Skeleton backend for brave volunteers.

callback based backend based on CoreAudio/Midi
backend (sans the actual system/HW _pcmio, 
_midiio)

5 files changed, 2362 insertions, 1 deletions

diff --git a/gtk2_ardour/ardev_common.sh.in b/gtk2_ardour/ardev_common.sh.in
index 9fd9531eef..fc287e16ba 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:$libs/backends/alsa:$libs/backends/coreaudio:$libs/backends/portaudio
+export ARDOUR_BACKEND_PATH=$libs/backends/jack:$libs/backends/wavesaudio:$libs/backends/dummy:$libs/backends/alsa:$libs/backends/coreaudio:$libs/backends/portaudio:$libs/backends/asio
 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/asio/asio_backend.cc b/libs/backends/asio/asio_backend.cc
new file mode 100644
index 0000000000..8d546ca582
--- /dev/null
+++ b/libs/backends/asio/asio_backend.cc
@@ -0,0 +1,1839 @@
+/*
+ * 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 "asio_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 ASIOBackend::_max_buffer_size = 8192;
+std::vector<std::string> ASIOBackend::_midi_options;
+std::vector<AudioBackend::DeviceStatus> ASIOBackend::_audio_device_status;
+
+
+/* static class instance access */
+static void hw_changed_callback_ptr (void *arg)
+{
+	ASIOBackend *d = static_cast<ASIOBackend*> (arg);
+	d->hw_changed_callback();
+}
+
+static void error_callback_ptr (void *arg)
+{
+	ASIOBackend *d = static_cast<ASIOBackend*> (arg);
+	d->error_callback();
+}
+
+static void xrun_callback_ptr (void *arg)
+{
+	ASIOBackend *d = static_cast<ASIOBackend*> (arg);
+	d->xrun_callback();
+}
+
+static void buffer_size_callback_ptr (void *arg)
+{
+	ASIOBackend *d = static_cast<ASIOBackend*> (arg);
+	d->buffer_size_callback();
+}
+
+static void sample_rate_callback_ptr (void *arg)
+{
+	ASIOBackend *d = static_cast<ASIOBackend*> (arg);
+	d->sample_rate_callback();
+}
+
+
+ASIOBackend::ASIOBackend (AudioEngine& e, AudioBackendInfo& info)
+	: AudioBackend (e, info)
+	, _run (false)
+	, _active_cb (false)
+	, _active_fw (false)
+	, _freewheeling (false)
+	, _freewheel (false)
+	, _freewheel_ack (false)
+	, _reinit_thread_callback (false)
+	, _measure_latency (false)
+	, _last_process_start (0)
+	, _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);
+	pthread_mutex_init (&_freewheel_mutex, 0);
+	pthread_cond_init  (&_freewheel_signal, 0);
+
+#if 0 // TODO
+	//_pcmio = new ASIOPCM ();
+	//_midiio = new WindowsMidiIo ();
+
+	_pcmio->set_hw_changed_callback (hw_changed_callback_ptr, this);
+	_pcmio->discover();
+#endif
+}
+
+ASIOBackend::~ASIOBackend ()
+{
+#if 0 
+	delete _pcmio; _pcmio = 0; // TODO
+	delete _midiio; _midiio = 0; // TODO
+#endif
+	pthread_mutex_destroy (&_port_callback_mutex);
+	pthread_mutex_destroy (&_process_callback_mutex);
+	pthread_mutex_destroy (&_freewheel_mutex);
+	pthread_cond_destroy  (&_freewheel_signal);
+}
+
+/* AUDIOBACKEND API */
+
+std::string
+ASIOBackend::name () const
+{
+	return X_("ASIO");
+}
+
+bool
+ASIOBackend::is_realtime () const
+{
+	return true;
+}
+
+std::vector<AudioBackend::DeviceStatus>
+ASIOBackend::enumerate_devices () const
+{
+	_audio_device_status.clear();
+#if 0 // TODO
+	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));
+	}
+#endif
+	return _audio_device_status;
+}
+
+std::vector<float>
+ASIOBackend::available_sample_rates (const std::string&) const
+{
+	std::vector<float> sr;
+#if 0 // TODO
+	_pcmio->available_sample_rates(_audio_device, sr);
+#endif
