From  Don McCroskey

Subject: Scan rate notes

 

The choice of the 525 line system adopted by the National Television Systems Committee in 1941 was far from arbitrary.  The RCA television development group headed by Elmer Engstrom conducted a series of studies on all aspects of television broadcasting from 1932 to 1933. A series of technical papers were published in the RCA Review and the Proceedings of the Institute of Radio Engineers delineating their findings.  The criteria for vertical resolution was based on observations of the angle of view that was preferred by people viewing paintings and projected images.  Most viewers preferred viewing these items at a distance between 5 to 8 picture heights.  Now, tests were conducted to determine how many lines were necessary so that the line structure would not be visible at this viewing angle.  This was done by using an embossed viewing screen to simulate the line structure of television image.  I believe, but cannot verify a reference, that these tests were conducted at 6 picture heights.  200-300 lines was judged POOR, 300-400 lines was FAIR, 400-500 lines rated GOOD, and 500-600 lines got a VERY GOOD grade.

 

The technology of 1933 was capable of fielding only a 240 line system. Resolution was a moving target. By 1936, RCA was showing a 343 line picture. Adoption of this standard was recommended by the Radio Manufacturers Association but rival manufacturers delayed the action. A 441 line system was shown by RCA in 1939, and a majority of the RMA members were again willing to approve it.  However, a strong minority (Zenith, Philco, Dumont) would not agree and the NTSC was formed to establish a consensus.  Philco promoted a 605 line 24 frame system. Dumont proposed a 625 line 15 frame (4 field interlaced) system. Zenith wanted to wait for even higher performance.  The majority felt that the latest RCA proposal of a 525 line 30 frame system was the best choice at this time--the Summer of 1941.  In less than 6 months, the entry of the USA into World War II set back the commercialization of television broadcasting for 7 years.

 

The adoption of our NTSC 483/485 line active scanning raster was well studied and contested.  It had nothing to do with size of the screens available at the time.

 

Actually, Dumont proposed such a system for NTSC.  This was for a 625 line, 15 frame, 4 field interlaced system.  About 10 years ago I asked Harry Lubcke, father of Los Angeles television, if he had seen it during the NTSC deliberations in 1941.  He had attended demonstrations and said that it seemed to work O.K.

 

Depends on what you have in mind with "shrunk color gamut". ... "the gamut area [of NTSC sets] was reduced because the new green primary was closer to red"

According to this thread, with the exception of only one very early and very expensive NTSC TV set, all TVs have had something approximating this "reduced gamut".

So my question is whether all this time TV cameras have remained ideologically pure and recorded pictures with colors that no one ever sees, or have they optimized their own primaries to better match what is displayed.

The implication is that if this be true, then improving the gamut of the display will attempt to display colors that are no longer in the signal, colors that have not sampled by the camera.

The cameras NTSC taking primaries are determined by the optical beam splitter color separation characteristics and are not adjustable. But the R-G-B mixing matrix usually offered several choices to give the "look" that the manufacturer felt would sell the product. A user adjustable matrix was often offered for "teachers".  Get a Mac Beth color chart and play around to get a feeling as to what you can do. But it's easy to get lost. You can move the colors around within the gamut, but you are not changing the primary coordinates.

Make a copy of a CIE chromaticity diagram and enter the coordinates for the specifications that Randy has given. Then draw the gamut triangle for each set and you will get a good appreciation for the limitations imposed by consumer color kinescope displays. It is not just the true greens that are shifted, but also the cyans. Another trick that was used in color receivers was to use demodulation axes other than 90 degrees (usually 110 degrees) to reduce skin tone hue shifts caused by transmission phase shifts. The name of the game has always been to show believable skin tones. The viewer usually has no reference with which to detect small hue errors in clothing and other areas. Not that the videotape archives are so great that this would necessarily make any difference...

Depends on the source and who is doing it. Networks "owned" a very small percentage of the shows they aired, and so had little control over how they are stored and preserved. It is expensive to obtain high quality transfers of first generation material, if it can be found. So the poor quality is often the result of an economical decision. Monochrome kinescope recordings, which were being made by networks just before the videotape transition, were of reasonably good quality. 35mm film with double system sound for the primary air copy, 16 mm sound on film for protection. For sound, ABC used 35mm full coat mag film, CBS used 1/4" Rangertone mag tape, and NBC used 16mm mag film; all interlocked to the 35 mm projector. About 3 years ago, PBS ran some retrospectives of the "Ed Sullivan Show" which were obviously taken from the original kinescopes. These were good examples of what was possible in the mid-50's. Vertical resolution had to be softened to avoid moiré patterns between the raster image on the film and the scanning lines of the telecine camera. Color recordings were another story. NBC pioneered a kinescope process using a lenticular film process. In 1959, color video recording was developed using a heterodyne color system similar to that used in today's consumer VCRs. It was being used as it was being invented, and there were approximately 18 recording/playback characteristics that were employed during its tenure. Ed Reitan was involved with a restoration of a Fred Astaire show that was done with this process.

