VIDEO SOURCESóPART ONE
(FIGURE 1: ARTWORK OF INCOMING SIGNALS WITH CAPTION: "Incoming signals.")
Great pictureóthat's a key element in home theater. So, to get a great picture, I just buy the best TV set I canóthe one with the highest number lines of resolution. Right? I mean, HDTV (High Definition Television) isn't here yet, but I want high definition, don't I?
Well, yes and no. Believe it or not, ultimately great picture is a subjective measure. But, to help understand the complex elements that contribute to this judgment, there are reams of technical information, including lines of resolution.
This two-part article will cover some of the considerations to take into account when deciding what's a great picture. It is split in two sections: This first part covers outside sourcesóbroadcast, satellite, cable, and tapes and discs; Part Two covers equipment used in the homeóTVs, VCRs, Camcorders, and Laserdisc Players.
Over the air (OTA) broadcasting is one sourceóthe national networks and local TV stations often land here. Satellite signals can be received directly in home and cable companies run "wires" to subscribers' houses to deliver the picture. In addition, there are the sources that are pre-recorded and that we record ourselvesótapes and discs. And the hardware that captures, records, enhances, transmits, receives, and displays these moving pictures affect the end resultóour perception of the image.
It's no wonder many in this industry use lines of resolution as a way to compare sourcesóit makes life easier if we can categorize and simplify. But, it is only one measure among many, and not necessarily the most important one.
Great picture is defined in a variety of waysóto some, bigger is better; to others, saturated color or a razor sharp image is better. And studies have shown that improved audio can improve perceptions of picture quality. These two articles are not an exhaustive study of all the elements, technical or otherwise, nor will they provide definitive answers to all your questions. It is a brief overview of video sourcesóultimately the ways we get the picture on our home theater screens. Hopefully, this information will help you formulate your own questions, leading you to making a personal choice that satisfies your own needs.
Here is what is happening today¼ which will no doubt change tomorrowó
BROADCAST TVóOVER THE AIRóFREE SERVICE:
(FIGURE 2: PHOTO OF OTA RELAY STATION WITH CAPTION: "Over the air broadcast relay station.") [Photo courtesy of KOAT-7]
Not too long ago, the only images most of us could receive in our homes were from broadcasters (the networks and local TV stations). Our sources were limited.
"The TV station receives 95% of its "product" via satellite, but some still comes in on video tape," said Ken Simpson, Assistant Chief Engineer, KOAT-7. "The station receives all this in analog mode. Video components are converted to digital for manipulation and then converted back to analog for distribution. For example, we might have a picture of President Clinton and General Powell, but want to use only Powell superimposed over an image of Desert Storm. This image would be manipulated (cropped, re-touched, cut & pasted) in digital. In analog it is difficult to capture one frame, so digital is usedóit's much easier."
He went on to talk about the new satellite system. "There is satellite system just launched, DSS, in which the transmitters and receivers are all digital. The tape machines at the uplink facilities are digital and the home receivers are digital. By rumor, the quality of the picture is betterónot necessarily by lines of resolution, but noise, clarity, color are significantly better."
Over the air broadcasts are about 230-240 horizontal lines of resolutionódue to signal processing in the analog world. The more lines of resolution, the more definition, the more clarity and details. Some TV sets today can deliver up to 700 lines, and HDTV is expected to go to 1100. These higher resolution sets may well deliver better picture quality even with a normal broadcast signal.
However, the quality of the picture is determined by many thingsóthe camera, the pick-up device, all the way to the transmitter. And the ultimate quality of the picture starts with the first image.
When asked about the future, Simpson said, "Digital may be the next step before HDTV. The equipment is available for a total digital plant (TV station) including cameras, switches, tape machines, and distribution equipment. The cost is still very expensive, and it's not practical yet to convert. Digital quality is better, there is less noise, resolution should be increased somewhat, but it will still be limited by the transmitters¼ I don't know of any digital transmitters being made right now."
In terms of HDTV Simpson cited a similar situationóequipment is being manufactured now, but due to lack of standardization, no one he knows is making HDTV transmitters. This is a subject the FCC is working on currently.
(FIGURE #3: PHOTO OF DSS SATELLITE SYSTEM WITH CAPTION: "DSS Satellite system.") [Photo courtesy of Thomson Consumer Electronics]
Two kinds of satellite systems exist todayóthe older, larger satellite system that has 300+ channels and the new DSS (Digital Satellite System) that provides access to 150 channels. The older systems were relatively expensive to install and had large satellite dishes, 6' and more across. The new system retails for under $1000 and has an 18" dish. The smaller dish is made possible by higher power on the satellites themselves. In addition, DSS is a full digital system. "The little satellite is supposed to be better in picture and audio quality due to use of wider bands, the number of lines available in the viewing medium," said Walt Brown, President of New Mexico Satellite, Inc. "But the DSS system still has bugs. There are variations in the picture quality. The digital DSS system has dropouts. In heavy rainstorms the signal breaks up. I don't know what will happen with snow. Digital is supposed to be betteróbut I haven't seen it."
Brown went on to talk about the potential of satellite to deliver the best signalóup to 450 lines of resolution. HDTV may have to go on satellite because OTA and cable won't have sufficient band width to handle it (higher frequencies need a wider band for recording, and higher frequencies often translates to higher lines of resolution.) He emphasized that picture quality is only one element in the whole home theater package. What is most important to Brown is looking at what their customers are most interested in. "In terms of home theater, it is a variety of programs, the best picture and best audio possible." And in the mountains of New Mexico, even the best signals may have to be processed to deliver satisfactorily.