+	return sr;
+}
+
+std::vector<uint32_t>
+ASIOBackend::available_buffer_sizes (const std::string&) const
+{
+	std::vector<uint32_t> bs;
+#if 0 // TODO
+	_pcmio->available_buffer_sizes(_audio_device, bs);
+#endif
+	return bs;
+}
+
+uint32_t
+ASIOBackend::available_input_channel_count (const std::string&) const
+{
+	return 128; // TODO query current device
+}
+
+uint32_t
+ASIOBackend::available_output_channel_count (const std::string&) const
+{
+	return 128; // TODO query current device
+}
+
+bool
+ASIOBackend::can_change_sample_rate_when_running () const
+{
+	return false;
+}
+
+bool
+ASIOBackend::can_change_buffer_size_when_running () const
+{
+	return true;
+}
+
+int
+ASIOBackend::set_device_name (const std::string& d)
+{
+	_audio_device = d;
+#if 0 // TODO
+	const float sr = _pcmio->current_sample_rate(_audio_device);
+#endif
+	//if (sr > 0) { set_sample_rate(sr); }
+	return 0;
+}
+
+int
+ASIOBackend::set_sample_rate (float sr)
+{
+	if (sr <= 0) { return -1; }
+	// TODO check if it's in the list of valid SR
+	_samplerate = sr;
+	engine.sample_rate_change (sr);
+	return 0;
+}
+
+int
+ASIOBackend::set_buffer_size (uint32_t bs)
+{
+	if (bs <= 0 || bs >= _max_buffer_size) {
+		return -1;
+	}
+	_samples_per_period = bs;
+#if 0 // TODO
+	_pcmio->set_samples_per_period(bs);
+#endif
+	engine.buffer_size_change (bs);
+	return 0;
+}
+
+int
+ASIOBackend::set_interleaved (bool yn)
+{
+	if (!yn) { return 0; }
+	return -1;
+}
+
+int
+ASIOBackend::set_input_channels (uint32_t cc)
+{
+	_n_inputs = cc;
+	return 0;
+}
+
+int
+ASIOBackend::set_output_channels (uint32_t cc)
+{
+	_n_outputs = cc;
+	return 0;
+}
+
+int
+ASIOBackend::set_systemic_input_latency (uint32_t sl)
+{
+	_systemic_audio_input_latency = sl;
+	return 0;
+}
+
+int
+ASIOBackend::set_systemic_output_latency (uint32_t sl)
+{
+	_systemic_audio_output_latency = sl;
+	return 0;
+}
+
+/* Retrieving parameters */
+std::string
+ASIOBackend::device_name () const
+{
+	return _audio_device;
+}
+
+float
+ASIOBackend::sample_rate () const
+{
+	return _samplerate;
+}
+
+uint32_t
+ASIOBackend::buffer_size () const
+{
+	return _samples_per_period;
+}
+
+bool
+ASIOBackend::interleaved () const
+{
+	return false;
+}
+
+uint32_t
+ASIOBackend::input_channels () const
+{
+	return _n_inputs;
+}
+
+uint32_t
+ASIOBackend::output_channels () const
+{
+	return _n_outputs;
+}
+
+uint32_t
+ASIOBackend::systemic_input_latency () const
+{
+	return _systemic_audio_input_latency;
+}
+
+uint32_t
+ASIOBackend::systemic_output_latency () const
+{
+	return _systemic_audio_output_latency;
+}
+
+/* MIDI */
+
+std::vector<std::string>
+ASIOBackend::enumerate_midi_options () const
+{
+	if (_midi_options.empty()) {
+		_midi_options.push_back (_("WindowsMidi"));
+		_midi_options.push_back (_("None"));
+	}
+	return _midi_options;
+}
+
+int
+ASIOBackend::set_midi_option (const std::string& opt)
+{
+	if (opt != _("None") && opt != _("WindowsMidi")) {
+		return -1;
+	}
+	_midi_driver_option = opt;
+	return 0;
+}
+
+std::string
+ASIOBackend::midi_option () const
+{
+	return _midi_driver_option;
+}
+
+void
+ASIOBackend::launch_control_app ()
+{
+	// TODO
+}
+
+/* State Control */
+
+static void * pthread_freewheel (void *arg)
+{
+	ASIOBackend *d = static_cast<ASIOBackend *>(arg);
+	d->freewheel_thread ();
+	pthread_exit (0);
+	return 0;
+}
+
+static int process_callback_ptr (void *arg, const uint32_t n_samples, const uint64_t host_time)
+{
