And yes, the sound plays ... although it is quite disconcerting and disorienting having all 9 play at once ...
The sources are PAL-format digital recordings transcoded to x264, i'm scaling them using libswscale and then simply using swing labels to display them. It's clocking up between 100% and 150% CPU usage on the java process (100% == 1 core on Linux). So even though i'm hardly trying to make it quick it's hardly taxing the box (albeit a very fast box).
For some reason the timing code gets messed up if I try to sync to the audio timestamp, but that might just be these videos.