Question / Help Low Stream fps but no dropped frames and low CPU usage

[Glomby]

I'm trying to set up a very high Quality stream. That means I'm using the max Bitrate of 3500kbit/s and depending on the game I stream in 720p60 or 1080p30.

The quality looks great but when there is a lot of motion the fps still seem to be stuck around 30fps instead of 60. My cpu however wont go above 50% CPU usage.

I'm trying to stream from a Laptop:

i7 2820qm @ 2.5Ghz (4 Cores + Hyperthreading)
16GB Ram + SSD Harddrive
nVidia Quadro 2800m
Upload: 42000kbit/s (thats definitly never an issue)

The log analyser doesn't say anything is wrong. I just had a 3 hour session with 729p60. It definitly runs at 60fps sometimes but when there is alot of Motion the fps go down. It has to be the cpu but why doesn't my CPU usage go up then? I don't get it.

You can watch the latest vod of my stream to take a look yourself http://twitch.tv/glomby

And here is the log file:

 

[Glomby]

Just an update on this. As it turned out my laptop's i7 gets extremely hot during encoding and actually starts to throttle down because of that and therefore creating micro stutter which makes the stream appear to run at a lower frame rate. OBS doesn't recognize this at all, that's why the logs don't show any problems.

I still have to confirm this but it's very likely to be the cause of my problem.