+	ASIOBackend *d = static_cast<ASIOBackend*> (arg);
+	return d->process_callback(n_samples, host_time);
+}
+
+int
+ASIOBackend::_start (bool for_latency_measurement)
+{
+	if ((!_active_cb || !_active_fw)  && _run) {
+		// recover from 'halted', reap threads
+		stop();
+	}
+
+	if (_active_cb || _active_fw || _run) {
+		PBD::error << _("ASIOBackend: already active.") << endmsg;
+		return -1;
+	}
+
+	if (_ports.size()) {
+		PBD::warning << _("ASIOBackend: 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();
+	}
+
+	assert(_active_cb == false);
+	assert(_active_fw == false);
+
+	_freewheel_ack = false;
+	_reinit_thread_callback = true;
+	_last_process_start = 0;
+
+#if 0 // TODO
+	_pcmio->set_error_callback (error_callback_ptr, this);
+	_pcmio->set_buffer_size_callback (buffer_size_callback_ptr, this);
+	_pcmio->set_sample_rate_callback (sample_rate_callback_ptr, this);
+
+	_pcmio->pcm_start (device1, device2, _samplerate, _samples_per_period, process_callback_ptr, this);
+
+	switch (_pcmio->state ()) {
+		case 0: /* OK */ break;
+		case -1: PBD::error << _("ASIOBackend: failed to open device.") << endmsg; break;
+		default: PBD::error << _("ASIOBackend: 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::info << _("ASIOBackend: 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::info << _("ASIOBackend: adjusted input channel count to match device.") << endmsg;
+	}
+
+	if (_pcmio->samples_per_period() != _samples_per_period) {
+		_samples_per_period = _pcmio->samples_per_period();
+		PBD::warning << _("ASIOBackend: samples per period does not match.") << endmsg;
+	}
+
+	if (_pcmio->sample_rate() != _samplerate) {
+		_samplerate = _pcmio->sample_rate();
+		engine.sample_rate_change (_samplerate);
+		PBD::warning << _("ASIOBackend: sample rate does not match.") << endmsg;
+	}
+#endif
+
+	_measure_latency = for_latency_measurement;
+
+	_preinit = true;
+	_run = true;
+	_port_change_flag = false;
+
+#if 0 // TODO
+	if (_midi_driver_option == _("WindowsMidi")) {
+		// TODO
+		//_midiio->set_enabled(true);
+		//_midiio->set_port_changed_callback(midi_port_change, this);
+		//_midiio->start(); // triggers port discovery, callback coremidi_rediscover()
+	}
+#endif
+
+	if (register_system_audio_ports()) {
+		PBD::error << _("ASIOBackend: 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 << _("ASIOBackend: Could not re-establish ports.") << endmsg;
+		_run = false;
+		return -1;
+	}
+
+	if (pthread_create (&_freeewheel_thread, NULL, pthread_freewheel, this))
+	{
+		PBD::error << _("ASIOBackend: failed to create process thread.") << endmsg;
+#if 0 // TODO
+		delete _pcmio; _pcmio = 0;
+#endif
+		_run = false;
+		return -1;
+	}
+
+	int timeout = 5000;
+	while ((!_active_cb || !_active_fw) && --timeout > 0) { Glib::usleep (1000); }
+
+	if (timeout == 0) {
+		PBD::error << _("ASIOBackend: failed to start.") << endmsg;
+	}
+
+	if (!_active_fw) {
+		PBD::error << _("ASIOBackend: failed to start freewheeling thread.") << endmsg;
+		_run = false;
+#if 0 // TODO
+		_pcmio->pcm_stop();
+#endif
+		unregister_ports();
+		_active_cb = false;
+		_active_fw = false;
+		return -1;
+	}
+
+	if (!_active_cb) {
+		PBD::error << _("ASIOBackend: failed to start ASIO.") << endmsg;
+		stop();
+		_run = false;
+		return -1;
+	}
+
+	engine.reconnect_ports ();
+
+	// force  an initial registration_callback() & latency re-compute
+	_port_change_flag = true;
+	pre_process ();
+
+	// all systems go.
