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Fields per second vs. Frames per second

Discussion in 'Electronic Basics' started by Radium, Oct 21, 2006.

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  1. Yeah! That's it!

    Thanks, Jukka (is that your given name or family name? I know that some
    Ugrics put their family name first, but I don't know about the Finno
    branch... :) ).
     
  2. On the other hand, it was in a reply to *my* post, not Grise's, and
    right below a comment of mine. Also, it was not particularly in any
    context of those posts.

    As I said, it was the nicest thing anyone had said to so far in the day
    :)
     
  3. Jukka Aho

    Jukka Aho Guest

    "Jukka" is my given name. Finns usually prefer marking their last name
    last, where possible. Common exceptions to this rule are alphabetized
    catalogs (such as phone books) or official forms and certificates (such
    as a driver's license, or the form you would fill when applying for
    one.) Those would typically place the last name before the given
    name(s).

    I have a second and a third given name as well, but I don't usually use
    the full form of my name, except if required by authorities or some
    other sort of bureaucrats. Those two other names really only live on
    paper and in official registers. I've sometimes considered taking the
    initials in use but have not yet found any sufficiently compelling
    reason for that. There just haven't been too many incidents where I
    would have been mistaken for someone else by the same name - even though
    there _are_ people by the same name.

    * * *

    The etymology of the name "Jukka" is discussed here (this is one of
    those "more information than you could possibly want" pages, but there's
    a brief "executive summary" at the beginning):

    <http://www.cs.tut.fi/~jkorpela/jukka.html>

    My last name ("Aho") means "a clearing in the forest; an open field".
    Not particularly poetical, is it? The meaning is all but forgotten now,
    though, and the word is not really actively used in that sense any
    longer. I don't think too many among the younger generation (or among my
    own generation, either) are even aware that it _has_ a meaning. For them
    it's "just a surname".
     
  4. Bob Myers

    Bob Myers Guest

    I realize now that it may not have been clear that I'd switched
    contexts in the above, from film-originated material to interlacing
    in general (and more specifically, the sort which originates AS
    "video", i.e., what comes out of a standard TV camera.
    Yes, but that's exactly where the "motion problem" in
    interlaced material (again, that which originates that way,
    from a camera) comes into play. You DO average out
    successive fields, but since they're being presented in an
    interlaced manner (at least in a properly-adjusted receiver
    or monitor), the effect is a blurring of details. This is one
    of the reasons that an interlaced system doesn't actually
    deliver the resolution one would assume from the scan
    format. For instance, the 525/60 scanning standard (as
    used in North America) provides a bit over 480 "active"
    lines per frame, but delivers only about 340 lines' worth
    of effective vertical resolution. (Another way this is often
    expressed is to say that the standard assumes a "Kell
    factor" of 0.7; 0.7 times 484 lines is 338.8 lines.)
    Another contributing factor to this effect, at least for CRT-
    based displays (which is all there was, of course, when the
    standard was written) is that a CRT running interlaced
    can't be focused to the point where the individual lines are
    fully resolved (to do so would result in horrible line
    "twitter" owing to the 30 Hz refresh rate for any single
    line).
    Well, "progressive" of course doesn't refer to it being a
    more advanced method. It IS, if you have the bandwidth, a
    better way to scan. Interlaced scanning really was adopted
    in the first place only because it's a crude-but-effective form
    of analog "compression," permitting a higher image resolution
    than otherwise would be the case in the available bandwidth.
    It surely doesn't benefit the system in any other way (it is harmful
    in terms of image quality, somewhat) and you wouldn't go to all
    the trouble involved in an interlaced system (the half-lines at the
    end of the fields, the "equalization" pulses, the need to adjust the
    relative field positions at the display end, etc., etc., etc.).

    Bob M.
     
  5. Bob Myers

    Bob Myers Guest

    Good point; a lot of things in TV standards, though, make sense only
    if you adopt a mid-1960s (or even earlier!) mindset when looking
    at them! :)

    Bob M.
     
