Implement proper vcodec copy support via characteristics.
This is just a thought and basicly a crossposting from an [issue](https://github.com/KhaosT/homebridge-camera-ffmpeg/pull/258) posted at `homebridge-camera-ffmpeg`.

`homebridge-camera-ui` allows to set `vcodec copy` to speed up the stream without re-enconding. This fails if homekit requests a stream with resolution, bitrate, etc. that conflicts with just copying the stream, i.e. my yi outdoor cam works fine on my iPhone, but not on my iPad with `vcodec copy`.

Homekit supports video stream configuration via characteristics: HAP-Specification-Non-Commercial-Version.pdf - Video Attributes:
> The Video attributes allow the accessory to indicate supported resolutions, frame rates etc., This information is encoded as a tlv8- the list of types for the value of this TLV are as follows [...]

Can we force Homekit to request the streams in their native resolution via characteristics, so we can use `vcodec copy`?
