DISCLOSURE: My company sells Felston products in the US but my post on this UK forum is based on my personal use of their DD340 and DD540 but I want to be up-front about my possible bias. That said:

In a review of the Felston DD540 lip-sync corrector Mr. Archer listed as one cause of lip-sync error:

"and big differences in the length of audio and video cables in a system (a common situation for people using projectors)"

ALL of the other things he mentions are causes of the widespread lip-sync problem, however cables are "not" one of them.

It would take a difference in cable length of 386 MILES (over two million feet!)to cause even a 1 ms delay!

I also disagree with his assessment that the lip-sync problem seems to be going away as better display technology evolves. That might be true if the only cause were the video delays created by the displays themselves but the increased size of Hidef images are creating much larger delays within the broadcast chain and the problem is getting worse rather than better as HiDef is deployed here in the US so I would assume it must be the same in the UK at least in my view. Mr. Archer correctly explains that many causes contribute to the cumulative delay which becomes noticeable to viewers whenever it passes their "threshold of recognition". He's right in that displays "have been" the "straw that broke the camels back" pushing the delay beyond that threshold but we are now seeing delays within broadcast alone exceeding that threshold even if the display contributed none at all. Incidentally I personally have both a Felston DD340 and their new DD540 and they are both excellent products that I would not consider being without as they allow me to easily change the delay even within a program if required to maintain lip-sync. Mr. Archer lists almost as a deficiency that it can't do that "automatically" but he doesn't mention that it is impossible to do since there is nothing in the audio and video signals to define their timing relationship. SMPTE has formed an Ad Hoc committee to try to address this deficiency in standards and perhaps there will some day be a signal or "watermark" that would allow this but it won't be any time soon. The best posible solution today is a subjective adjustment by the viewer which the Felston products make very easy. And to elabrate on another of Mr.Archer's "deficiencies": He says the DD540 can only handle digital inputs. While that is true it should be mentioned that a simple low cost A to D converter can be used to apply a legacy stereo analog input to the DD540. As Felston's US reseller we offer a package called the DD540+ADC which includes the converter for only $20 (about 11 GBP) above the cost of the DD540 alone and I have been using one on my system since late last year. We don't sell them in the Uk since they all have US mains connections but I feel sure felston's UK dealers can supply similar converters if you have analog inputs.

I also find Felston's enclosures to be excellent and at least as professional and well made as any other high end Home Theater equipment I own. It's remote control is infinitely better than the one that came with my Fujitsu 42" Plasma and its brushed aluminum cabinet is comparable to the enclosure of my Faroudja line doubler which originally cost about 40 times as much(and which inidentally adds 64 ms of video delay before it hands the signal to a display for possible further delay).

I would like to know something about this device and lip synch errors. If the errors are only intermittant (as they appeared to be in the three film mentioned in the article), will not a general delay on the audio signal cause errors in other parts of the film that did not exhibit problems?

Yes, you are absolutely right. And that's why we feel it is so important to be able to adjust the delay easily with buttons on a remote control and with presets like the Felston DD540 has.(Unlike any av receiver we've seen claiming lip-sync correction.)

Luckily most DVD's that are off seem to be consistently off, so usually one adjustment is sufficient.

The other thing that reduces the need to constantly "tweak" the Felston DD540 is that sound before the lip movement (or event) that produced it (which is what happens when the video is delayed) is impossible in nature and therefore "very" disturbing and noticeable when our brains try to process that "impossibility" and once that problem is corrected further delays are far less noticeable.

The reason is that in nature sound is always delayed reaching our ears "after" the event producing it by about 1 ms per foot of distance to the source.

So, even though "too much audio delay" is still a lip-sync error and we "can" notice it if we "focus" on the lips for that purpose, it doesn't jump out at us like a video delay (leading audio).

To illustrate that point, look closely for this delay the next time you are listening to a speaker in a large auditorium and at least 150 feet away. When you focus on his lips you will notice the "natural" lip-sync error but I'll bet it never bothered you at all before. Our brains are accustomed to that natural phenomenon which is why a little "too much" audio delay is infinitely preferable to "too little".

The short answer is: Once you use the Felston DD540 to eliminate leading audio, changes in your program or DVD that result in that delay setting being an "overcorrection" are far less noticeable but if they become noticeable a press of a button on the remote can fix that (or I should say LipFix™ it).

