AXINO-TECH HOME

GUIDE TO LIP-SYNC ISSUES between flat-panel TV's and HOME THEATRE systems

You bought a brand new LCD (or plasma) TV, hooked it up to your blu-ray player, connected the sound from the blu-ray player to your old home theatre system and sat back to enjoy the latest blockbuster. Almost immediately you think the actors are speaking another language because their lips don't move in sync with the words you hear from your speakers. Well, this has become a common problem since flat screen televisions appeared. This article outlines the issue and what you might do to fix it, or at least make it tolerable.

In brief, modern flat panel TV sets take a lot of time to process the pictures and display them on the screen. This is unlike the sound, which suffers no significant delay via the home theatre amplifier. The sound comes out the speakers before the corresponding picture. This is most disconcerting in the case where an actor is in close-up and speaks. You hear the start of the word before the lip moves, hence the name lip-sync error. The same problem might be apparent if say a gun was fired and you heard the gunshot slightly before the trigger was pulled.
Our human brains have come to regard a slight delay in the sound as tolerable because we are used to echoes. However, a sound arriving before the event is rather confusing for the brain and it is hard to adapt to. An TV owner whose audio-video setup has lip-sync error might tend to look away from a close up shot of an actor's face or will otherwise momentarily de-focus from the picture, either of which detracts from the entertainment value and becomes rather tiring.

OK, so what is the solution? Well there are several answers depending on how much money you want to spend. In order of cost:

(a) Listen via the TV set speakers.
(b) Connect the stereo audio output of your TV to the audio input of the home-theatre.
(c) Turn off some of the TV's picture processing
(d) Buy a converter box that converts the digital audio output (optical or coaxial) of the TV to analogue audio for your home theatre system.
(e) Buy a new home-theatre system that preferably has HDMI inputs and pass-through, or at least digital audio (SPIDF) input so that you can use option d without an external converter.

All of these solutions have problems of their own. Next we look at the difficulties for each.

Listen from the TV sets' own speakers

You can do this assuming you connected the audio from the player to the TV. If you use an HDMI connection, then audio connects through automatically. If you use component or composite video, you have to run audio separately to the TV. But the major issue is that the sound quality from TV set speakers is poor and with some models, it is abysmal. It is not good enough for home-theatre. However, the sound is usually synchronised with the picture because the TV manufacturer ensures the internal delays between picture and sound are reasonably matched.

Connect the TV audio output monitor to your home-theatre system

Most TV's have a stereo audio output at the back. The sound at that point will be synchronised to the picture. Connect that to a spare input on your home-theatre amp and the problem is solved. Well kind of. Of course it is only stereo and not 5.1 or 7.1 surround sound. That is the main problem with this solution. You can switch your home-theatre into Dolby Pro-Logic mode and get synthesised effects channels, but you will miss out on the higher fidelity and discrete multichannel sound now available on some movie sound-tracks. Still, this might be acceptable if you are plagued with lip-sync errors.

Turn off some picture processing in the TV

This involves getting into the serious parts of the TV menus and may not be for all. In fact on some TV's, it may not be possible to do much. I can only offer the solution I found for a Sony KDL-46X4500 set. (See the end of this article for the settings.) Some will ask how can you turn off picture processing features in a TV? Are they not there for a reason? Well, it is worth a try. In my experience, turning off or reducing the processing settings either makes a minor difference, makes no difference, or actually improves the picture. The latter is quite common. But, I cannot provide explicit descriptions of what will happen for each setting on every make of set. You have to try it. For the Sony set I have adjusted, the lip-sync error went from intolerable to barely noticeable.

