Every moment of processing is video taped with sound too. If you are not told why you have been arrested, read your rights, allowed legal advice, a phone call to anyone you wish and medical assistance you can use the video tape to prove this and sue the police.
Not getting in to the veracity or quality of the piece but that is important information that I wasn't aware of. A video record of police arrests seems an important safeguard that could prevent mass meltdowns over police abuse and the exact thing that Macron is trying to foolishly get rid of in France at the moment. The flip side is that the sharing of a video of abuse can also trigger an uprising but transparency is the healthier long term option.