get started on coreaudio/midi backend

9 files changed, 3274 insertions, 1 deletions

diff --git a/gtk2_ardour/ardev_common.sh.in b/gtk2_ardour/ardev_common.sh.in
index 57e9686a32..01426756d8 100644
--- a/gtk2_ardour/ardev_common.sh.in
+++ b/gtk2_ardour/ardev_common.sh.in
@@ -17,7 +17,7 @@ export ARDOUR_DATA_PATH=$TOP:$TOP/build:$TOP/gtk2_ardour:$TOP/build/gtk2_ardour:
 export ARDOUR_MIDIMAPS_PATH=$TOP/midi_maps:.
 export ARDOUR_MCP_PATH=$TOP/mcp:.
 export ARDOUR_EXPORT_FORMATS_PATH=$TOP/export:.
-export ARDOUR_BACKEND_PATH=$libs/backends/jack:$libs/backends/wavesaudio:$libs/backends/dummy:$libs/backends/alsa
+export ARDOUR_BACKEND_PATH=$libs/backends/jack:$libs/backends/wavesaudio:$libs/backends/dummy:$libs/backends/alsa:$libs/backends/coreaudio
 export ARDOUR_TEST_PATH=$TOP/libs/ardour/test/data
 export PBD_TEST_PATH=$TOP/libs/pbd/test
 export EVORAL_TEST_PATH=$TOP/libs/evoral/test/testdata
diff --git a/libs/backends/coreaudio/coreaudio_backend.cc b/libs/backends/coreaudio/coreaudio_backend.cc
new file mode 100644
index 0000000000..80f532c313
--- /dev/null
+++ b/libs/backends/coreaudio/coreaudio_backend.cc
@@ -0,0 +1,1791 @@
+/*
+ * Copyright (C) 2014 Robin Gareus <robin@gareus.org>
+ * Copyright (C) 2013 Paul Davis
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <regex.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+
+#include <glibmm.h>
+
+#include "coreaudio_backend.h"
+#include "rt_thread.h"
+
+#include "pbd/compose.h"
+#include "pbd/error.h"
+#include "pbd/file_utils.h"
+#include "ardour/filesystem_paths.h"
+#include "ardour/port_manager.h"
+#include "i18n.h"
+
+using namespace ARDOUR;
+
+static std::string s_instance_name;
+size_t CoreAudioBackend::_max_buffer_size = 8192;
+std::vector<std::string> CoreAudioBackend::_midi_options;
+std::vector<AudioBackend::DeviceStatus> CoreAudioBackend::_audio_device_status;
+std::vector<AudioBackend::DeviceStatus> CoreAudioBackend::_midi_device_status;
+
+CoreAudioBackend::CoreAudioBackend (AudioEngine& e, AudioBackendInfo& info)
+	: AudioBackend (e, info)
+	, _run (false)
+	, _active_ca (false)
+	, _active_fw (false)
+	, _freewheeling (false)
+	, _freewheel (false)
+	, _freewheel_ack (false)
+	, _reinit_thread_callback (false)
+	, _measure_latency (false)
+	, _audio_device("")
+	, _midi_driver_option(_("None"))
+	, _samplerate (48000)
+	, _samples_per_period (1024)
+	, _n_inputs (0)
+	, _n_outputs (0)
+	, _systemic_audio_input_latency (0)
+	, _systemic_audio_output_latency (0)
+	, _dsp_load (0)
+	, _processed_samples (0)
+	, _port_change_flag (false)
+{
+	_instance_name = s_instance_name;
+	pthread_mutex_init (&_port_callback_mutex, 0);
+	pthread_mutex_init (&_process_callback_mutex, 0);
+
+	_pcmio = new CoreAudioPCM ();
+	_midiio = new CoreMidiIo ();
+
+	_pcmio->discover();
+	_midiio->discover();
+}
+
+CoreAudioBackend::~CoreAudioBackend ()
+{
+	delete _pcmio; _pcmio = 0;
+	delete _midiio; _midiio = 0;
+	pthread_mutex_destroy (&_port_callback_mutex);
+	pthread_mutex_destroy (&_process_callback_mutex);
+}
+
+/* AUDIOBACKEND API */
+
+std::string
+CoreAudioBackend::name () const
+{
+	// XXX avoid name -conflict w/waves
+	return X_("CoreAudio2");
+}
+
+bool
+CoreAudioBackend::is_realtime () const
+{
+	return true;
+}
+
+std::vector<AudioBackend::DeviceStatus>
+CoreAudioBackend::enumerate_devices () const
+{
+	_audio_device_status.clear();
+	std::map<size_t, std::string> devices;
+	_pcmio->device_list(devices);
+
+	for (std::map<size_t, std::string>::const_iterator i = devices.begin (); i != devices.end(); ++i) {
+		if (_audio_device == "") _audio_device = i->second;
+		_audio_device_status.push_back (DeviceStatus (i->second, true));
+	}
+	return _audio_device_status;
+}
+
+std::vector<float>
+CoreAudioBackend::available_sample_rates (const std::string&) const
+{
+	// TODO ask _pcmio for available rates
+	std::vector<float> sr;
+	sr.push_back (44100.0);
+	sr.push_back (48000.0);
+	return sr;
+}
+
+std::vector<uint32_t>
+CoreAudioBackend::available_buffer_sizes (const std::string&) const
+{
+	// TODO ask _pcmio for available rates
+	std::vector<uint32_t> bs;
+	bs.push_back (64);
+	bs.push_back (128);
+	bs.push_back (256);
+	bs.push_back (512);
+	bs.push_back (1024);
+	bs.push_back (2048);
+	bs.push_back (4096);
+	return bs;
+}
+
+uint32_t
+CoreAudioBackend::available_input_channel_count (const std::string&) const
+{
+	return 128; // TODO query current device
+}
+
+uint32_t
+CoreAudioBackend::available_output_channel_count (const std::string&) const
+{
+	return 128; // TODO query current device
+}
+
+bool
+CoreAudioBackend::can_change_sample_rate_when_running () const
+{
+	return false;
+}
+
+bool
+CoreAudioBackend::can_change_buffer_size_when_running () const
+{
+	return false;
+}
+
+int
+CoreAudioBackend::set_device_name (const std::string& d)
+{
+	_audio_device = d;
+	return 0;
+}
+
+int
+CoreAudioBackend::set_sample_rate (float sr)
+{
+	if (sr <= 0) { return -1; }
+	_samplerate = sr;
+	engine.sample_rate_change (sr);
+	return 0;
+}
+
+int
+CoreAudioBackend::set_buffer_size (uint32_t bs)
+{
+	if (bs <= 0 || bs >= _max_buffer_size) {
+		return -1;
+	}
+	_samples_per_period = bs;
+	engine.buffer_size_change (bs);
+	return 0;
+}
+
+int
+CoreAudioBackend::set_interleaved (bool yn)
+{
+	if (!yn) { return 0; }
+	return -1;
+}
+
+int
+CoreAudioBackend::set_input_channels (uint32_t cc)
+{
+	_n_inputs = cc;
+	return 0;
+}
+
+int
+CoreAudioBackend::set_output_channels (uint32_t cc)
+{
+	_n_outputs = cc;
+	return 0;
+}
+
+int
+CoreAudioBackend::set_systemic_input_latency (uint32_t sl)
+{
+	_systemic_audio_input_latency = sl;
+	return 0;
+}
+
+int
+CoreAudioBackend::set_systemic_output_latency (uint32_t sl)
+{
+	_systemic_audio_output_latency = sl;
+	return 0;
+}
+
+int
+CoreAudioBackend::set_systemic_midi_input_latency (std::string const device, uint32_t sl)
+{
+	struct CoreMidiDeviceInfo * nfo = midi_device_info(device);
+	if (!nfo) return -1;
+	nfo->systemic_input_latency = sl;
+	return 0;
+}
+
+int
+CoreAudioBackend::set_systemic_midi_output_latency (std::string const device, uint32_t sl)
+{
+	struct CoreMidiDeviceInfo * nfo = midi_device_info(device);
+	if (!nfo) return -1;
+	nfo->systemic_output_latency = sl;
+	return 0;
+}
+
+/* Retrieving parameters */
+std::string
+CoreAudioBackend::device_name () const
+{
+	return _audio_device;
+}
+
+float
+CoreAudioBackend::sample_rate () const
+{
+	return _samplerate;
+}
+
+uint32_t
+CoreAudioBackend::buffer_size () const
+{
+	return _samples_per_period;
+}
+
+bool
+CoreAudioBackend::interleaved () const
+{
+	return false;
+}
+
+uint32_t
+CoreAudioBackend::input_channels () const
+{
+	return _n_inputs;
+}
+
+uint32_t
+CoreAudioBackend::output_channels () const
+{
+	return _n_outputs;
+}
+
+uint32_t
+CoreAudioBackend::systemic_input_latency () const
+{
+	return _systemic_audio_input_latency;
+}
+
+uint32_t
+CoreAudioBackend::systemic_output_latency () const
+{
+	return _systemic_audio_output_latency;
+}
+
+uint32_t
+CoreAudioBackend::systemic_midi_input_latency (std::string const device) const
+{
+	struct CoreMidiDeviceInfo * nfo = midi_device_info(device);
+	if (!nfo) return 0;
+	return nfo->systemic_input_latency;
+}
+
+uint32_t
+CoreAudioBackend::systemic_midi_output_latency (std::string const device) const
+{
+	struct CoreMidiDeviceInfo * nfo = midi_device_info(device);
+	if (!nfo) return 0;
+	return nfo->systemic_output_latency;
+}
+
+/* MIDI */
+struct CoreAudioBackend::CoreMidiDeviceInfo *
+CoreAudioBackend::midi_device_info(std::string const name) const {
+	return 0;
+}
+
+std::vector<std::string>
+CoreAudioBackend::enumerate_midi_options () const
+{
+	if (_midi_options.empty()) {
+		_midi_options.push_back (_("CoreMidi"));
+		_midi_options.push_back (_("None"));
+	}
+	return _midi_options;
+}
+
+std::vector<AudioBackend::DeviceStatus>
+CoreAudioBackend::enumerate_midi_devices () const
+{
+	_midi_device_status.clear();
+	std::map<std::string, std::string> devices;
+	//_midi_device_status.push_back (DeviceStatus (_("CoreMidi"), true));
+	return _midi_device_status;
+}
+
+int
+CoreAudioBackend::set_midi_option (const std::string& opt)
+{
+	if (opt != _("None") && opt != _("CoreMidi")) {
+		return -1;
+	}
+	_midi_driver_option = opt;
+	return 0;
+}
+
+std::string
+CoreAudioBackend::midi_option () const
+{
+	return _midi_driver_option;
+}
+
+int
+CoreAudioBackend::set_midi_device_enabled (std::string const device, bool enable)
+{
+	struct CoreMidiDeviceInfo * nfo = midi_device_info(device);
+	if (!nfo) return -1;
+	nfo->enabled = enable;
+	return 0;
+}
+
+bool
+CoreAudioBackend::midi_device_enabled (std::string const device) const
+{
+	struct CoreMidiDeviceInfo * nfo = midi_device_info(device);
+	if (!nfo) return false;
+	return nfo->enabled;
+}
+
+/* State Control */
+
+static void * pthread_freewheel (void *arg)
+{
+	CoreAudioBackend *d = static_cast<CoreAudioBackend *>(arg);
+	d->freewheel_thread ();
+	pthread_exit (0);
+	return 0;
+}
+
+static int process_callback_ptr (void *arg)
+{
+	CoreAudioBackend *d = static_cast<CoreAudioBackend*> (arg);
+	return d->process_callback();
+}
+
+static void error_callback_ptr (void *arg)
+{
+	CoreAudioBackend *d = static_cast<CoreAudioBackend*> (arg);
+	d->error_callback();
+}
+
+static void midi_port_change (void *arg)
+{
+	CoreAudioBackend *d = static_cast<CoreAudioBackend *>(arg);
+	d->coremidi_rediscover ();
+}
+
+
+int
+CoreAudioBackend::_start (bool for_latency_measurement)
+{
+	if ((!_active_ca || !_active_fw)  && _run) {
+		// recover from 'halted', reap threads
+		stop();
+	}
+
+	if (_active_ca || _active_fw || _run) {
+		PBD::error << _("CoreAudioBackend: already active.") << endmsg;
+		return -1;
+	}
+
+	if (_ports.size()) {
+		PBD::warning << _("CoreAudioBackend: recovering from unclean shutdown, port registry is not empty.") << endmsg;
+		_system_inputs.clear();
+		_system_outputs.clear();
+		_system_midi_in.clear();
+		_system_midi_out.clear();
+		_ports.clear();
+	}
+
+#if 0
+	assert(_rmidi_in.size() == 0);
+	assert(_rmidi_out.size() == 0);
+#endif
+
+	uint32_t device_id = UINT32_MAX;
+	std::map<size_t, std::string> devices;
+	_pcmio->device_list(devices);
+
+	for (std::map<size_t, std::string>::const_iterator i = devices.begin (); i != devices.end(); ++i) {
+		if (i->second == _audio_device) {
+			device_id = i->first;
+			break;
+		}
+	}
+
+	assert(_active_ca == false);
+	assert(_active_fw == false);
+
+	_freewheel_ack = false;
+	_reinit_thread_callback = true;
+
+	_pcmio->set_error_callback (error_callback_ptr, this);
+	_pcmio->pcm_start (device_id, device_id, _samplerate, _samples_per_period, process_callback_ptr, this);
+
+	switch (_pcmio->state ()) {
+		case 0: /* OK */ break;
+		case -1: PBD::error << _("CoreAudioBackend: failed to open device.") << endmsg; break;
+		default: PBD::error << _("CoreAudioBackend: initialization failed.") << endmsg; break;
+	}
+	if (_pcmio->state ()) {
+		return -1;
+	}
+
+	if (_n_outputs != _pcmio->n_playback_channels ()) {
+		if (_n_outputs == 0) {
+		 _n_outputs = _pcmio->n_playback_channels ();
+		} else {
+		 _n_outputs = std::min (_n_outputs, _pcmio->n_playback_channels ());
+		}
+		PBD::warning << _("CoreAudioBackend: adjusted output channel count to match device.") << endmsg;
+	}
+
+	if (_n_inputs != _pcmio->n_capture_channels ()) {
+		if (_n_inputs == 0) {
+		 _n_inputs = _pcmio->n_capture_channels ();
+		} else {
+		 _n_inputs = std::min (_n_inputs, _pcmio->n_capture_channels ());
+		}
+		PBD::warning << _("CoreAudioBackend: adjusted input channel count to match device.") << endmsg;
+	}
+
+#if 0 // TODO
+	if (_pcmio->sample_per_period() != _samples_per_period) {
+		_samples_per_period = _pcmio->sample_per_period();
+		PBD::warning << _("CoreAudioBackend: samples per period does not match.") << endmsg;
+	}
+
+	if (_pcmio->samplerate() != _samplerate) {
+		_samplerate = _pcmio->samplerate();
+		engine.sample_rate_change (_samplerate);
+		PBD::warning << _("CoreAudioBackend: sample rate does not match.") << endmsg;
+	}
+#endif
+
+	_measure_latency = for_latency_measurement;
+
+	_preinit = true;
+	_run = true;
+	_port_change_flag = false;
+
+	printf("MIDI: %s\n", _midi_driver_option.c_str());
+
+	if (_midi_driver_option == _("CoreMidi")) {
+		//register_system_midi_ports();