External SPDIF to audio converter

This kind of device takes a digital audio SPIDF input and produces 5.1 channels of audio at the output. I understand these can be bought and will be less expensive than replacing the home-theatre amp. (I have seen some versions that produce only stereo sound. That will be no better than using solution b above.) You would need to connect the digital audio (SPIDF) from the TV set (not the player), unless the device has the ability to add audio delay itself. TV set picture processing delays vary with settings but can be as high as 8 picture frames (or 320 milliseconds) in 50Hz countries. So, check the specs before buying to see if the box can delay the audio by something approaching this much. {But if you connect from the TV, you don't need any delay} Apart from the expense, the other problem with this solution is that the SPIDF connection may not pass the more exotic uncompressed multichannel audio streams now available. Dolby Digital 5.1 (640kb/s) and DTS 5.1(1509kb/s) are OK, but it is fair to say the SPDIF protocol in either optical or coaxial implementations will not carry DTS-HD Master audio at 24.5Mb/s.

By the way, if your home-theatre system is not quite as elderly as mine, it might have SPIDF inputs. This means that you can do this solution without buying an external converter.

Buy a new home theatre receiver

This is the ultimate solution but is a major expense. Generally, the less expensive models will not have all the facilities needed.
You need a model that has HDMI inputs; well at least one. The more comprehensive units will have 4 or more HDMI inputs and can switch either of them to the TV set, and select the audio data at the same time. The receiver will extract the audio stream and play the sound through the amp speakers, while passing the video to the TV set. A full and properly implemented HDMI 1.3b connection actually synchronises video with audio on the fly, but this feature doesn't always work well between different equipment. It is better if the home theatre receiver can add user-adjustable audio delay as well.

Lip-sync problems broadcast on digital TV

Some people have mentioned they see lip-sync errors from digital TV stations even when using the TV's own speakers. This can happen in programme production and is not uncommon. It is one of the 'difficulties' of making programmes in the digital age. Occasionally, lip-sync errors can occur at playout in the studio equipment. If this sort of problem annoys you, try to see if it is only one particular station, then complain to the station. If it happens on all stations, then it is possible that the TV set is causing it and you need to contact your retailer.
(I have seen this on rare occasions as well as on certain advertisements. These ads are poorly produced or the actors voices really are dubbed over in English.)

Checking lip-sync delay

I use the 'Digital Video Essentials' (DVE) test disc, either DVD or the blu-ray version. These have a track that has a rotating clock graphic and which gives a blip when the hand reaches the top position. By playing this track in repeat mode and listening to the sound from the home-theatre system, it is possible to demonstrate that the sound arrives before the picture, and see how it changes as picture settings are changed.

If you don't have access to one of these a good method is to play any DVD or blu-ray preferably with continuous dialogue going on. Turn the sound up on your home-theatre AND on your TV set. Any lip-sync error immediately shows up as an echo and when there is no error, the sound comes out of both home-theatre and TV at the same time. Easy.

Adjusting the Sony KDL-46X4500 TV

The client had a Panasonic DMP-BD80GN-K blu-ray player connected by HDMI to the Sony KDL-46X4500 set. The 5.1 audio from the Panasonic player fed the 5.1 audio inputs on the Yamaha home-theatre receiver. There was considerable and intolerable lip-sync when playing back "Casino Royale" on blu-ray. Other discs produced similar problems.

By default, the Sony set comes with 'DRC' mode on. Turning DRC off is the best way to reduce the processing delay so that lip-sync is barely noticeable. Other adjustments such as not using 24Hz refresh, using 1080i instead of 1080p did not make a significant difference. This Sony has the ability to set up different modes for every input. So it is only necessary to turn DRC off for external sources such as DVD or blu-ray. I saw no significant change to picture quality and it is hard to determine exactly the purpose of 'DRC'. You can leave settings alone for off-air sources, well in respect of lip-sync anyway. Other adjustments can benefit the picture quality generally, but that is the subject of another article.

Actually I think Panasonic missed a trick with the DMP-BD80 player. They produced this version with internal audio decoders, which is otherwise identical to the much cheaper DMP-BD60 model which has SPIDF only. The only possible reason why someone might buy the more expensive model with internal audio multichannel decoding would be if they had a legacy home-theatre system without HDMI or SPIDF support. But Panasonic did not include provision for audio delay. A rep from a local Panasonic agent stated there would be no firmware upgrades forthcoming for the DMP-BD80 that would 'add' audio delay.

Axino-tech Consulting & Services , May 2010.