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120hz versus 240hz

Discussion in 'Electronic Repair' started by Chris, Feb 25, 2010.

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  1. The 50 and 60 fields per second (a field being half an interlaced frame)
    That's what I heard, too. But that's not "interefence effects from
    electrical lights".
     
  2. You are assuming that all interference would be on the screen itself and none
    would be visual. Since flourescent and to some extent incandescent lights
    blink (what is the persistance of an incadescent light?) at 60 Hz, there is
    a strobing effect if there are lights on in the room with the TV.

    While some peope (me) like to watch TV in the dark, many people watch TV's
    with lights on. Some manufacturers went as far as to include light sensors
    in their TV sets automaticly adjusting the brightness to compensate for
    room lighting as it changes.

    Since some people live in places where only flourescent lights are allowed,
    they have no choice if there is interference, either turn off the lights
    entirely, or live with it.

    I guess that could be a new tourism slogan for this summer, "Visit Israel,
    and bring home real light bulbs." :)

    Geoff.
     
  3. That's what I heard, too. But that's not "interefence effects from
    Incandescent lights have almost no flicker, due to the thermal inertia of
    the filament. Fluorescent lighting was not common in living rooms at the
    time the standards were set.
     
  4. But this isn't so. A crap picture may, I agree, look 'ok' to someone
    The 32" Vizio LCD in my den has a very wide viewing angle and does not show
    significant smearing or blurring with rapid motion. (I paid about $380 for
    it.)

    With respect to scaling... People here and elsewhere have said they see no
    point to Blu-ray disks, as they see little or no difference with upscaled
    DVDs. Ergo, Blu-rays are a ripoff. I watched the Blu-ray of "The Sixth
    Sense" yesterday, which threw this issue into sharp perspective.

    The transfer is typical Disney -- extremely sharp and detailed, with rich
    colors. It's close to demo quality.

    Some of the supplemental material includes scenes from the Blu-ray transfer
    that have been letterboxed into a 4:3 image. (Got that?) When I select ZOOM
    on my Kuro, that section is blown up to full screen. ("The Sixth Sense" was
    shot at 1.85:1.) Viewing at these images in isolation -- they look fine.
    They're slightly soft, but one might believe it's the fault of the source
    material. They don't look upscaled -- until you compare them with
    full-resolution Blu-ray. There is no comparison!
     
  5. Chris

    Chris Guest

    The way it was described to me is there are seveal hundred LEDs which are
    each assigned specific "areas" of the screen. So it would seem that if you
    have a bright AND dark area within an individual LED's jurisdiction, there
    would be some sort of conflict. Unless, of course, such jurisdictions are
    actually blended into the others. But they would still have to average their
    brilliance. Either way, I could see how there would be a contrast
    improvement across the screen as a whole since more lights is always better
    than ONE.
     
  6. Phil Allison

    Phil Allison Guest

    "Geoffrey S. Mendelson"

    ** But the lights concerned were those being used to illuminate the TV
    studio.

    When frame rates are not locked to the AC supply frequency, faint shadows
    can be seen moving up or down studio images on a monitor or home TV set -
    due to the twice per cycle dip in brightness of incandescent lamps.

    Other fixes include using lamps with sufficient thermal inertia or groups of
    lamps on different phases to eliminate the light modulation.



    ...... Phil
     
  7. It's not nonstandard. MPEG4 is one of those "evolving standards", so that
    they can sell you a decoder box or TV that supports the current variants
    and next week turn around and sell you a new one.

    Or if you have a computer, provide a firmware update.

    It gets rid of the problem that CRT TVs had, they did not change fast enough
    to get people buying new ones in a fast enough cycle to keep the companies
    in business.

    I have a spare TV that I bought in 1986 and AFAIK, it still works. We have
    not yet switched to digital over the air here (Israel).

    Speaking of MPEG4, Israel chose H.264 with AAC audio, a combination no one
    had ever used before. The idea was to squeeze as many regular (520p 4:3)
    channels in one 8mHz DVD-T channel.
    Same here, but it's 40 NIS ($25).

    BTW, where do those HDTV BBC programs come from? They are not over the air?

    Geoff.
     
  8. Phil Allison

    Phil Allison Guest

    "Dave Plowman (Fucking Nut Case Pommy **** )
    ** DUUUUUHHHHHHHHHH !!!!!!!!!!

    WRONG CONTEXT - you fucking STUPID MORON !


