For 60 years, USA tv signals and European ones, etc. were not compatible.
Did they make digital tvs compatible from the US to Europe to Asia to Australia, etc?
I think they should have. If not, is it only the 50 versus 60 vertical scan rate that was the problem?
I don't think I've read anything about this.
The following gives an indirect answer...
...which appears to be "no". There is no law of nature that prohibits a multi-voltage, multi-standard receiver, but there is a law of economics -- there's little or no demand for one, as it would be useful only to people who travelled a lot.
As for a single-inventory non-portable "universal" receiver... It would cost more than a set that received only the local standard, so, again, you have economics working against a multi-standard receiver.
Digital is neither NTSC or PAL. Those are exclusively analogue. It rather annoys that DVDs are labelled as NTSC and PAL when what they're referring to is a region.
--
*He who laughs last, thinks slowest.
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
It wasn't just a 60Hz/50Hz scanrate issue. NTSC is 525 lines (480 of picture), versus 625 lines (576 picture) for PAL. They also use different methods of modulating the color in the signal. SECAM is similar to PAL, but the color was different yet again.
It depends a bit on how you will view the signals. The basic HD formats (720p, 1080i) seem to be the same everywhere, so connecting an HD receiver (satellite or cable or similar) or something like BluRay or upconverting DVD would be somewhat universal.
Many electronics these days have universal power supplies, and can handle 110-220V@50-60Hz.
The hard part is if you want to use an antenna. Frequencies and even the way the digital signal is modulated will vary from country to country, not to mention the differneces in SD format.
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Digital TV has its own formats and standards. It is NOT a "digitization" of NTSC or PAL.
The latter, probably. Check with the Wikipedia article to get an idea of what the actual formats are.
Who are these "they"?
Sort of. Multisystem TV's Were common in the 1980's. There were only 4 systems of video, although there there were lots of ways to transmit them.
They were NTSC (60Hz, 3.57mHz color carrier), 50Hz PAL, 60Hz PAL, and 50Hz SECAM. There also was 405 line UK TV (dropped in the early 1980's) and NTSC 4.43 (same signal, color carrier moved to make cheaper playback equipment).
I still have a 1985 Sharp TV set that will play both NTSC versions, All PAL versions, and SECAM from anywhere except France. I had a 14 system VCR that would play and record French SECAM and a different TV set to play it on.
My kids use a 21 inch 4:3 CRT that is simialr, except that it does not have a French tuner. It added component and S-video instead.
I also have had VCRS that included digital TV standards converters. They were multisystem VCRs with the conversion feature added on top.
But digital TV was not needed, analog TV's played the signals fine. It was just a matter of adding the correct hardware.
The color carrier. NTSC used a phase modulated color carrier at 3.5mHz. PAL used a similar carrier at 4.43mHz. To fix a problem noticed in NTSC signals the BBC adopted the practice (which was in the proposed NTSC spec but dropped to save money) of alternating the phase every other line, hence the name PAL (Phase Alternating Line).
TV sets which would lock on 50Hz or 60Hz signals as appropriate were not a technical issue and by 1980 almost all made would anyway.
SECAM used a different decoding method, but those chips were easily found, and it was common to see TV sets and VCRS that would play/record SECAM signals broadcast using PAL over the air standards. Eastern Europe (Warsaw Pact countries), most Arab countires, China, and the USSR used some form of SECAM encoded signals with PAL frequencies.
The French used a different channel spacing, and AM sound, which made their SECAM signals impossible to tune with the correct tuner. It also made Eastern European TVs worthless in France and vice versa.
You either must have head your head under a rock, or live in the US and never traveled out of there.
Note that I had several multisystem TV sets, VCRS (BETA and VHS), and even a portable combination AM/FM/SW receiver and TV set that looked like a Star Treck tri-corder, all puchased in the 1980's in Philly.
Geoff.
-- Geoffrey S. Mendelson N3OWJ/4X1GM Those who cannot remember the past are condemned to misquote it.
