user14444: I downloaded this video but its' audio has approximately a 600ms advance compared to its' audio.
How can I fix that in a lossless manner (i.e -c copy) with ffmpeg ?

user1871: 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.

14444: <p>I downloaded <a href="https://www.youtube.com/watch?v=XhmQxZiUYzg" rel="nofollow noreferrer">this video</a> but its' audio has approximately a 600ms advance compared to its' audio.</p>

<p>How can I fix that in a lossless manner (i.e <code>-c copy</code>) with ffmpeg ?</p>
 1871: <p>Basic method is</p>

<pre><code>ffmpeg -i in.mp4 -itsoffset -0.6 -i in.mp4 -map 0:v -map 1:a -c copy new.mp4
</code></pre>

<p>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.</p>
