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PAL Friendly Video Processors

Discussion in 'Projectors, Screens & Video Processors' started by cwinson, May 15, 2005.

  1. cwinson

    cwinson
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    There has been a number of comments on this furum about how some video processors are more PAL friendly than others.

    Can someone please explain how this manifests itself - what functionality do they have that others don't.

    Is it down to cadence detection, framerate conversion between 50Hz/60Hz, or something else altogether

    Chris
     
  2. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    In the past the main issue with video processors not being PAL friendly was that one of the main things a scaler can do is detect whether source material is progressively recorded or interlaced in order to apply the correct de-interlacing method before scaling. For 60Hz sources this is not to hard if it's a progressive film source as there is a 2:3:2:3 field sequence that gives the game away. This is called film detection/inverse telecine or 2:3 pulldown. With 30frame per second recordings and with PAL where we have a 2:2:2:2 field sequence for stuff originiating with film there is no repeated field and detection is alot harder. Even now you find that 2:2 detection, on any video processor, is not always robust and there are scenes that trip up every unit out there.

    Nowadays the majority of video processors are very capable at 2:2 detection for 50 Hz material (although there are some scenes that make exception). Due to some weird change in how some programming seems to be broadcast in UK we are also now seeing instances of processors mistaking material that was originally interlaced recording for that which is progressive. This results in various sorts of issues. One is combing and another is a slow down effect. Some manufacturers have been able to rewrite the code that controls certain paramters of their devices or have just changed some parameters of their devices to make detection of such instances more robust.

    Some manufacturers also continue to get feedback from the end users of their products as to scenes or material that shows artefacts. They then investigate and where possible bring out update code to stop the issue happening again.

    All in all though the PAL/NTSC issue is not what it once was when it comes to video processing.

    Gordon
     
  3. cwinson

    cwinson
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    Gordon,

    Thanks for the feedback - that makes a lot of sense.

    On a slightly separate note, my projector (Epson TW100) accepts 720p at 60Hz (not 50Hz). How good are the modern video processors at converting 576i@50Hz to 720p@60Hz. I presume this frame-rate conversion capability is part of the PAL freindliness of modern processors.

    The nirvana of native 1 for 1 fixel mapping into the PJ seems somewhat flawed unless both 50 and 60 Hz are supported.

    In your experience, what is the best solution for the above scenario

    1) De-interlace, scale and frame-rate convert in the processor
    2) De-interlace in the processor and scale in the PJ
    3) Buy more material at native frame rate of display device (i.e. buy NTSC discs) :)

    Chris
     
  4. David PluggedIn

    David PluggedIn
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    sorry Gordon, would have to disagree with you there. As video processor usage is becoming more widespread, and for more than just DVD viewing (i.e. for digital TV viewing as well) the importance of automated detection is becoming more important, and the level of compatibility with PAL (or lack of) more apparent.

    I use Crystalio as my main processor for all Sky viewing - and it is completely automatic in its detection - and very robust. Very, very occasionally (like say once a month) you might come across something that will catch it out, but it sorts itself out in less than a second - very impressive.

    We would say to anyone looking at an NTSC territory designed processor for use with PAL broadcasts to check carefully on the current status - for example DVDO have stated that a re-design may necessary to resolve their detection issues.

    Chris - with regard to your projector, then it is the same basic chassis as the Yamaha LPX-500 , which is what I run with Crystalio , via DVI , pixel perfect at 1280x720@50hz. I assume that your TW100 would be the same (there is even a dedicated TW100 preset in Crystalio)

    Scrolling is silky smooth - even on the ticker tape news channels.

    let us know if you want more information.

    cheers
     
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Chris: 1 and 3 are good options. 2 Can be a good solution if you go analogue to the display at a higher resolution than it is and let it do the downscaleing

    Most modern processors are good at frame rate conversion. There are differences though. The best bet is to try in your own situation. I did a show over a weekend where we played DVD and Freeview TV through a plasma display with everything converted to 60Hz and no-one mentioned that they could see any frc artefacts. This was with a Lumagen scaler and a 50" Panasonic D7 plasma.

    Gordon
     
  6. Chris5

    Chris5
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    Hi Gordon,

    Be careful in your assumptions, I have often seen judder and nasties at shows etc (not your kit), but have not come forward and mentioned it, why should I, I have nothing to gain, at best the rep will blame the source material, at worst I could end up in an arguement, or a nasty remark from the rep. I've learned to keep shtume
     
  7. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I am assuming nothing. I merely point out what happened over a well attended show. I like to think that I'm a pretty easy going guy. Lots of folk stopped to chat and ask questions about our set up but FRC was just not mentioned. When I do shows I'm happy to stand up and take a kicking but you are right that it may have been that folk were intimidated by my geekness.

    The most likely times you'd notice it obviously is on ticker tape on news channels. You notice it there as some scalers will tear the ticker tape and others will be so juddery t'll be unreadable. The good ones just add a slight judder while making the text still very legible. On football you may notice it as well if it's not being handled that cleverly. There are occasions where I've actually had to point out what the judder is as they couldn't see it. Of course we are all susceptible to these artefacts in varying degrees. There are those who cannot watch NTSC DVD's because of it and there are others who cannot watch R2 DVD's because of the speedup.....horses for courses.

    Gordon
     
  8. cwinson

    cwinson
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    It seems amazing to me that the display manufacturers don't assume that people would want to display either 50Hz or 60Hz material and ensure both are supported for all resolutions.

    Are the panels inherrently better suited (or even locked) to one refresh rate over another ? Indeed, is there ever any FRC that takes place internally for 'supported' resolution/frame rate inputs.

    Finally, out of interest, which type of FRC typically causes the most obvious judder

    50 - 60 (speed up)
    60 - 50 (slow down)

    Cheers,

    Chris
     
  9. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    60 to 50 could be quite unpleasant with dropped frames although it can be sort of OK with some processors. When it's bad it's unwatcheable though.
    in my experience going up is easier.

    There have been dlp's that convert everything to 60Hz, there have been plasma's that convert everything to 70Hz. Some displays run 50Hz in at 100Hz and leave 60 at 60 and there can be differences in contrast ratio because of this......nothing is ever simple in video.

    Gordon
     
  10. Chris5

    Chris5
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    Hi Gordon,
    'Hey!, No offence' ;) Just to clarify, I wasn't making a personal observation, just a general one about the industry. :)
     

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