Yeah, I realized the same thing as I was trouble shooting. Tried to install the intel drivers for 630, kept saying it wasn't supported.
Turned out I had integrated graphics switched off in bios.
Turned it on, installed the drivers and then... all video streams disappeared.
I turned off hardware acceleration in BI, and the streams came back on (no surprise). What's interesting though is that after I turned off HW acceleration, cpu usage for BI did drop (I'm only looking at the BI usage, not total usage, too much other crap going on). Not an enormous amount-- before turning on integrated graphics I was running 35-40% cpu usage, after I'm running 25-30% (8 cameras, 7 running at 4 k resolution, 1 running at 2k). I may switch back to h.264 now to see if having hardware acceleration properly enabled makes any difference.