Nick
11:25 AM - 17 April, 2015
It's hard to give precise numbers for the reduction in CPU usage because it depends on 1) the GPU, and 2) the videos.
Some older hardware is only capable of decoding a single Full HD video stream at a time - so the reduction in CPU usage isn't as great for these models when playing HD content on both channels (as one stream still gets decoded via the CPU). Some models (such as those using recent Intel GPUs) see much greater reductions. In tests over a wide variety of computers (playing 2 videos), it generally ranges from using around 60% of the CPU of MixEmergency 2.7.1, to using around 10%.
How you've encoded the videos has quite an effect too. Videos that use more CPU to decode also appear to use relatively less CPU with MixEmergency 3.