There may be something about his travails on his web site which I gave you previously. As I remember, this was shown on PBS about 8 years ago. The color was pleasing, but it was generally soft.

A more interesting question might be who has video tape archives that are in good shape, and what prospects there are for "restoring" video now that a much better transmission channel is (theoretically) available. (And DVD is quite available.)

Watch the game show channels and the soap opera channels on cable and you'll see. CBS, Los Angeles, has 8 quadraplex machines doing this kind of transfer work. I believe they did about 20,000 hours of game shows 4 years ago. I asked how many 2" reels they encountered which were not playable. The answer: only 5! Now they're working on the soaps. Any bets on the playability of some of today's VTR formats 40 years from now?

This is probably more than you ever wanted to know about ancient history.

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Tri and Quad Interlace

From Jim Mendrala

Larry Bloomfield asked the question "If interlacing is good, wouldn't tri- or quad- interlacing be even better? If you support 1080i, why not go the distance and advocate 1620t and 2160q as well?  Where does it end? Why is it that 2:1 interlace is perceived as the best trade between motion/format conversion artifacts and vertical sampling?

Back in the late 1970's Quad interlace was actually tried in Hollywood. Vanderveer Film Effects and I working for Sonex International Corp. both did some research in that area. The reason at that time that it didn't go anywhere was that it was tried with "off the shelf" vidicon camera tubes which had an electron beam spot diameter that was optimized for the standard 2:1 interlace of the day. Even though the idea was to scan motion picture film with >1K resolution for special effects, the needed resolution was impossible to achieve with the "off the shelf" camera tubes available at that time.

A few years later Hitachi did make a Saticon tube with a much finer electron beam spot diameter with approximately  5,000 lines of resolution. It was shown at the NAB held in Dallas around the later part of the 70's or early 80's. To my knowledge It did not become a marketing success. Later high definition cameras utilizing Saticon tubes were used to televise the XXII Winter Olympics from Osaka, Japan.

In regards to the statement that 2:1 interlace being perceived as the best trade off, well if you are to broadcast an image within the 6 MHz channel in real time I guess it is the best trade off. A 3:1 or 4:1 interlace at 30 fps would have way to much bandwidth for the broadcasters 6 MHz channel. In the film application mentioned above, real time was not a factor. Electronic scanning even today for example from Kodak's Cinesite takes upwards of 8 seconds per frame at 4K resolution and about 4 seconds per frame at 2K resolution.

In my garage I think I still have the prototype sync generator breadboard with it's 4:1 interlace. 

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What's in a name?

By Larry Bloomfield

Say "KFI, WOR or WGN" to most anyone in Los Angeles, New York or Chicago and they will almost immediately think of a radio station that's been broadcasting for over 75 years. As the result of international convention, countries around the world have agreed to identify their various broadcast stations with letter and/or numerical designations. The letter identifiers are referred to as "Call Letters" and the combination of letters and numbers are referred to as "Call Signs." The first letter or number usually identifies the country of origin. For example: "C" is used in Canada, "D" in the Philippines, "X" in Mexico, and "A,” "K," "W" etc. here in the United States.

Most people think that the K's are used only West of the Mississippi and the W's are east. Although this is generally true, there are currently 26 "Ks" calls in use East of the Mississippi and 32 "Ws" calls West of the Mississippi. There several thousand call letters in use, at last count. To confuse the issue, television translators and some low power TV stations use either a K or W to start with followed by the channel they're on and then two letters. Even this format is changing.

The changing face of Station Identification. -- Most broadcast stations have four-letter call signs, but not all. Approximately 180 AM stations received three-letter calls in 1921 and 1922 before it was necessary to start assigning four letter calls to the flood of broadcast applications. As of March, 1997, there are only 56 original three-letter AM broadcast station calls in active use.

The longest licensed station holding its original call is still, KDKA, Pittsburgh, PA, which was assigned in October 1920. For some reason the application from

Westinghouse was processed on the same day along with ship license applications and received its call in sequence between the vessels "Montgomery City" (KDJZ) and "Eastern Sword" (KDKB). Subsequent broadcast (fixed land) stations, like the maritime coast stations, were assigned three-letter calls. After KDKA, Westinghouse was licensed in early 1921 to use WJZ at Newark, NJ. WJZ that was changed to WABC in 1953.

Want more? Well on April 4, 1922, WAAB, "The Times-Picayune Station", New Orleans, was the first to receive a four-letter call from a new sequence to be assigned for broadcasting. (The call WAAA was skipped.) When WAAZ was reached the calls jumped to WBAA, still operated by Purdue University in Indiana.  For broadcast stations the third letter was kept as A. Thus many early famous stations had calls such as WBAA, WBAP, WCAU, WEAF, WFAA, WMAQ, etc.

