Comment 9 for bug 1319483

Actually, the problem was that the Output Driver was set to Pulse, when (according to "http://askubuntu.com/questions/106224/no-sound-after-lubuntu-installation" :

"Lubuntu unlike Ubuntu does not make use of Pulseaudio. Instead it uses Alsa for sound." the answer as of Feb 21 '12, anyway. There may be a quick way of finding out which my Lubuntu uses, but I was not able to find it.)

When I switched the Output Driver to Alsa from Pulse, I had sound.

Since I do not recall having any such problem with Lubuntu 13.10's smplayer, I must conclude that somehow someone accidentally set Lubuntu 14.04's default Output Driver to Pulse. (Either that, or for some reason Lubuntu 13.10 used Pulse, but used Alsa for 14.04...)