+		_midiio->setPortChangedCallback(midi_port_change, this);
+		_midiio->discover();
+	}
+
+	if (register_system_audio_ports()) {
+		PBD::error << _("CoreAudioBackend: failed to register system ports.") << endmsg;
+		_run = false;
+		return -1;
+	}
+
+	engine.sample_rate_change (_samplerate);
+	engine.buffer_size_change (_samples_per_period);
+
+	if (engine.reestablish_ports ()) {
+		PBD::error << _("CoreAudioBackend: Could not re-establish ports.") << endmsg;
+		_run = false;
+		return -1;
+	}
+
+	engine.reconnect_ports ();
+
+
+	if (pthread_create (&_freeewheel_thread, NULL, pthread_freewheel, this))
+	{
+		PBD::error << _("CoreAudioBackend: failed to create process thread.") << endmsg;
+		delete _pcmio; _pcmio = 0;
+		_run = false;
+		return -1;
+	}
+
+	int timeout = 5000;
+	while ((!_active_ca || !_active_fw) && --timeout > 0) { Glib::usleep (1000); }
+
+	if (timeout == 0) {
+		printf("CoreAudioBackend: failed to start.");
+		PBD::error << _("CoreAudioBackend: failed to start.") << endmsg;
+	}
+
+	if (!_active_fw) {
+		PBD::error << _("CoreAudioBackend: failed to start freewheeling thread.") << endmsg;
+		printf("CoreAudioBackend: fw .\n");
+		_run = false;
+		_pcmio->pcm_stop();
+		unregister_ports();
+		_active_ca = false;
+		_active_fw = false;
+		return -1;
+	}
+
+	if (!_active_ca) {
+		printf("CoreAudioBackend: ca .\n");
+		PBD::error << _("CoreAudioBackend: failed to start coreaudio.") << endmsg;
+		stop();
+		_run = false;
+		return -1;
+	}
+	_preinit = false;
+
+	return 0;
+}
+
+int
+CoreAudioBackend::stop ()
+{
+	void *status;
+	if (!_run) {
+		return 0;
+	}
+
+	_run = false;
+	_pcmio->pcm_stop();
+	_midiio->setPortChangedCallback(NULL, NULL);
+
+	if (pthread_join (_freeewheel_thread, &status)) {
+		PBD::error << _("CoreAudioBackend: failed to terminate.") << endmsg;
+		return -1;
+	}
+
+#if 0
+	while (!_rmidi_out.empty ()) {
+		CoreMidiIO *m = _rmidi_out.back ();
+		m->stop();
+		_rmidi_out.pop_back ();
+		delete m;
+	}
+	while (!_rmidi_in.empty ()) {
+		CoreMidiIO *m = _rmidi_in.back ();
+		m->stop();
+		_rmidi_in.pop_back ();
+		delete m;
+	}
+#endif
+
+	unregister_ports();
+
+	_active_ca = false;
+	_active_fw = false; // ??
+
+	return 0;
+}
+
+int
+CoreAudioBackend::freewheel (bool onoff)
+{
+	if (onoff == _freewheeling) {
+		return 0;
+	}
+	_freewheeling = onoff;
+	return 0;
+}
+
+float
+CoreAudioBackend::dsp_load () const
+{
+	return 100.f * _dsp_load;
+}
+
+size_t
+CoreAudioBackend::raw_buffer_size (DataType t)
+{
+	switch (t) {
+		case DataType::AUDIO:
+			return _samples_per_period * sizeof(Sample);
+		case DataType::MIDI:
+			return _max_buffer_size; // XXX not really limited
+	}
+	return 0;
+}
+
+/* Process time */
+framepos_t
+CoreAudioBackend::sample_time ()
+{
+	return _processed_samples;
+}
+
+framepos_t
+CoreAudioBackend::sample_time_at_cycle_start ()
+{
+	return _processed_samples;
+}
+
+pframes_t
+CoreAudioBackend::samples_since_cycle_start ()
+{
+	return 0;
+}
+
+
+void *
+CoreAudioBackend::coreaudio_process_thread (void *arg)
+{
+	ThreadData* td = reinterpret_cast<ThreadData*> (arg);
+	boost::function<void ()> f = td->f;
+	delete td;
+	f ();
+	return 0;
+}
+
+int
+CoreAudioBackend::create_process_thread (boost::function<void()> func)
+{
+	pthread_t thread_id;
+	pthread_attr_t attr;
+	size_t stacksize = 100000;
+
+	ThreadData* td = new ThreadData (this, func, stacksize);
+
+	if (_realtime_pthread_create (SCHED_FIFO, -21, stacksize,
+				&thread_id, coreaudio_process_thread, td)) {
+		pthread_attr_init (&attr);
+		pthread_attr_setstacksize (&attr, stacksize);
+		if (pthread_create (&thread_id, &attr, coreaudio_process_thread, td)) {
+			PBD::error << _("AudioEngine: cannot create process thread.") << endmsg;
+			pthread_attr_destroy (&attr);
+			return -1;
+		}
+		pthread_attr_destroy (&attr);
+	}
+
+	_threads.push_back (thread_id);
+	return 0;
+}
+
+int
+CoreAudioBackend::join_process_threads ()
+{
+	int rv = 0;
+
+	for (std::vector<pthread_t>::const_iterator i = _threads.begin (); i != _threads.end (); ++i)
+	{
+		void *status;
+		if (pthread_join (*i, &status)) {
+			PBD::error << _("AudioEngine: cannot terminate process thread.") << endmsg;
+			rv -= 1;
+		}
+	}
+	_threads.clear ();
+	return rv;
+}
+
+bool
+CoreAudioBackend::in_process_thread ()
+{
+	if (pthread_equal (_main_thread, pthread_self()) != 0) {
+		return true;
+	}
+
+	for (std::vector<pthread_t>::const_iterator i = _threads.begin (); i != _threads.end (); ++i)
+	{
+		if (pthread_equal (*i, pthread_self ()) != 0) {
+			return true;
+		}
+	}
+	return false;
+}
+
+uint32_t
+CoreAudioBackend::process_thread_count ()
+{
+	return _threads.size ();
+}
+
+void
+CoreAudioBackend::update_latencies ()
+{
+	// trigger latency callback in RT thread (locked graph)
+	port_connect_add_remove_callback();
+}
+
+/* PORTENGINE API */
+
+void*
+CoreAudioBackend::private_handle () const
+{
+	return NULL;
+}
+
+const std::string&
+CoreAudioBackend::my_name () const
+{
+	return _instance_name;
+}
+
+bool
+CoreAudioBackend::available () const
+{
+	return _run && _active_fw && _active_ca;
+}
+
+uint32_t
+CoreAudioBackend::port_name_size () const
+{
+	return 256;
+}
+
+int
+CoreAudioBackend::set_port_name (PortEngine::PortHandle port, const std::string& name)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreAudioBackend::set_port_name: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return static_cast<CoreBackendPort*>(port)->set_name (_instance_name + ":" + name);
+}
+
+std::string
+CoreAudioBackend::get_port_name (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreAudioBackend::get_port_name: Invalid Port(s)") << endmsg;
+		return std::string ();
+	}
+	return static_cast<CoreBackendPort*>(port)->name ();
+}
+
+PortEngine::PortHandle
+CoreAudioBackend::get_port_by_name (const std::string& name) const
+{
+	PortHandle port = (PortHandle) find_port (name);
+	return port;
+}
+
+int
+CoreAudioBackend::get_ports (
+		const std::string& port_name_pattern,
+		DataType type, PortFlags flags,
+		std::vector<std::string>& port_names) const
+{
+	int rv = 0;
+	regex_t port_regex;
+	bool use_regexp = false;
+	if (port_name_pattern.size () > 0) {
+		if (!regcomp (&port_regex, port_name_pattern.c_str (), REG_EXTENDED|REG_NOSUB)) {
+			use_regexp = true;
+		}
+	}
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		CoreBackendPort* port = _ports[i];
+		if ((port->type () == type) && (port->flags () & flags)) {
+			if (!use_regexp || !regexec (&port_regex, port->name ().c_str (), 0, NULL, 0)) {
+				port_names.push_back (port->name ());
+				++rv;
+			}
+		}
+	}
+	if (use_regexp) {
+		regfree (&port_regex);
+	}
+	return rv;
+}
+
+DataType
+CoreAudioBackend::port_data_type (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		return DataType::NIL;
+	}
+	return static_cast<CoreBackendPort*>(port)->type ();
+}
+
+PortEngine::PortHandle
+CoreAudioBackend::register_port (
+		const std::string& name,
+		ARDOUR::DataType type,
+		ARDOUR::PortFlags flags)
+{
+	if (name.size () == 0) { return 0; }
+	if (flags & IsPhysical) { return 0; }
+	return add_port (_instance_name + ":" + name, type, flags);
+}
+
+PortEngine::PortHandle
+CoreAudioBackend::add_port (
+		const std::string& name,
+		ARDOUR::DataType type,
+		ARDOUR::PortFlags flags)
+{
+	assert(name.size ());
+	if (find_port (name)) {
+		PBD::error << _("CoreAudioBackend::register_port: Port already exists:")
+				<< " (" << name << ")" << endmsg;
+		return 0;
+	}
+	CoreBackendPort* port = NULL;
+	switch (type) {
+		case DataType::AUDIO:
+			port = new CoreAudioPort (*this, name, flags);
+			break;
+		case DataType::MIDI:
+			port = new CoreMidiPort (*this, name, flags);
+			break;
+		default:
+			PBD::error << _("CoreAudioBackend::register_port: Invalid Data Type.") << endmsg;
+			return 0;
+	}
+
+	_ports.push_back (port);
+
+	return port;
+}
+
+void
+CoreAudioBackend::unregister_port (PortEngine::PortHandle port_handle)
+{
+	if (!_run) {
+		return;
+	}
+	CoreBackendPort* port = static_cast<CoreBackendPort*>(port_handle);
+	std::vector<CoreBackendPort*>::iterator i = std::find (_ports.begin (), _ports.end (), static_cast<CoreBackendPort*>(port_handle));
+	if (i == _ports.end ()) {
+		PBD::error << _("CoreAudioBackend::unregister_port: Failed to find port") << endmsg;
+		return;
+	}
+	disconnect_all(port_handle);
+	_ports.erase (i);
+	delete port;
+}
+
+int
+CoreAudioBackend::register_system_audio_ports()
+{
+	LatencyRange lr;
+
+	// TODO ask _pcmio for port latencies
+
+	const int a_ins = _n_inputs > 0 ? _n_inputs : 2;
+	const int a_out = _n_outputs > 0 ? _n_outputs : 2;
+
+	/* audio ports */
+	lr.min = lr.max = _samples_per_period + (_measure_latency ? 0 : _systemic_audio_input_latency);
+	for (int i = 1; i <= a_ins; ++i) {
+		char tmp[64];
+		snprintf(tmp, sizeof(tmp), "system:capture_%d", i);
+		PortHandle p = add_port(std::string(tmp), DataType::AUDIO, static_cast<PortFlags>(IsOutput | IsPhysical | IsTerminal));
+		if (!p) return -1;
+		set_latency_range (p, false, lr);
+		_system_inputs.push_back(static_cast<CoreBackendPort*>(p));
+	}
+
+	lr.min = lr.max = _samples_per_period + (_measure_latency ? 0 : _systemic_audio_output_latency);
+	for (int i = 1; i <= a_out; ++i) {
+		char tmp[64];
+		snprintf(tmp, sizeof(tmp), "system:playback_%d", i);
+		PortHandle p = add_port(std::string(tmp), DataType::AUDIO, static_cast<PortFlags>(IsInput | IsPhysical | IsTerminal));
+		if (!p) return -1;
+		set_latency_range (p, true, lr);
+		_system_outputs.push_back(static_cast<CoreBackendPort*>(p));
+	}
+	return 0;
+}
+
+int
+CoreAudioBackend::register_system_midi_ports()
+{
+	int midi_ins = _system_midi_out.size();
+	int midi_outs =  _system_midi_in.size();
+
+	for (uint32_t i = midi_ins; i < _midiio->n_midi_outputs(); ++i) {
+		char tmp[64];
+		snprintf(tmp, sizeof(tmp), "system:midi_playback_%d", ++midi_ins);
+		PortHandle p = add_port(std::string(tmp), DataType::MIDI, static_cast<PortFlags>(IsInput | IsPhysical | IsTerminal));
+		if (!p) {
+			continue;
+		}
+		LatencyRange lr;
+		lr.min = lr.max = _samples_per_period; // TODO add per-port midi-systemic latency
+		set_latency_range (p, false, lr);
+		//static_cast<CoreMidiPort*>(p)->set_n_periods(2);
+		_system_midi_out.push_back(static_cast<CoreBackendPort*>(p));
+	}
+
+	for (uint32_t i = midi_outs; i < _midiio->n_midi_inputs(); ++i) {
+		char tmp[64];
+		snprintf(tmp, sizeof(tmp), "system:midi_capture_%d", ++midi_outs);
+		PortHandle p = add_port(std::string(tmp), DataType::MIDI, static_cast<PortFlags>(IsOutput | IsPhysical | IsTerminal));
+		if (!p) {
+			continue;
+		}
+		LatencyRange lr;
+		lr.min = lr.max = _samples_per_period; // TODO add per-port midi-systemic latency
+		set_latency_range (p, false, lr);
+		//static_cast<CoreMidiPort*>(p)->set_n_periods(2);
+		_system_midi_in.push_back(static_cast<CoreBackendPort*>(p));
+	}
+
+	return 0;
+}
+
+void
+CoreAudioBackend::coremidi_rediscover()
+{
+	if (!_run) { return; }
+	assert(_midi_driver_option == _("CoreMidi"));
+
+	pthread_mutex_lock (&_process_callback_mutex);
+
+	while (_system_midi_out.size() > _midiio->n_midi_outputs()) {
+		CoreBackendPort* p = _system_midi_out.back();
+		_system_midi_out.pop_back();
+		unregister_port(p);
+	}
+
+	while (_system_midi_in.size() > _midiio->n_midi_inputs()) {
+		CoreBackendPort* p = _system_midi_in.back();
+		_system_midi_in.pop_back();
+		unregister_port(p);
+	}
+
+	register_system_midi_ports();
+
+	_port_change_flag = true;
+	_reinit_thread_callback = true; // XXX, rather hook into _pcmio's  hardwarePropertyChangeCallback
+	pthread_mutex_unlock (&_process_callback_mutex);
+}
+
+void
+CoreAudioBackend::unregister_ports (bool system_only)
+{
+	size_t i = 0;
+	_system_inputs.clear();
+	_system_outputs.clear();
+	_system_midi_in.clear();
+	_system_midi_out.clear();
+	while (i <  _ports.size ()) {
+		CoreBackendPort* port = _ports[i];
+		if (! system_only || (port->is_physical () && port->is_terminal ())) {
+			port->disconnect_all ();
+			delete port;
+			_ports.erase (_ports.begin() + i);
+		} else {
+			++i;
+		}
+	}
+}
+
+int
+CoreAudioBackend::connect (const std::string& src, const std::string& dst)
+{
+	CoreBackendPort* src_port = find_port (src);
+	CoreBackendPort* dst_port = find_port (dst);
+
+	if (!src_port) {
+		PBD::error << _("CoreAudioBackend::connect: Invalid Source port:")
