Can poor-quality HDMI cable cause ghosting?

Discussion in 'Cables & Switches' started by Alexei, Aug 19, 2006.

  1. Alexei

    Alexei
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    I am seeing a lot of ghosting from my Pioneer DV-696AV connected over HDMI. The ghost image is in a fixed position above the main picture. It is particularly pronounced when upscaling to 1080i.

    I was under the impression that ghosting could only happen on analogue interconnects. Is it so, or can a poor-quality HDMI cable be to blame? :confused:

    Before you ask, trying a different cable isn't going to be easy...
     
  2. Hi-Def

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    Alot of people say theres no difference in a £1 or £60 HDMI cable as there digital platform cables - and im just not going to get involved with that

    however this doesnt mean your cable isnt damaged maybe just trying another cable is your only option
     
  3. pjclark1

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    more likely a fault in your Tv or player
     
  4. Alexei

    Alexei
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    Any suggestions on how to establish where the fault lies? That is, short of swapping each component one by one, as unfortunately I don't have a spare HDMI-enabled DVD player or a TV. :confused:

    One observation is that when I change zoom factor/aspect ratio on the TV (i.e. 4:3, widescreen, 1080 exact scan, etc) the ghost image scales with the main picture. To me, that suggests that the ghost image is part of the signal by the time it gets to the TV.
     
  5. neilmcl

    neilmcl
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    Have you tried connecting the DVD player via another method, ie, component or scart.
     
  6. Alexei

    Alexei
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    Yes, I have. SCART does not exhibit any ghosting. However, it is not a like-for-like comparison since I can't output upscaled image via SCART.

    I have not yet tried connecting via component.

    I should probably mention that the HDMI cable I am using is fairly long (3m).
     
  7. Alexei

    Alexei
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    Also, for the record, the TV is Toshiba 42WLT66.
     
  8. arfster

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    I don't see how what you describe is possible. A screwed up HDMI connection will result in random image dropouts and sparklies etc, perhaps severe jitter at worse, as the bitstream transmission breaks down - ie different errors, not the constant type of ghosting you describe.
     
  9. Alexei

    Alexei
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    This is what one of the DVD player's menus looks like in 1080i:
    [​IMG]
    (full-size image here)

    The severity of ghosting does depend on screen resolution (720p is so-so, 1080i is quite bad).

    The TV has a variety of inputs and I don't have this kind of problems with any other input/source. This suggests that the TV is probably not to blame (unless the problem is somehow specific to the HDMI input I am using).

    The cable seems unlikely to cause this.

    How likely is this to be a fault of the DVD player?
     
  10. hamster

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    No, that's cruddy video performance, most likely due to interference between the HDMI receiver and video processing inside the TV.

    Cable effects would randomly break up the picture (sparklies mentioned earlier) as the signal is digital.
     
  11. JohnWH

    JohnWH
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    Can you post an image of what 720p looks like, as that's just plain odd...

    John.
     
  12. Alexei

    Alexei
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    If the problem was inside the TV, wouldn't it manifest itself with other sources? I don't experience this kind of issues when feeding 1080i from my PC via DVI/HDMI.

    Just for my own sanity, I've tried both HDMI inputs on the TV, and two different HDMI cables. The DVD picture looks exactly the same in all these combinations.

    I'll see if I can post a good photo of 720p.
     
  13. Alexei

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    I've revisited 720p, and it looks fine as far as ghosting is concerned:
    [​IMG]
    (full size: http://static.flickr.com/58/227108973_447b55fbea_b.jpg)

    To summarise: 1080i looks sharp but suffers from ghosting and other artefacts. 720p doesn't suffer from obvious artefacts but isn't anywhere near as sharp. (The LCD panel has 1080 lines of physical resolution.)

    I wonder if the fault lies with the DVD player. Any thoughts on that?
     
  14. JohnWH

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    The 1080i image looks like some kind of interlacing artifact, it could be the player or the TV or a combination of both.

    Sorry can't be more helpful!

    John.
     
  15. Alexei

    Alexei
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  16. Alexei

    Alexei
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    John, I think you may be on to something.

    I've just done a test with my PowerBook connected to the TV via DVI-to-HDMI. All non-interlaced modes look fine:
    [​IMG]
    (full size: http://static.flickr.com/64/227330098_d5f0b09fe3_b.jpg)

    However, interlaced modes are out of whack regardless of resolution:
    [​IMG]
    (full size: http://static.flickr.com/60/227330096_59890f786e_b.jpg)
    [​IMG]
    (This one might not be obvious unless you look at the full-size image: http://static.flickr.com/80/227330099_5046093d00_b.jpg)

    Oddly enough, static 1920x1080i output from my PC looks fine (moving images also behave strangely, however):
    [​IMG]
    (full size: http://static.flickr.com/65/227330094_9f9ab36797_b.jpg)

    I might give Toshiba a call tomorrow morning...
     
