What can I do if the police beat me up and I need their video?

It would be very unusual for the police to taser you and beat you up unless you argued, refused their request, fought with them, or resisted arrest. They will not give you a video that does not help them if it is in their possession. Retain a good lawyer and tell him the truth about every detail or he will not be able to advise you, represent you, or act in your best interest.

First was there a camera in the car? Did you see one? This can be found out by your attorney in the criminal case.

File a FOIA request (Freedom of Information Act) with the police department, or better yet, have an attorney do it for you. Consult with an attorney in your area that specializes in 1983 civil rights police brutality to review the evidence and see if you have a case.

This "missing video" issue happens all the time. When an officer stops a vehicle for a bad lane change or improper turn without signal, or something like that, the video "malfunctioned" and/or doesn't exist. When the video supports the cops version of events, miraculously, there it is. I hope you have an attorney to assist you with this matter. At the very least you should file a claim and a complaint with the police department for whom the officers worked. As to the video, you or your attorney are going to have to fight like heck either to get it, or to have the police department demonstrate that the device(s) were not operating correctly, or destroyed the video. One thing to keep in mind is that not all police departments have videos in their vehicles. CHP does, but many if not most local agencies do not. So if the agency you are dealing with does not, you're just out of luck.