According to statements from the time, the officer suffered a contusion to his spine and broke his right hand. The new video shows no violence against him at all. He punches a lot with his right hand.
Lukewarm reporting by public German news station NDR, relayed by the leading public news website Tagesschau
Somewhat better reporting by Der Spiegel
Some quotes back from when politicians, police and other groups seized upon the incident to demand restrictions on the right to assembly
English article from the same time by Deutsche Welle
Well, you could tell they were thinking about it!