I have an install of BI5 running on an i7 6700 with 16GB RAM. All (31) cameras are 4MP, running H265, direct to disk, dual stream processing, etc, and BI is reporting ~80% CPU usage, but meanwhile, in Task manager, CPU usage is being reported as ~25% (No surprise, almost entirely Blue Iris). I had thought that maybe it was BI taking into account GPU usage too, but while each camera is set to 'GPU: Any' under settings > Cameras, 'Hardware Accelerated Decode' is set to 'No' in the BI settings, so I'd take that to mean it is NOT using the GPU at all.

Any ideas why BI is reporting about 3x the CPU usage being reported by Task Manager?

It could be the “CPU Usage Factor” setting. It’s explained in the help PDF under More Options > Other. The setting itself is found in BI settings > Other > Advanced.

“The CPU usage factor can be used to adjust the way in which Blue Iris displays the CPU utilization in the status bar and as is reported for remote management. If Blue Iris shows 20%, but your task manager shows 40%, please set this value to 2.00.”

I adjusted that down to 0.33 and the usage reported by BI is pretty much in line with task manage. But what's the point to such a setting? Wouldn't it make more sense for BI to either report its CPU usage or the systems overall CPU usage, not 'skew' it in some fashon?

I think it was added precisely because some people reported wrong cpu loadings. Mine is set to 1.0 and is close to the Win10 cpu load.