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VGA15 Versus DVI input

Discussion in 'Plasma TVs' started by JetJockey, Oct 21, 2005.

  1. JetJockey

    JetJockey
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    Hi Folks

    Another quick one.

    Looking at the Panny PHD8 brochure and the specs on the input boards, I notice that the VGA15 input socket seems to take a much greater range of vertical frequencies than the DVI socket. The DVI socket for example, only accepts 800x600@60Hz, or 1024x768@60HZ, or 1280x1024@60Hz. The VGA15 (PC) input takes the same resolutions but at frame rates of up to 85Hz in some cases!

    Does this mean that a Home theatre PC, with a wide selection of output frequencies (fancy video card or Powerstrip) would be better off being fed into the VGA 15 input? :confused:

    Common sense would suggest that the higher the refresh rate the better the picture (less flicker (in the CRT world)). Perhaps this is not quite the case with Plasmas, although I cannot see why.

    Anybody help here please?

    Thanks, Gerald. :)
     
  2. BeelzebubUK

    BeelzebubUK
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    I'm not sure on the technical aspects of it but I had my scaler outputting 75Hz into the VGA port and I was getting awful stuttering on fast panning scenes etc.. Set it down to 50Hz and its much much better. Although maybe thats because 1024x768 only operates properly at 50Hz ??
     
  3. BeelzebubUK

    BeelzebubUK
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    I've just looked at the board specs of the PHD8 and the strange thing is that it only shows 1024x768 60Hz, 70Hz, 75Hz & 85Hz for vertical frequency ??
     
  4. steddyman

    steddyman
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    You will get the best results running at 50hz or 60hz and matching the native frequency of the source material.
     
  5. JetJockey

    JetJockey
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    Cheers Steddyman.

    No screen flicker then, at 50 or 60Hz?

    Gerald.
     
  6. JensH

    JensH
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    From:
    http://www.avforums.com/forums/showthread.php?t=252180&page=3


    These frequency boundaries, if they are the max limits, seem to explain the poor performance at 75Hz, since the display will do an internal frame rate conversion.
     
  7. JetJockey

    JetJockey
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    Yes

    but is this the case even if the signal is fed in through an analogue input such as the VGA 15 connector?

    The brochure clearly shows an 85Hz input signal resulting in the panel running at 85Hz!!

    Hmmmm...........

    Gerald :)
     
  8. BeelzebubUK

    BeelzebubUK
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    Well all I can say at the moment is a Sky+ feed coming in over Component at 576i to the scaler and then being output to the VGA port on the panel at 1024x768@75Hz is awful. at 50Hz its rock solid. The picture quality on some of the channels is bloody amazing :)
     
  9. JetJockey

    JetJockey
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    That is very very interesting. So it would appear that you can "fiddle" about with the picture resolution a lot, In order to try and get 1:1 pixel mapping or close to it, but any attempt to change the frame rate to say 75Hz is a disaster. I wonder is it the Plasma creating the Stuttering or the scaler? :confused:

    You are using the Iscan HD?

    When you say component coming in from the SKy+ box at 576I,
    I assume you mean RGB from the Scart socket? :)

    Regards, Gerald.
     
  10. BeelzebubUK

    BeelzebubUK
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    I have a cable thats RGB Scart going to RGBsync (4 RCA connections) to the scaler. The scaler shows it coming in as 576i

    Its quite possible it might be the scaler introducing the stuttering as I assume its 50Hz coming in and then it was trying to upconvert to 75Hz.
     
  11. Kalos Geros

    Kalos Geros
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    Yes it is trying to run 50 fields per sec as 75 fields per second...that's why I strongly support the principle a PC should never be used to watch home entertainment content and that media conversion should stop soon because it's ruining the viewing pleasure the computer gfx card can never run at native frame/field rate of original PAL video (except NTSC source which matches with 60Hz and is absolutely smooth even with interlaced NTSC source) and will always have trouble with stuttering...BTW, plasma and LCD do not scan the screen like CRTs thus there is no large area flicker even at "low" 50 Hz refresh!!!
     
  12. JetJockey

    JetJockey
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    Hi Kalos

    Thats an interesting point you make.

    Are we saying that it is impossible for a Graphics card to output 50Hz, Even when it is showing PAL footage played back from a DVD?? :confused:

    I had always assumed that the Graphics card always put out what it was fed but a quick visit to display properties in control panel shows the minimum refresh rate as 60Hz!!!

    Is it not possible to force 50Hz output using Powerstrip or something similar?

    Gerald. :)
     
  13. Saltrock

    Saltrock
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    Speaking to Gizlaroc about "analogue Vs digital" and I agree what he says.
    The quality on the panasonics over analogue is fantastic.