+				<< " (" << src <<")" << endmsg;
+		return -1;
+	}
+	if (!dst_port) {
+		PBD::error << _("CoreAudioBackend::connect: Invalid Destination port:")
+			<< " (" << dst <<")" << endmsg;
+		return -1;
+	}
+	return src_port->connect (dst_port);
+}
+
+int
+CoreAudioBackend::disconnect (const std::string& src, const std::string& dst)
+{
+	CoreBackendPort* src_port = find_port (src);
+	CoreBackendPort* dst_port = find_port (dst);
+
+	if (!src_port || !dst_port) {
+		PBD::error << _("CoreAudioBackend::disconnect: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return src_port->disconnect (dst_port);
+}
+
+int
+CoreAudioBackend::connect (PortEngine::PortHandle src, const std::string& dst)
+{
+	CoreBackendPort* dst_port = find_port (dst);
+	if (!valid_port (src)) {
+		PBD::error << _("CoreAudioBackend::connect: Invalid Source Port Handle") << endmsg;
+		return -1;
+	}
+	if (!dst_port) {
+		PBD::error << _("CoreAudioBackend::connect: Invalid Destination Port")
+			<< " (" << dst << ")" << endmsg;
+		return -1;
+	}
+	return static_cast<CoreBackendPort*>(src)->connect (dst_port);
+}
+
+int
+CoreAudioBackend::disconnect (PortEngine::PortHandle src, const std::string& dst)
+{
+	CoreBackendPort* dst_port = find_port (dst);
+	if (!valid_port (src) || !dst_port) {
+		PBD::error << _("CoreAudioBackend::disconnect: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return static_cast<CoreBackendPort*>(src)->disconnect (dst_port);
+}
+
+int
+CoreAudioBackend::disconnect_all (PortEngine::PortHandle port)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreAudioBackend::disconnect_all: Invalid Port") << endmsg;
+		return -1;
+	}
+	static_cast<CoreBackendPort*>(port)->disconnect_all ();
+	return 0;
+}
+
+bool
+CoreAudioBackend::connected (PortEngine::PortHandle port, bool /* process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreAudioBackend::disconnect_all: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<CoreBackendPort*>(port)->is_connected ();
+}
+
+bool
+CoreAudioBackend::connected_to (PortEngine::PortHandle src, const std::string& dst, bool /*process_callback_safe*/)
+{
+	CoreBackendPort* dst_port = find_port (dst);
+	if (!valid_port (src) || !dst_port) {
+		PBD::error << _("CoreAudioBackend::connected_to: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<CoreBackendPort*>(src)->is_connected (dst_port);
+}
+
+bool
+CoreAudioBackend::physically_connected (PortEngine::PortHandle port, bool /*process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreAudioBackend::physically_connected: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<CoreBackendPort*>(port)->is_physically_connected ();
+}
+
+int
+CoreAudioBackend::get_connections (PortEngine::PortHandle port, std::vector<std::string>& names, bool /*process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreAudioBackend::get_connections: Invalid Port") << endmsg;
+		return -1;
+	}
+
+	assert (0 == names.size ());
+
+	const std::vector<CoreBackendPort*>& connected_ports = static_cast<CoreBackendPort*>(port)->get_connections ();
+
+	for (std::vector<CoreBackendPort*>::const_iterator i = connected_ports.begin (); i != connected_ports.end (); ++i) {
+		names.push_back ((*i)->name ());
+	}
+
+	return (int)names.size ();
+}
+
+/* MIDI */
+int
+CoreAudioBackend::midi_event_get (
+		pframes_t& timestamp,
+		size_t& size, uint8_t** buf, void* port_buffer,
+		uint32_t event_index)
+{
+	assert (buf && port_buffer);
+	CoreMidiBuffer& source = * static_cast<CoreMidiBuffer*>(port_buffer);
+	if (event_index >= source.size ()) {
+		return -1;
+	}
+	CoreMidiEvent * const event = source[event_index].get ();
+
+	timestamp = event->timestamp ();
+	size = event->size ();
+	*buf = event->data ();
+	return 0;
+}
+
+int
+CoreAudioBackend::midi_event_put (
+		void* port_buffer,
+		pframes_t timestamp,
+		const uint8_t* buffer, size_t size)
+{
+	assert (buffer && port_buffer);
+	CoreMidiBuffer& dst = * static_cast<CoreMidiBuffer*>(port_buffer);
+	if (dst.size () && (pframes_t)dst.back ()->timestamp () > timestamp) {
+		fprintf (stderr, "CoreMidiBuffer: it's too late for this event. %d > %d\n",
+				(pframes_t)dst.back ()->timestamp (), timestamp);
+		return -1;
+	}
+	dst.push_back (boost::shared_ptr<CoreMidiEvent>(new CoreMidiEvent (timestamp, buffer, size)));
+	return 0;
+}
+
+uint32_t
+CoreAudioBackend::get_midi_event_count (void* port_buffer)
+{
+	assert (port_buffer);
+	return static_cast<CoreMidiBuffer*>(port_buffer)->size ();
+}
+
+void
+CoreAudioBackend::midi_clear (void* port_buffer)
+{
+	assert (port_buffer);
+	CoreMidiBuffer * buf = static_cast<CoreMidiBuffer*>(port_buffer);
+	assert (buf);
+	buf->clear ();
+}
+
+/* Monitoring */
+
+bool
+CoreAudioBackend::can_monitor_input () const
+{
+	return false;
+}
+
+int
+CoreAudioBackend::request_input_monitoring (PortEngine::PortHandle, bool)
+{
+	return -1;
+}
+
+int
+CoreAudioBackend::ensure_input_monitoring (PortEngine::PortHandle, bool)
+{
+	return -1;
+}
+
+bool
+CoreAudioBackend::monitoring_input (PortEngine::PortHandle)
+{
+	return false;
+}
+
+/* Latency management */
+
+void
+CoreAudioBackend::set_latency_range (PortEngine::PortHandle port, bool for_playback, LatencyRange latency_range)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreBackendPort::set_latency_range (): invalid port.") << endmsg;
+	}
+	static_cast<CoreBackendPort*>(port)->set_latency_range (latency_range, for_playback);
+}
+
+LatencyRange
+CoreAudioBackend::get_latency_range (PortEngine::PortHandle port, bool for_playback)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreBackendPort::get_latency_range (): invalid port.") << endmsg;
+		LatencyRange r;
+		r.min = 0;
+		r.max = 0;
+		return r;
+	}
+	return static_cast<CoreBackendPort*>(port)->latency_range (for_playback);
+}
+
+/* Discovering physical ports */
+
+bool
+CoreAudioBackend::port_is_physical (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("CoreBackendPort::port_is_physical (): invalid port.") << endmsg;
+		return false;
+	}
+	return static_cast<CoreBackendPort*>(port)->is_physical ();
+}
+
+void
+CoreAudioBackend::get_physical_outputs (DataType type, std::vector<std::string>& port_names)
+{
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		CoreBackendPort* port = _ports[i];
+		if ((port->type () == type) && port->is_input () && port->is_physical ()) {
+			port_names.push_back (port->name ());
+		}
+	}
+}
+
+void
+CoreAudioBackend::get_physical_inputs (DataType type, std::vector<std::string>& port_names)
+{
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		CoreBackendPort* port = _ports[i];
+		if ((port->type () == type) && port->is_output () && port->is_physical ()) {
+			port_names.push_back (port->name ());
+		}
+	}
+}
+
+ChanCount
+CoreAudioBackend::n_physical_outputs () const
+{
+	int n_midi = 0;
+	int n_audio = 0;
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		CoreBackendPort* port = _ports[i];
+		if (port->is_output () && port->is_physical ()) {
+			switch (port->type ()) {
+				case DataType::AUDIO: ++n_audio; break;
+				case DataType::MIDI: ++n_midi; break;
+				default: break;
+			}
+		}
+	}
+	ChanCount cc;
+	cc.set (DataType::AUDIO, n_audio);
+	cc.set (DataType::MIDI, n_midi);
+	return cc;
+}
+
+ChanCount
+CoreAudioBackend::n_physical_inputs () const
+{
+	int n_midi = 0;
+	int n_audio = 0;
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		CoreBackendPort* port = _ports[i];
+		if (port->is_input () && port->is_physical ()) {
+			switch (port->type ()) {
+				case DataType::AUDIO: ++n_audio; break;
+				case DataType::MIDI: ++n_midi; break;
+				default: break;
+			}
+		}
+	}
+	ChanCount cc;
+	cc.set (DataType::AUDIO, n_audio);
+	cc.set (DataType::MIDI, n_midi);
+	return cc;
+}
+
+/* Getting access to the data buffer for a port */
+
+void*
+CoreAudioBackend::get_buffer (PortEngine::PortHandle port, pframes_t nframes)
+{
+	assert (port);
+	assert (valid_port (port));
+	return static_cast<CoreBackendPort*>(port)->get_buffer (nframes);
+}
+
+void
+CoreAudioBackend::post_process ()
+{
+	bool connections_changed = false;
+	bool ports_changed = false;
+	if (!pthread_mutex_trylock (&_port_callback_mutex)) {
+		if (_port_change_flag) {
+			ports_changed = true;
+			_port_change_flag = false;
+		}
+		if (!_port_connection_queue.empty ()) {
+			connections_changed = true;
+		}
+		while (!_port_connection_queue.empty ()) {
+			PortConnectData *c = _port_connection_queue.back ();
+			manager.connect_callback (c->a, c->b, c->c);
+			_port_connection_queue.pop_back ();
+			delete c;
+		}
+		pthread_mutex_unlock (&_port_callback_mutex);
+	}
+	if (ports_changed) {
+		manager.registration_callback();
+	}
+	if (connections_changed) {
+		manager.graph_order_callback();
+	}
+	if (connections_changed || ports_changed) {
+		engine.latency_callback(false);
+		engine.latency_callback(true);
+	}
+}
+
+void *
+CoreAudioBackend::freewheel_thread ()
+{
+	_active_fw = true;
+	bool first_run = false;
+	while (_run) {
+		// check if we should run,
+		if (_freewheeling != _freewheel) {
+			if (!_freewheeling) {
+				// handshake w/ coreaudio
+				_reinit_thread_callback = true;
+				_freewheel_ack = false;
+			}
+
+			engine.freewheel_callback (_freewheeling);
+			first_run = true;
+			_freewheel = _freewheeling;
+		}
+
+		if (!_freewheel || !_freewheel_ack) {
+			// TODO use a pthread sync/sleep
+			Glib::usleep(200000);
+			continue;
+		}
+
+		if (first_run) {
+			first_run = false;
+			_main_thread = pthread_self();
+			AudioEngine::thread_init_callback (this);
+		}
+
+		// Freewheelin'
+		for (std::vector<CoreBackendPort*>::const_iterator it = _system_inputs.begin (); it != _system_inputs.end (); ++it) {
+			memset ((*it)->get_buffer (_samples_per_period), 0, _samples_per_period * sizeof (Sample));
+		}
+		for (std::vector<CoreBackendPort*>::const_iterator it = _system_midi_in.begin (); it != _system_midi_in.end (); ++it) {
+			static_cast<CoreMidiBuffer*>((*it)->get_buffer(0))->clear ();
+		}
+
+		if (engine.process_callback (_samples_per_period)) {
+			break;
+		}
+		_dsp_load = 1.0;
+		Glib::usleep (100); // don't hog cpu
+
+		post_process();
+	}
+
+	_active_fw = false;
+
+	if (_run && _freewheel) {
+		engine.halted_callback("CoreAudio Freehweeling aborted.");
+	}
+	return 0;
+}
+
+int
+CoreAudioBackend::process_callback ()
+{
+	uint32_t i = 0;
+	uint64_t clock1, clock2;
+
+	_active_ca = true;
+
+	if (_run && _freewheel && !_freewheel_ack) {
+		_freewheel_ack = true;
+	}
+
+	if (!_run || _freewheel || _preinit) {
+		return 1;
+	}
+
+	if (pthread_mutex_trylock (&_process_callback_mutex)) {
+		return 1;
+	}
+
+	if (_reinit_thread_callback || _main_thread != pthread_self()) {
+		printf("REINIT THREAD\n");
+		_reinit_thread_callback = false;
+		_main_thread = pthread_self();
+		AudioEngine::thread_init_callback (this);
+
+		manager.registration_callback();
+		manager.graph_order_callback();
+	}
+
+	const uint32_t n_samples = _pcmio->n_samples();
+
+#if 0 // here in RT callback ?? XXX
+	if (_samples_per_period != n_samples) {
+		_samples_per_period = n_samples;
+		engine.buffer_size_change (_samples_per_period);
+		// TODO update latencies
+	}
+#endif
+
+	// cycle-length in usec
+	const int64_t nominal_time = 1e6 * n_samples / _samplerate;
+
+	clock1 = g_get_monotonic_time();
+
+	// TODO get midi
+	i=0;
+	for (std::vector<CoreBackendPort*>::const_iterator it = _system_midi_in.begin (); it != _system_midi_in.end (); ++it, ++i) {
+		CoreMidiBuffer* mbuf = static_cast<CoreMidiBuffer*>((*it)->get_buffer(0));
+		mbuf->clear();
+		uint64_t time_ns;
+		uint8_t data[64]; // match MaxAlsaEventSize in alsa_rawmidi.cc
+		size_t size = sizeof(data);
+		while (_midiio->recv_event (i, nominal_time, time_ns, data, size)) {
+			pframes_t time = floor((float) time_ns * _samplerate * 1e-9);
+			assert (time < n_samples);
+			midi_event_put((void*)mbuf, time, data, size);
+			size = sizeof(data);
+		}
+	}
+
+	/* get audio */
+	i = 0;
+	for (std::vector<CoreBackendPort*>::const_iterator it = _system_inputs.begin (); it != _system_inputs.end (); ++it) {
+		_pcmio->get_capture_channel (i, (float*)((*it)->get_buffer(n_samples)), n_samples);
+	}
+
+	/* clear output buffers */
+	for (std::vector<CoreBackendPort*>::const_iterator it = _system_outputs.begin (); it != _system_outputs.end (); ++it) {
