Everything You Wanted To Know About HD TV
By Smarthouse Team | Thursday | 15/02/2007
We've all heard that high-definition TV is just around the corner. We explain exactly what it is and take a look at some of the best products to bring high-definition to your home.
High-definition television (HDTV) offers us the absolute in both visual and audio quality. The enhanced viewing experience of HDTV is unquestionably superior to anything previously known. Yet the truth is that we are now only in the early stage of the transition from analogue television to digital HDTV.
Analogue v digital
How does digital television (DTV) differ from the traditional analogue TV with which we all grew up?
Standard analogue transmits only the video and audio signal. A major problem with analogue signals is that between the transmitter and your TV set many things can interfere, thus distorting the picture you see. From a plane flying far overhead, to hilly terrain, tall buildings and even atmospheric conditions, all are obstacles that can interrupt the signal. Also, the strength of the analogue signal is critical; a weaker signal can cause "snowy" and distorted pictures.
Digital TV signals are made up of coded instructions, which are transmitted to your tuner or set-top box (STB), which in turn deciphers the code. Your receiver isn't concerned with the signal strength, or what conditions exist between you and the transmitter. As long as the signal gets to the receiver, and it can read the code, it can reproduce a near-perfect picture.
A distinct advantage of digital broadcasting is that bad reception is a thing of the past. DTV eliminates "snow" and "ghosting" caused by the weak signals from distant or blocked transmitting towers. If your analogue television set is not receiving a strong, undistorted signal from the tower, you will not get a perfectly clear picture.
Both digital and analogue television signals get weaker the farther they travel away from the transmitting tower. On an analogue TV, the picture slowly deteriorates from bad to worse for more distant receivers. However, the picture on a digital set will stay perfect until the signal becomes too weak for the receiver to distinguish between a (1) and a (0), at which point the image disappears completely. The bottom line is that you either receive a 100 percent quality image, or nothing at all.
What this means to you as a viewer is that you will never get a bad picture. Either you have a picture or you don't.
Essentially, high-definition television (HDTV) is digital TV. But it's important to understand that all digital TV is not HDTV.
|Baumann Meyer DT3220D|
HDTV is just one of the formats that comprise digital TV. In HDTV, the picture displayed on your television screen is digitally transmitted, but it must also meet certain standards in order for it to be 'true' HDTV.
The image you see on your television screen is comprised of a series of horizontal lines. An electron gun 'shoots' energy beams (light), which strike a layer of phosphor on the inside surface of the picture tube, causing it to glow. These glowing lines create the image displayed on your TV screen. How they are formatted, which resolution is used and what standards are met determine the type of television picture you are receiving.
Basically, TV 'resolution' refers to how many horizontal lines are displayed on your TV screen. Although it is the horizontal lines that are counted, this is usually referred to as 'vertical resolution' because the lines are counted from top to bottom - or vertically). Resolution is sometimes expressed as the total pixel count, which is a product of the number of lines and number of pixels per line - we will cover 'pixels' in more detail later on.
There are two methods that can be used to display the lines on the screen - either 'Interlaced' or 'Progressive Scan'. The interlaced standard was adopted to provide a method of compression that achieves a higher resolution using less-costly circuitry. The analogue standard is '525 lines - interlaced, at 30 fps (frames per second)'. This may be written as: 525-i/30 fps; however, only 480 lines are used to make the visible image, the remaining lines contain information pertaining to picture synchronisation and are not seen. For this reason, the stated 'resolution' usually refers only to the visible lines; ie... 480-i/30fps.
In using the interlaced method, the 480 lines are created in two fields (phases).
The 'scan-rate' for these fields is 60Hz (60 times per second). In phase number one, the first 1/60th of a second, 240 lines (the odd numbered lines - one, three, five, etc) are scanned on the tube. In the second 1/60th of a second (phase two), the remaining 240 (even-numbered) lines are scanned. Thus each field of 240 lines is scanned 30 times a second, and produces one complete frame (30) times per second; (1/60 second X 2 fields = 2/60 second = 1 complete frame, 30 times per second). It's the total lines per image that indicates the resolution of the system, that is 525i or 480i (with the 'i' standing for interlaced).
