HDTV FAQ

1. Who invented HDTV?

   High Definition Television was created by an alliance of companies working together to create the next generation of television. Members of the "Grand Alliance" included General Instrument, MIT, Zenith, AT&T and Sarnoff Labs (RCA).

2. What is HDTV?

   HDTV is an acronym for High Definition Television. HDTV was first introduced in the early 1980s in Japan. It was known there as the MUSE system, which was an analog HDTV storage and delivery system.

   HDTV today utilizes digital encoding which allows compression of the signal make transmission and storage easier. A digitally encoded a television picture is known as DTV, or Digital Television. A signal that is DTV is not necessarily HDTV; however, all HDTV signals are digital.

3. What is the difference between HDTV and Standard TV (NTSC)?

   HDTV displays a much more vivid picture when compared to Standard TV; this is because HDTV offers about twice as many "lines" of resolution. HDTV also offers better sound quality in the form of digitally encrypted five-channel sound.

   HDTV works entirely in the digital domain, which means HDTV signals are transmitted in the form of data bits. These data bits are stored and transmitted with parity checking and error correcting ability, as a result the picture does not suffer from quality degradation. As long as you can receive the data stream you will get the best picture without ghosting, noise, sparkles or static.

4. What are aspect ratios?

   The aspect ratio of a television picture describes the ratio of the pictures width to height. Current Standard TV (NTSC) pictures are 4 units wide by 3 units tall, nearly square. The 4X3 ratio was originally used for early motion pictures. It is also called the "Academy Ratio".

   Today aspect ratios are part of the cinematography of the film. Movies are intended to subtend a large angle of view in order to put the viewer into the action. The aspect ratio helps to create this effect.

   HDTV is presented in a 16X9 format. This is a wide-screen aspect ratio that is similar to the ratio of major movies. The wide aspect ratio of HDTV will allow the vision of the movie artists to be delivered to your home with less compromise and greater impact.

5. What is the difference between NTSC, 1080i, 720p and native?

   NTSC

   Standard TV (NTSC) systems shows us 30 picture frames-per-second (fps) using two fields. Each field consists of half the scanning lines of the frame. In the first 1/60 of a second, the television tubes illuminates odd numbered scanning lines 1 525. In the second 1/60 of a second the picture tube illuminates the even lines 2 524. These two fields of scanning lines are interlaced (alternated) every 1/60 of a second. Therefore it takes 2/60 of a second to show one frame on a NTSC system. These two fields are interlacing at a frequency of 15750Hz. Standard TV always has 525 vertical lines. However, the number of horizontal lines can change in NTSC format. The number of lines of horizontal resolution is often used to describe the sharpness of a Standard TV set.

   1080i

   The "i" in 1080i stands for "interlaced" which means the picture is constructed by alternating fields in the same manor as an NSTC system but at a much higher rate. Instead of using 525 vertical lines of information the 1080i system uses 1080 lines of information. 540 lines are illuminated every 1/60 second and interlaced with the remaining 540 lines at a frequency of 32400Hz. This faster scanning rate, coupled with more lines of information, creates a vivid image that does not exhibit the graininess, flicker and visible scanning lines of NTSC. The entire system carries with it a wider bandwidth (bandwidth is proportional to picture detail) allowing about twice as much information to be displayed when compared with NTSC.

   720p

   The "p" in 720p stands for progressive. Progressive scan systems operate like a computer system; they show each scanning line sequentially without interlace. Thus, a 720p system would posses 720 horizontal scanning lines, which are illuminated every 1/60-second. A 720p system operates at a frequency of about 43200Hz. As the scanning frequency of a set gets higher, the set gets more expensive and difficult to produce. This is why you do not find too many 35" computer monitors they can get very expensive.

   Native

   The General Instrument HDD200 offers the user the ability to choose a specific format output information; 1080i, 720p, 480p or "native". Native means the system automatically select the output format based on the input. 1080i is currently the dominant form for HDTV transmission and display, but the HDD200 is compatible with many combinations of programming and display devices.

6. What is the difference between RGB and YprPb?

   RGB stands for red, green and blue; the base colors from which all the colors your television monitor can display are derived. The HDD200 decoder offers RGB + sync (horizontal and vertical sync) connections so you can use front projection and professional quality CRT monitors to display the high definition image.

   YprPb is also supported. This is the HDTV equivalent of an S-Video connector. YprPb transmits the picture information in a luminance and phase-opposite chrominance pair over three coax cables. Most new HDTV monitors offer YprPb connections.

7. What is the difference between C-Band High Definition and small dish High Definition?

   The source of small dish programming, with the exception of certain pay-per-view movie channels, is from C-Band TV originated signals. Small dish companies, like cable companies, capture the C-Band TV Master Broadcast Quality signal encode it, compress it, and rebroadcast it in a secondary format. All this signal manipulation naturally results in compromised picture quality.

   HD broadcasts will be handled in the same manner. To provide a premium movie channel on a small dish, the small dish programmer will capture it from the C-Band TV Master Broadcast Quality, encode, compress and rebroadcast the program.

8. Will the HD box make non-HD channels look better?

   When a standard definition channel (SDTV) is processed through the HDD200 it is upconverted to a 1080i signal. While this process does not add any more "resolution" to the picture, the process can make scanning lines less intrusive and give the picture a smoother, more homogenous and film-like look.

9. Can I use the HD 200 on a small dish system?

   No. The HDD200 is expressly designed for use with DigiCipher II products. Those include General Instrument DigiCable, Starchoice and all 4DTV Receivers.

10. My HDTV monitor is in the basement and my 4DTV Receiver is in the living room upstairs. Can I run a long cable between the 4DTV and the HDD200?

    The MMAP (Multi-Media Access Port) is transmitting data at a fantastic rate to the HDD200. The integrity of this data is vital to the proper operation of your HDTV decoder. To assure data integrity the link between the 4DTV and the HDD200 must be kept to a maximum of two meters.

11. Will the 4DTV and HD box ever become one?

While it is certainly possible to combine the HDD200 and the 4DTV IRD onto a single chassis, the truth of the matter is that most consumers will not own an HDTV compatible display device for years to come. So long as the average consumer owns an SDTV display it is easier and more economical to create the 4DTV-HDD200 system in a two chassis configuration. In this way you can purchase just those capabilities you need to meet your requirements.