  17. JohnWH

    JohnWH
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    That is strange, does look like the tosh is having problems with interlaced input. I assume this is HDMI input only as the PC was via the 15 pin dsub connector?

    Any deinterlacing controls on the tosh?

    John.
     
  18. Alexei

    Alexei
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    D-sub is spot on: very sharp and no problems whatsoever. Unfortunately, the highest resolution it supports is 1280x1024.

    All screenshots in my previous post (both Mac and PC) are taken with DVI-to-HDMI feed.

    I couldn't find any deinterlacing controls in the menu. I assume there is a service menu, but I've not looked there yet as I don't know how to access it.
     
  19. Benedict

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    I have exactly the same problem with interlaced signals from my PC. I'm using an ATI Radion 9600 based graphics card. Your nvidea card appears to work fine and I know of at least one other forum member who's had no problems with interlaced signals from an nvidea card.

    Somebody recommended PowerStrip which I've downloaded but not tried yet (mainly as my PC is at the other end of the house to the Tosh!). It has a 30 day trial period so you can download and try for yourself for free. (Sorry, just realised you're using a Mac. I'm not sure if there's anything similar to PowerStrip for the Mac.)

    I'll post back once I've had a play.

    Ben
     
  20. JohnWH

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    Looking at your images again it looks like the odd/even fields are being reversed by the TV.

    Its a stab in the dark but if you have any controls on the source try messing with the sync polarities...

    John.
     
  21. Alexei

    Alexei
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    Thanks for the idea, but I couldn't find any relevant controls.
     
  22. Alexei

    Alexei
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    I should point out that only static nvidia pictures look fine. As soon as I start moving windows around, the image falls apart. It's hard to accurately describe the symptoms (as they are only present while the image is changing), but there's definitely a problem.
     
  23. Joe Fernand

    Joe Fernand
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    Hello Alexei

    Are you sure your ALIS panel (I'm assuming its ALIS from your reference to 1080i resolution) is designed to work with 1080i at 50hz - lots of them aren't.

    What happens with R1 (60Hz) material at 1080i?

    Joe
     
  24. JohnWH

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    Isn't teh 1024x768 intelaced image above at 60Hz? Although thats an odd resolution to interlace these days so could be...
     
  25. Joe Fernand

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    Hello JohnWH

    If its an HDMI Input then 1024x768 at any refresh rate is probably not properly supported.

    Joe
     
  26. Alexei

    Alexei
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    Hello Joe,

    I've not heard of ALIS before, but a quick google search suggests it is a plasma technology? I have an LCD TV (Toshiba 42WLT66), which I am trying to drive at its native resolution of 1920x1080.

    While experimenting with my PowerBook connected to the TV, I have tried both PAL and NTSC refresh rates (50/60Hz interlaced), and both look exactly the same.
     
  27. Joe Fernand

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    Hello Alexei

    Back to square one then :)

    Your TV ought to cope easily enough with 1080i - not sure if it can handle 1080p though!

    One thing I noticed with the 1080i screen shot was the moiré pattern in the background - it looks like some form of overscan is switched on; does the TV have a Dot to Dot mode within the Aspect Ratio control menu?

    The HDMI cable is going to be the simplest thing to test if you don't have access to another 1080i capable DVD player.

    Joe
     
  28. JohnWH

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    HDMI cable swapping fields round though? Sounds like a long shot...
     
  29. Alexei

    Alexei
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    To clarify: the TV does not support 1080p, and I am not trying to drive it at that resolution.

    The pictures I've posted were taken with a digital camera. The moiré pattern is due to the fact that the camera wasn't perfectly aligned with the TV. There is also some barrel distortion evident in the pictures - it too is an aterfact of the camera (more specifically, of the wide-angle lens I've used), and not the TV!

    As to Dot to Dot, I assume this is the same as Exact Scan on the Toshiba. With Exact Scan, each pixel in the input signal is mapped to one pixel on screen with no scaling or cropping. I do have it turned on for 1080i.

    I spoke to Toshiba and they agreed that the unit is faulty.
     
  30. Alexei

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    I have actually tried different cables, more for my own sanity than for any other reason. They make no difference.
     

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