(FIGURE #4: PHOTO OF MICROWAVE TRANSMITTERS WITH CAPTION: "Microwave transmitters at Jones Intercable headend facility.") [Photo credit: Paula Hendricks]
Most cable systems deliver an analog signal through coaxial cable or fiber optic lines. The quality of that signal is dependent on the signal they receive. "We pick up the signal from a satellite, it goes to our headend facility, where it is processed, amplified," said Kevin Bethke, General Manager of Jones Intercable Co.
The satellites can now send digital signals and the cable can carry analog or digital. "We talk about digital quality, yet TV sets are still analog," Bethke said. "Cable TV will start providing digital¼ not all at first. There will probably be an analog/ digital hybrid, with basic service still analog, and digital as an extra." Digital will require, initially, converter boxes, which are just starting to be built now, and the price is still high.
"This area is changing very rapidly," Bethke went on to say. "There are lots of possibilities. As we deploy fiber optics, we improve picture quality and reliability. It does a lot for us by reducing amplifiers in fieldówe can reduce our costs, become more efficient."
In terms of picture quality, Brian Throop, Chief Engineer, was very specificó"We have different measures to define picture quality. Carrier to noise ratio is our most important [This is a measure of the original signal vs. noise inherent in the hardware/ equipment]. The bigger the number, the farther away from noise, and the better the picture." Noise in analog is "snow."
"But picture quality ends up being subjective," Throop said. "Some will talk about a particular satellite system hooked up with Super VHS, and the quality is 'x.' But 90% of consumers don't have this system. So, the choice is subjective. Studies have shown that the same picture shown with mono vs. stereo, consumers say the stereo system has a better picture. We have a minimum carrier to noise spec of 47 dB [decibels], but studies show consumers can't see the difference between that and 48-50. With pretty good pictures, the differences are harder to see."
What about HDTV?
"There is a problem with standardization," Bethke said. "It needs more band width than OTA can easily handle. Channel 7 is right up against Channel 8 already. It may have to use a different format that gets reconverted in the home (like using UHF)ówe can't just start broadcasting this tomorrow."
Can we leap frog over HDTV? Throop responded, "This digital revolution going on now¼ seems to me will go past HDTV. The digital signal can be compressed and use a smaller band width¼ It all comes back to cost."
"But there are trade-offs," Bethke said. "As you compress digital more, you lose rapid movement across the screen. The digital rate can't keep up with a fast football across the screen. Different compression rates are needed for different pictures."
TAPES AND DISCS:
(FIGURE #5: PHOTO OF VIDEO TAPES BASF #15 WITH CAPTION: "Video tapes source.") [Photo courtesy of BASF Corp.]
"Quality depends on the sourceóthe result is only as good as the weakest link in the chain," said Claude Guerlain, Product Manager for Audio Video Retail, BASF Corp. BASF sells blank tape to retailers and companies that duplicate movies.
"We specialize in longer tape length, which has to be thinner to fit into the standard package. This is important because SP (standard play) will deliver the better quality picture than EP (extended play). So for longer movies, longer tapes are needed. The quality degrades with longer recording times. SP is the highest speed recording mode and will deliver a better picture," said Guerlain.
"Quality isn't so much lines of resolution, " said Angelo Cataldo, Video Engineer, Applications Engineering, BASF. "We have other measurements: dropoutsñmomentary losses of signal; chrominanceñnoise (unwanted signals, not part of ours) in the video signal, which can be produced by the tape itself; luminance (brightness). We also rate audio performance. And last, mechanically, it must withstand a lot of play. The coating must provide durability."
VHS and SVHS (Super VHS) are different formats. Both come in standard and high grade. The hardware systems themselves record differently. On Super VHS a higher frequency is used to giver higher resolution and reduce noise. The tape is designed to handle the higher frequencies as wellóit has finer particles to handle the shorter wavelength. Cataldo said, "If I were to record a video from a laser disc, I would use a Super VHS to get higher definition and higher resolution and better overall quality. With the standard grade I would get the same resolution, but more dropouts and more noise." And to really benefit from Super VHS tape, Super VHS equipmentóVCR, TV, and/ or Camcorderówould be used.
What about computer chips? Cataldo responded that "It's still expensive to get so much memory."
(FIGURE #6: PHOTO OF LASER DISC WITH CAPTION: "Laser disc source.") [Photo courtesy of Pioneer]
"The laser disc is the only medium of higher end quality¼ It's very difficult to compare," said Judy Anderson of the Laser Disc Association. "In terms of comparison, lines of resolution is the best there is, but it isn't very good. It is generally accepted that laser discs have the highest lines of resolution¼ ¼ But, digital video will look good too."
According to Kim Yost, of THX, laser discs are considered the best widely available medium for seeing and hearing movies at home. THX has established a laser disc certification program to ensure discs are of superior quality. Because there are so many steps in the production of a disc, from the original film and all the transfers and manipulations in between, THX tests the discs at every important stage to reduce the possibility of compromise. The discs they certify are compatible with any system, but they have just instituted a laser disc player program, discussed later in this article.
+/- 2000 words.