It would also be a drop in spurious complaints which have no merit. If there is recorded evidence, and the potential complainant knows that exists, then they are less likely to make things up.
Many of the people who deal with police on a frequent basis are skilled liars. They know how to stymie investigations by tying the officers up in paperwork. Having video evidence would prevent spurious complaints.
It will also make people less stressed when dealing with cops (as they know the cop will behave well), and it will discourage people from resisting arrest / attacking the police, because they know they'll be caught on camera.
Many of the people who deal with police on a frequent basis are skilled liars. They know how to stymie investigations by tying the officers up in paperwork. Having video evidence would prevent spurious complaints.