    I was running sky+ over s-video before I got the scaler then changed to scart-4phono-scaler-DVI-D

    There is so much noise over DVI i'm sourcing a DVI-VGA cable as we speak.
    The only down side is not being about to output HDCP over analogue but I hear there are ways around that ;)
     
  14. GranPremio

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    Saltrock is spot on. I have a 50PHD7 with HDMI board. The analogue input is far less fussy and significantly better picture.

    Using a DVI to VGA converter (that removes HDCP) a digital source through this into VGA is better than direct into the HDMI board. No contest!

    ...also removes the 50Hz issue of the pre 8 series......
     
  15. Kalos Geros

    Kalos Geros
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    Well, all I get from Powerstrip by default is 56 Hz non-inetrlaced or 43 or 47 Hz interlaced on my ATi IGP9100...I suppose that if you can force Powerstrip to think that he monitor can take 50Hz you may get this refresh rate listed because by default the monitor reports it's refresh and scan ranges and combinations...if you maybe enable TV output it may offer 50Hz for DVI/VGA as well...I surelly remember my previous ATI card could drop to 50Hz to VGA also flickering like hell on computer monitor and having a very strange sysnc and geometry...I currentlly cannot connect to my TV since it is in another room altogether and TV-out won't work without something attached to the other end of cable...but to draw a line here, a PC gfx card will not of its own accord adjust the refresh rate to the content you are playing from a PC DVD player - it's just pixels on your desktop mostly which you can run full screen although some cards can play DVD video independently from desktop altogether (Matrox...anyone?)
     
  16. Kalos Geros

    Kalos Geros
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  17. alwyn

    alwyn
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    On the 506 Pioneer there is a salection of either 75 or 100 Htz which is the best to use?
    Thank you
     
  18. Kalos Geros

    Kalos Geros
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    100Hz for PAL, of course...not sure Plasma can display it however, a projector might...
     
  19. JetJockey

    JetJockey
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    Thanks again Kalos, Saltrock and GranPremio.

    Very revealing.

    I had realised that 50Hz on a CRT monitor would flicker terribly. I just wondered if it flickered on the Plasma.

    Very interesting comments re the signal into the Panny PHD8 being better through Analogue than Digital. In theory of course the reverse is true.

    Has anyone else experienced this as I am now reconsidering the DVI or HDMI input boards on my PHD8 and thinking of opting for 5xBNC Component!! :confused:

    Thanks, Gerald.

    P.S. Is this DVI to VGA converter / lead, just a lead or a full blown Converter box, and if so, who manufactures it?
     
  20. Kalos Geros

    Kalos Geros
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    Jet,

    testemonials tell that HDMI is marginally better to the eye than component...DVI-I to VGA is just stupid cabling, i.e. it just passes ANALOG signal that already exist on the DVI-I connector beside the all-digital connectors (this was done for backward compatibility) and leads it to the appropriate RGBS pins on the VGA connector, nothing else...it does not do digital-analog conversion...however if you own a HDMI-only player this would be the only solution, but since you have a component output on the player, THIS is the best analog link you can get so why bother with a a digital DVI to VGA converter when it's already done inside the player???
    So if you are asking whether HDMI board for the Panny is worth while I'd say NO...unless of course in the next few months they decide to scrap all analog connections from future devices, which of course will not happen...
     
  21. JetJockey

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    Thanks Kalos.

    The position is that I am about to rebuild my system from the ground up!!

    This includes the display, scaler, all sources, A universal remote, a HTPC, a media streaming device such as the Snazzio Net DVD or Roku HD1500, and even possibly a control system of some sort.

    As a result, I have the possibility to specify almost any combination of Display - Scaler - Source - Controller - HTPC- Etc - Etc - Etc - Etc.

    Unfortunately, this offers me two possibilities:-

    1) To clean out my bank account at a rate of Knots! :eek:

    2) The ability to cock it up and make a disaster of it all by choosing the wrong components and interconnection interfaces.

    Soooooo........ I am purely asking all these questions at the moment, in an attempt to leave no stone unturned, and to try and make the best choice, with as few compromises as possible along the way. :oops:

    Hopefully, guided by some enthusiasts here, and to a greater extent by Experts such as Joe, Gordon, Liam, Piers and Maw, I will make a reasonable job of it. :lease:

    Gerald. :thumbsup:
     
  22. GranPremio

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    Kalos - Way off the mark !!!

    The 'box' I refer to takes a DVI digital signal and removes the HDCP before shipping out an analogue VGA signal. For thos with a pre 8 series Panny it enables us to display a digital 50Hz picture which is unavalable on the DVI and HDMI blades (60Hz only at 720p and 1080i).
     

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