• New Patreon Tier and Early Access Content available. If you would like to support AVForums, we now have a new Patreon Tier which gives you access to selected news, reviews and articles before they are available to the public. Read more.

Panasonic TX-50CX802B (CX800) lip Sync problem.


Novice Member
Anybody having issues with audio and video sync, or can anyone shed light on it?My audio and video are ever so slightly off.

I'm using a hardrive(HDMI to USB port on the TV), and TV through a set-top box which is connected to the TV via HDMI(the set-top box is connected to my router via ethernet). The set-top box has audio out so I was thinking I could buy some lip sync corrector to help, but I'm not sure about it. It still doesn't solve the problem with the hardrive. I'd much rather find what the real issue is. I have the latest firmware update for the TV.

The audio and video sync is off on both. Not a whole lot, but enough that it is noticeable.

Any ideas?


Established Member
To be honest this is a common issue with modern TV's, especially higher end sets with higher refresh rates and picture processing. This is due to the processing engine doing so much tweaking to the incoming picture but not doing anything to the sound (picture and sound in a digital file is in fact 2 separate files that are held in a container. Try turning intelligent frame creation down to its minimum setting and turning off some of the inessential noise reduction modes. Not only will you end up with a better more natural picture but the delay should be reduced.


Established Member
AndyRg4 is absolutely correct. Lip-sync error is almost always present due to video or audio being delayed too much allowing the other to get ahead. Normally it's the video but attempts by the broadcaster or sound editor to correct it can add too much audio delay but that's rare.

In the real world lip-sync is "never" off so this contradiction of reality is very disturbing to our senses and we subliminally try to avoid this impossibility by not focusing on the lips and faces of the characters. This defense mechanism works for most people up to about 42 ms and some viewers can even tolerate 60 to 80 ms before they consciously notice it. But the bigger problem is the negative impact on viewer perception this avoidance mechanism causes even when the viewer is able to ignore it. A study at Stanford showed viewers had feelings about the characters when lip-sync was off similar to the way we feel about people who don't make eye contact with us. They described the characters as less truthful, more agitated, less successful, etc and found the presentations less believable - even when they didn't notice a lip-sync problem.

The fact that you see it is a "good thing" since you can now correct it. Most people if asked to focus intently on the lips will see lip-sync error they never noticed before which shows how the avoidance of the impossible keeps us from noticing the problem whch is also what causes the negative impact on our perception of the characters and story.

What AndyRg4 suggested to speed up your video processing might lower the lip-sync error enough that it could fall below your threshold of recognition. For example if you are able to ignore 42 ms but not 60 ms and dispensing with those image enhancements speeds of the video 20 ms then you may not notice the remaining 40 ms of lip-sync error. But if your objective is to eliminate the negative impact and not just mask the problem you will probably want to adjust an audio delay by remote control while focusing on the lips until perfect.

Do a search for lip-sync correction and you will find several manufacturers who make products to do that. Most are s/pdif delay boxes. Alchemy2, Felston and Primare are examples but I don't quite follow your statement: "I'm using a hardrive(HDMI to USB port on the TV)". Can you be a little more specific about that equipment? The products I mentioned have multiple s/pdif inputs but if that device really sends audio to the TV over USB I am not sure what to do. I haven't actually seen a TV with USB audio in. But one solution to get around those issues might be to use the optical (s/pdif) output from the TV to a sound bar and use the s/pdif delay box between TV and sound bar to correct lip-sync. If you do that be sure to set the TV audio delay to zero if it has a delay option.


Established Member
To be clear, if you set the TV delay to zero and let one of the adjustable delay boxes provide all correction you effectively have an adjustable video delay which can allow you to correct audio that's already delayed up to your TV's inherent video delay. For example if your TV has 80 ms processing delay you would add 80 ms audio delay to offset that but if the arriving signals were in sync but if a signal arrived with audio "already delayed" by 50 ms you could correct that by lowering your adjustable delay from 80 ms to 30 ms using 50 ms of your TV's video delay to correct the arriving audio delay. Arriving audio delay is far more rare but it does happen. The units I mentioned all adjust in 1 ms steps and all have at least 600 ms delay. I use a Felston which can actually be adjusted in 1/3 ms steps but I always adjust in 1 ms steps.


Novice Member
Thanks for the responses guys. The set-top box is connected to the TV via hdmi, and to my router via ethernet. The HDMI input on the TV doesn't have audio delay. I was thinking the sound bar option with delay box could be the solution.

Regarding the hardrive, I just connected my WD drive directly to the TV, and tried to play the video content on it. It's just a HDMI(from HD) to usb(On TV) cable. I guess this is not the best way to deliver content.

