-vf drawtext="fontfile=C\:/Windows/Fonts/Arial.ttf:
text='Stack Overflow': fontcolor=white: fontsize=24: box=1: boxcolor=black:
x=(w-text_w)/2: y=(h-text_h-line_h)/2"

x=w-tw:y=h-th

x=w-tw-10:y=h-th-10

x=w-tw

x=w-tw-10:y=10

x=0:y=0

x=10:y=10

y=h-th

x=10:h-th-10