From an armchair quarterback perspective: In the video it appears that the driver in the vehicle was refusing to exit, thus the knocks to the noggin. I'm no legal scholar but as I understand it, police have been given the authority to force (and I emphasize FORCE) compliance to the law. So using elbows, knees, tasers, clubs, or even guns at times is totally justified when a person refuses to abide. So the bottom line is, guilty or not, don't resist. Solve the issues in a courtroom at a later time and if totally innocent, take legal action against the police for violating your Constitutional Rights.
As far as the audio is concerned, god only knows. The recording device could have simply malfunctioned or maybe there was some silly policy in place as to when audio can be used. Maybe the audio mic was in the cop's vehicle and he simply forgot to put it on, no one knows for sure. All we have on the audio is mere speculation at this point. What we do know however, is....the driver made himself a victim of his own stupidity by resisting it appears.
