When a sound bar is connected to an HDTV by optical cable (audio out on TV to sound bar input) the video and audio will be slightly out of sync. Is it enough to be noticeable?

Thanks,

When a sound bar is connected through directly to a TV, the delay is normally very small (less than 10 msec). It's quite unlikely that you will be able to notice them.

Source : Sound Bar Reviews | The Best of Home Entertainment