It's the video that is behind on both. I do some video editing, so this kind of thing really bothers me. It basically makes the TV superfluous if I can't correct it. I turned off some of the video processing options, but it's still there. It's quite bad on snappy dialogue.

I'm not sure what hdmi cable came with the set-top box. It's unidentifiable. Do you think HDMI 2.0 could solve the issue, or is this lip-sync synchronization quality already present in most cables? I think my current cable is probably the lowest quality they could get away with providing.

DO you think I should just go with the sound bar option? I guess it's my only way to actually solve the issue in some way.

Sorry about the idiotic questions, but I'm really not sure what I'm doing. Thanks for the in depth response too, it helped me understand the issue a bit.


Distinguished Member
A lot of sources e.g. Sky HD boxes have 20ms steps which isn't that good.


Established Member
Cables won't matter as far as lip-sync goes. Because you are an editor you have already overcome your natural avoidance to this impossibility and are likely to notice very samll lip-sync errors.

Many people are confused by HDMI 1.3's claim of "automatic lip-sync correction". Most think it somehow automatically responds to lip-sync error in the signals and corrects it but that is NOT the case. It simply allows the TV to tell an Av receiver a FIXED delay that will offset the TV's video delay.

It is NOT dynamic and has nothing to do with the actual lip-sync error in the signals. It would always apply the same fixed delays. One for progressive and one for interlaced video regardless of whether the delay is even needed. That feature will make lip sync error worse when audio arrives delayed. Most major manufacturers like Samsung, Vizio, etc. don't even support it.

Currently the TV's tell the AV receiver (which provides the delay) those two fixed values during what's called an EDID sesion at start up. Like "plug and play" for computers. HDMI 2.0 will allow that information to be passed any time so it could be considered dynamic but again even if a TV manufacturer decided to send more than those 2 fixed delays during a program (highly unlikely since their video processing delay won't change unless the format changes and formats don't normally change during a movies) it would still have nothing to do with the actual lip-sync error in the signals.

Lip-sync error is not a FIXED problem that can be corrected with a fixed "set and forget" delay. It potentially changes between every programme, every DVD and BluRay since they were all produced by different processes and had different sound editors, etc. For perfect lip-sync you have to focus on the lips when a talking head scene first appears and make a few tweaks to the delay and it's usually good for the rest of "that programme" but all bets are off for the next programme.


Established Member
A lot of sources e.g. Sky HD boxes have 20ms steps which isn't that good.
I couldn't agree more! You really need 1 ms steps. Some people apparently even need 1/3 ms steps but I'm fine with 1 ms. It's amazing how many people - even those in the industry - think it can't matter if you are within a video frame. But you've personally witnessed half a frame (20 ms for PAL) can't get it perfect. They apparently think the 25 pictures per second we are seeing is what the sound needs to be synchronized to but that's not the case at all. Those separate frames in rapid succession create a "perception" of continuous motion and "that perceived continuous motion" is what the sound needs to be synchronized to.
This is what Panasonic said to me,

The lipsync is normally due to broadcast compression and adding another unit such as the TV in the loop can sometime cause some video processing delay in the loop through function, so using optical direct to the sound source can overcome this issue sometimes. I hope this helps somewhat? Kind regards, Paul Online Support[/QUOTE]

You say by adding another unit such as a TV into the loop can cause this is bonkers. Are you saying that if I take the TV out of the loop will cure the problem? If so what am I suppose to watch!!! As I have said bypassing the tv, HDMI from sky q to my Denon 2200( same with Samsung blu ray) all is fine. But HDMI from Sky q to TV all is not good. From sky pass through my amp and all is not good. The only way to solve is to set the sky to standard rather than Dolby Digital, which when paying that sort of money it should be able to decode normal dd source correctly. My Samsung js 8000 could. And yes I did try different HDMI leads. Anyone with any ideas.
Panasonic 902b
Why is it that going to my AV using either HDMI or optical there is no lip sync. Using on board apps such as Netflix and Amazon no probs. But anything connected (Sky q or blu ray) by HDMI straight to the TV or pass through from the AV has a long delay. There is no way to delay the TV or sky HDMI inputs. There is no delay if disable DD in the sky settings. It seems that this TV has a bit of problem with external HDMI sources.


Established Member
Even though this thread is old, it's still relevant. When purchasing a new TV I actually took my soundbar into store and tested it on a few TVs! I tried the Sony AF8, LG C8, Panasonic EZ which unfortunately all had different lengths of delay. The only one that didn't was the Samsung q9fn .

I did this same thing a few years ago and the Samsung KS again was the only one without a delay.

Only problem is they don't do oled :(

The latest video from AVForums

Spielberg, Shyamalan, Aronofsky, Chazelle, Eddie Murphy and Mel Gibson - all the latest movies
Subscribe to our YouTube channel
Support AVForums with Patreon

Top Bottom