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VGA on radeon > RGB SCART on tv

Discussion in 'Computer Systems' started by mholgate, Feb 3, 2004.

  1. mholgate

    mholgate Member

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    Help!

    I have been trying to output video from the VGA port of my ATI Radeon 9600XT to my TV via RGB SCART.

    I can successfully connect the HTPC to the TV via s-video, but I thought I'd try out this other route for improved quality. After tackling with this for the last 3 days, I'm seriously considering just giving up and just going down the s-video route. The quality difference IS worth it, isn't it?

    I live in the UK (PAL broadcasts), and my TV is a Loewe Aconda (CRT, Widescreen, 100Hz). It has 3 SCART sockets on the back, and I have manually set the 'AV2' SCART to expect RGB input via the OSD.

    I am using a VGA > SCART cable I have wired-up as: http://www.idiots.org.uk/vga_rgb_scart/
    ...I have tried with and without the 'Blanking' connection.

    I have powerstrip installed. I use WinVNC to remotely change the display settings & connect to the HTPC. I have tried switching between Interlaced & Progressive, and Composite Sync. I've tried many resolutions, including 640x480p@60Hz, 640x480i@60Hz, 640x540p@50Hz, 640x540i@50Hz, 640x540i@100Hz, 640x576i@50Hz, 640x576i@100Hz.
    I've tried stepping-up and down through the various resolutions and frequencys, hoping that I would get close to displaying a fixed computer image.

    I've attached a photograph of the best result (flicking-image) I have achieved so far on the TV. This photograph was taken using powerstrip settings of Interlaced, 720x540, 100Hz...

    [Custom Resolutions]
    720x540=720,50,72,126,540,25,5,54,60403,312

    This image 'travels' up and left on the tv.
    The 'composite sync' checkbox doesn't make any difference to the TV image when turning ON / OFF

    1) Do I need to flash my Radeon's bios with RadEdit to enable correct RGB Scart output, even though I have powerstrip installed?
    2) Is this flicking effect normal during powerstrip setup, or is it my hardware?

    Thanks in advance,

    Marc.

    Attached Files:

  2. Ivan8192

    Ivan8192 Member

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    Marc,

    The fact that you can manually set the TV to expect RGB on the SCART means you probably don't need to worry about the blanking input. The TV is at least showing something.

    I found my Panasonic (32" Flat CRT, 100Hz) EXTREMELY sensitive to the vertical refresh rate.

    I certainly needed Composite Sync & Interlaced checked.

    I managed to get a stable picture with the following parameters:

    H Scan Rate 15.581
    V Refresh Rate 24.970
    Pixel Clock 15.082

    Horizontal Vertical
    Active Pixels 720 540
    Front Porch 56 25
    Sync Width 72 5
    Back Porch 120 54
    Total 968 624

    (Damn thing keeps stripping out my tabs + whitespace, hope you can read it!)

    Then a bit of playing around with the flicker control on the TV improved the picture.

    Hope this helps.
    Ivan.
  3. wyerd

    wyerd Member

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    Sorry to hijack the thread, but I've also tried this cable connected to my Sony KD32DX40 TV without success. I do get a stable screen but the colours are distorted - namely the white at the bottom 2/3rds of the screen is pink - see http://www.avforums.com/forums/showthread.php?s=&threadid=116414

    I don't know if it's the TV, graphics card or Powerstrip. Any ideas?
  4. mholgate

    mholgate Member

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    wyerd

    I seem to get colour distortion too, but only at certain positions when the image flys-by.
    I'm hoping this colour problem will go away once i get the image positioned correctly (the right clock phase, freq, etc)

    Anyway, playing with the POwerstrip settings, I've managed to get the picture placed a bit better, and flying-past slower...


    PowerStrip timing parameters:
    720x540=720,36,24,196,540,7,5,74,15250,316

    Generic timing details for 720x540:
    HFP=36 HSW=24 HBP=196 kHz=16 VFP=7 VSW=5 VBP=74

    Hz=25

    Linux modeline parameters:
    "720x540" 15.250 720 756 780 976 540 547 552 626

    interlace +hsync -vsync




    composite sync, hsync and vsync changes don't make any differences in the image. Should they?
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV Well-Known Member Assured Advertiser

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    The SCART socket of Loewe TV's, in fact all TV's I know of, require a RGBsignal with a composite sync. The electronics on the other side is also only expecting a 15Khz 576i or480i signal. So a PC's VGAoutput is beyond the bandwidth the thing will process.

    The way to get progressive PC signal to a Loewe is to buy the optional VGA connection kit. Even then you are going to be limited to 640x480, (it does take in 800x600 but will re-interlace this for viewing)

    This is as far as my knowledge goes with this.

    Gordon
  6. jwexqm

    jwexqm Member

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    The ATi Radeon series is capable of generating a composite sync signal (enabled with PowerStrip). The composite sync signal is outputted on Pin 13 of the VGA connector (usually horizontal sync). Last time I looked, GeForce cards could not do this (or at least were not supported in PowerStrip).

    So with composite sync and a custom interlaced display mode you can obtain an output from a PC's VGA connector that is directly compatible with RGB SCART.
  7. wyerd

    wyerd Member

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    Why isn't working for me???
  8. mholgate

    mholgate Member

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    YES! I've got it working using the following Powerstrip settings. Took me ages to just go through tweaking through all the parameters...

