"<a href=""https://www.youtube.com/watch?v=iZnLZFRylbs&amp;t=1m23s"">1:23</a> HOW",(reply>), @Rodrigues. what do you mean? The twist is knowing how long the video will be. Knowing how much time was spent is elementary, the recorder tells you. Or any simple chronometer will do.,(reply>), @Rolu but the ending does not change the beggining,(reply>)," not that hard actually no one would notice if you change the playing speed so that the video length will become <a href=""https://www.youtube.com/watch?v=iZnLZFRylbs&amp;t=5m10s"">5:10</a>. go ahead and tell some one to adjust video playback speed and come back to see if you can tell.",(reply>), same question,(reply>), It's one cut