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23.976 Hz refresh rate - impossible?

Discussion in 'Rivatuner Statistics Server (RTSS) Forum' started by puntloos, Apr 22, 2009.

  1. puntloos

    puntloos Member

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    Your question answers it exactly. I have a HTPC that has a HDMI out and a blu-ray player.
    No. 3:2 pulldown is a way to shoehorn, and force, and degrade a source into a different refresh frequency. I could do this as a last resort but I prefer to fix the actual cause of my problem.
    The only problem I have is that the nvidia driver seems to not support 23.976 as a HDMI output frequency. It supports 24. I am trying to get it to go down a notch.
     
  2. puntloos

    puntloos Member

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    The problem is that windows XP, or the video driver, or something at least, is assuming that 24 Hz is the same as 23.976 Hz. Video is being played back at 24, there is only enough audio for 23.
    Everything -works- at 60, but it is sub-optimal.
     
  3. puntloos

    puntloos Member

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    You do sound like a TV salesman. Why did you quit?
    Which I have.
    No. Hertz is a unit. Look it up. (http://en.wikipedia.org/wiki/Hertz). While it is a touch misused in 'video' context, I am pretty sure I've used it correctly.
     
  4. Anarion

    Anarion Ancient Guru

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    This is interesting question, AFAIK Blu-Ray standard supports 1080p material either at 24fps or 23.976fps. I think you should contact to NVIDIA about this since they do support 24p (my TV support that, by the way).
     

  5. Pill Monster

    Pill Monster Banned

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    Where are you getting your info from? I mean, have you yourself actually experienced any of the issues you're describing?
     
  6. puntloos

    puntloos Member

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    A fair point, I did wonder about this. The only reason I could think of is buffering. With a difference of 'only' 4 seconds per hour it wouldn't exceed too large a buffer. The moment I pause, then seek, the AV sync is fixed.
     
  7. puntloos

    puntloos Member

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    Me? Of course. Would be a bit of a waste of time if I was argueing for fun :)
     
  8. puntloos

    puntloos Member

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    Exactly. Mostly 23.976, in fact.
    Tried, failed :( Maybe they don't like my attitude :3eyes:
     
  9. Pill Monster

    Pill Monster Banned

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    Don't worry - if you were you wouldn't be the first....:)

    No, it has nothing to do with the refresh rate, it has to to with the framerate as far as I my understanding of it goes. The recording is done at a different framerate than the format it gets converted to. So therefore the a/v sync is affected. But the 3:2 pulldown is done during the encoding, not the decoding process.
     
    Last edited: Apr 25, 2009
  10. puntloos

    puntloos Member

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    Incorrect, 3:2 pulldown is done to convert 24Hz footage into 30(120)Hz.
    http://en.wikipedia.org/wiki/Telecine#2:3_pulldown

    In this case, if the videocard is set at 23.976, the TV will deal with the signal. If the videocard is set at 60, the computer will do it. Badly.
     

  11. Pill Monster

    Pill Monster Banned

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    You should probably have another read of the link you posted....


    http://electronics.howstuffworks.com/tv-buying-guide18.htm
     
  12. HeavyHemi

    HeavyHemi Ancient Guru

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    I'm just an old country boy, but will somebody explain how synchronized A/V tracks encoded on a Blu-ray disk lose sync? No in msec amounts which could be explained by processing overhead, but by 4 seconds?
     
  13. bp9801

    bp9801 Ancient Guru

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    puntloos, why do you insist on calling the hertz, the frequency of the television, the same as fps? Frames do not equal hertz, you should get a new source of information. The hertz of the tv will not affect the frames, get some new equipment then.

    good question, I don't see how its the fault of the player. its more than likely a fault of the audio equipment he is using. this is why I always recommended a good, quality, name brand piece of audio equipment that is hooked up instead of breaking up the sources like he is doing. its not a fault of the video, its a fault of the audio source.
     
    Last edited: Apr 25, 2009
  14. puntloos

    puntloos Member

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    Thanks, but no. We are speaking about Blu-ray, not DVD.

    (incidentally, sometimes DVDs do 24p: http://en.wikipedia.org/wiki/24p#24p_on_DVD)

    At any rate, the point here is that the source is 24fps and that at some point you can choose to switch to 30fps and try to fix associated problems by this reframing, or you can try to play stuff as intended, which I'm doing.
     
  15. puntloos

    puntloos Member

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    Hertz is defined as cycles per second. In this specific case, a cycle is a frame. To say "this movie is played back at 25 Hz" and "this movie is played back at 25 frames per second" is equivalent.

    As I indicated earlier, the refresh frequency of the TV (i.e. how often the display panel refreshes its screen) is not that relevant to the discussion, the input circuitry of the TV should deal with the incoming signal, no matter what amount of frames per second get sent in. My point is:

    Before the signal enters the TV I don't want to transform/resample/re-frame or otherwise mangle the source

    No. I did the math earlier. The audio track is of exactly the right length, playing an intended-for-23.976 video track at 24 will make the movie play a little quicker, end a little early, which will cause AV sync issues.

    (at least, that is my theory.. if you have a theory as to why audio is the problem then let me know, although I've taken quite a bit of care trying to pick consistently high quality stuff, and everything works with a PS3 playing back the disk)
     

  16. Pill Monster

    Pill Monster Banned

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    Your quote I believe???



    My quote
    http://electronics.howstuffworks.com/tv-buying-guide18.htm


    Are we clear now?


    Look you came here wanting answers yet when you get them all you do is argue so wtf?? I wish Santa Claus was real too but he's not and no matter how much I debate the point, he's not gonna come down my chimney at Christmas....
    To be completely honest you'd be better of asking over at avsforums.
     
    Last edited: Apr 26, 2009
  17. Pill Monster

    Pill Monster Banned

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    Depending on the type of HDMI used some types of digital audio can't be transferred from the source without being re encoded first.
     
  18. puntloos

    puntloos Member

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    Great question. I dont know. All I know is the desync happens, and -something- in my system apparently buffers audio while video is trailing behind.

    The math works out on my theory (playing 23.976 @ 24) but I have no idea if it is actually true.
     
  19. puntloos

    puntloos Member

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    Only if there are pre-HDMI-1.3 devices in the system. There aren't.
     
  20. puntloos

    puntloos Member

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    Clear enough. I'm quite up to speed :)
    All I asked was:
    How can I force nvidia drivers to set refresh to 23.976 instead of 24

    The rest was you guys asking for details and argueing :)
     

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