MP4 is a highly compressed keyframe based format, and it's not recommended to use with Resolume.
It's being decoding on the CPU, so playing multiple 4k mp4 files at once can have a big hit on your CPU usage for example.
We recommend to use DXV encoded video clips with uncompressed audio for best performance. DXV can be decoded on the GPU, taking the load off your CPU.
You can use Alley, our free encoder and player to convert supported media formats to DXV.
Alley is bundled with Resolume 6 and up, but you can also get it as a standalone installer from our download page.
http://resolume.com/download
Resolume installers also install a plugin for Quicktime, and Adobe products so DXV should also show up as an option in the Quicktime formats, or stand alone in the Format list - depending on which converter you use.