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Herringbone interference on Capture

Discussion in 'Desktop & Laptop Computers Forum' started by Mr.D, Oct 7, 2002.

  1. Mr.D

    Mr.D
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    Hey nearly finished the latest blockbuster so back to my HTPC.

    I had the pinnacle PCTV rave ( quite good but had some noise : also had a herring bone pattern which seems to oscillate from about 315 to 045 directionwise) Bought the falcon for mucho wonga hoping it would improve things : not much improvement to be honest slightly less noise but herringbone still there.

    Bought an enermax power supply ... quieter than the quietPC one and better cooling ( machine was stable before but now its rock solid). No visible improvement to picture however. Reinserted all PCI cards and plugs : internal cables are all well away from capture card.

    The normal signal path is from a nokia digibox to an RGB to s-video convertor through a 15ft s-video cable ( decent quality shielded). Alternative input from a dvd player using straight s-video and a different shorter cable (again good quality but different cable : Ixos) also shows herringbone pattern. Both signal paths into normal 32" widescreen show as clean.

    Using the HTPC in a different room with a CRTmonitor shows the herringbone.

    Removed modem from HTPC ( I use it for surfing as my other PC is in bits for the time being) No change to herringbone.
    Removed internal case speaker : no change to herringbone.

    Changing Dscaler hardware settings from PCTV rave to normal BT878 (or thereabouts) and back makes no difference to the herringbone.

    Capture card is in slot furthest away from AGP port : Has 3 slots between it and the soundcard.

    Will try to better shield capture card using earthed aluminium/paper envelope trick.

    In the meantime anyone know what the herringbone interference would be indicative of ?
     
  2. JohnS

    JohnS
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    What about trying an independent earth from the case.

    Cant say I notice the effect you speak of with the rave card you sold me, just a slight general noise across the whole picture. It makes me think that it has got to be interfernce from somewhere so perhaps better earthing might help.
     
  3. Mr.D

    Mr.D
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    Yep I'm pretty sure its not the card(s).
    When you say independent earth you mean bolt a seperate earth lead from the case to a seperate earthed plug ??

    sounds like a plan anyway.
     
  4. JohnS

    JohnS
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    Yeah exactly that, got to be worth a try, Ive heard that it can help with a digibox too.
     
  5. Mr.D

    Mr.D
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    Just done it to the HTPC. Will take a look and post back tomorrow.
    Moved the capture card to a different slot also.(can't hurt and if it does it might tell me something.
     
  6. JohnS

    JohnS
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    Let us know the result.
     
  7. Mr.D

    Mr.D
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    zip nada!

    No difference to the herringbone pattern.
    Only things left to do are try some some sort of diy shielding for the card and or get a proper mains purifier ( instead of the belkin 4way surge protected/RFU shielded one currently in use)

    I just hope its not the TUSL2 mobo thats at fault: I notice that the A7V board I also have has a feature that limits EMI that the TUSL2 lacks.

    Firing up the A7V machine with the falcon in it and dscaler might give me an indicator as to whether its a mains or hardware problem ( pain to be honest as the HTPC is pretty much perfect when it comes to TT playback).

    The herringbone is fairly subtle ( my wife can't see it) there is a little additional picture noise that is unobjectionable to be honest ( the adaptive helps but I prefer the picture with it off) I wonder if the herringbone could be indicative of the card retrieving a little too much information : maybe it needs a high pass filter or something .

    I'd be interested in knowing if anyone else has come across similar problems ( Gordon has a similarly spec'd HTPC).

    Update:I've found a few reports on the AVS forum of herringbone interference on a lot of cards including the falcon. Also some references to it possibly being down to the PSU. Man what a drag...
     
  8. JohnS

    JohnS
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    I seem to remeber reading about an enermax mod to reduce noise, (cant remember if it was audible or visual though) that involved removing/changing a capacitor or something....sorry to be vague and I did a search here and it turned up nothing, maybe it was on AVS but I seem to remember a link with JohnAd (though it might not, it was a while back when it wasn't relevent to me at the time).

    I'll bang my head against a wall for you:(
     
  9. Mr.D

    Mr.D
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    Removed the soundcard (maudio 2496) now only the capture card and the radeon in the machine. Unplugged the dvd drive and the floppy.

    Herringbone is still there.

    I doubt its the capture card.
    Video engineer mate of mine doubts its the PSU as I've used two different ones with no change in behaviour.

