You can always tell the pioneers; they are the ones with the arrows in their backs. We Americans were the pioneers of color television and have had arrows sticking in our backs (or a bit lower) ever since. In 1953 our National Television Systems Committee (NTSC) standardized how color TV signals would be made (although some would argue that American TV has no standards whatsoever). Because the system had to be totally compatible with a well entrenched black & white system, the design involved many compromises. Although our NTSC system was electronically amenable to modernization, its infinite range of subjective adjustments (hue, saturation) lead cynics to refer to NTSC as "Never Twice the Same Color". Our pictures are made of 525 lines displayed nearly thirty times per second. The United States and Japan are the biggest users.
Color came to parts of Europe and Asia in the sixties, and by then technology had improved. France instituted SEquential Couleur Avec Memoire (SECAM) in 1962. From there it spread with some modification to the Soviet Union, parts of the Middle East, and eastern Europe. Critics at the time dubbed it "Something Essentially Contrary to the American Method". Color information is transmitted sequentially (R-Y followed by B-Y) for each line. The system required very simple video recorders, is impervious to many time base errors, lacks many of the color problems we have with the NTSC system, but was not fully black & white compatible. This didn't matter much to its proponents at the time because there was not a large installed population of black & white TVs. The system makes pictures comprising 625 scan lines (sharper than NTSC's 525) at 25 frames per second. Why 25? Most foreign electric power is at 50 Hz, making it easy to produce 50 fields per second; in the US, the electricity is 60 Hz making it easy to produce 60 fields per second. Why the US changed from the black & white standard of 60 fields per second to a color system of 59.94 is a long technical story I'll mercifully spare you.
In 1966 England, West Germany, and Holland introduced to the European market Phase Alternate Line (PAL), an improvement over the pioneers, NTSC and SECAM. At the time, engineers affectionately called it "Peace At Last". It consists of 625 lines per picture at 25 frames per second and reverses the relative phase of the color signal components on alternate scanning lines. NTSC and PAL colors are encoded similarly, but PAL TV sets require some extra circuitry making them more expensive than their NTSC brothers.
Since the '60s there have been further modifications to each of the standards. There's PAL-I, B, G, H, M, N, and SECAM D, L, K, etc. all describing variations in the color subcarrier frequencies, scan rates (frames per second) and number of lines per field. Put it all together and what does it spell? Headaches for anyone producing tapes in one country for playback in another. Additional migraines come to those who discover differences in electrical outlet voltages and even the shape of the plugs and pins on foreign TV equipment. And just one more throb to the cranium: TV signals in foreign countries are broadcast on different frequencies from us (making your TV or VCR tuner useless overseas) and they combine the sound with the picture in different ways in different countries.
How do you play a tape that arrives in the mail from Brazil or Bulgaria (assuming you're reading this article in the US)? Options:
1. Convert the foreign tape to NTSC.
2. Play the tape on foreign standard-capable equipment. Standards
converters cost about $1000-$20,000 (depending on quality). Having
a tape copied to another standard at a duplication house costs
$50-$300 per hour (depending on quality). And, depending on quality
(notice a recurring theme here?) you will see strange artifacts
(jitter, judder, smearing, weird motion) on your converted tape.
But I'm getting ahead of myself here. Let's start low tech and
work our way up.
Cheap solutions - The best converter is no converter. Don't mess with the signal and you won't mess it up. Play your foreign tape on a foreign VCR and TV and everything will look exactly the way it should. All you need is about 18 VCRs and TVs to cover all the bases. Or, you could buy a multistandard VCR that can play NTSC, PAL, SECAM, and all their cousins. Just because a multilingual VCR can play a tape, doesn't mean your TV can show it; you also need a multi-standard TV set, capable of displaying NTSC, PAL, SECAM, etc. Multi-standard VCRs and TVs generally cost about 50% more than their single standard counterparts. One company specializing in multi-standard VCRs, monitors, and video tapes is Cartridge King, 825 West End Avenue, New York, NY 10025 (212-749-0961). Duping houses that are called upon to make 100 PAL copies of a PAL master, will use multi-standard VCRs for their dubbing.