+#if 0 // TODO
+	_pcmio->set_xrun_callback (xrun_callback_ptr, this);
+#endif
+	_preinit = false;
+
+	return 0;
+}
+
+int
+ASIOBackend::stop ()
+{
+	void *status;
+	if (!_run) {
+		return 0;
+	}
+
+	_run = false;
+#if 0 // TODO
+	_pcmio->pcm_stop();
+	_midiio->set_port_changed_callback(NULL, NULL);
+	_midiio->stop();
+#endif
+	pthread_mutex_lock (&_freewheel_mutex);
+	pthread_cond_signal (&_freewheel_signal);
+	pthread_mutex_unlock (&_freewheel_mutex);
+
+	if (pthread_join (_freeewheel_thread, &status)) {
+		PBD::error << _("ASIOBackend: failed to terminate.") << endmsg;
+		return -1;
+	}
+
+	unregister_ports();
+
+	_active_cb = false;
+	_active_fw = false; // ??
+
+	return 0;
+}
+
+int
+ASIOBackend::freewheel (bool onoff)
+{
+	if (onoff == _freewheeling) {
+		return 0;
+	}
+	_freewheeling = onoff;
+	// wake up freewheeling thread
+	if (0 == pthread_mutex_trylock (&_freewheel_mutex)) {
+		pthread_cond_signal (&_freewheel_signal);
+		pthread_mutex_unlock (&_freewheel_mutex);
+	}
+	return 0;
+}
+
+float
+ASIOBackend::dsp_load () const
+{
+	return 100.f * _dsp_load;
+}
+
+size_t
+ASIOBackend::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
+ASIOBackend::sample_time ()
+{
+	return _processed_samples;
+}
+
+framepos_t
+ASIOBackend::sample_time_at_cycle_start ()
+{
+	return _processed_samples;
+}
+
+pframes_t
+ASIOBackend::samples_since_cycle_start ()
+{
+	if (!_active_cb || !_run || _freewheeling || _freewheel) {
+		return 0;
+	}
+	if (_last_process_start == 0) {
+		return 0;
+	}
+
+#if 0 // TODO
+	const uint64_t now = AudioGetCurrentHostTime ();
+	const int64_t elapsed_time_ns = AudioConvertHostTimeToNanos(now - _last_process_start);
+	return std::max((pframes_t)0, (pframes_t)rint(1e-9 * elapsed_time_ns * _samplerate));
+#else
+	return 0;
+#endif
+}
+
+void *
+ASIOBackend::asio_process_thread (void *arg)
+{
+	ThreadData* td = reinterpret_cast<ThreadData*> (arg);
+	boost::function<void ()> f = td->f;
+	delete td;
+	f ();
+	return 0;
+}
+
+int
+ASIOBackend::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, asio_process_thread, td)) {
+		pthread_attr_init (&attr);
+		pthread_attr_setstacksize (&attr, stacksize);
+		if (pthread_create (&thread_id, &attr, asio_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
+ASIOBackend::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
+ASIOBackend::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
+ASIOBackend::process_thread_count ()
+{
+	return _threads.size ();
+}
+
+void
+ASIOBackend::update_latencies ()
+{
+	// trigger latency callback in RT thread (locked graph)
+	port_connect_add_remove_callback();
+}
+
+/* PORTENGINE API */
+
+void*
+ASIOBackend::private_handle () const
+{
+	return NULL;
+}
+
+const std::string&
+ASIOBackend::my_name () const
+{
+	return _instance_name;
+}
+
+bool
+ASIOBackend::available () const
+{
+	return _run && _active_fw && _active_cb;
+}
+
+uint32_t
+ASIOBackend::port_name_size () const
+{
+	return 256;
+}
+
+int
+ASIOBackend::set_port_name (PortEngine::PortHandle port, const std::string& name)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::set_port_name: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return static_cast<ASIOBackendPort*>(port)->set_name (_instance_name + ":" + name);
+}
+
+std::string
+ASIOBackend::get_port_name (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::get_port_name: Invalid Port(s)") << endmsg;
+		return std::string ();
+	}
+	return static_cast<ASIOBackendPort*>(port)->name ();
+}
+
+int
+ASIOBackend::get_port_property (PortHandle port, const std::string& key, std::string& value, std::string& type) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::get_port_name: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	if (key == "http://jackaudio.org/metadata/pretty-name") {
+		type = "";
+		value = static_cast<ASIOBackendPort*>(port)->pretty_name ();
+		if (!value.empty()) {