  6. Jukka Aho

    Jukka Aho Guest

    The origins of interlaced scanning (as a patented invention) and the
    contemporary reasoning behind adopting that scheme were discussed some
    time ago in another thread. Most of s.e.b readers probably missed that
    thread because it was not crossposted there. Here's a link to that
    discussion: (You may need to manually copy and paste the two-line URL
    together.)

    <http://google.com/[email protected]
    der1.news.jippii.net>

    The message linked above contains an excerpt from Randall C. Ballard's
    1932 patent, and provides a link to the full patent text. (Note that
    Ballard's tv system - the one described in the patent - has a different
    field rate and a much coarser resolution than modern tv systems.)
    There are two other benefits:

    1) When compared to a progressive scan system that has the same
    bandwidth and (nominally) the same spatial resolution for full screen
    images, interlaced scanning provides twice the temporal resolution (that
    is, motion updates per second.)

    The price to be paid for this is that objects in motion will only
    receive half the (perceived) vertical resolution when compared to
    objects that stay still. It can be argued whether this difference is
    noticeable enough that anyone should care. Some people say it is, some
    others think it isn't. In any case, motion will appear very smooth and
    fluid with 50 Hz or ~60 Hz updates, which is great for e.g. sports, and
    allows for fast, smooth pans and zooms without making the picture
    incomprehensible flickery jumble. (Those who have ever shot Super8 film
    know how careful and slow one must be with zooms and pans when dealing
    with a medium that has a low temporal resolution.)

    2) Scanning through the whole CRT screen twice as many times per second
    will dramatically reduce perceived flicker. (Again, when compared to a
    corresponding progressive scan system that has the same bandwidth and
    [nominally] the same spatial resolution.)

    This benefit comes with a price as well: it will introduce some annoying
    twitter in thin, contrasty horizontal lines. Line twitter can be reduced
    quite nicely by employing modern image processing algorithms, though.
    (There are video encoder chips that do this kind of parameter-based
    intelligent, adaptive, dynamic vertical filtering in real time.)
     
  7. Smarty

    Smarty Guest

    Jukka,

    Having traveled as an English-speaking American in Helsinki and elsewhere in
    Finland, I have to add that the majority of Finnish words including names
    and proper nouns is among the most daunting languages I have encountered, in
    some respects exceeding Japanese and Chinese which I also find totally
    intimidating. On the bright side, the many Finns I have met are truly
    wonderful and kind, and your Lakka cloudberry liquor is heavenly, and among
    my absolute favorites, despite the fact that is nearly impossible to find in
    the U.S.

    Smarty
     
  8. jasen

    jasen Guest

    He was talking cinema not tv. cinema projectors have the shutter close
    several times per frame.

    also where TV is 25 frames per second they run the film at 25FPS, and
    have more time for advertising.
     
  9. Jukka Aho

    Jukka Aho Guest

    That's to be expected when you're dealing with a language that belongs
    to a completely different language family. Speakers of major
    Indo-European languages get it easy: they share much of similar
    grammatical structures and vocabulary among each other. It should be
    relatively straightforward to pick up, say, Dutch if you already speak
    English, and German once you know Dutch. Or if you know Spanish or
    French, Portuguese or Italian newspaper stories might already appear
    nearly readable. But when you switch from one major language family to
    the other, all bets are off: nothing you previously knew about sentence
    structures and vocabulary is any longer relevant, or in any way useful.
    :(
    To commemorate that liquor, the obverse side of Finnish 2 euro coins is
    minted with a depiction of a cloudberry plant. [1] Or was it the liquor
    that commemorates the coin? One can never know these things for sure.

    (Just pulling your leg. :) I'd better Finnish now before I tell more
    lies!)

    _____

    [1] <http://en.wikipedia.org/wiki/Finnish_euro_coins>
     
  10. Yeah, Finland is nice, except for the mosquitos ;-)

    -m-
    --
     
  11. Or three times each, giving a flicker rate of 72 Hz. This is better for
    smaller theatres, where the screen brightness tends to be higher, since
    the eye's flicker fusion frequency is higher in frequency at higher
    brightness.

