How you add the playlist to your page ? Do you use our "Playlist module" or the "Player plugin" ? The "Playlist module" itself have an config option "Order By" which allows to do this easy. If you're using the plugin short-code, then you can use the "orderby" property to configure this. Kindly check "Adding video playlist" section in
yendifplayer.com/joomla-video-share-player-plugin.html