The three-letter broadcast call sign in longest continuous use is WBZ in Boston. It was licensed on September 15, 1921 to Westinghouse. The longest continuously used three-letter call starting with the letter K is KWG, Stockton, CA. And by the way, you know those K's east of the Mississippi? Well, also in September, 1921, Westinghouse was assigned by administrative chance or error, the call KYW for the station is still operates in Philadelphia, PA

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By Larry Bloomfield

Actually, in the books I referenced it states pretty clearly that once everyone settled on the same NTSC scanning standard the viewer's risk of buying the wrong receiver was resolved, and the FCC allowed experimental stations that were operating as of 1949 to begin accepting fees for commercials.

The television standard in the United States is 525-line 60-field (30 frames). The 625-line system used in Argentina, Paraguay, and Uruguay. Unlike the other 625 line systems,  fits into a 6 MHz channel.

The FCC authorized commercial television broadcasting on July 1, 1941 and most of the experimental stations changed their call signs to standard broadcast station call signs on that date. In New York, NBC's W2XBS became WANT (now WEB) and CBS's W2XOY became WEB (now WEBS-TV). In Philadelphia, Pico's W3XE became WETS (now KEW-TV). The DuMont station in New York, W2XWV, remained an experimental operation with an experimental call sign until 1944 or 1945, when it became WAD (now WYNN). Some of these companies retained experimental licenses for the UHF band or for other reasons, but these experimental stations could not accept money for any commercials simulcast from other stations, nor could they sell advertising themselves.

By 1949, most of the remaining experimental stations were used for development of UHF transmitters, as the FCC explored the possibility of moving television to the UHF band after imposing a freeze on TV station construction in 1948. DuMont had operated WAD commercially on Channel 5 and KE2XDR experimentally on UHF around 1950 or 1951.  

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A German fellow by the name of Fritz Pfleumer, building on an 1898 design for a magnetic tape recorder, discovered that by coating paper with a magnetizable powder he could reproduce sound. Later versions substituted plastic for the paper. By 1939, a related invention was announced by Bell Laboratories -- It was a wire recorder. I'll bet that was fun to splice.

In those Early Days

Of all the radio stations on the air, which one was the first to begin "daily" commercial broadcasts? It was a station located in Detroit, MI with the call sign of 8MK and it began commercial operations on August 20, 1920. It has continuously served Detroit for 77 years and is known today as WWJ. 

And then someone added pictures. Television has been around for a lot longer than you most folks would suspect. The first experimental television station on the West Coast went on the air on December 23, 1932 as W6XAO atop Mt. Lee just north of the little hamlet of Hollywood, CA. This station became KTSL. It was later purchased by CBS, became KNXT and the transmitters were moved to Mt. Wilson, just north of Pasadena, CA. Mt. Wilson has the highest concentration of broadcast transmitters (Television and FM) of any location in the United States and quite possibly the world. The remnants of W6XAO, their tower, can be seen in pictures just above the notorious Hollywood sign. Both the City and County of Los Angeles now use the tower for their public safety services. 

The FCC granted two commercial (not experimental) television station licenses at the same time on July 1, 1941. They are reputed to be the first "commercial" television licenses issued in the United States. They are WNBT issued to NBC (RCA) & WCBW issued to CBS. Both were in New York City. 

Harry Lubcke, the Chief Engineer of W6XAO, gave a talk to a group of engineers several years ago. When asked why they operated during the hours they did, he said that the reason for the original broadcast hours, from 6 to 7 PM, was so that the staff could get home for diner at a reasonable hour. A young lad could be overheard whispering to the person sitting next him: "How could they exist not being able to see more than an hour of TV and I'll bet they weren't even on the weekends."

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Ditty Dumb Dumb Ditty

Guillermo Marconi wasn't the first one to ever transmit a message by what was then known as the "Wireless." What he did do in 1901 was to prove that communications over long distances was possible when he transmitted the first wireless message, using Morse code, across the Atlantic Ocean via radio waves.

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Not all discs are flying saucers!

It all started back in 1877 when Thomas A. Edison recorded on cylindrical "records." Shortly there after the 78 RPM records became the rage. The first electric jukebox, which was called the "audiophone," took the place of the wind up Victrola. It was invented around 1927, by J. P. Seeburg in Sweden. You had a choice of eight records to choose from. It wasn't too long after that the expression, "Gee dad, it's a Wurlitzer," came into vogue. They all sported 78's. The 78 gave way to the 45 and in 1947 CBS came out with the 33-1/3 RPM vinyl disc, which sported the nick name of "LP." Although several forms of magnetic tape, such as the 2 track and 4 track reel-to-reel in 1957 and then followed by 4 and 8 track cassette held sway for a while, we found our way back to the disc again when the CD hit the streets. Today we still have the disc, but as a DVD, it holds ten times the information contained on those early CDs. The new FDVDs (Flourescent Digital Versatile Disc) is said to hold more than 10 times that!