There are other analogue systems that have resolutions of less than 480 lines per image. For instance, DVDs have 450 lines; while VHS players come in with a poor showing of only 240 lines.
Digital TV has formats that use the interlaced system; however, DTV also uses progressive scan. The progressive system scans the total number of lines, 60 times a second; not half and half as in interlaced. This means you see the complete image displayed on your TV screen two-times more often. This results in smoother motion in moving images, having less motion artefacts and none of the visible flicker. A progressive scan system with 480 lines of resolution is written 480p.
HDTV v SD
With HDTV we are primarily concerned with two formats: 1080i and 720p. True HDTV may have either 1080 interlaced or progressive-scanned lines, or 720 progressive-scanned lines. Digital broadcasts in 480i or 480p are classified as SDTV (standard definition TV).
SDTV has a sharper, crisper picture than analogue because the signal is digital. It can be either (480i) or (480p) but is more often 480p. However, SDTV can not compare to HDTV's formats.
1080i displays more lines and thus delivers more information. The native resolution for this format is 1920 picture pixels wide by 1080 picture pixels high. This produces sharper pictures when the image is 'still' or has little motion. Manufacturers have generally preferred the interlaced format because more lines of resolution can be delivered with less bandwidth, resulting in lower costs. Many viewers, including those in the computer world, prefer the 720p format (1280 pixels wide by 720 pixels deep resolution) because its full-frame, progressive scanning enables it to reproduce fast-moving action and graphics without blurring the image.
Progressive images, without delving too deeply, have roughly twice the vertical resolution per sixtieth of a second of a comparable interlaced image. This gives the 720p format roughly three times the vertical resolution and over twice as much horizontal resolution as a normal TV signal. This resolution also matches with many digital display technologies, like plasma, DLP and LCoS. In fact, few displays as of yet can take advantage of 1080i's full horizontal resolution. Whilst 720p HD resolution has yet to be broadcast in Australia's free-to-air networks, 1080i has been so since 2001.
Regardless of which HDTV screen you buy, be sure it is capable of 'up-converting' or 'down-converting', enabling you to view all transmitted signals in your set's designated (native) format.
HDTV displays pictures that contain significantly more detail, resulting in much 'crisper' pictures. This is because the pixels in HDTV sets are square; they are also smaller and spaced closer together. There can be 4.5 HDTV pixels in the same space that a single analogue pixel requires. The result is that HDTV can display at least 4.5 times more detail than analogue TV
DTV sets are sold in two 'Aspect Ratios'. Aspect Ratio refers to the ratio between the horizontal (width) measurement and the vertical (height)
measurement of the screen. This ratio is also used in reference to how the picture is transmitted and displayed on the screen. The two aspect ratios used in DTV are 4:3 and 16:9.
That is, 4 units wide by 3 units high, and 16 units wide by 9 units high respectively.
The 16:9 'widescreen' format is approximately one-third larger than a comparable 4:3 set. The 16:9 widescreen aspect ratio is the standard for HDTV, because significantly more information can be displayed on the screen.
The reasoning that led to wide-screen formats is simply that the wider view is closer to the human field of vision. Because the viewer is visually drawn more into the action with wide-screen, the enjoyment level is enhanced.
HDTV is more than just great images. The audio is equally as impressive as the video that accompanies it. The same Dolby Digital soundtrack heard on DVD and in the best movie theatres can now accompany all of your favourite TV shows (though so far its use has been extremely limited). This includes left, centre, right, left surround and right surround channels, as well as a low-frequency effects channel for a totally enveloping audio experience.
Dialogue stays anchored to the screen while other sound effects travel around the room. Ambient sounds from the two rear speakers immerse you in the middle of an action scene or sporting event, while the subwoofer fills in ultralow frequencies, making the sound rich and full-bodied. As it was with the introduction of stereo TV broadcasts, the full 5.1 soundtrack may not be used for all shows, or may not be passed along by your local station, but when it is and you have an audio system to accommodate it, you'll hear the difference.
Most of the major manufacturers have either already brought out a flat panel capable of displaying 'true' HDTV, or are about to.
