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iScan HD+: Getting Rid of Flicker and Noise

Discussion in 'Projectors, Screens & Video Processors' started by dublinpole, Jan 14, 2005.

  1. dublinpole

    dublinpole
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    Dear Experts

    After a good 7 hours trying various sync and framerate settings on my iScan HD+ "output settings" trying to match it at 1280x720x60Hz for my pj, I had succeeded getting a perfect pixel-match both horizontally and vertically, according to the two test patterns. :)

    What I cannot solve :( however is three pq problems: a random pixel "snow" noise (typically blue on black areas) AND/OR a "flicker" of any saturated coloured patterns AND/OR jumpy "judder" - this is not visible on the VLIN/HLIN screens but on anything else that has colour, such as the colour bar patterns. I tried playing with h-sync, porches and the frame rate, and I can never solve all those three problems. I can eliminate the "noise" by lowering fr to about 49.17Hz, but then I have a framerate "judder". If I get a lovely smooth moving bar on VJUD (at 60Hz), then the other two problems appear. If I minimise the "snow" then I get the "flicker" of coloured areas... And so on...

    The iScan is connected to the PE8700 (BenQ) via a 10m DVI-D lead.

    If anyone has suggestions (settings, kit, tests), I'd be grateful. If anyone is in or near Dublin and would like to get paid for a visit to solve it for me - let me know too. :)

    Oh: if I use lower resolutions I lose the pixel-perfection (on VLIN/HLIN and visibly when watching movies) but I have none of the snow/flicker/judder problems.

    Many many thanks,
    R.
     
  2. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Sounds like your at the limit of resolution for the DVI cable. Can you move the scaler closer and try a shorter lead? Do you have an alternative manufacturers DVI cable you can try?

    Gordon
     
  3. dublinpole

    dublinpole
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    Gordon,

    Thanks for the advice, I'll see if I can solve the problem with a shorter cable. In the end I'll still need 8-10m cable (PJ is ceiling-mounted and equipment must be in the cabinets that far away), so perhaps I'll have to replace the existing one - do you have suggestions for a good quality one I could buy?

    My luck, of course, is that the cable has already been neatly chased into the thick walls of the 1815 cottage... :( I guess I'll have to re-drill the walls!
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    ONe of the things I was doing over in US was trying to find a manufacturer of quality low loss HDMI/DVI cables that didn't cost a bomb. Think I found one....no prices yet but not silly money. In the meantime Bettercables hgher quality cable shold work

    Gordon
     
  5. KraGorn

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    Silly money as in BetterCables? :laugh:
     
  6. PhilB1234

    PhilB1234
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    I've found a 10m Lindy cable could support 1080p/50Hz without problem so I'd consider giving that atry as 1280x720/60 is a far less demanding data rate.... They're extremely good value too. See www.lindy.co.uk
     
  7. KraGorn

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    Once upon a time Lindy 10m cables caused problems to several people here, particularly autumn 2003 when the Z2 came out and helped popularise DVI connections. Maybe they've improved their product since then, but it was the case 7.5m was about the longest that could be relied upon.
     
  8. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I don't consider Bettercables that silly.

    I would suggest that whatever you try you get on sale or return and you confirm it solves your issues and doesn't cause anymore before sticking in wall(but that's a bit obvious isn't it)

    Gordon
     
  9. dublinpole

    dublinpole
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    Many thanks to all - I'll try a "better" DVI cable - if any of you sell them, pls message me so that by buying from you at least I can reciprocate for the advice.

    On another hand, I have a, perhaps, silly question. Should I consider not using a DVI cable between the iScan and PJ and instead go with an analogue output "VGA-style" connector to 3 (4 or 5) BNCs on my 8700, as the pj can use those to take RGB input?

    Many thanks again,
    Raf
     
  10. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I sell them. Will try to get you price Monday am.