+			return 0;
+		}
+	}
+	return -1;
+}
+
+PortEngine::PortHandle
+ASIOBackend::get_port_by_name (const std::string& name) const
+{
+	PortHandle port = (PortHandle) find_port (name);
+	return port;
+}
+
+int
+ASIOBackend::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) {
+		ASIOBackendPort* 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
+ASIOBackend::port_data_type (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		return DataType::NIL;
+	}
+	return static_cast<ASIOBackendPort*>(port)->type ();
+}
+
+PortEngine::PortHandle
+ASIOBackend::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
+ASIOBackend::add_port (
+		const std::string& name,
+		ARDOUR::DataType type,
+		ARDOUR::PortFlags flags)
+{
+	assert(name.size ());
+	if (find_port (name)) {
+		PBD::error << _("ASIOBackend::register_port: Port already exists:")
+				<< " (" << name << ")" << endmsg;
+		return 0;
+	}
+	ASIOBackendPort* port = NULL;
+	switch (type) {
+		case DataType::AUDIO:
+			port = new ASIOPort (*this, name, flags);
+			break;
+		case DataType::MIDI:
+			port = new WindowsMidiPort (*this, name, flags);
+			break;
+		default:
+			PBD::error << _("ASIOBackend::register_port: Invalid Data Type.") << endmsg;
+			return 0;
+	}
+
+	_ports.push_back (port);
+
+	return port;
+}
+
+void
+ASIOBackend::unregister_port (PortEngine::PortHandle port_handle)
+{
+	if (!_run) {
+		return;
+	}
+	ASIOBackendPort* port = static_cast<ASIOBackendPort*>(port_handle);
+	std::vector<ASIOBackendPort*>::iterator i = std::find (_ports.begin (), _ports.end (), static_cast<ASIOBackendPort*>(port_handle));
+	if (i == _ports.end ()) {
+		PBD::error << _("ASIOBackend::unregister_port: Failed to find port") << endmsg;
+		return;
+	}
+	disconnect_all(port_handle);
+	_ports.erase (i);
+	delete port;
+}
+
+int
+ASIOBackend::register_system_audio_ports()
+{
+	LatencyRange lr;
+
+	const uint32_t a_ins = _n_inputs;
+	const uint32_t a_out = _n_outputs;
+
+	const uint32_t asio_reported_input_latency =  0; // TODO _pcmio->get_latency(_audio_device, true);
+	const uint32_t asio_reported_output_latency = 0; // TODO _pcmio->get_latency(_audio_device, false);
+
+	/* audio ports */
+	lr.min = lr.max = asio_reported_input_latency + (_measure_latency ? 0 : _systemic_audio_input_latency);
+	for (uint32_t i = 0; i < a_ins; ++i) {
+		char tmp[64];
+		snprintf(tmp, sizeof(tmp), "system:capture_%d", i+1);
+		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);
+		ASIOBackendPort *cp = static_cast<ASIOBackendPort*>(p);
+		//cp->set_pretty_name (_pcmio->cached_port_name(i, true)); // TODO
+		_system_inputs.push_back(cp);
+	}
+
+	lr.min = lr.max = asio_reported_output_latency + (_measure_latency ? 0 : _systemic_audio_output_latency);
+	for (uint32_t i = 0; i < a_out; ++i) {
+		char tmp[64];
+		snprintf(tmp, sizeof(tmp), "system:playback_%d", i+1);
+		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);
+		ASIOBackendPort *cp = static_cast<ASIOBackendPort*>(p);
+		//cp->set_pretty_name (_pcmio->cached_port_name(i, false)); // TODO
+		_system_outputs.push_back(cp);
+	}
+	return 0;
+}
+
+void
+ASIOBackend::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 ()) {
+		ASIOBackendPort* 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
+ASIOBackend::connect (const std::string& src, const std::string& dst)
+{
+	ASIOBackendPort* src_port = find_port (src);
+	ASIOBackendPort* dst_port = find_port (dst);
+
+	if (!src_port) {
+		PBD::error << _("ASIOBackend::connect: Invalid Source port:")
+				<< " (" << src <<")" << endmsg;
+		return -1;
+	}
+	if (!dst_port) {
+		PBD::error << _("ASIOBackend::connect: Invalid Destination port:")
+			<< " (" << dst <<")" << endmsg;
+		return -1;
+	}
+	return src_port->connect (dst_port);
+}
+
+int
+ASIOBackend::disconnect (const std::string& src, const std::string& dst)
+{
+	ASIOBackendPort* src_port = find_port (src);