    ** WRONG CONTEXT - you fucking STUPID MORON !


    ** WRONG CONTEXT - you fucking STUPID MORON !


    ** WRONG CONTEXT - you fucking STUPID MORON !

    Someone PLEEEEASE go and SHOOT this imbecile through the head !!!



    ..... Phil
     
  9. I'm not sure what exactly you mean by "an evolving standard".
    To the best of my understanding, all audio and video codecs carry with them
    the information need to correctly decode the transmission. This allows (for
    example) DVDs and Blu-rays to use varying bitrates and different codecs. (If
    this isn't right, please correct me.)
     
  10. No. It's much more complicated than that. AVI files carry imformation about the
    file, such as a codec number each for audio and video, the bit rate,
    the frame rate, number of audio channels, and so on.

    Satellite (and DBS) data feeds contain some information, some feeds contain
    none at all.

    DVD's, Blu-Ray, VCD's, etc, all have a very specific format. DVD's are also
    limited to MPEG-2 video encoding (with a limited range of resolutions, frame
    rates, etc.) They also have a very limited range of audio encoding.

    Sometimes it amazes me that a program such as mplayer or VLC can play a
    random file and it works.

    The reason the Chinese DVD players can play so many files now is that they
    either use the freeware Linux based player, Mplayer, or the proprietary
    clone of it written in a language for embedded systems.

    Just as an example, someone gave me a sample of the files created by their
    DVB-T TV decoder. They are raw MPEG-TS files, encoded with H.264 and AAC.
    Nothing I have can open them. :-(

    Geoff.
     
  11. Guest

    You can do that yourself. The concept is simple - insert the muzzle
    of the pistol in your ear and pull the trigger. If you are too stupid
    to understand the concept, let me know, I'll gladly break it down into
    a series of steps even you can follow.

    PlainBill
     
  12. Mark Zenier

    Mark Zenier Guest

    Both VHF-High (channels 7-13, 170something to 220? MHz) (3 stations, here)
    and UHF (channels 14-51(?), around 500-700 MHz) (another 10, here).
    There are some VHF-low band stations in other parts of the country
    but I gather that 54-88 MHz has real problems with thunderstorms and
    interference.

    The US channels are all 6 MHz wide, both UHF and VHF. ATSC using 8VSB
    with something around 19 MBPS, using MPEG-3. As I understand it, HD
    will use about 12 MBPS. The over the cable version uses a different
    modulation, [mumble]-QAM, and has twice the number of bits per second.
    HD in the case of ATSC may be only 720p, or 1080i.

    I can't get them all, (They're clustered in 5 different locations),
    but at least 8 (maybe 10) are in HD.

    The bucks from auctioning off channels 52(?) to 69 to the cell phone
    and wireless companies is what got the government to push this through.
    Around here, since nobody had to be nice and share, they just toss off
    a few crap channels when they shift to HD. (The PBS non-commercial
    stations were about the only ones to do this, as they were early adopters,
    and had their transmitters going long before they rebuilt their inside
    equipment).

    One of the things you have there, judging from the web pages I surfed
    a while back, are the audio only transmissions from the various
    national stations. I wish they had done that here, but most of the
    stations that used to be combined radio and TV split up into separate
    corporations back 15-20 years ago, so there no organizational connection
    anymore.
    Sounds cheap to me, I gather you can spend $90 a month (not including
    pay per view) to get the full load. Minimum, $30-$40 a month.

    Mark Zenier
    Googleproofaddress(account:mzenier provider:eskimo domain:com)
     
  13. It is cheap. The 10 quid (UKP) is an EXTRA fee for HD. You buy whatever
    package you want, and if you want HD, you buy the HD package, which is a
    few channels in HD.

    Most channels are not available in HD.

    Here for example, the DBS system I use has 4 movie channels, in HD they have
    one. If you want all four channels, or a different movie than the HD channel
    is showing, you have to watch it in regular, which means you had to pay
    for that channel.

    Regular def here is a mixed bag, about 10% of the programs are 16:9, most
    are 4:3. The decoder box gives you a choice of always 16:9 (which means the
    TV set has to detect the difference and switch), always 4:3, or letterboxed
    16:9 on a 4:3 set.

    I have no idea of what really is on HD, I don't have a TV capable of it.

    Note that if I were to upgrade to an HDTV, I would not upgrade the service,
    I get so much of my program material from other sources, it's not worth it.

    Geoff.
     
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