    I know its not the incoming signal as its clean on normal TV and a different source/cable/path gives the herringbone also.

    So either its the mobo in which case I'd have to rebuild the machine which is a pain as its pretty much perfect for dvd playback. Or its the mains in the house which probably entails a decent mains conditioner and yet another purchase.

    The herringbone is weird though: it oscillates between 045 and 315 and it rises up and sometimes it fades away ... and then comes back again.
    So its apparent at switch on its static its at 045 then it starts to roll vertically unti;l it effectively disappears then it becomes apparent again moving rapidly then it stabilises and its at 315.

    Another possibility is that the card/PC signal path resolves much more resolution compared with the normal 32" CRT route and the signal itself has this problem and its only the PC that shows it up. the only thing that counts against this is the similar behavious from two different sources (dvd and digibox) although if its the mains that causes it it could affect both these sources to a simialr effect.

    heck
     
  10. JohnS

    JohnS
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    What about trying turning off all the elctric in the house except th pj and pc, might give an idea if it is noise on the mains or of course borrow a sniffer from RA and then return it under there satisfaction policy if it makes no difference.
     
  11. Mr.D

    Mr.D
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    Yep I think its mains malarkey time.
     
  12. Mr.D

    Mr.D
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    Update : made some progress.
    I moved my stand alone dvd player from its cabinet nearer to the HTPC for testing and used the "raw" s-video from the player than the RGB to s-video convertor. result ; no herringbone picture is very clean! The player is plugged into the same mainsblock as the HTPC.

    I moved the RGB to s-video connector to the dvd player and plugged it into the same mains block:No herringbone , slightly more picture noise than the raw s-video out of the dvd player but nothing terrible.

    So now I know the falcon is fine as is the cabling and the RGB to s-video convertor.

    Plug it all back together and take a look at the digibox : herringbone instantly comes back.

    I hook up my SVHS deck which is plugged into the same mainsblock as the digibox ; clean as a whistle no herringbone. ( gave me some ideas about maybe routing the s-video out of the convertor to use the the TBC and noise reduction in the SVHS vcr:its one of those JVC flagship models with all the bells and whistles...however thats for the future).

    I figure its the digibox. So I've put a seperate earth on the chassis: not tried it with the HTPC yet that will happen tonight. However I immediately noticed the RF output ( which I never use) cleaned up enormously: previously it was very noisy with patterning.

    I'm pretty confident the HTPC isn't the culpret now ...touchwood.
     
  13. JohnS

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    I hate it when evrything you try comes up the same, at least you seem to be moving in the right direction.

    I must try the digibox earth myself, the picture in the kitchen off of RF2 is awfull.
     
  14. Mr.D

    Mr.D
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    Earthed digibox.
    Herringbone still there. Its more intermittent than it was previously (sometimes its clear for minutes at a time)

    The temporal filter does remove some of it ( I don't like the way it softens the rest of the image however.

    Next plan... wonder if its possibel to get a dtv ( freeview) tuner card for the PC itself and pump that through Dscaler.
     
  15. SeaneyC

    SeaneyC
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    I believe the Hauppage WinTV range of cards have a few digital models, both satellite and terestrial. Enjoy!
     
  16. Mr.D

    Mr.D
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    Ah but will they work with Dscaler and ...big one.... are they clean??? (would have thought so if they never go analogue).
     
  17. jamesrich

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    yes they are clean, no they won't work with dscaler :(
     
  18. Mr.D

    Mr.D
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    I'm sure I remember JamesAd mentioning this method as a potential future implimentation ??
     
  19. JohnS

    JohnS
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    I think its JohnAd.;)
     
  20. Mr.D

    Mr.D
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    No no its his better looking brother I'm on about !

    ;)
     
  21. JohnAd

    JohnAd
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    Keith

    Both Jim & I think that DScaler support for the digital cards is too hard even for us.

    What I am planning to do is to write (or assist in the writing of) a BDA driver for the Nova-T, that way we can get the MPEG stream and do all sorts of nice things with it including deinterlacing if required. In my tests so far the MPEG stream is pretty well flagged so there isn't much need for film detection at the display end.

    John
     
  22. Mr.D

    Mr.D
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    Very cool John thanks for the update.
    Dscaler works brilliantly by the way ( just need to sort out my herringbone somewhere and I'll be happy)

    My regards to your sibling.
     

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