Akai, Sony, Toshiba, JVC, NEC, Hitachi, Sharp, Panasonic (National), Memorex (Radio Shack house brand) are just the TV's and VCR's I've owned.
Geoff.
-- Geoffrey S. Mendelson N3OWJ/4X1GM Those who cannot remember the past are condemned to misquote it.
"Geoffrey S. Mendelson" wrote in news: snipped-for-privacy@cable.mendelson.com:
AFAIK,the TV systems are STILL incompatible; Europe uses different broadcast modulation schemes and different frequency assignments.
-- Jim Yanik jyanik at localnet dot com
The frequencies which suit small densely populated countries close together might well not suit a large one with large distances between centres of population.
--
*Starfishes have no brains *
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
"William Sommerwerck"
** False argument.The video signal that is digitised varies in the number of lines and fields per second.
PAL is synonymous with 50 fields per second.
NTSC is synonymous with 60 fields per second.
"NTSC" badged DVDs when played on most DVD players come out as " PAL 60" video - where the number of lines is correct but the field rate is 60 Hz..
The TV set in use must be able to cope with this.
.... Phil
I assume in this case you are talking about digital TV. It all depends upon how you look at it. I don't know about the pre-war 405 line English system, which finally was stopped in the 1980s. However the 525 line US system and and 625 line English/French systems were basicly the same, a "flying spot" of light, zero volts being white and about one volt being black. The scanning speed was the same, the US system had less lines because it scanned 60 times a second, the English/French 50.
A DC syncrchronization aka "sync" pluse was included to keep everything together so if signal got scrambled, the TV would bring it back together quickly.
Those rates were chosen because the studio lights were arc lights and flashed on and off at the power line rate, so the TV cameras had to be syncronized to them or you would get moving black stripes across the screen.
The RCA system for compatible color TV (compatible with black and white), used 1/4 of the color information based on the fact that your eye only sees about that much. The color information was encoded on a phase modulated
3.57mHz subcarrier, which at the time was beyond the picture information, but still within the transmitted signal.The original RCA system, alternated the phase of the carrier every line, so that it would fix itself if there was a transmssion or syncrhonization problem. To save money, the National Television Standards Commitee (NTSC) which chose the standard, dropped the alternating phase.
When the BBC adopted their 625 line system to replace the 405, they used a modification of the original RCA system with a 50 Hz field rate (25Hz frame rate) which gave them 625 lines. Because there was more modulation, 3.57mHz was still inside the picture, so they moved the color subcarrier up to 4.43 mHz. As an "in your face" they called the system PAL, Phase Alternating Line, to differentiate it from the NTSC choice.
The French used a different color encoding system called SECAM, which was also based on the RCA system (1/4 color, 4.43mHz color carrier) but designed to be totally incompatible so that you could not watch French TV in England and vice versa.
NTSC stands for National Television Standrds Comittee, PAL for Phase Alternating Line, and SECAM is a French acronym for what could be loosely translated as system of transmitting color TV.
Although the frame rates were different, and the color carriers at different frequencies, the information was basicly the same, and pretty much encoded the same way. So it was pretty easy, but expensive to build multisystem TVs.
Except for the people in the channel Islands, or on the coasts of England or France, there was no reception of signals anyway, so no one would buy them anyway.
As the 1960's progressed and TV spread throught the world, variations of NTSC, PAL and SECAM were adopted either because the standards fit the former colonial powers that ran the countries or they did not fit the country next door. So the UK used PAL, the French SECAM, Germany PAL (but modified so that the tuners would not work with UK signals), East Germany used SECAM (but modified to use the cheaper west German tuners) and so on.
So there were many ways of encoding the video, but it all came down to a number between 0 and 1 for brightness and 1/4 color information.
In the early 1980's satellite TV became a problem. Multisystem TV sets existed, once you put a signal up, there was no way to stop someone from receiving it if they could see your signal. In the US, the requirment for a Federal license for a satellite dish was dropped, and in many places there never was one.
