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Lip Sync Issues (asynchronous sound)



When synchronizing of picture and sound on TV screen does not match (lips moving after words spoken), the viewer can directly adjust the sound sync. User can tweak video’s sync and sound output (TV speaker or SPDIF) by adjusting the Audio Video Synchronization.

There are still a lot of content material out there such as infomercials and old TV advertisements that never got updated with any sound delay to prevent asynchronous issues on televisions displaying much greater resolution than the days of analog broadcast TV.

AV Sync Adjustment


Adjusts the synchronization of the sound from the operational speaker.

The closer to >, the slower the audio output (greater delay).

If you select Bypass , TV will output the broadcast signal or the soundtrack from the external peripheral device without any audio delay. The audio signal may be output before the video because of the time the TV takes to process much greater resolution video input.

HDMI Input Audio Format 

Instructions HDMI audio format  

You can set the audio format for each HDMI input port. When the voice delivered through HDMI does not appear synchronized, set the input audio format to PCM.


Since the introduction of HDTV it is not uncommon to notice very obvious terrible lip synch on screen.

These incidents mostly occur during advertisement breaks. Reason being that HDTV requires more

processing than its predecessor analog broadcast, the audio portion of the signal having remained

virtually the same, now, in HD mode some segments have the voice coming across faster than the

image causing bad lip synch effect.

Most broadcasters and some advertisers quickly adapted by forcing the sound signal segment through

a delay process so that both synchronized picture and sound appear at the same time on screen.

Should this obvious lip sync situation only be noticeable here and there and mostly on some older

advertisements and definitely not always, do not adjust your set. Again, some producers have not yet

fully understood the move to digital TV and therefore haven’t adapted the process of introducing some

delay to their products’ audio track.


TV Speaker

    - [Varies by model] Adjust sync of sound that is outputted from TV’s internal speaker. Speed up

     sound output when moving cursor towards minus sign (-), delay sound output when moving towards

     plus sign (+) .


External Speaker

  -  Control sound sync from external speakers such as LG Home Theatre System, headphone or Surround

     Sound System connected to optical digital audio output terminal. Speed up sound output when moving

     cursor towards minus sign (-), delay sound output when moving towards plus sign (+) .



  -  Matches video signal on screen and sound from external audio device to perfect synchronism without

     any video or audio delay. Again, depending on how long it takes to produce the image on screen the

     audio signal may jump ahead by a fraction of second and create this very awkward viewing experience .

[ In case of Video lagging]

In Settings Menu -> Sound -> Additional  Settings -> AV Sync Adjustment, implement Audio Delay to control AV Sync (range is about 300ms)

[In case of Audio lagging]

Most field environments (depending on various connections, settings risk causing audio delay)

Connect devices in 2-depth method

Basically, audio delay during the ARC or Optical Audio output results from various factors such as decoding time, Sound Engine time, output buffer, etc. Also, Audio/Video delay takes place depending on the device connection method.

HDMI 2-depth connection  

Audio process time loss can be minimized by directly connecting the audio input device (Blu-ray player, set top box, gaming console, etc.) to the audio output device.

In the television’s settings menu, set HDMI ARC -> Digital Sound Out: Pass Through.

Total audio processing time can be reduced. If a home theater system is connected to your TV with an optical cable, there may be an audio delay that requires a manual adjustment on the home theater system. There may even be a setting on your TV that's causing the issue.

Peripheral device issue

Note: If the TV is connected to a sound bar or home theater system with an HDMI or optical cable, the sound may be delayed due to the audio processing delays in the sound bar or home theater system. In this case, there is no issue with the TV speakers.

Change Device Audio Output to PCM:

    Step 1. Set PCM in the Device’s Setting Menu (e.g. STB, Xbox, etc.)

Step 2. Change TV menu if the device settings cannot be changed:

Settings Menu -> Sound -> Additional Settings -> HDMI Input Audio Format

Change format to PCM

Audio process time loss can be minimized since the decoding processing has been changed to a quick mode .


Netflix Atmos issues troubleshooting guide overview

Instructions to enable H D M I   A R C

Instructions to adjust A V synchronization

For any individual still experiencing asynchronous audio video (lip sync) issues on their LG Smart TV from hooking up peripheral device to the television and viewing 4K content material, please ensure TV software has been updated to latest version or greater.


Another suggestion is to keep the setup simple and have the Audio Video Receiver or Sound Bar take the role of the entertainment hub instead of the television. To avoid any further aggravation, make sure the external audio equipment’s HDMI output is connected to any HDMI port at the rear of the television at the exception of the ARC port.

The Audio Return Channel (ARC) is designed to get used when all audio video sources are hooked up to the TV for the screen to display the picture while the HDMI ARC input port gets to alter direction sending the audio signal to the external audio device.

If the entertainment hub gets shifted to the audio video receiver or sound bar, there is no point incorporating ARC function in the equation. Instead, every other audio video source such as Internet streaming and/or USB video playability can get to sound to the audio video receiver or sound bar via the Optical Audio Output connection.


Should none of above troubleshooting steps resolve your unfortunate situation, we would encourage you to report the incident by reaching out to LG Customer Information Center along with corroborating supporting evidence and facts (TV model number? Software version? Erratic asynchronous video source? If TV broadcast, which channel? New TV shows or old reruns? TV show content or the ads? Continuous or sporadic?), so that we may get engineers to investigate and resolve the matter promptly.

Your patience and comprehension in this matter are greatly appreciated,