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LCD - lipsync problems?

Discussion in 'LCD & LED LCD TVs' started by Rob100, May 17, 2003.

  1. Rob100

    Rob100
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    Hi,

    Do LCD's suffer from the same lip sync problems as plasma's?

    Thanks,

    Rob.
     
  2. StooMonster

    StooMonster
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    In a word, yes.

    StooMonster
     
  3. Rob100

    Rob100
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    Okay, thanks. Does the smaller size of a 17" LCD make it less noticable than on a 42/50" plasma? I am quite susceptable to lip-sync problems, so I think it would still drive me mad (like it did on the plasma until I got a delay box).

    Looks like a nice cheap 50Hz CRT for the conservatory it is then.

    Rob.
     
  4. taimur

    taimur
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    which delay box did you get?
    Taimur
     
  5. StooMonster

    StooMonster
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    Much less noticeable on smaller display IMO.

    As you are aware, lipsync issues vary not only within a channel, or a programme, but within segments of a programme -- news with "live" feeds being the worst offenders; with some sections with problems others, others with none, some with moderate.

    As far as I know, this has gone unnoticed for years and it's only with the introduction of large screens that one can see this -- accepting a small delay due to processing, and most lipsync is due to broadcasters and is much greater delay than caused by processing alone.

    I'd suggest that if you have your audio delay set to the time of processing, and don't notice any further lipsync problems then LCD won't bother you.

    I can't say that I've ever noticed lipsync on my 17" LCD, but I've never looked for it; whereas different story on my plasma and iScan Ultra (although a lot better these days). Perhaps it's just not noticeable per se, or there is a delay in the inbuilt audio -- as it's certainly still prog-scanning and therefore processing the picture.

    Only way to see is go and get a demo, if you fancy a 17" widescreen LCD check out the Grundig as IMHO the picture is "best in class" and price is reasonable.

    StooMonster
     
  6. Rob100

    Rob100
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    taimur - Behringer 2024 from Joe @ TMF

    StooMonster - as you suggest maybe I should have a look for myself in some stores. I don't like buying "old" technology and buying a CRT would be just that, plus they take up so much room! I have always been a bit sensitive to lip sync issues (ever since video editing/encoding etc on PC) but I seem very sensitive to it these days. Even my wife notices - that is no doubt my fault going on and on about it... She still thinks I'm obsessed with PQ, but that's a different story...

    Rob.
     
  7. Nexsen

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    As mentioned above the lip-sync error in the source material changes between broadcast programmes and DVD's and adds to (or subtracts from) the fixed processing delay caused by the display (whether plasma, LCD, or DLP all have a processing delay).

    Yes, "subtracts from" in cases where the audio arrives delayed instead of ahead of the video. It can happen in broadcasts but seems more common on DVD's for some reason (encoding errors?). In such cases the video processing delay of the display helps correct the delayed audio.

    For example I now use a Felston DD740 digital audio delay (previously had a 2 input DD540 and upgraded to their 4 input DD740) but they both are identical in the way they allow you to press a plus or minus button and tweak the audio delay while watching without image disturbance. That's essential for true lip-sync correction since it changes so often (every programme and every DVD).

    The DD540 adjusted in 1 ms increments and the DD740 does too but offers a fine mode with 1/3 ms steps for the very sensitive. I still use 1 ms steps.

    Back to my point: My display requires about 60 ms delay from my DD740 to offset its fixed video delay. So when the Felston DD740 is set on 60 ms you can think of that as "zero". If the arriving material were in perfect sync (seldom the case) that setting could be left alone and lip-sync would be perfect. But usually there will be 30 to 60 ms of additional video delay in broadcasts (changing between programmes) so I normally tweak the delay up from 60 ms to between 90 to 120 ms to achieve perfect lip-sync. It only takes a few seconds but often a suitable talking head scene won't come along until well into the programme or movie so the adjustment needs to be transparent and not overlay the screen with distracting menus. That's why I use a delay box instead of the receiver's internal delay. Receiver internal delays require going back and forth to a set-up menu disrupting the movie every time you want to make a delay change and it can take quite a few experimental changes to get lip-sync perfect. All of the delay boxes I've seen (Alchemy2, Felston, and Primare) allow adjusting the delay in 1 ms steps without disturbing the image and that's really essential.

    When audio arrives delayed instead of ahead of the video such as with Denzel Washington's "Inside Man" DVD (audio delayed about 40 ms), I use the minus button and back the DD740's delay down from 60 ms until I see perfect sync. For that DVD the DD740 delay would end up at 20 ms since I'd be using 40 ms of the display's 60 ms delay to offset the arriving 40 ms delayed audio and the DD740 would be providing 20 ms audio delay to cancel the display's remaining video delay..

    In that case I'm effectively using the display's video delay in 1 ms steps to correct for the arriving delayed audio. So far I haven't encountered delayed audio above my display's 60 ms video delay but if it happened I couldn't correct it. Ironically when you use a delay box the display's video processing delay becomes an "advantage" and the higher the delay the better since it allows you to correct larger incoming audio delays.

    This is the case (audio arriving delayed) in which HDMI 1.3's "automatic lip-sync correction" will actually make lip-sync "worse". All that feature does is add a fixed audio delay equal to your display's video delay (the same as you can do manually with most ordinary receivers) so in the example above (Inside Man) the added audio delay would be a fixed 60 ms and you'd see a 40 ms lip-sync error when it would have only been 20 ms if left alone.

    I think most people don't understand HDMI 1.3's "automatic lip-sync correction" feature. They don't realize all it does is "automatically" set the same fixed audio delay you can set manually to cancel your display's fixed video delay and it does nothing to correct the varying lip-sync error changing from programme to programme or DVD to DVD. True automatic lip-sync correction is actually impossible because there is no watermark put in the audio and video content when created to define when they were ever in sync.

    When using the DD740 or any delay box you need to always turn off any lip-sync correction provided by your receiver (whether HDMI 1.3 or regular manual set delay) so that you can use your display's video delay to correct incoming delayed audio when it happens - and it happens more with DVD's than you would think.
     

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