How do I retain video-thumbnail quality?

[kaneswriting]

Hi there, 

I am trying to upload a video to my profile. However, whenever I upload the file to the gig, it reduces the quality of the thumbnail. I have attached a picture to show what I mean, but you can also see it on my profile: https://www.fiverr.com/kaneswriting?public_mode=true

Is there a way to upload a video but also retain the quality of the thumbnail? 

Thanks in advance,
Kane