Watching a video and your audio and video are out of sync. Try reloading video. If that doesn’t work try the audio delay option (which will delay the audio by 50 millisecond increments = 50ms increments). By default the audio delay option is set to 0 (or off)
You can have negative audio delay, or positive audio delay.
Pressing j will give you more negative audio delay. So you can go from 0 to -50ms to -100ms to -150ms etc. This brings the audio back.
Pressing k will give you positive audio delay. So you can go from 0 to +50ms to +100m etc. This moves the audio forward.
Imagine that the video and audio are on two different stills. You cant control the video still with this option, you only control the audio still. The video still is controller by when you play the video (rewind, fastforward, play and pause)
How to tell if you need to go negative or positive:
Look at the video and listen. Watch the way people say things or wait for an audible action (like a light switch being turned on, or somebody dropping something).
First we find out if the audio is behind or ahead of the video. Then before changing try to count off in your head the delay time. Remember that you change the delay in 50ms increments. 1000ms is 1 second. 1second delay is very noticeable. Even 100ms is noticeable. Im working with a video right not is 600ms off sync (the video comes first, so I have to put in -600ms audio delay to line it up)
If you notice that the video happens first then a few split moments later the audio follows. Then you can fix it by brining the audio back (back = negative), so press the j button.
If you notice that the audio happens first then the video follows, you can fix that by brining the audio forward (forward = positive), so press the k key.
Tip: when trying to find the delay and adjust it its good to know a few good hot keys (not just the j and k). First find a good point in the video (i.e. light switch is turned on, and there is clear audio and video; the click and light change should be on top of each other; or people speaking and you hear their voices and their mouths moving). You can pause on that moment with Spacebar. You can rewind a few seconds with Shift + Left Arrow. You can rewind even more by holding Shift and pressing the Left Arrow a few times. You can fast forward in a similar manner with Shift – Right Arrow.
Sidenote: the human ears are pretty good at fixing most delay and out of syncs, so we just need to get in the ball part within 100ms. So if the audio is actually 633ms behind the video. You can get away with -600ms and -650ms and -700ms. -650 will obviously be better.
Sidenote: this guide says to use the f and g keys. f is for negative, g is for positive. Might be the old keys: https://wiki.videolan.org/Adjust_Audio_Delay/