+	ASIOBackendPort* dst_port = find_port (dst);
+
+	if (!src_port || !dst_port) {
+		PBD::error << _("ASIOBackend::disconnect: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return src_port->disconnect (dst_port);
+}
+
+int
+ASIOBackend::connect (PortEngine::PortHandle src, const std::string& dst)
+{
+	ASIOBackendPort* dst_port = find_port (dst);
+	if (!valid_port (src)) {
+		PBD::error << _("ASIOBackend::connect: Invalid Source Port Handle") << endmsg;
+		return -1;
+	}
+	if (!dst_port) {
+		PBD::error << _("ASIOBackend::connect: Invalid Destination Port")
+			<< " (" << dst << ")" << endmsg;
+		return -1;
+	}
+	return static_cast<ASIOBackendPort*>(src)->connect (dst_port);
+}
+
+int
+ASIOBackend::disconnect (PortEngine::PortHandle src, const std::string& dst)
+{
+	ASIOBackendPort* dst_port = find_port (dst);
+	if (!valid_port (src) || !dst_port) {
+		PBD::error << _("ASIOBackend::disconnect: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return static_cast<ASIOBackendPort*>(src)->disconnect (dst_port);
+}
+
+int
+ASIOBackend::disconnect_all (PortEngine::PortHandle port)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::disconnect_all: Invalid Port") << endmsg;
+		return -1;
+	}
+	static_cast<ASIOBackendPort*>(port)->disconnect_all ();
+	return 0;
+}
+
+bool
+ASIOBackend::connected (PortEngine::PortHandle port, bool /* process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::disconnect_all: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<ASIOBackendPort*>(port)->is_connected ();
+}
+
+bool
+ASIOBackend::connected_to (PortEngine::PortHandle src, const std::string& dst, bool /*process_callback_safe*/)
+{
+	ASIOBackendPort* dst_port = find_port (dst);
+	if (!valid_port (src) || !dst_port) {
+		PBD::error << _("ASIOBackend::connected_to: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<ASIOBackendPort*>(src)->is_connected (dst_port);
+}
+
+bool
+ASIOBackend::physically_connected (PortEngine::PortHandle port, bool /*process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::physically_connected: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<ASIOBackendPort*>(port)->is_physically_connected ();
+}
+
+int
+ASIOBackend::get_connections (PortEngine::PortHandle port, std::vector<std::string>& names, bool /*process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackend::get_connections: Invalid Port") << endmsg;
+		return -1;
+	}
+
+	assert (0 == names.size ());
+
+	const std::vector<ASIOBackendPort*>& connected_ports = static_cast<ASIOBackendPort*>(port)->get_connections ();
+
+	for (std::vector<ASIOBackendPort*>::const_iterator i = connected_ports.begin (); i != connected_ports.end (); ++i) {
+		names.push_back ((*i)->name ());
+	}
+
+	return (int)names.size ();
+}
+
+/* MIDI */
+int
+ASIOBackend::midi_event_get (
+		pframes_t& timestamp,
+		size_t& size, uint8_t** buf, void* port_buffer,
+		uint32_t event_index)
+{
+	if (!buf || !port_buffer) return -1;
+	WindowsMidiBuffer& source = * static_cast<WindowsMidiBuffer*>(port_buffer);
+	if (event_index >= source.size ()) {
+		return -1;
+	}
+	WindowsMidiEvent * const event = source[event_index].get ();
+
+	timestamp = event->timestamp ();
+	size = event->size ();
+	*buf = event->data ();
+	return 0;
+}
+
+int
+ASIOBackend::midi_event_put (
+		void* port_buffer,
+		pframes_t timestamp,
+		const uint8_t* buffer, size_t size)
+{
+	if (!buffer || !port_buffer) return -1;
+	WindowsMidiBuffer& dst = * static_cast<WindowsMidiBuffer*>(port_buffer);
+	if (dst.size () && (pframes_t)dst.back ()->timestamp () > timestamp) {
+#ifndef NDEBUG
+		// nevermind, ::get_buffer() sorts events
+		fprintf (stderr, "WindowsMidiBuffer: unordered event: %d > %d\n",
+				(pframes_t)dst.back ()->timestamp (), timestamp);
+#endif
+	}
+	dst.push_back (boost::shared_ptr<WindowsMidiEvent>(new WindowsMidiEvent (timestamp, buffer, size)));
+	return 0;
+}
+
+uint32_t
