FPS doesn't have anything to do with pixelation as far as I know, but the visual is usually something that has to do with your computers video card or capture card.
And what is the FPS set at anyways? If it's high, you can try lowering it or you can try changing your blockland's visual settings to low so it doesn't use most of the video card so you can have better quality.
And you could use a video formatter and editor to get better quality.
If I'm wrong (which is definitely indeed a possibility since I don't know much about visuals), please say so and have a better explanation anyone.