Instant Replay (2601 S. Bayshore Drive, Miami, FL, 33133) came up with a different solution. They modified NTSC VCRs so that they could play PAL and SECAM tapes yielding signals that could play on NTSC TVs. You might not see a color SECAM picture, and the picture might look slightly squashed, but you could at least see the image. You couldn't record Instant Replay's output on an NTSC VCR expecting to make an NTSC tape. The VCR didn't convert PAL or SECAM to NTSC; it only made the recording viewable on your TV.
Instant Replay makes its Image Translator 610 IT4 VCR (catchy name) for about $850. This may be the answer for the person who occasionally needs to view foreign tapes, doesn't care about SECAM color, and doesn't mind making a few TV adjustments. More recent VCRs from Instant Replay actually convert foreign TV signals into recordable NTSC signals, as well as making them viewable on NTSC TV sets. Costing $1295 to $2195, these VCRs may have two heads, four heads, or may work in Super VHS with hi fi. Their 77IT6 Image Translator VCR incidentally, not only records and plays Super VHS at 400 lines resolution, but will even make SVHS recordings using regular VHS tape (with some degradation of picture quality).
The Image Translator VCRs are single voltage machines designed for use in the US playing foreign tapes. If you want a VCR to take with you to foreign countries, try one of their $2395-$2795 World Traveler models. It runs on 50/60 Hz, multivoltages, has a tuner able to pick up foreign stations and can record in NTSC, PAL, and SECAM. It will convert SECAM and PAL to NTSC yielding a recordable signal. You can play PAL and SECAM tapes unconverted, in PAL or SECAM standards. You can play SECAM and NTSC tapes on PAL TVs (meaning you don't have to lug your TV from home, you may be able to use the foreign TV in your hotel room). The RF generator even switches to the foreign standards so that you can connect to a foreign TV's antenna inputs. You can't record NTSC, however, and convert it to PAL or SECAM with the machine. In short, the World Traveler covers most of the bases for those who won't leave home without their VCR.
Another popular low cost VCR/standards converter is the Panasonic AG-W3. It will record or play back in PAL, SECAM, NTSC, N-PAL, M-PAL, or ME-SECAM, and will transfer any of these standards to any of the others. This $2000 wonder can work as an interformat converter alone (just using its inputs and outputs) or as a VCR. In the play mode, it automatically recognizes the type of recording, and switches itself to the appropriate standard. You manually select the output standard desired (ie. NTSC). It will also throughput a signal with no conversion, working like a regular VCR. It will play and record Super VHS. It plays hi fi and can run on 110 or 220 volts AC (found in many foreign countries).
Comparing the AGW3 with similar Instant Replay VCRs, the AGW3 converts a greater number of standards from one to another than does the Instant Replay. The Instant Replay, however, costs a little less, includes a multi-standard tuner/timer, and includes an RF out for common TV sets(foreign and domestic). Professional solutions - The VCR/standard converters costing around $2000 make a fairly decent picture, satisfactory for most consumers and prosumers. At this price, however, neither can put horsepower into motion processing, and that's where the big guys come in.
Three things happen when you convert from one standard to another: 1. The number of scan lines in the picture has to change (625 to 525 or vice versa). 2. The number of pictures per second has to change (25 fps to 30 or vice versa). 3. The color encoding method has to be changed. There are presently five different systems for making color.
Somehow the standards converter has to delicately excise 100 lines of a PAL or SECAM picture without the viewer missing them. Going in the opposite direction, a 525 line NTSC picture has to have 100 lines added before it can become PAL or SECAM. Somehow information from those 525 lines has to stretch.
