Comment 91 for bug 743323

As far as I know, unless you set the "aout" vlcrc parameter expliticitly to "alsa,none", VLC will fall back to whatever it can if/when ALSA refuses to work. And whatever it can means PulseAudio on Ubuntu, if the selected ALSA output device is busy (or non-existent).

I have never heard of the memory leak occurring with the decade-old VLC ALSA output. You can check which audio output plugin is really used from Tools -> Messages -> Modules tree