I tried to watch few of the lang.next presentations but it seems the audio recording is botched in quite a few of these (all three videos I tried to watch!).
If we were all lip readers, then quality HD video would be critical. But I doubt many of us are, and thus testing the audio recording setup is something worth scheduling time for.
It seems like many of the presentations were recorded too "hot" and clipped when turned into bits.
I don't know who recorded these, but if you don't have ability to test record, live meter (recording level display) the recording and adjust the recording gain so that there's plenty of headroom (15 dB if it was "test 1,2,3"), then the last resort is probably to have your target audience (to be recorded) all talk loudly over each other, take quick sample of that and listen it back (ideally with well isolated headphones if your recording equipment lacks volume level display).
There are some portable recording boxes that would allow setting a more professional level recording up relatively quickly but you'd still be looking at good 10 minutes to setup (after practising) and a bag full of stuff to haul around. Probably too much hassle compared to just taking 5 minutes to verify that your audio on the camera isn't clipping by getting the interviewees to talk loud for a moment.