KYES HDTV TV Comments

KYES-DT

OBSERVING HDTV

Sharpness of the image you see on DTV depends on several steps in image processing. Do not assume you are seeing the best quality HDTV. 1080i is the highest resolution broadcast standard, and your set may say it can display 1080i. But did the producers use a camera lens that captures enough detail? Will your display show each picture element broadcast? Can your eyeball discern each picture element?

Full resolution depends on resolution capacity at each step from the camera lens to your retina. For highest resolution:

Lenses: The producers of the program must shoot with lenses and cameras that can render 1920x1080.
Studio wiring: Wiring in a studio, and especially stadium sports wiring will affect HD picture quality. It is best if producers use optical fiber transmission.
Bitrate: More bits per second equals better pictures. But bits per second are costly. The transmission path has incentive to reduce bit rate to squeeze in more programs. Bit rates for uncompressed high definition TV can exceed one gigabit per second. The bit rate of a satellite transponder is limited to about 50 megabits per second. The bit rate from the TV transmitter to you is only 19.37 megabits per second. Thus, some detail must be removed from the picture before it is transmitted to you. Satellite operators, and cable programmers such as Echostar or HBO HD are probably limiting bit rates a lot more. E.G., we checked Starz HD and saw they were transmitting from 4-10 Mb/s. See A chart of HBO's bit rate . The rate is changed with content. By way of comparison, a standard 2 hour DVD runs at an average 5 Mb/s varying up to 10 Mb/s depending upon scene.
So the owner of the transmission channel wants to use bit capacity to transmit more programs, and remove ever more detail to cram in more programs over the same transmission channel. Therefore, the same program could look better over one system than another, even though both are 1080i resolution with full 1920 by 1080 pixel resolution.
- Over The Air (OTA)6 MHz 19.37mb/s
- Satellite Transponder 36 MHz 45Mb/s
- Cable TV 6 MHz 27 or 39 Mb/s depending on equipment
Receiver: Your receiver may receive one standard, like 1080i and output another, such as 720p.
Display-Monitor :Your display device, including the cathode ray tube, or plasma display, or what ever you use has an inherent resolution capability. It must equal or exceed 1920 by 1080 or you cannot see every pixel. When you buy a monitor, be sure to ask, "What is the native resolution of this monitor." Just because it will display a 1080i signal does not mean it can resolve each of the 2,073,600 picture elements (pixels) in the 1920 by 1080 transmission. On the other hand, maybe you want a less expensive monitor that gets most of the way there, but cost a whole lot less money.
Eyeball: Your eyeball has a visual spatial resolution limit. Here find a calculator to determine distance for average eyes. Your distance from the display will determine the pixel resolution capability of your eye. It is pretty silly to pay for that high resolution, if you sit too far from the screen to see it.

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-Jeremy
Jan 31, 04