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LCD Television lip-sync
November 6, 2005 3:36 AM   Subscribe

I've just bought a shiny new LCD television. It's very beautiful but there's a serious problem with audio and video synchronisation. Sounds come out, then the lips move. The effect is weird. It hadn't occurred to me that this was a problem but apparently it is, a known one. Is there anything I can do?

Specifically the model is an LG 32LZ50 and it was cheap (by the exhorbitant standards of these things ... I got a bargain). I'm not sure I can live with this sychronisation effect. I never noticed it on my old CRT set (same sources, Sky +). Is it a general problem affecting more sophisticated TVs as the linked article suggests? Is my dream of a beautiful 32" budget flat screen therefore folly?
posted by grahamwell to Technology (15 answers total)
 
Cheaper models save money by using slow de-interlacing/scaling processors. They have to buffer more data, and as such the video signal is delayed to an unreasonable extent. Your only hope is to find some sort of hardware thingy that you can run your audio through to delay the signal so that you can align it with the delayed video. I spent a few minutes googling and came up with this, but at that price, you might as well return your TV and buy a better one. I'm pretty sure there are cheaper things to look for – try googling things like dsp, delay compensation, lip-sync and maybe you'll turn up something.

Keep in mind that if you ever plan on playing video games, you'll be screwed. The huge delay will throw you off and make playing almost any game unbearable.
posted by tumult at 3:48 AM on November 6, 2005


It depends also on how you are sending your video signal to the TV. Using RCA cables (red/white/yellow), for example, will make the problem much more pronounced. If you are using RCA cables, try switching to straight coax (tv cable). This should help address the problem significantly.

If you are currently using coax, then try calling your cable company. Explain the problem to them without mentioning that it was caused by purchasing a new TV. Rather, tell them that the sound was in-sync until recently and then suddenly went out of sync. They should be able to adjust the sync at your cable box.
posted by richardhay at 6:21 AM on November 6, 2005


Save yourself a lot of trouble and just return the tv. Without going into too much detail, I can say I've had this problem; it's awful; you'll never get used to it. It will only bother you more, the more you watch it.
posted by Evstar at 6:21 AM on November 6, 2005


Thinking aloud: does the television have a DVI or VGA socket? If as tumult says it's a scaling issue, it's possible that you could get rid of the delay by using an external scaling device: plug all your devices into that and get it to output to the TV at its full resolution. If the TV doesn't have to do any work on the signal, it might not get a delay. You're looking at about a hundred quid for a half-decent scaler, though, which is a lot of cash to throw at something that might not work.

If you do return the television it's worth looking at the Samsung LE32R41B, and its 26 inch little brother. Given the number of gamers who are terrifically happy with theirs, and that it's the TV Microsoft are using to pimp the 360, it's unlikely to have that annoying delay problem.
posted by ArmyOfKittens at 6:39 AM on November 6, 2005


Since light travels faster than sound, you can synch it up by getting far enough away.
posted by StickyCarpet at 7:36 AM on November 6, 2005


If you are using RCA cables, try switching to straight coax

You know that the first thing a TV does with a coax signal is convert it to RCA (composite video), right?
posted by cillit bang at 8:23 AM on November 6, 2005


Another thought: if your new LCD telly is in the same room as your PC a cheap way to sort this out could be to get a TV card for your PC and plug Sky+ etc. into this via s-video. Your nice powerful PC and graphics card can do the tricky de-interlacing work without introducing a delay (with the help of this software) and you can just plug the VGA or DVI out from your PC into the telly. The LG website claims this TV has "PC input", so it should work. You basically want to be giving the TV its native resolution and refresh rate so that is has to do nothing to picture itself but display it. Powerstrip may help if it's a funny resolution, but recent Nvidia drivers have allowed custom resolutions, too.

TV cards supported by DScaler are here. You should be able to pick one up on Ebay for ten or twenty quid. Good luck!

(Note the word "could" up there; I haven't tried this, but it should work. Also you may notice a slight drop in colour quality if you're switching from RGB Scart to s-video, but you ought to be able to compensate for this in software.)

See also.
posted by ArmyOfKittens at 8:39 AM on November 6, 2005


Thanks for the feedback. Yup, tried sitting far away. Need to be in the next street I think, alternatively arranging an enormous loop of copper wire for the audio channel.

