Lossless A/V delay with ffmpeg
Basic method is

ffmpeg -i in.mp4 -itsoffset -0.6 -i in.mp4 -map 0:v -map 1:a -c copy new.mp4


FFmpeg will write an editlist in new.mp4. Players like VLC, Potplayer which parse the editlist will honor the delay whereas players like WMP, which don't, will start the streams at the same time.