Why is my camera depth of field very low quality?

PPRMO Posts: 17 Just Starting Out*

As you can see in the video above, I keyframed a camera's focus distance in a composite shot and the output is very low quality.

If it helps, my sequence is in 1920x960 in 30fps. Min bitrate is 45 and max 60. I'm on windows 10 and Hitfilm 16