Blender adds noise to my camera footage for some reason

Hi, I have a problem. I imported my real life camera footage to blender 2.8 (footage was clean) and then after removing the green screen and compositing blender added an incredible amount of noise to exported files. I tried everything, TIFF with no compression does not work, PNG either. Where is the problem? I rendered it as mp4 file to show you. Can not attach my file directly bcoz I just registered. Link to gdrive. You can see the noise on the floor and on the wall, basically everywhere.
I need your help. Thank you.

Inspect your alpha black and white values, Blender’s keying tools require a lot of tweaks to achieve a decent matte. Keying is a broad topic to discuss but a did a very basic example to show alpha. Also color depth from footage will influence a lot in your results. Use OpenEXR to avoid compression artefacts. ZIP or PIZ has a good lossless compresion ratio.