History of Television

Television provides the main source of information for many of us, and since the 1960 United States Presidential Election, it has helped us choose our leaders.

Let's take a quick look at the history of television and honor a few of the people responsible for bringing us a piece of furniture that entertains and teaches us.

Origins of Television

The first ancestor of the modern televsion was a little invention by Paul Nipkow in 1884 that consisted of a disk with holes spiraling into its center. Amazingly, this little disk shaped the development of television. Engineers like John Logie Baird and Charles Francis Jenkins, among others, used Nipkow's disk to create the first systems for scanning, transmitting, and receiving images in the 1920's. These first television systems were based on mechanical image scanning and receiving. Cathode Ray Tubes (CRTs) didn't exist.

Electric Television comes of Age

Electronic television systems lagged behind mechanical systems for several years, mostly because mechanical television was cheaper to build and it didn't use delicate parts. Not only that, but it was really hard to get financial backing to develop electronic TV when mechanical TV worked so much better at the time. With a cheaper system that already worked, few people saw the need to change. Then Vladimir Kosmo Zworykin and Philo T. Farnsworth made some critical breakthroughs, and electronic television began to catch up.

Vladimir Zworykin found financial backing from David Sarnoff, Senior Vice President of RCA. Sarnoff was watching mechanical television development and correctly predicted electronic TV would eventually be more commercially viable. Later, when Philo Farnsworth found some investors to back his ideas, he and Zworykin competed to get their electronic televisions to the public first.

Struggling to get TV going

Like any new technology, at the beginning, there is a chicken or the eqq situation.

How do you get someone to buy a TV if there are no programs to watch?

How do you create programming when there are few TV's that can view that programming?

All the players at the time made great advances towards commercial television and affordable TV sets. By 1935, both were broadcasting intermittently, using all-electronic systems. Baird Television was first in 1928 with an all mechanical television system.

At the time, very few people had television sets and the viewing experience was less than impressive. The small audience of viewers was watching a blurry picture on a 2 or 3 inch screen. The future of television looked bleak, but the competition for dominance in television broadcasting was hot. Iconoscope

The worlds fair create good PR

By 1939, RCA and Zworykin were ready for regular programming and they kicked it all off by televising the World's Fair in New York. Things moved quickly, and in 1941 the National Television Standards Committee (NTSC) decided it was time to write guidelines for television transmission in the United States. Five months later, all 22 of the nation's television stations converted to the new electronic standards.

In the early years, during the Great Depression, television sets were too expensive for most of the public. When prices eventually dropped, the U.S. was knee-deep in World War Two. But when a new age dawned after the war, the time was right for the Golden Age of Television. Unfortunately, everyone had to watch it in black and white.

TV in Color

CBS was the first to develop a workable color system year. This revolution was stiffled by the fact that the signal was incompatible with the huge number of black and white sets in homes around the country. Despite CBS spending a lot of money into their new color system, it was all for nothing. RCA, learning from CBS's work on a color system, built on their own color system. Soon RCA had a color system that could display on monochrome monitors too. The NTSC soon adopted it for commercial broadcasting in 1953.

Today, nearly 40 years after the introduction of Color TV, the system is essentially the same. There have been a few incremental advances, such as stereo sound, closed captioning, and better receivers, but nothing has come along to shake up the way we think about television. Finally we are moving to Tevevision 2.0. Now Television will be digital.

The United States is converting to both digital signals and high-definition pictures at the same time. While some countries already broadcast high-definition pictures, they use an analog signal. To send more picture detail, they just expanded the amount of frequency bandwidth for each. Broadcasters in the United States won't have the option to expand the size of their signal. They'll have to squeeze more picture detail into the same bandwidth they were using for analog television.

Why Bandwidth is Important

One advantage digital has over analog is that analog signals can't be compressed as well as a digital signal can. Transimitting an image on analog television, requires every pixel to be included in the signal. A standard NTSC screen includes 525 lines of 720 pixels, for a total of 378,000 pixels per frame. That's a lot, but it fits into the 6MHz bandwidth of a television channel. Japanese HDTV takes 20 MHz of bandwidth to send pictures with over 675,000 pixels. That's over twice as much signal to send a high definition picture and higher quality sound, but no other data.

In the United States, a standard ATSC (Advanced Television Systems Committee) screen can have up to 1080 lines of 1920 pixels each, or 2,073,600 pixels per frame. Somehow, more than five times as much information will need to squeeze into the same bandwidth of 6Mhz. That doesn't include the compressed audio or data. So how are they going to do that? Easy, they compress the digital data the same way we compress software on your computer. It's not exactly the same, but it's close.

