Rotary encoders with OSC?

Just got midi controller which has rotary encoders, and they can be also configured to send relative values. I know ardour control surface with generic midi has support for encoders, but what about OSC? REason for preferin OSC, I understood that with OSC there is possibility to control wider scale of Ardour (or actually, Mixbus) features, but not sure about it.

My first idea was use https://github.com/x42/jackmidi2osc but not sure would there be something more suitable? And is there some way to sen relative values with OSC, or should the app translating midi to OSC read values from ardour, and translate relative movements to absolute values?

OSC expects absolute values. Either as dB gain (-200ish to +6) or as fader position (0.0 to 1.0) for the faders. Almost everything else is control position from 0.0 to 1.0. So to convert from MIDI CC to OSC means ((float) MIDI_value)/127=osc value in most cases. To convert from encoder… means setting up a variable that is set from OSC feedback and incremented by the encoder in your conversion middleware.