+		memset ((*it)->get_buffer (n_samples), 0, n_samples * sizeof (Sample));
+	}
+
+	_midiio->start_cycle();
+
+	if (engine.process_callback (n_samples)) {
+		fprintf(stderr, "ENGINE PROCESS ERROR\n");
+		//_pcmio->pcm_stop ();
+		_active_ca = false;
+		pthread_mutex_unlock (&_process_callback_mutex);
+		return -1;
+	}
+
+	// mixdown midi
+	for (std::vector<CoreBackendPort*>::const_iterator it = _system_midi_out.begin (); it != _system_midi_out.end (); ++it) {
+		//static_cast<CoreMidiPort*>(*it)->next_period();
+		static_cast<CoreMidiPort*>(*it)->get_buffer(0);
+	}
+	// queue outgoing midi
+	i = 0;
+	for (std::vector<CoreBackendPort*>::const_iterator it = _system_midi_out.begin (); it != _system_midi_out.end (); ++it, ++i) {
+		const CoreMidiBuffer *src = static_cast<const CoreMidiPort*>(*it)->const_buffer();
+		for (CoreMidiBuffer::const_iterator mit = src->begin (); mit != src->end (); ++mit) {
+			_midiio->send_event (i, (*mit)->timestamp() / nominal_time, (*mit)->data(), (*mit)->size());
+		}
+	}
+
+	/* write back audio */
+	i = 0;
+	for (std::vector<CoreBackendPort*>::const_iterator it = _system_outputs.begin (); it != _system_outputs.end (); ++it, ++i) {
+		_pcmio->set_playback_channel (i, (float const*)(*it)->get_buffer (n_samples), n_samples);
+	}
+
+	_processed_samples += n_samples;
+
+	// calc DSP load.
+
+	clock2 = g_get_monotonic_time();
+	const int64_t elapsed_time = clock2 - clock1;
+	_dsp_load = elapsed_time / (float) nominal_time;
+
+	//engine.Xrun (); // TODO, if any
+
+	// port-connection change
+	post_process();
+	pthread_mutex_unlock (&_process_callback_mutex);
+	return 0;
+}
+
+void
+CoreAudioBackend::error_callback ()
+{
+	printf("ERROR CALLBACK\n");
+	_pcmio->set_error_callback (NULL, NULL);
+	engine.halted_callback("CoreAudio Process aborted.");
+}
+
+
+/******************************************************************************/
+
+static boost::shared_ptr<CoreAudioBackend> _instance;
+
+static boost::shared_ptr<AudioBackend> backend_factory (AudioEngine& e);
+static int instantiate (const std::string& arg1, const std::string& /* arg2 */);
+static int deinstantiate ();
+static bool already_configured ();
+static bool available ();
+
+static ARDOUR::AudioBackendInfo _descriptor = {
+	"CoreAudio2",
+	instantiate,
+	deinstantiate,
+	backend_factory,
+	already_configured,
+	available
+};
+
+static boost::shared_ptr<AudioBackend>
+backend_factory (AudioEngine& e)
+{
+	if (!_instance) {
+		_instance.reset (new CoreAudioBackend (e, _descriptor));
+	}
+	return _instance;
+}
+
+static int
+instantiate (const std::string& arg1, const std::string& /* arg2 */)
+{
+	s_instance_name = arg1;
+	return 0;
+}
+
+static int
+deinstantiate ()
+{
+	_instance.reset ();
+	return 0;
+}
+
+static bool
+already_configured ()
+{
+	return false;
+}
+
+static bool
+available ()
+{
+	return true;
+}
+
+extern "C" ARDOURBACKEND_API ARDOUR::AudioBackendInfo* descriptor ()
+{
+	return &_descriptor;
+}
+
+
+/******************************************************************************/
+CoreBackendPort::CoreBackendPort (CoreAudioBackend &b, const std::string& name, PortFlags flags)
+	: _osx_backend (b)
+	, _name  (name)
+	, _flags (flags)
+{
+	_capture_latency_range.min = 0;
+	_capture_latency_range.max = 0;
+	_playback_latency_range.min = 0;
+	_playback_latency_range.max = 0;
+}
+
+CoreBackendPort::~CoreBackendPort () {
+	disconnect_all ();
+}
+
+
+int CoreBackendPort::connect (CoreBackendPort *port)
+{
+	if (!port) {
+		PBD::error << _("CoreBackendPort::connect (): invalid (null) port") << endmsg;
+		return -1;
+	}
+
+	if (type () != port->type ()) {
+		PBD::error << _("CoreBackendPort::connect (): wrong port-type") << endmsg;
+		return -1;
+	}
+
+	if (is_output () && port->is_output ()) {
+		PBD::error << _("CoreBackendPort::connect (): cannot inter-connect output ports.") << endmsg;
+		return -1;
+	}
+
+	if (is_input () && port->is_input ()) {
+		PBD::error << _("CoreBackendPort::connect (): cannot inter-connect input ports.") << endmsg;
+		return -1;
+	}
+
+	if (this == port) {
+		PBD::error << _("CoreBackendPort::connect (): cannot self-connect ports.") << endmsg;
+		return -1;
+	}
+
+	if (is_connected (port)) {
+#if 0 // don't bother to warn about this for now. just ignore it
+		PBD::error << _("CoreBackendPort::connect (): ports are already connected:")
+			<< " (" << name () << ") -> (" << port->name () << ")"
+			<< endmsg;
+#endif
+		return -1;
+	}
+
+	_connect (port, true);
+	return 0;
+}
+
+
+void CoreBackendPort::_connect (CoreBackendPort *port, bool callback)
+{
+	_connections.push_back (port);
+	if (callback) {
+		port->_connect (this, false);
+		_osx_backend.port_connect_callback (name(),  port->name(), true);
+	}
+}
+
+int CoreBackendPort::disconnect (CoreBackendPort *port)
+{
+	if (!port) {
+		PBD::error << _("CoreBackendPort::disconnect (): invalid (null) port") << endmsg;
+		return -1;
+	}
+
+	if (!is_connected (port)) {
+		PBD::error << _("CoreBackendPort::disconnect (): ports are not connected:")
+			<< " (" << name () << ") -> (" << port->name () << ")"
+			<< endmsg;
+		return -1;
+	}
+	_disconnect (port, true);
+	return 0;
+}
+
+void CoreBackendPort::_disconnect (CoreBackendPort *port, bool callback)
+{
+	std::vector<CoreBackendPort*>::iterator it = std::find (_connections.begin (), _connections.end (), port);
+
+	assert (it != _connections.end ());
+
+	_connections.erase (it);
+
+	if (callback) {
+		port->_disconnect (this, false);
+		_osx_backend.port_connect_callback (name(),  port->name(), false);
+	}
+}
+
+
+void CoreBackendPort::disconnect_all ()
+{
+	while (!_connections.empty ()) {
+		_connections.back ()->_disconnect (this, false);
+		_osx_backend.port_connect_callback (name(),  _connections.back ()->name(), false);
+		_connections.pop_back ();
+	}
+}
+
+bool
+CoreBackendPort::is_connected (const CoreBackendPort *port) const
+{
+	return std::find (_connections.begin (), _connections.end (), port) != _connections.end ();
+}
+
+bool CoreBackendPort::is_physically_connected () const
+{
+	for (std::vector<CoreBackendPort*>::const_iterator it = _connections.begin (); it != _connections.end (); ++it) {
+		if ((*it)->is_physical ()) {
+			return true;
+		}
+	}
+	return false;
+}
+
+/******************************************************************************/
+
+CoreAudioPort::CoreAudioPort (CoreAudioBackend &b, const std::string& name, PortFlags flags)
+	: CoreBackendPort (b, name, flags)
+{
+	memset (_buffer, 0, sizeof (_buffer));
+	mlock(_buffer, sizeof (_buffer));
+}
+
+CoreAudioPort::~CoreAudioPort () { }
+
+void* CoreAudioPort::get_buffer (pframes_t n_samples)
+{
+	if (is_input ()) {
+		std::vector<CoreBackendPort*>::const_iterator it = get_connections ().begin ();
+		if (it == get_connections ().end ()) {
+			memset (_buffer, 0, n_samples * sizeof (Sample));
+		} else {
+			CoreAudioPort const * source = static_cast<const CoreAudioPort*>(*it);
+			assert (source && source->is_output ());
+			memcpy (_buffer, source->const_buffer (), n_samples * sizeof (Sample));
+			while (++it != get_connections ().end ()) {
+				source = static_cast<const CoreAudioPort*>(*it);
+				assert (source && source->is_output ());
+				Sample* dst = buffer ();
+				const Sample* src = source->const_buffer ();
+				for (uint32_t s = 0; s < n_samples; ++s, ++dst, ++src) {
+					*dst += *src;
+				}
+			}
+		}
+	}
+	return _buffer;
+}
+
+
+CoreMidiPort::CoreMidiPort (CoreAudioBackend &b, const std::string& name, PortFlags flags)
+	: CoreBackendPort (b, name, flags)
+	, _n_periods (1)
+	, _bufperiod (0)
+{
+	_buffer[0].clear ();
+	_buffer[1].clear ();
+}
+
+CoreMidiPort::~CoreMidiPort () { }
+
+struct MidiEventSorter {
+	bool operator() (const boost::shared_ptr<CoreMidiEvent>& a, const boost::shared_ptr<CoreMidiEvent>& b) {
+		return *a < *b;
+	}
+};
+
+void* CoreMidiPort::get_buffer (pframes_t /* nframes */)
+{
+	if (is_input ()) {
+		(_buffer[_bufperiod]).clear ();
+		for (std::vector<CoreBackendPort*>::const_iterator i = get_connections ().begin ();
+				i != get_connections ().end ();
+				++i) {
+			const CoreMidiBuffer * src = static_cast<const CoreMidiPort*>(*i)->const_buffer ();
+			for (CoreMidiBuffer::const_iterator it = src->begin (); it != src->end (); ++it) {
+				(_buffer[_bufperiod]).push_back (boost::shared_ptr<CoreMidiEvent>(new CoreMidiEvent (**it)));
+			}
+		}
+		std::sort ((_buffer[_bufperiod]).begin (), (_buffer[_bufperiod]).end (), MidiEventSorter());
+	}
+	return &(_buffer[_bufperiod]);
+}
+
+CoreMidiEvent::CoreMidiEvent (const pframes_t timestamp, const uint8_t* data, size_t size)
+	: _size (size)
+	, _timestamp (timestamp)
+	, _data (0)
+{
+	if (size > 0) {
+		_data = (uint8_t*) malloc (size);
+		memcpy (_data, data, size);
+	}
+}
+
+CoreMidiEvent::CoreMidiEvent (const CoreMidiEvent& other)
+	: _size (other.size ())
+	, _timestamp (other.timestamp ())
+	, _data (0)
+{
+	if (other.size () && other.const_data ()) {
+		_data = (uint8_t*) malloc (other.size ());
+		memcpy (_data, other.const_data (), other.size ());
+	}
+};
+
+CoreMidiEvent::~CoreMidiEvent () {
+	free (_data);
+};
diff --git a/libs/backends/coreaudio/coreaudio_backend.h b/libs/backends/coreaudio/coreaudio_backend.h
new file mode 100644
index 0000000000..0460e57476
--- /dev/null
+++ b/libs/backends/coreaudio/coreaudio_backend.h
@@ -0,0 +1,428 @@
+/*
+ * Copyright (C) 2014 Robin Gareus <robin@gareus.org>
+ * Copyright (C) 2013 Paul Davis
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __libbackend_coreaudio_backend_h__
+#define __libbackend_coreaudio_backend_h__
+
+#include <string>
+#include <vector>
+#include <map>
+#include <set>
+
+#include <stdint.h>
+#include <pthread.h>
+
+#include <boost/shared_ptr.hpp>
+
+#include "ardour/audio_backend.h"
+#include "ardour/types.h"
+
+#include "coreaudio_pcmio.h"
+#include "coremidi_io.h"
+
+namespace ARDOUR {
+
+class CoreAudioBackend;
+
+class CoreMidiEvent {
+	public:
+		CoreMidiEvent (const pframes_t timestamp, const uint8_t* data, size_t size);
+		CoreMidiEvent (const CoreMidiEvent& other);
+		~CoreMidiEvent ();
+		size_t size () const { return _size; };
+		pframes_t timestamp () const { return _timestamp; };
+		const unsigned char* const_data () const { return _data; };
+		unsigned char* data () { return _data; };
+		bool operator< (const CoreMidiEvent &other) const { return timestamp () < other.timestamp (); };
+	private:
+		size_t _size;
+		pframes_t _timestamp;
+		uint8_t *_data;
+};
+
+typedef std::vector<boost::shared_ptr<CoreMidiEvent> > CoreMidiBuffer;
+
+class CoreBackendPort {
+	protected:
+		CoreBackendPort (CoreAudioBackend &b, const std::string&, PortFlags);
+	public:
+		virtual ~CoreBackendPort ();
+
+		const std::string& name () const { return _name; }
+		PortFlags flags () const { return _flags; }
+
+		int set_name (const std::string &name) { _name = name; return 0; }
+
+		virtual DataType type () const = 0;
+
+		bool is_input ()     const { return flags () & IsInput; }
+		bool is_output ()    const { return flags () & IsOutput; }
+		bool is_physical ()  const { return flags () & IsPhysical; }
+		bool is_terminal ()  const { return flags () & IsTerminal; }
+		bool is_connected () const { return _connections.size () != 0; }
+		bool is_connected (const CoreBackendPort *port) const;
+		bool is_physically_connected () const;
+
+		const std::vector<CoreBackendPort *>& get_connections () const { return _connections; }
+
+		int connect (CoreBackendPort *port);
+		int disconnect (CoreBackendPort *port);
+		void disconnect_all ();
+
+		virtual void* get_buffer (pframes_t nframes) = 0;
+
+		const LatencyRange& latency_range (bool for_playback) const
+		{
+			return for_playback ? _playback_latency_range : _capture_latency_range;
+		}
+
+		void set_latency_range (const LatencyRange &latency_range, bool for_playback)
+		{
+			if (for_playback)
+			{
+				_playback_latency_range = latency_range;
+			}
+			else
+			{
+				_capture_latency_range = latency_range;
+			}
+		}
+
+	private:
+		CoreAudioBackend &_osx_backend;
+		std::string _name;
+		const PortFlags _flags;
+		LatencyRange _capture_latency_range;
+		LatencyRange _playback_latency_range;
+		std::vector<CoreBackendPort*> _connections;
