DVD playback problems via modulator

Discussion in 'Cables & Switches' started by alpinista, Aug 31, 2004.

  1. alpinista

    alpinista
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    I am trying to use a Philips DVD728 with an early-90s Philips TV set that has only a 75 Ohm RF input. I can watch DVDs, after a fashion, by connecting via a mid-90s Philips VCR which has a Scart input. I am also trying to use a Philex SLxRF modulator to avoid the need to route via the VCR.

    The DVD728 is outputting RGB via Scart using the supplied Scart cable and no trick picture settings.

    With both options I am experiencing unusual picture problems which I will try to describe. These seem to be related to the relative brightness level of the picture at any time. At low brightness levels the picture starts to 'jump' vertically. It's a bit like the old loss of vertical hold problem but the frame does not unlock completely.

    When the picture is brighter, it stops jumping, but then another effect comes into play: a periodic brightness/contrast transition with a period of about one second. It's as if someone was switching a colour enhancement function on and off.

    When the picture is bright, the colours do seem significantly oversaturated. When darker, the contrast seems lacking.

    It's also worth noting that the picture instability was apparent even in the player's home state, i.e. without a disc playing, which is what leads me to suspect there is an RF modulation problem.

    I have yet to try connecting the player's composite output via the Philex or the VCR. I note from the player specs that the composite o/p is typically 1V
    peak to peak whereas the RGB outpupt is 0.7V. I do not know whether this would make a difference.

    I would be interested to hear from anyone who has witnessed anything similar in the past, and could offer any potential solutions. I am resigned to the fact that I may need to buy a new TV.

    Thanks for reading!
     
  2. LV426

    LV426
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    The symptoms you describe sound like the effects of macrovision. Whilst this is a likely explanation...

    1: I'm puzzled as to why the DVD player is outputting macrovision with no disc loaded. Although I guess it's possible that the macrovision signal is "on" by default and only off when the disc tells it to be off (rather than only on when it's told to be)

    2: I'm puzzled as to why the standalone RF modulator is affected. It's to be expected with a VCR.

    To verify this suspicion, you could try using the RF modulator with
    a) the composite output from the DVD
    b) the composite output from the VCR, playing a tape you've recorded yourself from the TV (not a bought one)

    and see if anything changes. If (b) works and (a) doesn't, it would tend to point at a macrovision signal from the DVD. And you can buy a special SCART cable to suppress macrovision.
     
  3. mdinch

    mdinch
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    What you're seeing is the effect of Macrovision. Most DVD's, not all, have macrovision on to stop people from making copies of DVD's. E.g. Lord of the Rings does not have macrovision. You should be able to see 'Macrovision' printed on the disc some ware if it has macrovision on it.

    There are cables available to eliminate this effect. Here is one site.
    http://www.sonel.com/?cf0A2C7014=SUNBUFxNRUhNRVREOm50bG06XwnLMnWuF24UxSHNNElHEg==
     
  4. Reiner

    Reiner
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    I think the problem lies in using the RGB output (via Scart) at the DVD player. Once activated the composite (also inside the Scart) acts as synchronization signal.
    Most if not all VCRs do not take RGB as input, so your choice is either S-Video (if it's a S-VHS deck) or composite (standard VCR).

    I don't know the modulator but those that I know also do not take RGB, so I assume you are watching the synchronization signal at this time.

    Edit: Did a quick search for the modulator, it states AV signal as connection (via Scart or AV input).
    Thus switching off the RGB output and use composite only instead.
     
  5. alpinista

    alpinista
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    Thank you very much for all of these detailed responses. I shall try the DVD player's composite output and report back in due course.
     

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