LG 42PM4700 Owner's Manual page 84

To set AV Sync
❐
HOME ➾ Settings
Synchronizes unmatched video and audio. Select
audio output (TV speaker or SPDIF) with the video.
TV Speaker
SPDIF
➙ SOUND ➙
Adjusts the sync of the sound from the TV's internal speakers.
The "-" button makes the sound output faster and the "+"
button slower than the default value.
(Sony Philips Digital InterFace) Adjusts the sync of the sound
from speakers connected to digital audio out terminal.
The "-" button makes the sound output faster and the "+"
button slower than the default value.
AV Sync.
AV Sync. to On to synchronize