I think I'll take Evstar's advice, return the TV and put up with my trusty old CRT - but before I do (I have 14 days), could I fix this myself? I had in mind breaking the audio channels out of the SCART cable and arranging a simple analog delay circuit - like an echo effect? Sounds as though it could be a simple and rather useful little black box. Could anyone point me to the right kind of circuit?

One last question, forgive me. Am I unduly sensitive? Are there lots of people with TV's like this who just put up with it? I'm surprised a product that's flawed like this could ever make it to market.

Oh, and I found this which is just what I want (and seems to answer that question above), - it's digital and seems over-engineered at $225, but it may be the best option.
posted by grahamwell at 8:52 AM on November 6, 2005


If you are passing your television signal though a receiver/amp, the receiver may have a sync / delay setting that will let you adjust for timing.

My Yamaha has it, and I use an LCD projector. I have found that certain sources (specifically those with scaled output) benefit from it.
posted by Crosius at 11:01 AM on November 6, 2005


I had in mind breaking the audio channels out of the SCART cable and arranging a simple analog delay circuit - like an echo effect? Sounds as though it could be a simple and rather useful little black box. Could anyone point me to the right kind of circuit?

An analog circuit for a delay of any size is going to distort the sound a lot, I think. You'd need to go digital and that means a D/A converter, about 100K of RAM for half a second of stereo (more if you're going to need to delay 5.1), and an A/D converter, and it's still going to distort the sound a little probably. (24-bit would be better than 16-bit.) And that's gonna cost...

If there were a cheap circuit that could do the job, they'd probably just put one in the TV.

Am I unduly sensitive? Are there lots of people with TV's like this who just put up with it?

No, you're not unduly sensitive, it's just that there are a lot of people who are not at all sensitive to things like this. My dad would probably never notice even after I pointed it out. Their threshold of simultaneity is just higher.
posted by kindall at 11:04 AM on November 6, 2005


Check the TV's settings for an audio delay option. I'm sure LG handles audio delay, it's basic requirement of any AV device that does video processing (e.g. deinterlacng or scaling). If there's nothing in there then the automatic audio delay function is broken and you need to return it.
posted by intermod at 1:23 PM on November 6, 2005


My Sharp 32" Aquos doesn't do this. If it did, it'd drive me nuts.

I highly recommend it, by the way. It's fabulous.
posted by ikkyu2 at 7:00 PM on November 6, 2005


It's not just a little off, is it? Because some HD broadacsts look slightly off-sync on our tv, but it's only on PBS and I have a feeling it has to do more with the source than the TV.
posted by yerfatma at 5:09 AM on November 7, 2005


I would look for a factory setting that could adjust this parameter, as others have said. Failing that I would take the thing back.

However...

Here is a good discussion of how analogue delays can be achieved. There are basically three solutions discussed: Bucket brigade delays, an all pass filter built using the padé approximation (here is a first order padé circuit) and transducer spring delay, where you literally pass vibrations through a coiled spring with transducers at either end.

Here is a digital delay circuit, but it is assuming telephone quality audio... Not so good...

Running all your TV signals through Dscaler as ArmyOfKittens suggests is a great idea if you are that kind of person (lots more wiring, more things to go wrong, but more control and probably better quality). But if you were going to choose that solution you would be better off getting an LCD monitor - better display for the money.
posted by Chuckles at 12:28 PM on November 7, 2005


An update, if anyone is still interested.

I received this intriguing message from LG support:

Thank you for your email. There are lip sync issues with most digital products, mainly compounded by connection to SKY or any digital box. There is a modification available to clear this problem. We would respectfully request that you contact our Customer Service Department directly ....

I called, they had no idea what the message meant. They promise to get back with an answer three days ago, so far nothing and I'm not hopeful.

However I should cut them some slack. The TV does add a small delay, in doing so it highlights the delays already there, in gorgeous 32" detail. The problem is really with Sky, sometimes laughably so - for example on Fox News which (Murdoch's) Sky succeeds in making even more ridiculous (as if that were possible).

It's suggested that there's some kind of incompatibility between the Decoder/PVR and the TV. This and blaming the cables. In neither case can I quite see how that would work.

So after considering all the great advice here (and I'll confess ignoring much of it) I've shelled out on an AV amplifier with lip-sync compensation. It was an unwelcome and rather large expense but it's cured the problem and given me beautiful sound into the bargain. Result.

I am interested however in getting the PC to render the picture. The sound issues are not the reason now, the visual results are stunning.

If LG get back to me with another answer, I'll let you know.
posted by grahamwell at 6:46 PM on November 12, 2005


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