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3:2 Pull down... 24fps from NTSC Discs?

Discussion in 'Projectors, Screens & Video Processors' started by djsky, Jun 11, 2005.

  1. djsky

    djsky
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    Hi, I'm a little confused...

    Is there a scaler or even a DVD Player or something that will take a NTSC DVD and produce a good image?

    I'll elaborate... obviously the frame rate of an NTSC dvd film, is 30 fps repeating every 4th frame in theory. is there a device that will delete the repeated frame and present a true 24 fps output?

    Things appear to have 3:2 pull down, but surely this feature is the method of actually doing the field/frame repeating etc...

    ?

    Cheers
     
  2. kurtz

    kurtz
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    I take it you're referring to motion judder on NTSC material such as films.

    I think what you're after is 48Hz or 72Hz output - which will eliminate the superfluous frame and smooth any NTSC motion artifacts. This is because 48Hz and 72Hz are direct multiples of 24 fps.

    I don't think a DVD player will do this, but a video processor can. There could still be an issue of whether your display device will accept 48Hz or 72Hz (some will always convert to their internal refresh rate regardless of what input rate they 'accept') but a lot do and the results are nice.
     
  3. djsky

    djsky
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    OK, so what device am i looking for that will do this? and what is the process called that does this process to 48 or 72hz?

    Will a Kramer VP720DS scaler Do this?
     
  4. kurtz

    kurtz
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    I think its just referred to as frame-rate conversion. Its not specific to 48Hz/72Hz; some people use a scaler to convert from 50Hz to 60Hz because it can do it better than the processsor in their display, others try 50Hz to 75Hz (with PAL) and so on.

    I've had a look at the VP720/723 spec here and it refers to 3:2 pulldown - but it states the VFreq as 50-100Hz and I think you'd need 48Hz to be supported, so I don't think it would manage it.

    I think a Lumagen scaler (that's what I'm most familiar with) can do what you need; see the specs here. They do 48-75Hz or 48-120Hz depending on the model.

    I think other scalers such as iScan, Crystalio etc. could do the job also.

    There's also a feature called 'Genlock' to look out for which maintains strict syncronisation of the input and output frames (to prevent frames getting dropped) which can make the picture more stable. I have no experience of this - but it's expected to be appearing in an imminent release of Lumagen firmware.
     
  5. djsky

    djsky
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    Cool, i'll make some phonecalls and see about getting a demo on some of the products.

    Cheers ever so much for your help Kurtz.
     
  6. Dale Adams

    Dale Adams
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    The iScan HD and HD+ will both convert a 60 Hz source with 3:2 pulldown to either 48 Hz with each original film frame repeated twice (i.e., 2:2) or to 72 Hz with each original film frame repeated three times (3:3). A similar process is used to produce a 75 Hz, 3:3 output from a 50 Hz source with 2:2 pulldown. In these modes the iScan locks to the original 24 Hz film source rate and outputs each original film frame exactly 2 times or 3 times, without dropping or adding frames in the sequence as long as the iScan has lock on the source's 3:2 or 2:2 cadence.

    There is also an output mode where one output frame is produced for every input field (i.e., 1:1), which is closer to what is typically considered as 'genlock'. These output modes have been provided by the iScan HD and HD+ since they began shipping over a year ago.

    - Dale Adams
     

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