Blue Iris

I changed hardware acceleration from none to Nvidia NVDEC (this PC has a fancy gaming video card).

CPU usuage went from about 70% to %35. awesome! But I'm a little confused:

I have all my cameras set to record "direct to disk". I ASSumed that meant BI was just dumping the raw streams from the camera straight to the disk. So why would HW acceleration make such a big difference?

hmm, thinking about it, I guess BI still needs to decode the video streams to run the motion detection algorithms.... That makes sense. I'm glad I finally sat down to read and follow the "Optimizing Blue Iris's CPU Usage" wiki article!

You've got it. (and it needs to decode the stream to display it )

And, in the old days if you wanted on-screen overlays to be recorded you needed to have BI re-encode the stream again to save it to disk.

I think recent BI5 has improvements where overlays are stored in a database of some kind and can be regenerated on demand for replay. That isn't possible in BI4 without re-encoding the stream to disk.