Changing from 25 frames per second to 30 and vice versa presents a similar conundrum. Somehow the converter has to manufacture 5 extra frames per second for NTSC, or dispose of 5 frames when converting to PAL or SECAM. When a TV picture is standing still, no one notices the added or missing frames, but when something moves across the scene or the camera is panned, suddenly you see "motion jitter" called judder , or you see "smearing".
It is hard for a converter to yield sharp pictures with motion. If the converter simply drops frames or repeats them, you see a juddery picture with the right number of frames per second. If the converter uses "interfield interpolation" to create new pictures by averaging adjacent ones, the moving image gets smeared. One solution is "adaptive motion interpolation whereby the converter looks for stationary parts in the scene and doesn't process these parts (except to add/subtract lines or frames). Moving parts of the scene must get targeted and treated specially.
The evils of motion are easily hidden by fuzziness, and your eyes aren't too sensitive to the sharpness of moving objects anyway. Many of the converters take advantage of this fact by determining which parts of the picture are stationary, letting that signal pass through with high resolution. The fast moving parts of the picture, however, go through motion adaptations and sometimes bandwidth reduction, making them fuzzy, but less jumpy. The big difference between one professional converter and the next is its method of motion handling.
Motion compensation algorithm - You'll only care about the following technobabble if you plan to buy a standards converter - it describes the finer points of what to look for.
Spatio-temporal gradients (also called pel-recursive gradients) are one method of tracking moving objects. Moving objects tend to have a blurred edge in their direction of motion. The faster the movement, the longer and more gradual this blurred "gradient". Because edges of objects are often poorly defined, this calculation is made over several fields to improve the estimate and accuracy. The process is relatively simple (less expensive) and yields good resolution, but gets confused by some images (CCD vs. tube cameras, enhancement, noise reduction, digital data compression). Cuts and complex moves such as rotations also baffle the converter.
Block matching is a process of dividing the image into tiny blocks, about 8 pixels by 8 lines each, "memorizing" the content of each block, and in the following field, trying to see where they went. If they stayed the same, they received relatively little processing. If a block changed, the converter would make a search in every direction from where the block was, looking for a match. Farther and farther out it would look, and when the block was "matched," the converter would calculate how far it moved and in which direction, storing this data momentarily as a motion vector .
This vector could be used to calculate where the block was likely to be in a subsequent field or in an inserted field. The process is fairly inexpensive for low resolution applications, but becomes complex (expensive) for high resolution video. Because of the computing power needed to search in many directions (64 for an 8 x 8 block) and great distances (32 pixels sometimes) tradeoffs are made. The system can detect fast moving objects, but loses small objects (fine details). Or it tracks small objects while losing fast moving ones.
One of block matching's weird artifacts is that sometimes the edges of an object get confused with its background and the whole works gets transported. The golf ball when struck carries the grass background with it (or maybe that really was grass). Phase correlation , a third algorithm, is highly complex, but has excellent resolution, works with quick motion, has few artifacts, and doesn't get confused easily. The video signal undergoes a mathematical Forier Transform, whereby the waves representing the signal are compared one field to the next. The phase differences between the spectra are compared and objects in motion are represented by peaks in a new three dimensional wave that looks like rolling plains with mountain peaks. It is computationally efficient for the computer to track just the mountain peaks and assign motion vectors to just those parts of the picture. The process is expensive, but elegant.
Other features in standards converters - There are very few 7 bit models around, but the 8 bit converters are preferred, yielding twice the number of shades of gray in the digitized image.
To do a really nice job, requires an eight bit converter. Four field machines track motion more accurately over a longer period than 2 field models, and thus can make better predictions about motion. Some converters compare 6 or 8 fields. Film-to-NTSC-to-PAL or SECAM -
Converting movie film to tape in Europe is easy. Movie film runs at 24 frames per second. Television runs at 25. By running the projectors 4% faster than normal, the film rate matches the video rate making film-to-tape transfers a snap. In the U.S.A., the process is way more complex. If we sped the film speed up to our 30 frames per second, the Minute Waltz would last only 48 seconds and everyone would sound like they'd been breathing helium. Our film-to-tape transfers require a more complex technique.
