Here are your tags:

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:quality=high (Defaults to a high quality stream, depending on availability)


EXTRAS:

&fmt=18 --- High Quality
&fmt=22 --- High Definition