Ffmpeg: How to delay (sync with video) audio channel in video file
Delay by 5 seconds (the audio starts 5 seconds after the video):
ffmpeg -i in.mp4 -itsoffset 5 -i in.mp4 -map 1:v -map 0:a -c copy out.mp4
Trim by 5 seconds using negative number. Remember: it's the opposite way of how VLC displays this (negative is positive).