MPEG-2 - Compressed Digital Signal

Video on digital TV will be compressed using a scheme called MPEG-2. MPEG-2 takes advantage of how the eye perceives color variations and motion. Inside each frame, an MPEG-2 encoder records just enough detail to make it look like nothing is missing. The encoder also compares adjacent frames and only records the sections of the picture that have moved or changed.(mpeg-2 compression scheme) If only a small section of the picture changes, the MPEG-2 encoder only changes that area and leaves the rest of the picture unchanged. On the next frame in the video, only that section of the picture is changed.

MPEG-2 is not perfect, but it's a good compression scheme and it's already the industry standard for digital video for DVD-Videos and some satellite television services. One problem with MPEG-2 is that it's a "lossy" compression method. That means that a higher compression rate gives a poorer picture. There's some loss in picture quality between the digital video camera and what you'll see on your television. However, the quality is still a lot better than an average NTSC image. This compression scheme allows the signal to be compressed to 2% of it's original size.

Compressing a file that much means there's a lot of information that get's thrown away, fortunately, we won't notice the difference. The human ear is not as easy to fool, though. It's much more sensitive to subtle changes in sound. Fortuneately, Digital TV is going to improve the sound by using some of the advances in digital audio from the last two decades.

Just like digital audio recordings on CD have a wider frequency range, finer sampling and allow almost everyone to hear an obvious improvement, so will digital audio improve the television experience.

Dolby Digital Sound

Taking the next logical step, HDTV will broadcast sound using the Dolby Digital/AC-3 audio encoding system. It's the same digital sound used in most movie theaters, DVDs, and many home theater systems since the early 1990's. It can include up to 5.1 channels of sound: three in front (left, center, and right), two in back (left and right), and a subwoofer bass for a sound you can feel (that's the .1 channel). Sound on digital TV will be "CD quality" with a range of frequencies lower and higher than most of us can even hear.

Advantages of a Digital signal vs. Analog signal

A basic natural law that our technology can't overcome is the weakening of television signals as they travel away from the transmitter and around or through objects. Both analog and digital signals get weaker with distance. However, while the picture on an analog TV slowly gets worse for more distant receivers, a picture on a digital set will stay perfect until the signal becomes too weak for the receiver to pick it up. By perfect I mean the picture on the TV is exactly the same picture the broadcaster started with at the transmitter. In a digital signal, a one is always a one and a zero is always a zero.

Digital broadcasters are not kust restricted to sending a high-definition picture. They can still broadcast a standard-definition picture, but why would they want to do that? There's a very good reason. In the same amount of signal they can "multi-cast" four standard-definition pictures instead of only one high-definition picture. (four channels of multicasted broadcast) Some broadcasters, including many PBS stations, are already planning to multi-cast four choices of programming during the day, and then switch to high-definition for prime-time. When you tune to your local Public Broadcasting station during the day, you may have a choice between children's programming, do-it-yourself shows, adult education, popular documentaries, or other programming. All from the same broadcaster.

Digital TV is going to offer us more choice, and it's going to make our viewing experience more interactive.

The Future of Television

Digital television is heading toward a convergence with computers -- and students, sports fans, news junkies, and anybody with an interest in anything will get more out of television. Nobody really knows how we'll interact with our televisions in the next few years, but TV is never going to be the same.

This will be possible because digital TV broadcasts are just long streams of bits that can contain any data the broadcaster wants to add to their signal. Each channel has about 19.2 Mbs (that's megabits per second) of data they can add to their broadcast. Most of it will be video and audio, but some of the signal can be other forms of data. Imagine a very fast network connection sending pictures, sounds, multimedia games, and illustrated articles, all related to the television program you're watching. You can still passively watch TV, but you can also customize the experience and make it your own.

Interactive television isn't really a new idea. Almost every television station sends data with their signals already. Closed captioning and descriptive audio are sent to millions of televisions everyday, but only a small percentage of the viewers actually see (or hear) any of it. These are a great benefit to those who can't hear or see the television, but they are very limited in their interactivity.

The convergence of television and computers is going to take a major step with digital broadcasts. Data will be sent along with video and audio. How we'll use the data is still largely unknown, but one of the more practical options is the set-top box.

The set top box will most likely start as something similar to the the DVR (i.e. Tivo ). A DVR work just like your VCR does, a set-top box will take input from the cable connected to your antenna or cable service, and output to your television.

The key difference is that the stored programming can be accessed in a non-linear way. You can watch any program at any time without having to fast forward or rewind the find the beginning. The set-top box will process the data sent with the broadcast, storing some of the data and executing applications. How it will do all this is still being developed. There are a few steps in the process which still need to be defined and implemented, including the format of the data, the set-top box's operating system, and the application environment.

Today, it looks like these set-top boxes will be based on something like Windows CE or Java. No matter which system is chosen, though, TV is becoming an interactive experience with endless possibilities.