    PowerStrip timing parameters:
    720x540=720,76,24,156,540,19,5,62,15274,316

    Generic timing details for 720x540:
    HFP=76 HSW=24 HBP=156 kHz=16 VFP=19 VSW=5 VBP=62 Hz=25

    Linux modeline parameters:
    "720x540" 15.274 720 796 820 976 540 559 564 626 interlace +hsync -vsync



    Thanks all for a step in the right direction,

    Marc
  9. jwexqm

    jwexqm Member

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    wyerd:
    I have no concrete suggestions for your colour problem other than the following...
    - As people have noticed, sets seem to be very picky about the exact signal frequency. I have seen some strange effects on my set when the signal geometry isn't quite right. I know you said it worked on another set but maybe it's a tolerance issue.
    - The other thing is to verify that your RGB SCART input on the set is working correctly with another source (DVD player, Sky Digital etc). Triple check that RGB (as opposed to composite) is being used during the test though.

    James
  10. wyerd

    wyerd Member

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    I'll try some tweaking then. Any pointers on where to start?

    It works fine with the DVD player and Sky. I get the AV1 & 3 squares symbol.
  11. jwexqm

    jwexqm Member

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  12. wyerd

    wyerd Member

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  13. Gordon @ Convergent AV

    Gordon @ Convergent AV Well-Known Member Assured Advertiser

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    I stand corrected! Never realised you could get such a low res signal out of a PC.

    G
  14. mholgate

    mholgate Member

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    ok...

    Currently I'm successfully using 720x540i @25Hz and there is flickering in a few areas (moiré type maybe).
    Other than that, picture is pretty much perfect, albeit a bit stretched horizontally too.

    In theory, I think I need to increase the number of horizontal pixels to something like 848, but considering the TV is 16:9 PAL 100Hz Widescreen (Loewe Aconda), should I try getting 960x540i or 1024x576i on there (or am I being a bit too adventurous)?

    Seeing as I got 720x540i going at 25Hz what is the next logical resolution AND frequency step to try? Do I need to stick with 540i seeing as this works, or is there a chance I may be able to get 576i?

    I thought the whole point of 100Hz TV's is that it is supposed to remove flicker?? I guess I'm using the wrong frequency perhaps.

    Just trying to save myself a few more hours of powerstrip tweaking :(
  15. jwexqm

    jwexqm Member

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    you may be able to defeat the flicker by playing with your TV's digital framestore 100Hz picture controls. I have seen a Sony KV32FX60 clean it up nicely, but a KV32DS65 didn't seem to have such a good algorithm.

    I would advise against using RGB-out for a situation where you want to be able to navigate the Windows user interface all the while. Interlacing doesn't get on particularly well with 1 pixel wide high contrast horizontal lines and Windows is full of that kind of stuff. No broadcaster in their right mind would use on-screen graphics that in any way resemble the Windows UI for exactly the flickering reason. They tend to choose larger, soft antialiased features to defeat the effect.

    I'm not so interested in anamorphic modes but I don't see any reason why you couldn't increase the horizontal pixel resolution so long as you keep the timing consistent. I guess that way you could keep the set in 16:9 mode all the while and Windows would look 'normal'.

    Playing anamorphic DVDs in 720x540 is fine though. You just play it fullscreen "tall and thin" in a 4:3 frame and use your set to expand the picture to 16:9.

    As a footnote:
    You can use this connection method to display full-frame interlaced video on your telly without having to deinterlace and that looks very nice indeed.
  16. mholgate

    mholgate Member

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    jwexqm,

    I've already tried the TV's Picture settings ('Soft', 'Video CD', etc.) - this does slightly vary/soften the degree of flicker, but not significantly enough.

    Wouldn't it be worth my while trying 576i @25Hz or @50Hz to give more pixels in the image and possibly alter the flicker effect, or is there something I'm overlooking?

    Since the TV is digital 100Hz, can I not provide it with an interlaced source image that is 100Hz also?


    ..great, I'll try this next. I seem to have problems restricting Powerstrip to changing just one setting without throwing-out all the other settings too. (I'll eventually figure it out!)
  17. jwexqm

    jwexqm Member

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    The anamorphic mode would need to be added as a new mode in PowerStrip. This may need a re-boot for the driver to 'take it'.

    Been looking on the Loewe site and reading some usenet articles. It seems Loewe have invented a 'bastard' component input SCART and are using it on some of their sets. I'm wondering if it's via this interface that you could convince it to do progressive scan. They are very high-end sets and with things like VGA input modules as options I think it's entirely possible that it could support other modes. Whether you'll be able to make it believe that it should sync up to some non-standard RGB mode over SCART is another matter. I can't think of any other AV device that would output progressive scan via RGB so they probably haven't designed it to work that way. I'm running out of knowledge now but I thought progressive scan transmission was something that usually goes on over a component video link(?).

    Doubt it over RGB for the reasons above, it's just not a standard input.

    You can increase the viewable lines I suppose (e.g. 576) but it may just end up as overscan, it would on my set anyway. What I think you're trying to do is to increase the line density on the screen, to do this you'd be effectively changing the mode and hence I don't think that'd work for the same reason as above.

    FYI you can get a DVI to component dongle for your Radeon from ATi so this might be worth looking at. Otherwise call/mail Loewe and see if you can find out what modes the thing is suppose to be able to handle and over what interfaces.
  18. mholgate

    mholgate Member

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    jwexqm,

    Could you point me in the right direction to finding these specs for Loewe's RGB / SCART? All I have been able to find are the usual obvious stuff printed in the tv manual - no mention of the expected RGB resolutions, timings, etc.
    If these specs don't exist, I've also sent Loewe an email as you suggested, but something tells me they will be reluctant to give me that information and will probably direct me to buying a VGA module.

    Thanks,

    Marc

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