+
+		void _connect (CoreBackendPort* , bool);
+		void _disconnect (CoreBackendPort* , bool);
+
+}; // class CoreBackendPort
+
+class CoreAudioPort : public CoreBackendPort {
+	public:
+		CoreAudioPort (CoreAudioBackend &b, const std::string&, PortFlags);
+		~CoreAudioPort ();
+
+		DataType type () const { return DataType::AUDIO; };
+
+		Sample* buffer () { return _buffer; }
+		const Sample* const_buffer () const { return _buffer; }
+		void* get_buffer (pframes_t nframes);
+
+	private:
+		Sample _buffer[8192];
+}; // class CoreAudioPort
+
+class CoreMidiPort : public CoreBackendPort {
+	public:
+		CoreMidiPort (CoreAudioBackend &b, const std::string&, PortFlags);
+		~CoreMidiPort ();
+
+		DataType type () const { return DataType::MIDI; };
+
+		void* get_buffer (pframes_t nframes);
+		const CoreMidiBuffer * const_buffer () const { return & _buffer[_bufperiod]; }
+
+		void next_period() { if (_n_periods > 1) { get_buffer(0); _bufperiod = (_bufperiod + 1) % _n_periods; } }
+		void set_n_periods(int n) { if (n > 0 && n < 3) { _n_periods = n; } }
+
+	private:
+		CoreMidiBuffer _buffer[2];
+		int _n_periods;
+		int _bufperiod;
+}; // class CoreMidiPort
+
+class CoreAudioBackend : public AudioBackend {
+	friend class CoreBackendPort;
+	public:
+		CoreAudioBackend (AudioEngine& e, AudioBackendInfo& info);
+		~CoreAudioBackend ();
+
+		/* AUDIOBACKEND API */
+
+		std::string name () const;
+		bool is_realtime () const;
+
+		std::vector<DeviceStatus> enumerate_devices () const;
+		std::vector<float> available_sample_rates (const std::string& device) const;
+		std::vector<uint32_t> available_buffer_sizes (const std::string& device) const;
+		uint32_t available_input_channel_count (const std::string& device) const;
+		uint32_t available_output_channel_count (const std::string& device) const;
+
+		bool can_change_sample_rate_when_running () const;
+		bool can_change_buffer_size_when_running () const;
+
+		int set_device_name (const std::string&);
+		int set_sample_rate (float);
+		int set_buffer_size (uint32_t);
+		int set_interleaved (bool yn);
+		int set_input_channels (uint32_t);
+		int set_output_channels (uint32_t);
+		int set_systemic_input_latency (uint32_t);
+		int set_systemic_output_latency (uint32_t);
+		int set_systemic_midi_input_latency (std::string const, uint32_t);
+		int set_systemic_midi_output_latency (std::string const, uint32_t);
+
+		int reset_device () { return 0; };
+
+		/* Retrieving parameters */
+		std::string  device_name () const;
+		float        sample_rate () const;
+		uint32_t     buffer_size () const;
+		bool         interleaved () const;
+		uint32_t     input_channels () const;
+		uint32_t     output_channels () const;
+		uint32_t     systemic_input_latency () const;
+		uint32_t     systemic_output_latency () const;
+		uint32_t     systemic_midi_input_latency (std::string const) const;
+		uint32_t     systemic_midi_output_latency (std::string const) const;
+
+		bool can_set_systemic_midi_latencies () const { return false; /* XXX */}
+
+		/* External control app */
+		std::string control_app_name () const { return std::string (); }
+		void launch_control_app () {}
+
+		/* MIDI */
+		std::vector<std::string> enumerate_midi_options () const;
+		int set_midi_option (const std::string&);
+		std::string midi_option () const;
+
+		std::vector<DeviceStatus> enumerate_midi_devices () const;
+		int set_midi_device_enabled (std::string const, bool);
+		bool midi_device_enabled (std::string const) const;
+
+		// really private, but needing static access:
+		int process_callback();
+		void error_callback();
+
+	protected:
+		/* State Control */
+		int _start (bool for_latency_measurement);
+	public:
+		int stop ();
+		int freewheel (bool);
+		float dsp_load () const;
+		size_t raw_buffer_size (DataType t);
+
+		/* Process time */
+		framepos_t sample_time ();
+		framepos_t sample_time_at_cycle_start ();
+		pframes_t samples_since_cycle_start ();
+
+		int create_process_thread (boost::function<void()> func);
+		int join_process_threads ();
+		bool in_process_thread ();
+		uint32_t process_thread_count ();
+
+		void update_latencies ();
+
+		/* PORTENGINE API */
+
+		void* private_handle () const;
+		const std::string& my_name () const;
+		bool available () const;
+		uint32_t port_name_size () const;
+
+		int         set_port_name (PortHandle, const std::string&);
+		std::string get_port_name (PortHandle) const;
+		PortHandle  get_port_by_name (const std::string&) const;
+
+		int get_ports (const std::string& port_name_pattern, DataType type, PortFlags flags, std::vector<std::string>&) const;
+
+		DataType port_data_type (PortHandle) const;
+
+		PortHandle register_port (const std::string& shortname, ARDOUR::DataType, ARDOUR::PortFlags);
+		void unregister_port (PortHandle);
+
+		int  connect (const std::string& src, const std::string& dst);
+		int  disconnect (const std::string& src, const std::string& dst);
+		int  connect (PortHandle, const std::string&);
+		int  disconnect (PortHandle, const std::string&);
+		int  disconnect_all (PortHandle);
+
+		bool connected (PortHandle, bool process_callback_safe);
+		bool connected_to (PortHandle, const std::string&, bool process_callback_safe);
+		bool physically_connected (PortHandle, bool process_callback_safe);
+		int  get_connections (PortHandle, std::vector<std::string>&, bool process_callback_safe);
+
+		/* MIDI */
+		int midi_event_get (pframes_t& timestamp, size_t& size, uint8_t** buf, void* port_buffer, uint32_t event_index);
+		int midi_event_put (void* port_buffer, pframes_t timestamp, const uint8_t* buffer, size_t size);
+		uint32_t get_midi_event_count (void* port_buffer);
+		void     midi_clear (void* port_buffer);
+
+		/* Monitoring */
+
+		bool can_monitor_input () const;
+		int  request_input_monitoring (PortHandle, bool);
+		int  ensure_input_monitoring (PortHandle, bool);
+		bool monitoring_input (PortHandle);
+
+		/* Latency management */
+
+		void         set_latency_range (PortHandle, bool for_playback, LatencyRange);
+		LatencyRange get_latency_range (PortHandle, bool for_playback);
+
+		/* Discovering physical ports */
+
+		bool      port_is_physical (PortHandle) const;
+		void      get_physical_outputs (DataType type, std::vector<std::string>&);
+		void      get_physical_inputs (DataType type, std::vector<std::string>&);
+		ChanCount n_physical_outputs () const;
+		ChanCount n_physical_inputs () const;
+
+		/* Getting access to the data buffer for a port */
+
+		void* get_buffer (PortHandle, pframes_t);
+
+		void* freewheel_thread ();
+		void post_process ();
+		void coremidi_rediscover ();
+
+	private:
+		std::string _instance_name;
+		CoreAudioPCM *_pcmio;
+		CoreMidiIo *_midiio;
+
+		bool  _run; /* keep going or stop, ardour thread */
+		bool  _active_ca; /* is running, process thread */
+		bool  _active_fw; /* is running, process thread */
+		bool  _preinit;
+		bool  _freewheeling;
+		bool  _freewheel;
+		bool  _freewheel_ack;
+		bool  _reinit_thread_callback;
+		bool  _measure_latency;
+		pthread_mutex_t _process_callback_mutex;
+
+		static std::vector<std::string> _midi_options;
+		static std::vector<AudioBackend::DeviceStatus> _audio_device_status;
+		static std::vector<AudioBackend::DeviceStatus> _midi_device_status;
+
+		mutable std::string _audio_device;
+		std::string _midi_driver_option;
+
+		/* audio settings */
+		float  _samplerate;
+		size_t _samples_per_period;
+		static size_t _max_buffer_size;
+
+		uint32_t _n_inputs;
+		uint32_t _n_outputs;
+
+		uint32_t _systemic_audio_input_latency;
+		uint32_t _systemic_audio_output_latency;
+
+		/* midi settings */
+		struct CoreMidiDeviceInfo {
+			bool     enabled;
+			uint32_t systemic_input_latency;
+			uint32_t systemic_output_latency;
+			CoreMidiDeviceInfo()
+				: enabled (true)
+				, systemic_input_latency (0)
+				, systemic_output_latency (0)
+			{}
+		};
+
+		mutable std::map<std::string, struct CoreMidiDeviceInfo *> _midi_devices;
+		struct CoreMidiDeviceInfo * midi_device_info(std::string const) const;
+
+		/* processing */
+		float  _dsp_load;
+		uint64_t _processed_samples;
+
+		pthread_t _main_thread;
+		pthread_t _freeewheel_thread;
+
+		/* process threads */
+		static void* coreaudio_process_thread (void *);
+		std::vector<pthread_t> _threads;
+
+		struct ThreadData {
+			CoreAudioBackend* engine;
+			boost::function<void ()> f;
+			size_t stacksize;
+
+			ThreadData (CoreAudioBackend* e, boost::function<void ()> fp, size_t stacksz)
+				: engine (e) , f (fp) , stacksize (stacksz) {}
+		};
+
+		/* port engine */
+		PortHandle add_port (const std::string& shortname, ARDOUR::DataType, ARDOUR::PortFlags);
+		int register_system_audio_ports ();
+		int register_system_midi_ports ();
+		void unregister_ports (bool system_only = false);
+
+		std::vector<CoreBackendPort *> _ports;
+		std::vector<CoreBackendPort *> _system_inputs;
+		std::vector<CoreBackendPort *> _system_outputs;
+		std::vector<CoreBackendPort *> _system_midi_in;
+		std::vector<CoreBackendPort *> _system_midi_out;
+
+		//std::vector<CoreMidiOut *> _rmidi_out;
+		//std::vector<CoreMidiIn  *> _rmidi_in;
+
+		struct PortConnectData {
+			std::string a;
+			std::string b;
+			bool c;
+
+			PortConnectData (const std::string& a, const std::string& b, bool c)
+				: a (a) , b (b) , c (c) {}
+		};
+
+		std::vector<PortConnectData *> _port_connection_queue;
+		pthread_mutex_t _port_callback_mutex;
+		bool _port_change_flag;
+
+		void port_connect_callback (const std::string& a, const std::string& b, bool conn) {
+			pthread_mutex_lock (&_port_callback_mutex);
+			_port_connection_queue.push_back(new PortConnectData(a, b, conn));
+			pthread_mutex_unlock (&_port_callback_mutex);
+		}
+
+		void port_connect_add_remove_callback () {
+			pthread_mutex_lock (&_port_callback_mutex);
+			_port_change_flag = true;
+			pthread_mutex_unlock (&_port_callback_mutex);
+		}
+
+		bool valid_port (PortHandle port) const {
+			return std::find (_ports.begin (), _ports.end (), (CoreBackendPort*)port) != _ports.end ();
+		}
+
+		CoreBackendPort * find_port (const std::string& port_name) const {
+			for (std::vector<CoreBackendPort*>::const_iterator it = _ports.begin (); it != _ports.end (); ++it) {
+				if ((*it)->name () == port_name) {
+					return *it;
+				}
+			}
+			return NULL;
+		}
+
+}; // class CoreAudioBackend
+
+} // namespace
+
+#endif /* __libbackend_coreaudio_backend_h__ */
diff --git a/libs/backends/coreaudio/coreaudio_pcmio.cc b/libs/backends/coreaudio/coreaudio_pcmio.cc
new file mode 100644
index 0000000000..a1615d8583
--- /dev/null
+++ b/libs/backends/coreaudio/coreaudio_pcmio.cc
@@ -0,0 +1,483 @@
+/*
+ * Copyright (C) 2015 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "coreaudio_pcmio.h"
+#include <string>
+
+
+static OSStatus hardwarePropertyChangeCallback (AudioHardwarePropertyID inPropertyID, void* arg) {
+	if (inPropertyID == kAudioHardwarePropertyDevices) {
+		CoreAudioPCM * self = static_cast<CoreAudioPCM*>(arg);
+		self->hwPropertyChange();
+	}
+	return noErr;
+}
+
+CoreAudioPCM::CoreAudioPCM ()
+	: _auhal (0)
+	, _deviceIDs (0)
+	, _inputAudioBufferList (0)
+	, _state (-1)
+	, _capture_channels (0)
+	, _playback_channels (0)
+	, _in_process (false)
+	, _numDevices (0)
+	, _process_callback (0)
+	, _error_callback (0)
+	, _device_ins (0)
+	, _device_outs (0)
+{
+#ifdef COREAUDIO_108 // TODO
+	CFRunLoopRef theRunLoop = NULL;
+	AudioObjectPropertyAddress property = { kAudioHardwarePropertyRunLoop, kAudioObjectPropertyScopeGlobal, kAudioHardwarePropertyDevices };
+	AudioObjectSetPropertyData (kAudioObjectSystemObject, &property, 0, NULL, sizeof(CFRunLoopRef), &theRunLoop);
+#endif
+	AudioHardwareAddPropertyListener (kAudioHardwarePropertyDevices, hardwarePropertyChangeCallback, this);
+}
+
+CoreAudioPCM::~CoreAudioPCM ()
+{
+	if (_state == 0) {
+		pcm_stop();
+	}
+	delete _deviceIDs;
+	free(_device_ins);
+	free(_device_outs);
+	AudioHardwareRemovePropertyListener(kAudioHardwarePropertyDevices, hardwarePropertyChangeCallback);
+	free(_inputAudioBufferList);
+}
+
+
+void
+CoreAudioPCM::hwPropertyChange() {
+	printf("hardwarePropertyChangeCallback\n");
+	discover();
+}
+
+void
+CoreAudioPCM::discover() {
+	OSStatus err;
+	UInt32 propSize = 0;
+
+	// TODO trymutex lock.
