The problem was: OSX i386 builds used --dist-target=leopard
which forced the deprecated 10.5 CoreAudio API.
(build-host config has been changed now).
There is currently insufficient support in ardour’s
CoreAudioPCM::create_aggregate_device() for the old API,
COREAUDIO_108 needs to be defined or aggregate devices stop
working on OSX 10.8 or later.
* allow to change buffersizes
* subscribe to buffersize & samplerate changes
* add support for half-duplex devices.
* aggregate Devices (not yet used) code from JACK2
* unify deprecated API wrappers
* properly keep track of MIDI ports
* disable MidiI/O during freewheeling
* various small fixes & cleanup
