals.

480p: Enhanced Definition Television (EDTV) provides a sharper image and looks closer to HDTV than regular television. Today all DVDs can be played on EDTV.

720p: a HDTV format that provides an image close in quality to 1080i, but allows 480p signals to be broadcast as well.

1080i: the most detailed HDTV image available from broadcast TV

* The numbers above represent the vertical resolution, while the letters represent interlaces (i)or progressive (p) scan. For example, 1080i represents 1080 vertical resolution, interlaced scanning.

In addition to offering a higher resolution, DTV also offers a higher television aspect ratio when compared to analog. Television aspect ratio compares the the screens width to its height. Traditional televisions offer a 4×3 aspect ratio. A standard 32-inch screen would be 25 1/2 inches wide and 19 inches tall. DTV allows for widescreen aspect ratio, which is measured as 16×9. A 32-inch widescreen would be 28 inches wide and 19 inches tall, allowing viewers to see a much bigger image area.

HDTV or HDTV Ready?

One thing you may find confusing is that buying an HDTV will not guarantee you immediate access to HDTV programming. When purchasing a HD television, you’ll have a choice between integrated HDTVs and those that are often called “HDTV-ready” or “HDTV compatible.” To receive HDTV broadcast, you need an HDTV tuner — a device capable of receiving and decoding HDTV signals. HDTV tuners can be a stand-alone device or it can integrated in the HDTV display. A high-definition television or display that has the HDTV tuner built into the set is called “integrated HDTV” while “HDTV-ready” refers to a television set that does not come with an integrated HDTV tuner. An HDTV-ready set means you must purchase the tuner separately.

Difference between 1080p and 1080i

In the ad’s for high definition televisions we often see 1080p and 1080i actually what is this?1080i and 1080p are both High Definition display formats for HDTVs. 1080i and 1080p signals actually contain the same information. Both 1080i and 1080p represent a 1920×1080 pixel resolution (1,920 pixels across the screen by 1,080 pixels down the screen). The difference between 1080i and 1080p is in the way the signal is sent from a source component or displayed on an HDTV screen.

In 1080i each frame of video is sent or displayed in alternative fields. The fields in 1080i are composed of 540 rows of pixels or lines of pixels running from the top to the bottom of the screen, with the odd fields displayed first and the even fields displayed second. Together, both fields create a full frame, made up of all 1,080 pixel rows or lines, every 30th of a second.

In 1080p, each frame of video is sent or displayed progressively. This means that both the odd and even fields (all 1,080 pixel rows or pixel lines) that make up the full frame are displayed together. This results in a smoother looking image, with less motion artifacts and jagged edges.

Differences Within 1080p

1080p can also be displayed (depending on the video processing used) as a 1080p/60 (most common), 1080p/30, or in 1080p/24 formats.

1080p/60 is essentially the same frame repeated twice every 30th of a second. (enhanced video frame rate).

1080p/30 is the same frame displayed once every 30th of a second. (standard live or recorded video frame rate).

1080p/24 is the same frame displayed every 24th of a second (standard motion picture film frame rate),

The Key is in the Processing

1080p processing can be done at the source, such as on a Upscaling DVD Player, Blu-ray Disc Player, or HD-DVD player – or it can be done by the HDTV itself.

Depending on the actual video processors used, there may or may not be a difference in having the TV do the final processing (referred to as deinterlacing) step of converting 1080i to 1080p.

For instance, if the TV is utilizing a Faroudja Genesis, DVDO, Silicon Optix HQV, or homegrown processors, such as the ones used in higher-end Sony, Pioneer, Hitachi, and Panasonic sets for example, may be equal to the processors used in many source components – so the results displayed on screen should be equivalent, or very close. Any differences would be more noticable on larger screen sizes.

1080p, Blu-ray Disc and HD-DVD

Also, keep in mind that with both Blu-ray and HD-DVD, the actual information on the disc itself is in the 1080p/24 format. Players, such as LG BH100 Blu-ray/HD-DVD combo player, have the ability to output 1080p/24 direct from the disc to its output.

However, since most current HDTVs cannot display 1080p/24, when you connect the LG BH100 to an HDTV that does not have 1080p/24 input and display capability but only has 1080p/60/30 or 1080i input capability, the LG BH100 automatically sends its 1080p/24 signal from the disc to its own video processor which then outputs a 1080i/60 signal. This leaves the HDTV to do the final step of deinterlacing and displaying the incoming 1080i signal in 1080p.

Another example of 1080p processing, is the Samsung BD-P1000 Blu-ray Disc Player – what it does is even more complicated. This Blu-ray player reads the 1080p/24 signal off the disc, then it actually reinterlaces the signal to 1080i, and then deinterlaces its own internally made 1080i signal in order to create a 1080p/60 signal for output to a 1080p input capable television. However, if it detects that the HDTV cannot input a 1080p signal, the Samsung BD-P1000 just takes its own internally created 1080i signal and passes that signal through to the HDTV, letting the HDTV do the final deinterlacing step.

Just as with the previous LG BH100 example. The final 1080p display format depends what deinterlacing processor is used by the HDTV for the final step. In fact, in the Samsung case, it may that a specific HDTV has better 1080i-to-1080p deinterlacer than Samsung has, it which case you may see a better result using the deinterlacer built into the HDTV.

1080p/60 and PC Sources

It is also important to note that when you connect a PC to an HDTV via DVI or HDMI, the graphic display signal of the PC may indeed be sending out 60 discreet frames every second (depending on source material), instead of repeating the same frame twice, as with film or video based material from DVD or Blu-ray Disc. In this case, no additional processing is required to “create” a 1080p/60 frame rate via conversion.


About aronnirmal

A student pursuing Masters in Compter Applications. Intrested in Linux, Computer Hardware and networking,eco-enviorment related issues and politics.

Posted on October 9, 2009, in Entertainment, Technical and tagged , , , , , , . Bookmark the permalink. Comments Off on What is HDTV.

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