HBO was the leader of the movement to prevent people watching these signals and pushed for a way of encrypting satellite video. What they did was to embrace the original MPEG-1 video standard, which was then encrypted using the US DES (Data Encryption Standard). DES was chosen because it was illegal to export DES chips from the US, which made it illegal to export HBO receivers.
The MPEG-1 standard was simply a digital compression based by taking the two relevant bits of information, brightness and color and combining them and using various mathematical compression algorythms. In the end though what went in was very much the same INFORMATION in an analog TV signal because that's what they had coming in and that's what they wanted coming out.
The MPEG-1 standard included various other things, such as the ability to have more than one video program, more than one audio channel per program, and several different digial audio compression choices from none to what later became MP3 (shortend form of it's full name).
Over the years there have been improvements to the MPEG-1 standard, to become the MPEG-2 (aka MP2) which is used in DVDs. DVD's for those that don't know are MPEG-2 video streams represented in flat files, with some extra indexing information.
In some places there was a short flirtation with encoding MPEG-1 signals on CDs (video CDs). Commodore made a version of the Amiga called the PC-TV, using the Philips system and I think there was a competing Sony one.
VCDs took off eventually because video tapes and players and later DVDs were taxed over 200% in some countries, but computers with CD drives were not. :-)
There are many compression techniques in use, but the ones used for TV transmission still work very much the same way, with the light level and color information being the same as it was in the RCA system.
The data transmitted is still almost universally MPEG transmission streams, with different compression and encoding methods. Because some countries still have TV sets that flash at 60 times a second and others at 50, the frame rates of 25 and 30 have been kept, but are really meaningless. There really are three rates in use, 24 (film), 25 (used for film and video) and
30 (video). TV set's just play them and whatever decoder box you use or disk player just converts them to the national standard that is expected of them.What is loosely called MPEG-4 standards have no frame rate per se, a frame changes only when the information on the screen changes. So a live action sporting event may have the full 25 or 30 frames per second, but a photo of two people watching a sunset in silence may only have 10 or 12.
As for over the air, there are three currently used systems of digital TV. It's up to the country to decide which standard is used in their country and I'm sure politics matters. The most common is the DVB-T (digital video broadcast terrestrial), which has been in use in the EU for a long time now. It's relatively simple, cheap to produce and unencumbered by expensive patents.
The US uses a system called ATSC (American Television Standards Committee), which is different than the DVB-T, although it does basicly the same thing. Compared to the DVB-T system, which is much older, it uses more sophistocated chips, with more expensive patent licenses.
DVB-T and ATSC tuners are incompatible. My guess is that was done so that US manufacturers could get a financial incentive for choosing that system, in terms of licensing fees, instead of fighting cheap knock-offs from China.
There are companies that manufacture dual DVB-T/ATSC tuner chipsets, they are targetd to laptops but will eventually find their way into pocket TVs for travelers.
The third system which I mentioned is Japanese in origin and is incompatble with the other two. I know nothing about it, except that a few south asian countries have chosen it.
So if you are still reading, the answer is basicaly that while the INFORMATION has not changed since the early 1950's, the way of encoding, compressing and transmitting it has changed, but that does not make it inaccessable.
While you could buy a multisystem analog TV or VCR to cross borders as it were you can still do so digitally. Since the videos transmitted are basicaly the same (MPEG transport streams) world wide, it's just a matter of a tuner chip if you go (signally) from country to country, and if you receive your signals in another method (over the internet, from a recording, etc), then they are pretty much the same.
Geoff.
-- Geoffrey S. Mendelson N3OWJ/4X1GM Those who cannot remember the past are condemned to misquote it.
"Geoffrey S. Mendelson"
** Everyone knows that NTSC stands for:" Never Twice the Same Color"
and SECAM =
" Something Essentially Contrary to the American Method "
.... Phil
As stupid as always. VITS took care of that over 30 years ago. That was long before you had your last cohernet thought.
-- You can't fix stupid. You can't even put a band-aid on it, because it's Teflon coated.
The real problem was not that the NTSC system did not have the autocorrection that was in the original design and used in the PAL system. The real problem was that there was a knob on the TV set that could make everything change color.