One of the more exciting of these offerings is the Pioneer PDP-5000EX, Australia's first 50-inch plasma screen with 1920x1080 native resolution. In other words, it can display 720p, 1080i and even 1080p broadcasts. We've got a full review of this screen on page xx.
Hitachi is also about to release a 42-inch plasma with 1080 line technology, complete with an integrated HDTV digital tuner for Australia.
Also due in November from LG is a 50-inch plasma panel with a built-in digital tuner and hard drive. This means that with the assistance of the 50PB2DR (RRP $6999) you can instantly record HD content to the hard drive for time shift and to view later.
Then there are the LCD offerings from Samsung and Philips. The Philips 37PF931 (RRP $5999) is a 37-inch LCD offering 1920x1080p resolution. Meanwhile, Samsung has its popular R7 LCD series, which have an HD tuner built-in.
There are also a number of HD projectors on the market for a home cinema setting. One of our favourites is the InFocus IN76, an HD-ready DLP projector with a very reasonable $4999 price tag.
What about Blu-ray?
Blu-ray is one of the biggest buzzwords we've heard bandied around in connection with high-definition content, but what does it actually mean?
|Samsung BD P1000|
The bottom line is that high-definition content take up more space in storage than standard content. For that reason, a group of the world's leading companies, including Hitachi, Pioneer, Samsung, Philips, Sony and LG, among others, banded together to develop an alternative format to DVD for storing large amounts of data.
The result is Blu-ray, which offers over five times the storage capacity of traditional DVDs. In fact, you can hold up to 50GB of data on a dual-layer disc. Storing high-definition content simply wouldn't be possible on a regular DVD.
The first dedicated Blu-ray disc player arrived in Australia last year. The Samsung BD-P1000 plays content of resolution up to and including 1080p, and is backwards compatible with DVDs and CDs. For DVD playback, it will upscale the source signal to 1080p. Supported DVD formats include DVD-RAM, DVD-RW, DVD-R, DVD+RW, and DVD+R. Additional features of the BD-P1000 include memory card reader, full audio format support, pop-up and always-on menu options; and improved bitmap and text subtitles.
You can also find Blu ray players in select Sony VAIO notebooks and of course the soon to be released Playstation 3. According to Sony, Blu-ray is already in the hands of two million people worldwide due to PS3 sales.
There's also a rival format to Blu-ray: HD DVD (high-definition DVD). This holds a similar capacity to Blu-ray but is supported by different manufacturers, including Toshiba, NEC and Sanyo. Toshiba has released an HD DVD player and of course you can also buy the optional HD DVD add on drive for your Xbox 360.
The importance of cables
It's not just the display and the source that are important when it comes to displaying high-definition content. It's also the cables that count.
HDMI (high-definition multimedia interface) is the only interface in consumer electronics that can carry both uncompressed HD video and uncompressed multi-channel audio in all the HD formats, even 1080p. So not only should your devices have an HDMI input, but you should also use HDMI cabling so you don't lose any of the audio or video quality.
Many manufacturers such as local company Kordz are now making cables that comply with the standards of the latest HDMI 1.2a specification.
Another aspect of your home cinema setup you need to consider is the set-top box. Topfield released their first high-definition receiver back in April, and it's one of our favourites.
The TF7000HT (RRP $599) incorporates HDMI technology, as well as component, RGB, S-Video, composite and optical and coaxial audio outputs. You can also output HD and SD simultaneously so you can connect directly to a VCR or DVD recorder for easy recording. You can even use two HD outputs at the same time (for example, you can connect the HDMI to your plasma and the RGB to the projector with no switching required.
It will also switch to match the transmission resolution (eg 1080i) automatically, otherwise you can set it to match your display and it will up-convert accordingly.
The benefits of HDTV
So what does all this mean? When it comes down to it, consider shows like Alias, ER, The West Wing and CSI, to name just a few. In HDTV and on your HD-ready display, these shows take on a near-cinematic quality, which means you no longer have to wait until the weekend DVD rental to enjoy a movie at home. The bottom line is, if you like TV, you'll love HDTV.
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