[LAU] Connect pipewire to running JACK server

[Wim Taymans]

> Speaking of PipeWire as a potential JACK replacement, what's the status
> of JACK Transport? there are hints in the FAQ [1] and an old version of
> the Wiki [2]

All of the JACK functionality should be implemented, this includes
reposition, start/stop,
slow-sync clients, timebase master.

At the lower levels there are some extensions that are not yet exposed
in any API (And I have no
real plan on how to do this yet..):

* multiple timebase owners for different aspects (bars-beat, video, ...)
* reposition to other than frames, ie bar/beat, video frames, etc
* reposition requests can have a duration + looping flag.
* variable rate playback/reverse
* an 8 slot lookahead windows for repositions and tempo changes (let clients
  prefetch data in time)

Wim