LG 50LA6200 User Manual page 28

Adjusts how the sound is synced from external speakers, such
as an external speaker connected to the digital audio output
port, LG audio device and headphone.
Moving the slider to the left will add a delay to the sound
External
output. Moving the slider to the right will add a delay to the
Speaker
video output.
✎ LG audio device is supported only for models with the
optical digital port.
Outputs broadcasting signals or the audio of an external
Bypass device without audio delay. Audio may be output before video
as it takes time to process video input into the TV.