recording of sound without someones knowledge is the problem. If you put some stickers around the car as a warning of recording audio and video, that will help. Also, if you have a run in with the police, it would be in your best interest to immediately explain to them that you are recording video and audio. If they don't want to be recorded, they'll tell you, and you should turn the microphone off. They can not tell you to stop taking pictures or recording video (just a bunch of pictures anyways).