+
+	if (_deviceIDs) {
+		delete _deviceIDs; _deviceIDs = 0;
+		free(_device_ins); _device_ins = 0;
+		free(_device_outs); _device_outs = 0;
+	}
+	_devices.clear();
+
+#ifdef COREAUDIO_108
+	AudioObjectPropertyAddress propertyAddress;
+	propertyAddress.mSelector = kAudioHardwarePropertyDevices;
+	propertyAddress.mScope = kAudioObjectPropertyScopeGlobal;
+	propertyAddress.mElement = kAudioObjectPropertyElementMaster;
+	err = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &propSize);
+#else
+	err = AudioHardwareGetPropertyInfo (kAudioHardwarePropertyDevices, &propSize, NULL);
+#endif
+
+	_numDevices = propSize / sizeof (AudioDeviceID);
+	propSize = _numDevices * sizeof (AudioDeviceID);
+
+	_deviceIDs = new AudioDeviceID[_numDevices];
+	_device_ins = (uint32_t*) calloc(_numDevices, sizeof(uint32_t));
+	_device_outs = (uint32_t*) calloc(_numDevices, sizeof(uint32_t));
+
+#ifdef COREAUDIO_108
+	propertyAddress.mSelector = kAudioHardwarePropertyDevices;
+	err = AudioObjectGetPropertyData(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &propSize, _deviceIDs);
+#else
+	err = AudioHardwareGetProperty (kAudioHardwarePropertyDevices, &propSize, _deviceIDs);
+#endif
+
+	for (size_t deviceIndex = 0; deviceIndex < _numDevices; deviceIndex++) {
+		propSize = 64;
+		char deviceName[64];
+#ifdef COREAUDIO_108
+		propertyAddress.mSelector = kAudioDevicePropertyDeviceName;
+		propertyAddress.mScope = kAudioDevicePropertyScopeOutput;
+		err = AudioObjectGetPropertyData(_deviceIDs[deviceIndex], &propertyAddress, 0, NULL, &propSize, deviceName);
+#else
+		err = AudioDeviceGetProperty(_deviceIDs[deviceIndex], 0, 0, kAudioDevicePropertyDeviceName, &propSize, deviceName);
+#endif
+
+		if (kAudioHardwareNoError != err) {
+			fprintf(stderr, "device name query failed: %i\n", err);
+			continue;
+		}
+
+		UInt32 size;
+		UInt32 outputChannelCount = 0;
+		UInt32 inputChannelCount = 0;
+		AudioBufferList *bufferList = NULL;
+
+		/* query number of inputs */
+#ifdef COREAUDIO_108
+		size = 0;
+		propertyAddress.mSelector = kAudioDevicePropertyStreamConfiguration;
+		propertyAddress.mScope = kAudioDevicePropertyScopeOutput;
+		err = AudioObjectGetPropertyDataSize(_deviceIDs[deviceIndex], &propertyAddress, 0, NULL, &size);
+		if (kAudioHardwareNoError != err) {
+			fprintf(stderr, "kAudioDevicePropertyStreamConfiguration failed: %i\n", err);
+			continue;
+		}
+
+		bufferList = (AudioBufferList *)(malloc(size));
+		assert(bufferList);
+		if (!bufferList) { fprintf(stderr, "OUT OF MEMORY\n"); break; }
+
+		err = AudioObjectGetPropertyData(_deviceIDs[deviceIndex], &propertyAddress, 0, NULL, &size, bufferList);
+
+#else
+		err = AudioDeviceGetPropertyInfo (_deviceIDs[deviceIndex], 0, AUHAL_OUTPUT_ELEMENT, kAudioDevicePropertyStreamConfiguration, &propSize, NULL);
+		if (kAudioHardwareNoError != err) {
+			fprintf(stderr, "kAudioDevicePropertyStreamConfiguration failed: %i\n", err);
+			continue;
+		}
+		bufferList = (AudioBufferList *)(malloc(size));
+		assert(bufferList);
+		if (!bufferList) { fprintf(stderr, "OUT OF MEMORY\n"); break; }
+
+		bufferList->mNumberBuffers = 0;
+		err = AudioDeviceGetProperty(_deviceIDs[deviceIndex], 0, AUHAL_OUTPUT_ELEMENT, kAudioDevicePropertyStreamConfiguration, &size, bufferList);
+#endif
+		if(kAudioHardwareNoError != err) {
+			fprintf(stderr, "kAudioDevicePropertyStreamConfiguration failed: %i\n", err);
+			free(bufferList);
+			continue;
+		}
+
+		for(UInt32 j = 0; j < bufferList->mNumberBuffers; ++j) {
+			outputChannelCount += bufferList->mBuffers[j].mNumberChannels;
+		}
+		free(bufferList);
+
+
+		/* query number of inputs */
+#ifdef COREAUDIO_108
+		size = 0;
+		propertyAddress.mSelector = kAudioDevicePropertyStreamConfiguration;
+		propertyAddress.mScope = kAudioDevicePropertyScopeInput;
+		err = AudioObjectGetPropertyDataSize(_deviceIDs[deviceIndex], &propertyAddress, 0, NULL, &size);
+		if (kAudioHardwareNoError != err) {
+			fprintf(stderr, "kAudioDevicePropertyStreamConfiguration failed: %i\n", err);
+			continue;
+		}
+
+		bufferList = (AudioBufferList *)(malloc(size));
+		assert(bufferList);
+		if (!bufferList) { fprintf(stderr, "OUT OF MEMORY\n"); break; }
+
+		err = AudioObjectGetPropertyData(_deviceIDs[deviceIndex], &propertyAddress, 0, NULL, &size, bufferList);
+#else
+		err = AudioDeviceGetPropertyInfo (_deviceIDs[deviceIndex], 0, AUHAL_INPUT_ELEMENT, kAudioDevicePropertyStreamConfiguration, &propSize, NULL);
+		if (kAudioHardwareNoError != err) {
+			fprintf(stderr, "kAudioDevicePropertyStreamConfiguration failed: %i\n", err);
+			continue;
+		}
+		bufferList = (AudioBufferList *)(malloc(size));
+		assert(bufferList);
+		if (!bufferList) { fprintf(stderr, "OUT OF MEMORY\n"); break; }
+
+		bufferList->mNumberBuffers = 0;
+		err = AudioDeviceGetProperty(_deviceIDs[deviceIndex], 0, AUHAL_INPUT_ELEMENT, kAudioDevicePropertyStreamConfiguration, &size, bufferList);
+#endif
+		if(kAudioHardwareNoError != err) {
+			fprintf(stderr, "kAudioDevicePropertyStreamConfiguration failed: %i\n", err);
+			free(bufferList);
+			continue;
+		}
+
+		for(UInt32 j = 0; j < bufferList->mNumberBuffers; ++j) {
+			inputChannelCount += bufferList->mBuffers[j].mNumberChannels;
+		}
+		free(bufferList);
+
+
+
+		{
+			std::string dn = deviceName;
+			_device_ins[deviceIndex] = inputChannelCount;
+			_device_outs[deviceIndex] = outputChannelCount;
+			printf("CoreAudio Device: #%ld '%s' in:%d out:%d\n", deviceIndex, deviceName, inputChannelCount, outputChannelCount);
+			if (outputChannelCount > 0 && inputChannelCount > 0) {
+				_devices.insert (std::pair<size_t, std::string> (deviceIndex, dn));
+			}
+		}
+	}
+}
+
+void
+CoreAudioPCM::pcm_stop ()
+{
+	printf("CoreAudioPCM::pcm_stop\n");
+	if (!_auhal) return;
+
+	AudioOutputUnitStop(_auhal);
+	AudioUnitUninitialize(_auhal);
+#ifdef COREAUDIO_108
+	AudioComponentInstanceDispose(_auhal);
+#else
+	CloseComponent(_auhal);
+#endif
+	_auhal = 0;
+	_state = -1;
+	_capture_channels = 0;
+	_playback_channels = 0;
+
+	free(_inputAudioBufferList);
+	_inputAudioBufferList = 0;
+
+	_error_callback = 0;
+	_process_callback = 0;
+}
+
+#ifndef NDEBUG
+static void PrintStreamDesc (AudioStreamBasicDescription *inDesc)
+{
+    printf ("- - - - - - - - - - - - - - - - - - - -\n");
+    printf ("  Sample Rate:%f", inDesc->mSampleRate);
+    printf ("  Format ID:%.*s\n", (int)sizeof(inDesc->mFormatID), (char*)&inDesc->mFormatID);
+    printf ("  Format Flags:%X\n", inDesc->mFormatFlags);
+    printf ("  Bytes per Packet:%d\n", inDesc->mBytesPerPacket);
+    printf ("  Frames per Packet:%d\n", inDesc->mFramesPerPacket);
+    printf ("  Bytes per Frame:%d\n", inDesc->mBytesPerFrame);
+    printf ("  Channels per Frame:%d\n", inDesc->mChannelsPerFrame);
+    printf ("  Bits per Channel:%d\n", inDesc->mBitsPerChannel);
+    printf ("- - - - - - - - - - - - - - - - - - - -\n");
+}
+#endif
+
+static OSStatus render_callback_ptr (
+		void* inRefCon,
+		AudioUnitRenderActionFlags* ioActionFlags,
+		const AudioTimeStamp* inTimeStamp,
+		UInt32 inBusNumber,
+		UInt32 inNumberFrames,
+		AudioBufferList* ioData)
+{
+	CoreAudioPCM * d = static_cast<CoreAudioPCM*> (inRefCon);
+	return d->render_callback(ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, ioData);
+}
+
+
+
+int
+CoreAudioPCM::pcm_start (
+		uint32_t device_id_in, uint32_t device_id_out,
+		uint32_t sample_rate, uint32_t samples_per_period,
+		int (process_callback (void*)), void *process_arg)
+{
+
+	assert(_deviceIDs);
+	_state = -2;
+
+	if (device_id_out >= _numDevices || device_id_in >= _numDevices) {
+		return -1;
+	}
+
+	_process_callback = process_callback;
+	_process_arg = process_arg;
+	_max_samples_per_period = samples_per_period;
+	_cur_samples_per_period = 0;
+
+	ComponentResult err;
+	UInt32 enableIO;
+	AudioStreamBasicDescription srcFormat, dstFormat;
+	
+	AudioComponentDescription cd = {kAudioUnitType_Output, kAudioUnitSubType_HALOutput, kAudioUnitManufacturer_Apple, 0, 0};
+	AudioComponent HALOutput = AudioComponentFindNext(NULL, &cd);
+	if (!HALOutput) { goto error; }
+
+	err = AudioComponentInstanceNew(HALOutput, &_auhal);
+	if (err != noErr) { goto error; }
+
+	err = AudioUnitInitialize(_auhal);
+	if (err != noErr) { goto error; }
+
+	enableIO = 1;
+	err = AudioUnitSetProperty(_auhal, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, AUHAL_INPUT_ELEMENT, &enableIO, sizeof(enableIO));
+	if (err != noErr) { goto error; }
+	enableIO = 1;
+	err = AudioUnitSetProperty(_auhal, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, AUHAL_OUTPUT_ELEMENT, &enableIO, sizeof(enableIO));
+	if (err != noErr) { goto error; }
+
+	err = AudioUnitSetProperty(_auhal, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, AUHAL_OUTPUT_ELEMENT, &_deviceIDs[device_id_out], sizeof(AudioDeviceID));
+	if (err != noErr) { goto error; }
+
+	err = AudioUnitSetProperty(_auhal, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, AUHAL_INPUT_ELEMENT, &_deviceIDs[device_id_in], sizeof(AudioDeviceID));
+	if (err != noErr) { goto error; }
+
+	// Set buffer size
+	err = AudioUnitSetProperty(_auhal, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, AUHAL_INPUT_ELEMENT, (UInt32*)&_max_samples_per_period, sizeof(UInt32));
+	if (err != noErr) { goto error; }
+	err = AudioUnitSetProperty(_auhal, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, AUHAL_OUTPUT_ELEMENT, (UInt32*)&_max_samples_per_period, sizeof(UInt32));
+	if (err != noErr) { goto error; }
+
+
+	// set sample format
+	srcFormat.mSampleRate = sample_rate;
+	srcFormat.mFormatID = kAudioFormatLinearPCM;
+	srcFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked | kLinearPCMFormatFlagIsNonInterleaved;
+	srcFormat.mBytesPerPacket = sizeof(float);