I assume by intermittant, you are meaning on one film but not another? Or are you meaning it seems to be intermittant throughout the same film? Ive just bought a new system and Im beginning to wonder if this is something that IM just going to have to live with...
My current problems are here!
http://www.avreview.co.uk/forum/threadreply.asp

I experienced lip sync errors on a rather naff film '40 Year Old Virgin' (Yes I know!), just last night and it was way out. My girlfriend even thought that it looked strange and usually she never notices. The trouble with us pureist AV lot, is that we spend a fortune only to run into more proplems. What's more aggrevating is that friends with far, far lesser systems almost delight in mentioning the lip sync errors. As if we've been ripped off in some way. OK I am venting, but when like a lot of us, we spend over £7000 on a high end AV system and this happens and friends delight in that - it's frustrating. So, I am awaiting delivery of the gadget and hope that I can get to enjoying films that suffer with lip sync errors sorted once and for all. I will let you know how it goes.

LOL- Exactly the same with my Mrs and mates... Im thinking of changing the amp to one with HDMi input so maybe in theory the signal for the audio and vision should be taking the same route. has anyone got a setup like this but still suffers lip sync? What setups you got?

I got the Felston thingamy and it does do the trick with DVD's that are ahead of themselves. Although, I have found it had to be cranked up all the on the above film - but that is probably an extreme. On other films, where I have noticed slippage, it does the trick really well. Plus it's relatively small and discreet. Very well made too which is a bonus.

I have HDMI being feed to my LCD and the COAX goes through to the Felston then SPDIF into the amp.

Here's my setup:

Dell 37inch Hidef LCD TV (I bought it because they use Philips panels)
Yamaha DSPAX757SE AV Amp
Denon 1920 DVD (may upgrade this soon)
QUAD L12 front speakers
QUAD Centre channel
QUAD Subwoofer (superb)
QUAD L11s speakers on back
Philips DVD/VCR/HDD 200GB recorder
Sony Freeview (as the one on the Dell is crap)
Cambridge Audio D500 DAB Tuner
QUAD 99 CDP-2 CD PLAYER/PRE AMPLIFIER (astounding)
Felston DD550 Digital Delay
QED Silver Anniversary cables and gold bananas all round. QED cables and HDMI.

That's about it I think. Cost a few quid, all recently purchased.

Stu

Hmm your running the same amp/ DVD as me, Im using the Hitachi 42pd7500 plasma. Is your problem the sound being ahead of the picture like mine or vice-versa? Also Do you find this varys with films?

Only noticed the sound being ahead of the picture - hence the digital delay dragging it back in sync. Not noticed it the other way around. Sadly it does vary from DVD to DVD. Some DVD's don't suffer from it at all - well not in such a way that it causes a problem. However, creating a standard delay of 120ms brings most DVD's back into line. Then using the presets I created of 120, 200, 275,350, 400, 475 - to quickly click through when the problem arrises. You can of course change any of these.

I am thinking of upgrading the DVD. It's a great DVD but there are better ones out there and I am not doing the rest of the system any justice with the DVD as it is.

I cant seem to suss why the sound would be ahead of the picture. Ive swopped the DVD and the Amp thinking it was faulty (it wasnt)so unless the Tv has some kind of fault processing the image,Im lost... :-(

That really is quite weird. As it's the TV that takes the time to process the image, causing the delay. Hence the audio being heard slightly ahead of the image. Are there any DVD's specifically that it is happening on? I may have them and can try it out.

Am thinking of upgrading to the following:
PIONEER DV989AVi DVD PLAYER

One of the worst is the fast and the furious.
Setup- Hitachi 427500.Denon1920dvd,yamaha DSP757SE amp. DVD to Plasma via hdmi, dvd to amp via coax.tried using a optical,same thing. Went out and bought a samsung DVD today from currys to try, problem is not as bad for some reason but the sound is still ahead of the pic! Nobody Ive spoken to has experienced this before, it always the sound lagging behind.

found this
http://www.audioholics.com/techtips/specsformats/AV_lip_sync_delay.html
it mentions audio being ahead of video then seems to go onto audio being behind?.
anyone had experience of using an amp with audio delay such as the denon 1906?
(BTW Im a total newbie when it comes to AV as you can prolly tell)