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TVs compatible, from one continent to the next??

Discussion in 'Electronic Repair' started by mm, Jan 8, 2011.

  1. mm

    mm Guest

    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.
     
  2. Did they make digital TVs compatible from
    The following gives an indirect answer...

    http://en.wikipedia.org/wiki/Digital_terrestrial_television

    ....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.
     
  3. Smitty Two

    Smitty Two Guest

    The North and South American standard is NTSC, which transmits 30 frames
    per second, while PAL, used in Europe, is 25 frames per second. The
    switch to digital didn't affect that.
     
  4. 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.
     
  5. 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 [email protected]

    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.
     
  6. The North and South American standard is NTSC,
    Digital TV has its own formats and standards. It is NOT a "digitization" of
    NTSC or PAL.
     
  7. Smitty Two

    Smitty Two Guest

    Digital TV has its own formats and standards. It is NOT a "digitization" of
    NTSC or PAL.[/QUOTE]

    Nevertheless, European TV is still 25 fps, and US TV is still 30 fps, is
    it not? Or am I more confused than normal today?
     
  8. Digital TV has its own formats and standards. It is NOT
    The latter, probably. Check with the Wikipedia article to get an idea of
    what the actual formats are.
     
  9. Who are these "they"?
     
  10. 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.
     
  11. 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.
     
  12. The frequencies which suit small densely populated countries close
    together might well not suit a large one with large distances between
    centres of population.
     
  13. Phil Allison

    Phil Allison Guest

    "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
     
  14. 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.
     
  15. Phil Allison

    Phil Allison Guest

    "Geoffrey S. Mendelson"


    ** Everyone knows that NTSC stands for:

    " Never Twice the Same Color"

    and SECAM =

    " Something Essentially Contrary to the American Method "



    ..... Phil
     
  16. 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.
     
  17. Phil Allison

    Phil Allison Guest

    "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
     
  18. 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.
     
  19. 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.
     
  20. A DC synchronization aka "sync" pluse was included to
    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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