Various tweaks

Sorry for a pull request with a bunch of unrelated stuff in it!

Each commit has a message which should describe the thoughts behind it. The final commit (0447b18) is the one I'm least sure and would be interested to discuss if you think it's a good idea or not.

I'm just leaving the office now so sorry I haven't given all of the information here. I will try to add to it tomorrow if there is anything that needs clarification!
I'm not sure if anybody would ever want to release the video and not stop the capturing at the same time...

I guess probably not and it keeps the API simpler if the function doesn't exist...