The first 6-18 seconds of the video is blurry and then the picture sharpens. This is especially problematic for short videos where there is a title page / wording as an introduction to the video. Microsoft Support says that this is a known issue and the Stream team is aware of it. Please fix!
Notes on the issue: https://techcommunity.microsoft.com/t5/Microsoft-Stream-Forum/Video-Playback-Blurry-first-half-of-video/td-p/79251