    On the other hand, it wastes light (since each of the dark periods needs
    to be the same length, and each dark period needs to be as long as the
    pulldown time, having 3 dark periods per 1/24 second always wastes more
    light than two) so there's no point doing it when screen brightness is
    already low with a two-flash shutter.

    Dave
     

  12. Then the audio frequencies would be off by about 4%.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     

  13. WHat kind of day WAS it? ;-)


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  14. Smarty

    Smarty Guest

    Thanks Jukka for your comments. The Slavic influence on your language is
    apparently one of the reasons Americans like myself are daunted.

    I was unaware of the coin image of the cloudberry, but can understand why it
    is so exalted. Maybe the U.S. dollar will someday get a Budweiser beer
    emblem...

    Smarty


     
  15. Smarty

    Smarty Guest

    Never encountered them. In Lapland and the Arctic Circle portion of Finland,
    they are not as likely an issue, but Jukka may know for sure...

    Smarty
     
  16. Bob Myers

    Bob Myers Guest

    Yes, they are - but it still often IS done that way, and they
    simply live with the errors that result.

    Bob M.
     
  17. Jukka Aho

    Jukka Aho Guest

    There's Baltic, Germanic, and Slavic influence in the vocabulary, but
    I'm not sure how significant the Slavic influence alone has been when
    compared to the others. Wikipedia has something on the subject:

    <http://en.wikipedia.org/wiki/Finnish_language#Borrowing>

    I'd imagine the Swedish influence is probably the strongest - at least
    among the relatively recent loans - since Swedish has been the
    admistrative language for most of the written history of the country.
    Loan words will usually assimilate fast, though, becoming more
    "Finnishized" in the process in both their pronunciation and spelling,
    so the origins of a given word may not always be too obvious.

    Moreover, for the last 150 years (or so), there has also been an
    on-going conscious effort of producing new "truly Finnish" words for new
    concepts instead of just importing words from other languages. (Compare
    to the French language and the French Academy.) This doesn't always work
    out as intended, but many concepts and gadgets that were originally
    called by their foreign names when they were first introduced now have
    firmly rooted Finnish names because of this policy (i.e. the original
    loan word has fallen into disuse and oblivion.)

    Geography will also play part, of course. For example, the dialects
    spoken near the Eastern border have some Russian influence in their
    vocabulary - this can be witnessed most easily in the religious
    vocabulary of those Karelians who subscribe to the Eastern Orthodox
    faith - whereas the dialects spoken on or near the West coast (such as
    in Ostrobothnia, where I come from) borrow many words from Swedish.

    TV - the great equalizer - has made those differences much less
    pronounced, though. When not among their "own people", most people will
    speak Finnish in a fairly neutral or "standard" way, without necessarily
    giving away the part of the country where they're from.
    Heh. That's a coin I'd like to see! :)
     
  18. Jukka Aho

    Jukka Aho Guest

    Actually - as strange as it might seem - Lapland is kind of notorious
    for its mosquitos. They're fierce and plentiful in there, but will only
    reign during the summertime, of course! There's more about them on these
    pages:

    <http://www.virtualtourist.com/travel/Europe/Finland/Lap
    pi/Ivalo-240898/Warnings_or_Dangers-Ivalo-BR-1.html>

    <http://www.ebnitalia.it/trips/trip08.htm>

    <http://wikitravel.org/en/Finland#Stay_healthy>

    Mosquitos can be found all over the country during the summer -
    especially near swamps, streams, and lakes, since they need a bit of
    water in order to reproduce - but the ones in Lapland usually seem to
    get particularly bad rap. I have never been to Lapland during the
    mosquito season myself so I can't really say whether this notoriety is
    justified or not.
     
  19. Jukka Aho

    Jukka Aho Guest

    ....or time-compress the sound track without changing the pitch. (The
    wonders of modern technology, and all that.)
     
  20. Sounds like the north woods of Canada!
     
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