Using a system called 3:2 pulldown , we display film picture number 1 for 3 TV fields (3/60 of a second total), then move to picture number 2. This we display for 2 TV fields (2/60 of a second). The next picture we show for 3 fields, the next 2 fields and so on. At the end of a second, after 24 movie pictures have been played, 12 have been converted into 24 TV fields (2 times 12), and the remaining 12 have been converted into 36 TV fields (3 times 12). The sum is 60 TV fields, just right for video (the actual number comes to 59.94 fields per second, but that's a minor electronic detail).
If you projected a movie so that one picture stayed on the screen for 2/60 of a second and the next picture stayed on the screen for 3/60 of a second, followed by 2/60, then 3/60 etc., you would see slightly jerky motion. It wouldn't be as smooth as if the pictures were played evenly at 24 per second. Our American TV-eyes have grown used to this slight jerkiness. Interestingly, most of us can tell immediately when a TV picture is shown live or shot directly on video tape, as opposed to shot on film. We've grown so accustomed to the jerkiness that perfectly smooth motion startles us.
Before proceeding much further I should note that professional American film shot-for-video is nowadays imaged at 30 frames per second, yielding a simple conversion process without jerkiness. Converting 24 fps film to 30 fps video yields jerkiness. Converting 30 fps NTSC video to 25 fps PAL/SECAM video adds a second layer of jumpiness, making the image too stroboscopic to enjoy. Normal standards converters equipped with motion processing get confused when the motion isn't steady. Current temporal interpolation techniques operate by continually sampling four adjacent fields in weighted ratios. If the four fields do not have a continuous temporal flow as in the case of 3:2 pulldown, the results are appalling.
The solution is to use a standards converter that takes the film jerkiness into consideration, then calculates for it. Snell & Wilcox of Hampshire, England developed the Digital Electronic Film Transfer (DEFT) system which fixes this problem with a that stores 8 fields digitally and takes note of where the pulldown occurred, compensating for it. The resulting image looks almost indistinguishable from the original film.
In the U.S. we use 110 volt house current. Many other countries use 220 volts. Their wall sockets are also different from ours.
Some video equipment, especially battery chargers will work with 110 or 220 volts. Some require you to throw a switch to convert the device to the proper voltage. In these cases, all you need is a simple adapter plug which changes the bladed plug on your U.S. charger to the rounded prongs found on European gear. Most other U.S. video equipment requires a transformer to change the foreign 220 volt AC into 110 volts. The more watts a machine requires, the bigger and heavier the transformer needs to be. Transformers for a 5 watt electrical shaver are the size of your thumb. Transformers for 1000 watt hair dryers weigh 25 pounds. One place to obtain transformers is a company called Magellans in Santa Barbara, California (call 800-962-4943 for catalog).
Remember that most of Europe uses 50 Hz AC power while we use 60 Hz. Some machines, especially those with motors, will slow down when fed 50 Hz. Also, the power transformers in some 60 Hz devices overheat when fed 50 Hz.
I advise most of my friends traveling
abroad to bring U.S.A. battery powered equipment with them and
chargers capable of working at various frequencies and voltages.
Such chargers are pretty common and lightweight. This way their
TV equipment never comes in direct contact with the electrical
systems, always being fed by the batteries. If anything does go
wrong, only the battery charger or battery get fried. Low wattage
LCD TV monitors (Citizen makes one costing about $160) are handy
for viewing footage using batteries. If you have to run non-battery
devices, you can buy an inverter which converts DC power from
batteries to 110v AC.
STANDARDS CONVERTERS MENTIONED IN THIS ARTICLE Panasonic 1 Panasonic
Way Secaucus, NJ 07094 201-348-7000 Instant Replay 2601 South
Bay Shore Drive Suite 1050 Coconut Grove, FL 33133 305-854-8777
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