Even with the early 1960's transmission errors, and differences between the actual colors of various sources, if the color control was set and left at 'about right", it always would have been a watchable picture.
The problem was that almost no one had any clue of how to adjust it properly, and most were set and left in a very wrong postion, while others were being constantly misadjusted.
All of the TV magazines, science mags, etc had articles on how to properly adjust your TV set, and I'm sure that for everyone who read and followed them, there were 10 times the people who didn't.
It was really bad in area where there were many TVs, such as a department store. For some strange reason, the cheap TV's were never adjusted properly and the expensive ones always were. :-)
Geoff.
-- Geoffrey S. Mendelson N3OWJ/4X1GM Those who cannot remember the past are condemned to misquote it.
"Geoffrey S. Mendelson"
** Most any TV set has internal adjustments for colour quality as well as the usual external ones. However, each maker has their own ideas of how to set the colour balance ( or colour temp) of a screen - possibly to be technically accurate OR to look " nice " to most viewers.Means that a row of different TVs in a shop all look different.
Baffles the brains of nearly all potential customers who insist on the totally specious notion that they can immediately decide which is the best by just comparing them with their eyeballs.
A similar nonsense goes on with stereo speakers and other bits of audio gear too.
You have go NO hope WHATEVER of convincing anyone that merely looking at a pix on a screen or listening to a pair of speakers is NO WAY to tell how good either is.
.... Phil
Don't arc lights work on DC?
But I don't think that's correct. For it to work, TV would have to be mains locked. It was in the very early days, but later was pulse generator locked with no direct reference to mains other than being nominally the same frequency. Mains lock was really just to make receiver design simpler.
The only type of light I've seen which gives problems flicker wise on a TV camera is fluorescent. Before high frequency ballasts became available, the work round was to use them in groups of three - from different phases.
--
*No husband has ever been shot while doing the dishes *
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
You sort of danced around it. In the very early days is when the frequency was set. Once set it stayed.
That really was the point of my very long explanation. A long time ago someone decided to fix the scan rate and representation of data. The actual information used in all the TV systems was the same, it was just used with incompatable frame rates, encoding systems and transmission systems mostly for politcal reasons. TV sets that could receive, decode and play any and all signals existed.
The reason that everyone did not have a universal TV set was because the price was kept lower with single system sets and countries like the UK, which made a substansial income from the TV license did not want you watching tv from France or the Republic of Ireland for free.
From a technology point of view, it was obvious that the digitial TV standards MPEG and so on were designed with existing TV sets in mind. If not they would not have been a continuation of the old limited national standards with their horrible color encoding choice (1/4 of the resolution that the monochrome signal had) and instead gone with the more extensible, accurate and easily compressable RGB system used in computer data.
Geoff.
-- Geoffrey S. Mendelson N3OWJ/4X1GM Those who cannot remember the past are condemned to misquote it.
Actually, the sync pulses keep the horizontal and vertical scanning in the receiver at the same frequency and phase as the transmitted signal.
This might have been a consideration, but the principal concern was "hum bars" in the receiver. Modern power supplies are sufficiently well-filtered that this isn't a concern.
Actually, it's more like 1/3.
Actually, it was within the picture (luminance) information. NTSC has always had a potential video bandwidth of 4.2 MHz.
Actually, it was dropped because it didn't seem possible at the time to design a reasonably priced receiver that would take full advantage of this feature (in particular, the elimnation of the Hue control). Also, the US distribution system didn't have problems with non-linear phase, so PAL had little practical advantage.
Also, the original proposal used red and blue color-difference signals, rather than the more-efficient I and Q. The original NTSC proposal was virtually identical to PAL. (If you don't believe this, I have a copy of "Electronics" magazine that confirms it.)
SECAM stands for "sequential avec memoire".
SECAM was actually adopted because the French were idiots. They wanted a system that was relatively easy to record on videotape. Unfortunately, it made the receiver more-complex and expensive. A classic example of lousy engineering.
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