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To Beep or Not to Beep

The first pager or beeper became available as early as 1949. It was a huge cumbersome thing that ate batteries like a kid with a candy bar and it cost a mint. Not too much improvement was made and the features were few and far between. Coverage was a problem in those early days too. As late as 1975, pagers were still the size of large cigarette packs and did little more than make noises and when you could understand them it seemed like a miracle. As technology improved the pagers became smaller and the features improved and coverage increased. There's hardly a place in the United States where you can't be beeped today. As recently as December 1995, Motorola offered a unit that not only received messages, but it would send a reply as well.

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Progress means change

We've seen several major changes and additions in the development of television over the years. Change should not be anything new to any of us. Probably the first significant change was when the decision was made to adopt an all-electronic scan system, replacing the mechanical disc.

Frequency and channel allocation changes are not uncommon to our industry either. In the early days when Television Productions, Inc., W6XYZ (Paramount Pictures excursion into early television) first signed on the air in Los Angeles, they were on Channel 4. With FCC changes, their commercial successor, KTLA, operates to this day on Channel 5. The same action that made that channel change, also did away with Channel 1. The John Pool experimental UHF station on Signal Hill, just north of Long Beach, California, first operated on a frequency somewhere close to the modern day successors, KWHY, Channel 22. The same kinds of things were happening all over the United States.

Since the very first black and white picture was produced, someone said: "Why isn't it in color?" Two main systems survived until the end; the CBS color wheel and the RCA all electronic system. It is logical that the next significant change happened when an all-electronic color system was settled on in the late 50's. It may not have been the best system, but we've been living with it for over 40 years. We've gone from image dissectors and iconoscopes, which required hundreds of foot-candles of light, to the CCDs, and other devices, which will produce a very clean and clear picture in almost total darkness. And let's not forget the addition of Stereo, SAP and Pro audio. I'm probably leaving some things out that you may think are important, but you get my point. Oh and by the way, don't sell your CBS color wheel stock, a projection system, developed by Texas Instruments, the Digital Mirror Display (DMD) uses color wheels and it looks great!

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Stereo Audio In the Beginning

by Jim Mendrala

The 1984 XXIII Summer Olympics opening ceremonies were broadcast in stereo to the Los Angeles area via KABC-TV. The audio from the Coliseum was brought back to the studio as Lt and Rt. The audio after mixing was sent to the transmitter where it was encoded and transmitted in stereo. It was believed that their were only 200 TV sets in the greater Los Angeles area that could receive the stereo signal. Only Los Angeles got the stereo broadcast as the ABC network didn't have a second channel available for the stereo. The rest of the nation had a Mono (L+R) feed.

The night before the opening ceremonies KNBC-TV transmitted the "Tonight Show, Starring Johnny Carson" in stereo. Ron Estes had recorded L+R onto the main track of the VTR and a L-R onto the cue track of the VTR. When NBC heard that ABC was to transmit stereo for the Olympics they couldn't wait to be first. Ron Estes, who almost lost his job at NBC because of using the cue track for the "difference" signal without permission, was a hero. 

Ron Estes and I both worked at KOGO-TV in San Diego prior to coming to Los Angeles. We had many good ideas about two, three and more channels of sound to enhance the viewing experience. We, along with Bob Marankovich, who I believe still works at CBS, were planning to start a stereo post-production service in the Hollywood area back in the late 60's but couldn't find financial backing. We were ahead of our time!

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ACR-25 vs. TCR-100s

By: Charles Hintz

 

When I left Sony Training in San Jose in 1988, I was AMAZED to see ACRs running as I thought BetaCart had cornered the market. KTVU bought 1Betacart in 1994 and that was the end of the Quads (no tape stock!). A failure for an ACR included a thread crash. The 200mS pre-roll was hard to beat! TCR had a 2 second pre-roll though most used more, especially later.

The secret of ACR operation was matching transistors in the MDAs. KTVU was down to one ACR glitch about every 2 - 3 days (of 24/7 operation). A real "repair" was required only 2-3 times a year by the time I settled in at KTVU. They had 3 machines running and a forth 'parts machine' when they called in BetaMan in 1994! The machines were sold to TV-20 where the ran another 3 years!

ACRs required the hiring, training, and retention of good technical staff - something the used refrigerator salesman upstairs never caught
on to. When RCA Broadcast bit the dust in 1984, that was the end of TCR service life although Bill Bowen managed to keep some limping along past 1990!
 

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