yt:quality=high | Defaults to a high quality stream (available based on the size of the viewer’s player and the size of the browser window)
yt:crop=16:9 | Zooms in on the 16:9 area, removes windowboxing
yt:stretch=16:9 | Fixes anamorphic content by scaling to 16:9
yt:stretch=4:3 | Fixes 720x480 content that is the wrong aspect ratio by scaling to 4:3
yt:crop=off | Deactivates cropping effects on the video and reestablishes cropped areas