if you try to play a video with 1080p and your CPU usage goes up almost 100% you know that the GPU is doin‘ nuthin‘ and all the encoding is done via CPU which also reduces framerate.

luckily the fix for jessie is easy:

hostnamectl 
  Operating System: Debian GNU/Linux 8 (jessie)
            Kernel: Linux 3.16.0-4-686-pae
      Architecture: x86
echo "deb http://http.debian.net/debian jessie-backports main" >> /etc/apt/sources.list.d/jessie-backports.list;
apt-get update;
apt-get -t jessie-backports install xserver-xorg-video-intel;
reboot;

now check your cpu usage while playing 1080p – it should be like: (this is a quadcore i3 Intel(R) Core(TM) i3-5010U CPU @ 2.10GHz)

https://unix.stackexchange.com/questions/207855/cant-get-intel-hd-5500-graphics-to-work-with-debian

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