+	srcFormat.mFramesPerPacket = 1;
+	srcFormat.mBytesPerFrame = sizeof(float);
+	srcFormat.mChannelsPerFrame = _device_ins[device_id_in];
+	srcFormat.mBitsPerChannel = 32;
+
+	err = AudioUnitSetProperty(_auhal, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, AUHAL_INPUT_ELEMENT, &srcFormat, sizeof(AudioStreamBasicDescription));
+	if (err != noErr) { goto error; }
+
+	dstFormat.mSampleRate = sample_rate;
+	dstFormat.mFormatID = kAudioFormatLinearPCM;
+	dstFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked | kLinearPCMFormatFlagIsNonInterleaved;
+	dstFormat.mBytesPerPacket = sizeof(float);
+	dstFormat.mFramesPerPacket = 1;
+	dstFormat.mBytesPerFrame = sizeof(float);
+	dstFormat.mChannelsPerFrame = _device_outs[device_id_out];
+	dstFormat.mBitsPerChannel = 32;
+
+	err = AudioUnitSetProperty(_auhal, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, AUHAL_OUTPUT_ELEMENT, &dstFormat, sizeof(AudioStreamBasicDescription));
+	if (err != noErr) { goto error; }
+
+	UInt32 size;
+	size = sizeof(AudioStreamBasicDescription);
+	err = AudioUnitGetProperty(_auhal, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, AUHAL_INPUT_ELEMENT, &srcFormat, &size);
+	if (err != noErr) { goto error; }
+	_capture_channels = srcFormat.mChannelsPerFrame;
+#ifndef NDEBUG
+	PrintStreamDesc(&srcFormat);
+#endif
+
+	size = sizeof(AudioStreamBasicDescription);
+	err = AudioUnitGetProperty(_auhal, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, AUHAL_OUTPUT_ELEMENT, &dstFormat, &size);
+	if (err != noErr) { goto error; }
+	_playback_channels = dstFormat.mChannelsPerFrame;
+
+#ifndef NDEBUG
+	PrintStreamDesc(&dstFormat);
+#endif
+
+	_inputAudioBufferList = (AudioBufferList*)malloc(sizeof(UInt32) + _capture_channels * sizeof(AudioBuffer));
+
+	// Setup callbacks
+	AURenderCallbackStruct renderCallback;
+	memset (&renderCallback, 0, sizeof (renderCallback));
+	renderCallback.inputProc = render_callback_ptr;
+	renderCallback.inputProcRefCon = this;
+	err = AudioUnitSetProperty(_auhal,
+			kAudioUnitProperty_SetRenderCallback,
+			kAudioUnitScope_Output, AUHAL_OUTPUT_ELEMENT,
+			&renderCallback, sizeof (renderCallback));
+	if (err != noErr) { goto error; }
+
+	printf("SETUP OK..\n");
+
+	if (AudioOutputUnitStart(_auhal) == noErr) {
+		printf("Coreaudio Started..\n");
+		_state = 0;
+		return 0;
+	}
+
+error:
+	pcm_stop();
+	_state = -3;
+	return -1;
+}
+
+
+OSStatus
+CoreAudioPCM::render_callback (
+		AudioUnitRenderActionFlags* ioActionFlags,
+		const AudioTimeStamp* inTimeStamp,
+		UInt32 inBusNumber,
+		UInt32 inNumberFrames,
+		AudioBufferList* ioData)
+{
+	OSStatus retVal = 0;
+
+	assert(_max_samples_per_period >= inNumberFrames);
+	assert(ioData->mNumberBuffers = _playback_channels);
+
+	_cur_samples_per_period = inNumberFrames;
+
+
+        _inputAudioBufferList->mNumberBuffers = _capture_channels;
+	for (int i = 0; i < _capture_channels; ++i) {
+		_inputAudioBufferList->mBuffers[i].mNumberChannels = 1;
+		_inputAudioBufferList->mBuffers[i].mDataByteSize = inNumberFrames * sizeof(float);
+		_inputAudioBufferList->mBuffers[i].mData = NULL;
+	}
+
+        retVal = AudioUnitRender(_auhal, ioActionFlags, inTimeStamp, AUHAL_INPUT_ELEMENT, inNumberFrames, _inputAudioBufferList);
+
+        if (retVal != kAudioHardwareNoError) {
+		char *rv = (char*)&retVal;
+		printf("ERR %c%c%c%c\n", rv[0], rv[1], rv[2], rv[3]);
+		if (_error_callback) {
+			_error_callback(_error_arg);
+		}
+		return retVal;
+	}
+
+	_outputAudioBufferList = ioData;
+
+	_in_process = true;
+
+	int rv = -1;
+
+	if (_process_callback) {
+		rv = _process_callback(_process_arg);
+	}
+
+	_in_process = false;
+
+	if (rv != 0) {
+		// clear output
+		for (int i = 0; i < ioData->mNumberBuffers; ++i) {
+			float* ob = (float*) ioData->mBuffers[i].mData;
+			memset(ob, 0, sizeof(float) * inNumberFrames);
+		}
+	}
+	return noErr;
+}
+
+int
+CoreAudioPCM::get_capture_channel (uint32_t chn, float *input, uint32_t n_samples)
+{
+	if (!_in_process || chn > _capture_channels || n_samples > _cur_samples_per_period) {
+		return -1;
+	}
+	assert(_inputAudioBufferList->mNumberBuffers > chn);
+	memcpy((void*)input, (void*)_inputAudioBufferList->mBuffers[chn].mData, sizeof(float) * n_samples);
+	return 0;
+
+}
+int
+CoreAudioPCM::set_playback_channel (uint32_t chn, const float *output, uint32_t n_samples)
+{
+	if (!_in_process || chn > _playback_channels || n_samples > _cur_samples_per_period) {
+		return -1;
+	}
+
+	assert(_outputAudioBufferList->mNumberBuffers > chn);
+	memcpy((void*)_outputAudioBufferList->mBuffers[chn].mData, (void*)output, sizeof(float) * n_samples);
+	return 0;
+}
diff --git a/libs/backends/coreaudio/coreaudio_pcmio.h b/libs/backends/coreaudio/coreaudio_pcmio.h
new file mode 100644
index 0000000000..179f1aec02
--- /dev/null
+++ b/libs/backends/coreaudio/coreaudio_pcmio.h
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2015 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <CoreServices/CoreServices.h>
+#include <CoreAudio/CoreAudio.h>
+#include <AudioUnit/AudioUnit.h>
+
+#include <AudioUnit/AudioUnit.h>
+#include <AudioToolbox/AudioToolbox.h>
+
+#include <map>
+#include <string>
+
+#define AUHAL_OUTPUT_ELEMENT 0
+#define AUHAL_INPUT_ELEMENT 1
+
+
+class CoreAudioPCM {
+public:
+	CoreAudioPCM (void);
+	~CoreAudioPCM (void);
+
+
+	int      state (void) const { return _state; }
+	uint32_t n_playback_channels (void) const { return _playback_channels; }
+	uint32_t n_capture_channels (void) const { return _capture_channels; }
+
+	void     discover();
+	void     device_list(std::map<size_t, std::string> &devices) const { devices = _devices;}
+
+	void     pcm_stop (void);
+	int      pcm_start (
+			uint32_t input_device,
+			uint32_t output_device,
+			uint32_t sample_rate,
+			uint32_t samples_per_period,
+			int (process_callback (void*)),
+			void * process_arg
+			);
+
+	void     set_error_callback (
+			void ( error_callback (void*)),
+			void * error_arg
+                        ) {
+                _error_callback = error_callback;
+                _error_arg = error_arg;
+        }
+
+	// must be called from process_callback;
+	int      get_capture_channel (uint32_t chn, float *input, uint32_t n_samples);
+	int      set_playback_channel (uint32_t chn, const float *input, uint32_t n_samples);
+	uint32_t n_samples() const { return _cur_samples_per_period; };
+
+	// really private
+	OSStatus render_callback (
+			AudioUnitRenderActionFlags* ioActionFlags,
+			const AudioTimeStamp* inTimeStamp,
+			UInt32 inBusNumber,
+			UInt32 inNumberFrames,
+			AudioBufferList* ioData);
+
+        void hwPropertyChange();
+
+private:
+	AudioUnit _auhal;
+	AudioDeviceID* _deviceIDs;
+	AudioBufferList* _inputAudioBufferList;
+	AudioBufferList* _outputAudioBufferList;
+
+	int _state;
+
+	uint32_t _max_samples_per_period;
+	uint32_t _cur_samples_per_period;
+	uint32_t _capture_channels;
+	uint32_t _playback_channels;
+	bool     _in_process;
+	size_t   _numDevices;
+
+	int (* _process_callback) (void*);
+	void * _process_arg;
+
+	void (* _error_callback) (void*);
+	void  * _error_arg;
+
+	std::map<size_t, std::string> _devices;
+        // TODO proper device info struct
+	uint32_t * _device_ins;
+	uint32_t * _device_outs;
+
+};
diff --git a/libs/backends/coreaudio/coremidi_io.cc b/libs/backends/coreaudio/coremidi_io.cc
new file mode 100644
index 0000000000..9ded1f4e6a
--- /dev/null
+++ b/libs/backends/coreaudio/coremidi_io.cc
@@ -0,0 +1,275 @@
+/*
+ * Copyright (C) 2015 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "coremidi_io.h"
+#include <CoreAudio/HostTime.h>
+
+static void notifyProc (const MIDINotification *message, void *refCon) {
+	CoreMidiIo *self = static_cast<CoreMidiIo*>(refCon);
+	self->notify_proc(message);
+}
+
+static void midiInputCallback(const MIDIPacketList *list, void *procRef, void *srcRef) {
+	// TODO skip while freewheeling
+	RingBuffer<uint8_t> * rb  = static_cast<RingBuffer < uint8_t > *> (srcRef);
+	if (!rb) return;
+	for (UInt32 i = 0; i < list->numPackets; i++) {
+		const MIDIPacket *packet = &list->packet[i];
+		if (rb->write_space() < sizeof(MIDIPacket)) { 
+			fprintf(stderr, "CoreMIDI: dropped MIDI event\n");
+			continue;
+		}
+		rb->write((uint8_t*)packet, sizeof(MIDIPacket));
+	}
+}
+
+
+CoreMidiIo::CoreMidiIo() 
+	: _midiClient (0)
+	, _inputEndPoints (0)
+	, _outputEndPoints (0)
+	, _inputPorts (0)
+	, _outputPorts (0)
+	, _inputQueue (0)
+	, _rb (0)
+	, _n_midi_in (0)
+	, _n_midi_out (0)
+	, _time_at_cycle_start (0)
+	, _active (false)
+	, _changed_callback (0)
+	, _changed_arg (0)
+{
+	OSStatus err;
+	err = MIDIClientCreate(CFSTR("Ardour"), &notifyProc, this, &_midiClient);
+	if (noErr != err) {
+		fprintf(stderr, "Creating Midi Client failed\n");
+	}
+
+}
+
+CoreMidiIo::~CoreMidiIo() 
+{
+	cleanup();
+	MIDIClientDispose(_midiClient); _midiClient = 0;
+}
+
+void
+CoreMidiIo::cleanup() 
+{
+	_active = false;
+	for (uint32_t i = 0 ; i < _n_midi_in ; ++i) {
+		MIDIPortDispose(_inputPorts[i]);
+		_inputQueue[i].clear();
+		delete _rb[i];
+	}
+	for (uint32_t i = 0 ; i < _n_midi_out ; ++i) {
+		MIDIPortDispose(_outputPorts[i]);
+	}
+
+	free(_inputPorts); _inputPorts = 0;
+	free(_inputEndPoints); _inputEndPoints = 0;
+	free(_inputQueue); _inputQueue = 0;
+	free(_outputPorts); _outputPorts = 0;
+	free(_outputEndPoints); _outputEndPoints = 0;
+	free(_rb); _rb = 0;
+
+	_n_midi_in = 0;
+	_n_midi_out = 0;
+}
+
+void
+CoreMidiIo::start_cycle() 
+{
+	_time_at_cycle_start = AudioGetCurrentHostTime();
+}
+
+void
+CoreMidiIo::notify_proc(const MIDINotification *message) 
+{
+	switch(message->messageID) {
+		case kMIDIMsgSetupChanged:
+			printf("kMIDIMsgSetupChanged\n");
+			discover();
+			break;
+		case kMIDIMsgObjectAdded:
+			{
