First time using Chaos Player

Hi, I am struggling to export a simple rendered Image sequence to video (mp4). This is usually very simple using Premier Pro, but thought I would try Chaos Player as its cheaper alternative
Currently any Image sequence video I export is black in windows media player, only works using VLC, but now the resolution is very low, even though I’ve set it to quality 100, and rendered in 4K resolution, which is shown in the viewport of chaos player

Any input on this would be much appreciated - I thought this would be quite a simple process

Since the .mp4 plays correctly in VLC, then it’s probably a Windows thing (missing codecs for example). Make sure you are exporting a Composition Sequence instead of a Layer sequence. Also, check if there’s any cropping going on (right-click on the resolution at the bottom of the view and select “No composition mask”.