    Are you using a DVI HDCP or HDMI outputting DVD player to the scaler? If so then you will not be able to go RGBHV out to the PJ as the scaler will turn off its analogue output.

    If you are going analogue to scaler then you could try the VGA/RGBHV route. I wouldn't go component YPrPb to PJ as you are adding lots of colourspace conversions that way.

    The benefit of the DVI connection is that you are removing an analogue to digital connection in the signal path. However with some devices the DVI inpout may be optimised for a PC image and the gamma may be all wrong. I've never looked at one of these with an Iscan HD+ for calibration so can't comment on what is optimum configuration. I would expect the dealer who sold you them should know though....hopefully.

    Gordon
     
  11. dublinpole

    dublinpole
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    Gordon,

    Thank you and will await quote eagerly - I've figured out that 7m should do for me.

    I've experimented with a shorter DVI cable today and all problems got solved: no noise etc.

    My DVD is an older Denon 2800 connected with component leads to the iScan HD+. On the Denon I get best results with de-interlacing switched off and the video type set to "video" rather than "film".
    As you mentioned the colour spaces: I was wondering which of the two iScan output settings I should use: DVI-P (PC sig lev) or DVI-V (video signal levels). Any suggestions to use with my BenQ PE8700+? :)

    Thanks a lot,
    Raf

    PS. Do you also sell calibration DVDs, those blue glasses etc.?
     
  12. digibluh

    digibluh
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    Yo Guys, I just got a Iscan HD+ for my Benq... What was you're settings for 1:1 pixel matching? did you also set it to through? when i do that its in the center of the screen horizontally, but not vertically like it usually is. when i adjust the pic it just goes inbetween that and dosent move, just shifts from inside. I dont want the projector to do any scaling of course... I hope my cable is ok too.. hehe, using the DVI-D as well with component input from the DVD player to bypass any A/D convertsion in the PJ. I also have the AVIA disk too.

    I'm going to play myselfe, but was curious was the settings you used were and if through is what i must used and keep scaling till it just maps 1:1 from the iscan.
     
  13. digibluh

    digibluh
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    I noticed i think i have the same problem with my cheapo DVI cable as well. I get offset color, not noticable when watching TV (except on the sides), but using the AVIA disk, on a Complete Full RED screen for example, the left side leaks blue a few pixels and the right has a bit of grey (aside from the usual black space) showing the colors are aligned improperly. I can get rid of it using a lower resolution but its only gone from the sides, in wich i beleive its cause the PJ's scaler kicks in once lower and cuts it off, but in between the bars on the color bar test, you can tell its still offset. This is gone using the Analog RGBHV cable, but i have another problem with the cable i have, hehe.. its blurry! but the color problem is gone. I rather watch the sharper DVI with offset color than the RGBHV cable i have, but i assume the cable is the problem? all i have is a single link and dual link unknown brand, probably generic. i beleive it came with something else i bought.


    Is this the cable or somthing else? i assume its the cable though...
     
  14. digibluh

    digibluh
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    OK, using the AVIA CD, i see the problem, using the built in test patterns i dont see it, but satellite via s-video seems to have it too, at least somthing a little weird on the sides... i need to check against a pure color or color bars from someplace i guess, hehe.

    I dont notice any of these going right into the PJ though, #@$#@$@#!!
     
  15. binbag

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    I went for a 9m Bettercable DVI after the 10m premium Lindy produced sparklies and occasional solarisation from my HD on what was otherwise a great picture. Problem solved = money well spent IMO. How can you perform any kind of setup on an inconsistant signal?
     
  16. dublinpole

    dublinpole
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    It took me more than a year, but I finally replaced the DVI-D lead with a Bettercables Display Magic 8m one. Everything is fine and the image is quite stable at the 100% pixel-match res (1280x720x60Hz). I also want to point out that I tried two Lindy cables and they did not work well. Clearly, there are significant limits to what different cables can do.

    Regards,
    R.
     

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