+			const MIDIObjectAddRemoveNotification *n = (const MIDIObjectAddRemoveNotification*) message;
+			printf("kMIDIMsgObjectAdded\n");
+			}
+			break;
+		case kMIDIMsgObjectRemoved:
+			{
+			const MIDIObjectAddRemoveNotification *n = (const MIDIObjectAddRemoveNotification*) message;
+			printf("kMIDIMsgObjectRemoved\n");
+			}
+			break;
+		case kMIDIMsgPropertyChanged:
+			{
+			const MIDIObjectPropertyChangeNotification *n = (const MIDIObjectPropertyChangeNotification*) message;
+			printf("kMIDIMsgObjectRemoved\n");
+			}
+			break;
+		case kMIDIMsgThruConnectionsChanged:
+			printf("kMIDIMsgThruConnectionsChanged\n");
+			break;
+		case kMIDIMsgSerialPortOwnerChanged:
+			printf("kMIDIMsgSerialPortOwnerChanged\n");
+			break;
+		case kMIDIMsgIOError:
+			printf("kMIDIMsgIOError\n");
+			cleanup();
+			//discover();
+			break;
+	}
+}
+
+size_t
+CoreMidiIo::recv_event (uint32_t port, double cycle_time_us, uint64_t &time, uint8_t *d, size_t &s)
+{
+	if (!_active || _time_at_cycle_start == 0) {
+		return 0;
+	}
+	assert(port < _n_midi_in);
+
+	while (_rb[port]->read_space() >= sizeof(MIDIPacket)) {
+		MIDIPacket packet;
+		size_t rv = _rb[port]->read((uint8_t*)&packet, sizeof(MIDIPacket));
+		assert(rv == sizeof(MIDIPacket));
+		_inputQueue[port].push_back(boost::shared_ptr<CoreMIDIPacket>(new _CoreMIDIPacket (&packet))); 
+	}
+
+	UInt64 start = _time_at_cycle_start;
+	UInt64 end = AudioConvertNanosToHostTime(AudioConvertHostTimeToNanos(_time_at_cycle_start) + cycle_time_us * 1e3);
+
+	for (CoreMIDIQueue::iterator it = _inputQueue[port].begin (); it != _inputQueue[port].end (); ) {
+		if ((*it)->timeStamp < end) {
+			if ((*it)->timeStamp < start) {
+				uint64_t dt = AudioConvertHostTimeToNanos(start - (*it)->timeStamp);
+				//printf("Stale Midi Event dt:%.2fms\n", dt * 1e-6);
+				if (dt > 1e-4) { // 100ms, maybe too large
+					it = _inputQueue[port].erase(it);
+					continue;
+				}
+				time = 0;
+			} else {
+				time = AudioConvertHostTimeToNanos((*it)->timeStamp - start);
+			}
+			s = std::min(s, (size_t) (*it)->length);
+			if (s > 0) {
+				memcpy(d, (*it)->data, s);
+			}
+			_inputQueue[port].erase(it);
+			return s;
+		}
+		++it;
+
+	}
+	return 0;
+}
+
+int
+CoreMidiIo::send_event (uint32_t port, double reltime_us, const uint8_t *d, const size_t s)
+{
+	if (!_active || _time_at_cycle_start == 0) {
+		return 0;
+	}
+
+	assert(port < _n_midi_out);
+	UInt64 ts = AudioConvertHostTimeToNanos(_time_at_cycle_start);
+	ts += reltime_us * 1e3;
+
+	// TODO use a single packet list.. queue all events first..
+	MIDIPacketList pl;
+
+	pl.numPackets = 1;
+	MIDIPacket *mp = &(pl.packet[0]);
+
+	mp->timeStamp = AudioConvertNanosToHostTime(ts);
+	mp->length = s;
+	assert(s < 256);
+	memcpy(mp->data, d, s);
+
+	MIDISend(_outputPorts[port], _outputEndPoints[port], &pl);
+	return 0;
+}
+
+void
+CoreMidiIo::discover() 
+{
+	cleanup();
+
+	assert(!_active && _midiClient);
+
+	ItemCount srcCount = MIDIGetNumberOfSources();
+	ItemCount dstCount = MIDIGetNumberOfDestinations();
+
+	if (srcCount > 0) {
+		_inputPorts = (MIDIPortRef *) malloc (srcCount * sizeof(MIDIPortRef));
+		_inputEndPoints = (MIDIEndpointRef*) malloc (srcCount * sizeof(MIDIEndpointRef));
+		_inputQueue = (CoreMIDIQueue*) calloc (srcCount, sizeof(CoreMIDIQueue));
+		_rb = (RingBuffer<uint8_t> **) malloc (srcCount * sizeof(RingBuffer<uint8_t>*));
+	}
+	if (dstCount > 0) {
+		_outputPorts = (MIDIPortRef *) malloc (dstCount * sizeof(MIDIPortRef));
+		_outputEndPoints = (MIDIEndpointRef*) malloc (dstCount * sizeof(MIDIEndpointRef));
+	}
+
+	for (ItemCount i = 0; i < srcCount; i++) {
+		OSStatus err;
+		MIDIEndpointRef src = MIDIGetSource(i);
+		CFStringRef port_name;
+		port_name = CFStringCreateWithFormat(NULL, NULL, CFSTR("midi_capture_%lu"), i);
+
+		err = MIDIInputPortCreate (_midiClient, port_name, midiInputCallback, this, &_inputPorts[_n_midi_in]);
+		if (noErr != err) {
+			fprintf(stderr, "Cannot create Midi Output\n");
+			// TODO  handle errors
+			continue;
+		}
+		_rb[_n_midi_in] = new RingBuffer<uint8_t>(1024 * sizeof(MIDIPacket));
+		_inputQueue[_n_midi_in] = CoreMIDIQueue();
+		MIDIPortConnectSource(_inputPorts[_n_midi_in], src, (void*) _rb[_n_midi_in]);
+		CFRelease(port_name);
+		_inputEndPoints[_n_midi_in] = src;
+		++_n_midi_in;
+	}
+
+	for (ItemCount i = 0; i < dstCount; i++) {
+		MIDIEndpointRef dst = MIDIGetDestination(i);
+		CFStringRef port_name;
+		port_name = CFStringCreateWithFormat(NULL, NULL, CFSTR("midi_playback_%lu"), i);
+
+		OSStatus err;
+		err = MIDIOutputPortCreate (_midiClient, port_name, &_outputPorts[_n_midi_out]);
+		if (noErr != err) {
+			fprintf(stderr, "Cannot create Midi Output\n");
+			// TODO  handle errors
+			continue;
+		}
+		MIDIPortConnectSource(_outputPorts[_n_midi_out], dst, NULL);
+		CFRelease(port_name);
+		_outputEndPoints[_n_midi_out] = dst;
+		++_n_midi_out;
+	}
+
+	if (_changed_callback) {
+		_changed_callback(_changed_arg);
+	}
+
+	_active = true;
+}
diff --git a/libs/backends/coreaudio/coremidi_io.h b/libs/backends/coreaudio/coremidi_io.h
new file mode 100644
index 0000000000..312b9d171e
--- /dev/null
+++ b/libs/backends/coreaudio/coremidi_io.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2015 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <CoreServices/CoreServices.h>
+#include <CoreAudio/CoreAudio.h>
+#include <AudioUnit/AudioUnit.h>
+
+#include <AudioUnit/AudioUnit.h>
+#include <AudioToolbox/AudioToolbox.h>
+
+#include <map>
+#include <vector>
+#include <string>
+
+#include <boost/shared_ptr.hpp>
+#include "pbd/ringbuffer.h"
+
+typedef struct _CoreMIDIPacket { 
+	MIDITimeStamp timeStamp; 
+	UInt16 length; 
+	Byte data[256]; 
+#if 0 // unused
+	_CoreMIDIPacket (MIDITimeStamp t, Byte *d, UInt16 l)
+		: timeStamp(t)
+		, length (l)
+	{
+		if (l > 256) {
+			length = 256;
+		}
+		if (length > 0) {
+			memcpy(data, d, length);
+		}
+	}
+#endif
+	_CoreMIDIPacket (const MIDIPacket *other) 
+		: timeStamp(other->timeStamp)
+		, length (other->length)
+	{
+		if (length > 0) {
+			memcpy(data, other->data, length);
+		}
+	}
+} CoreMIDIPacket;
+
+typedef std::vector<boost::shared_ptr<CoreMIDIPacket> > CoreMIDIQueue;
+
+class CoreMidiIo {
+public:
+	CoreMidiIo (void);
+	~CoreMidiIo (void);
+
+	// TODO explicit start/stop, add/remove devices as needed.
+	void discover ();
+	void start_cycle ();
+
+	int send_event (uint32_t, double, const uint8_t *, const size_t);
+	size_t recv_event (uint32_t, double, uint64_t &, uint8_t *, size_t &);
+
+	uint32_t n_midi_inputs (void) const { return _n_midi_in; }
+	uint32_t n_midi_outputs (void) const { return _n_midi_out; }
+
+	void notify_proc (const MIDINotification *message);
+
+	void setPortChangedCallback (void (changed_callback (void*)), void *arg) {
+		_changed_callback = changed_callback;
+		_changed_arg = arg;
+	}
+
+private:
+	void cleanup ();
+
+	MIDIClientRef     _midiClient;
+	MIDIEndpointRef * _inputEndPoints;
+	MIDIEndpointRef * _outputEndPoints;
+	MIDIPortRef *     _inputPorts;
+	MIDIPortRef *     _outputPorts;
+	CoreMIDIQueue *  _inputQueue;
+	RingBuffer<uint8_t> ** _rb;
+
+	uint32_t _n_midi_in;
+	uint32_t _n_midi_out;
+
+	MIDITimeStamp _time_at_cycle_start;
+	bool _active;
+
+	void (* _changed_callback) (void*);
+	void  * _changed_arg;
+};
diff --git a/libs/backends/coreaudio/rt_thread.h b/libs/backends/coreaudio/rt_thread.h
new file mode 100644
index 0000000000..3d2efe2063
--- /dev/null
+++ b/libs/backends/coreaudio/rt_thread.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2014 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __libbackend_alsa_rthread_h__
+#define __libbackend_alsa_rthread_h__
+
+#include <pthread.h>
+#include <sched.h>
+
+static int
+_realtime_pthread_create (
+		const int policy, int priority, const size_t stacksize,
+		pthread_t *thread,
+		void *(*start_routine) (void *),
+		void *arg)
+{
+	int rv;
+
+	pthread_attr_t attr;
+	struct sched_param parm;
+
+	const int p_min = sched_get_priority_min (policy);
+	const int p_max = sched_get_priority_max (policy);
+	priority += p_max;
+	if (priority > p_max) priority = p_max;
+	if (priority < p_min) priority = p_min;
+	parm.sched_priority = priority;
+
+	pthread_attr_init (&attr);
+	pthread_attr_setschedpolicy (&attr, policy);
+	pthread_attr_setschedparam (&attr, &parm);
+	pthread_attr_setscope (&attr, PTHREAD_SCOPE_SYSTEM);
+	pthread_attr_setinheritsched (&attr, PTHREAD_EXPLICIT_SCHED);
+	pthread_attr_setstacksize (&attr, stacksize);
+	rv = pthread_create (thread, &attr, start_routine, arg);
+	pthread_attr_destroy (&attr);
+	return rv;
+}
+
+#endif
diff --git a/libs/backends/coreaudio/wscript b/libs/backends/coreaudio/wscript
new file mode 100644
index 0000000000..b0e6f4af12
--- /dev/null
+++ b/libs/backends/coreaudio/wscript
@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+from waflib.extras import autowaf as autowaf
+import os
+import sys
+import re
+
+I18N_PACKAGE = 'coreaudio-backend'
+
+# Mandatory variables
+top = '.'
+out = 'build'
+
+def options(opt):
+    autowaf.set_options(opt)
+
+def configure(conf):
+    autowaf.configure(conf)
+
+def build(bld):
+    obj = bld(features = 'cxx cxxshlib')
+    obj.source = [ 'coreaudio_backend.cc',
+                   'coreaudio_pcmio.cc',
+                   'coremidi_io.cc'
+                 ]
+    obj.includes = ['.']
+    obj.name     = 'coreaudio_backend'
+    obj.target   = 'coreaudio_backend'
+    obj.use      = 'libardour libpbd'
+    obj.framework = [ 'CoreAudio', 'AudioToolbox', 'CoreServices', 'CoreMidi' ]
+    obj.install_path  = os.path.join(bld.env['LIBDIR'], 'backends')
+    obj.defines = ['PACKAGE="' + I18N_PACKAGE + '"',
+                   'ARDOURBACKEND_DLL_EXPORTS', 'COREAUDIO_108'
+                  ]