+ASIOBackend::get_midi_event_count (void* port_buffer)
+{
+	if (!port_buffer) return 0;
+	return static_cast<WindowsMidiBuffer*>(port_buffer)->size ();
+}
+
+void
+ASIOBackend::midi_clear (void* port_buffer)
+{
+	if (!port_buffer) return;
+	WindowsMidiBuffer * buf = static_cast<WindowsMidiBuffer*>(port_buffer);
+	assert (buf);
+	buf->clear ();
+}
+
+/* Monitoring */
+
+bool
+ASIOBackend::can_monitor_input () const
+{
+	return false;
+}
+
+int
+ASIOBackend::request_input_monitoring (PortEngine::PortHandle, bool)
+{
+	return -1;
+}
+
+int
+ASIOBackend::ensure_input_monitoring (PortEngine::PortHandle, bool)
+{
+	return -1;
+}
+
+bool
+ASIOBackend::monitoring_input (PortEngine::PortHandle)
+{
+	return false;
+}
+
+/* Latency management */
+
+void
+ASIOBackend::set_latency_range (PortEngine::PortHandle port, bool for_playback, LatencyRange latency_range)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackendPort::set_latency_range (): invalid port.") << endmsg;
+	}
+	static_cast<ASIOBackendPort*>(port)->set_latency_range (latency_range, for_playback);
+}
+
+LatencyRange
+ASIOBackend::get_latency_range (PortEngine::PortHandle port, bool for_playback)
+{
+	LatencyRange r;
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackendPort::get_latency_range (): invalid port.") << endmsg;
+		r.min = 0;
+		r.max = 0;
+		return r;
+	}
+	ASIOBackendPort* p = static_cast<ASIOBackendPort*>(port);
+	assert(p);
+
+	r = p->latency_range (for_playback);
+	if (p->is_physical() && p->is_terminal() && p->type() == DataType::AUDIO) {
+		if (p->is_input() && for_playback) {
+			r.min += _samples_per_period;
+			r.max += _samples_per_period;
+		}
+		if (p->is_output() && !for_playback) {
+			r.min += _samples_per_period;
+			r.max += _samples_per_period;
+		}
+	}
+	return r;
+}
+
+/* Discovering physical ports */
+
+bool
+ASIOBackend::port_is_physical (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("ASIOBackendPort::port_is_physical (): invalid port.") << endmsg;
+		return false;
+	}
+	return static_cast<ASIOBackendPort*>(port)->is_physical ();
+}
+
+void
+ASIOBackend::get_physical_outputs (DataType type, std::vector<std::string>& port_names)
+{
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		ASIOBackendPort* port = _ports[i];
+		if ((port->type () == type) && port->is_input () && port->is_physical ()) {
+			port_names.push_back (port->name ());
+		}
+	}
+}
+
+void
+ASIOBackend::get_physical_inputs (DataType type, std::vector<std::string>& port_names)
+{
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		ASIOBackendPort* port = _ports[i];
+		if ((port->type () == type) && port->is_output () && port->is_physical ()) {
+			port_names.push_back (port->name ());
+		}
+	}
+}
+
+ChanCount
+ASIOBackend::n_physical_outputs () const
+{
+	int n_midi = 0;
+	int n_audio = 0;
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		ASIOBackendPort* 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
+ASIOBackend::n_physical_inputs () const
+{
+	int n_midi = 0;
+	int n_audio = 0;
+	for (size_t i = 0; i < _ports.size (); ++i) {
+		ASIOBackendPort* 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*
+ASIOBackend::get_buffer (PortEngine::PortHandle port, pframes_t nframes)
+{
+	if (!port || !valid_port (port)) return NULL;
+	return static_cast<ASIOBackendPort*>(port)->get_buffer (nframes);
+}
+
+void
+ASIOBackend::pre_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 *
+ASIOBackend::freewheel_thread ()
+{
+	_active_fw = true;
+	bool first_run = false;
+	/* Freewheeling - use for export.   The first call to
+	 * engine.process_callback() after engine.freewheel_callback will
+	 * if the first export cycle.
+	 * For reliable precise export timing, the calls need to be in sync.
+	 *
+	 * Furthermore we need to make sure the registered process thread
+	 * is correct.
+	 *
+	 * _freewheeling = GUI thread state as set by ::freewheel()
+	 * _freewheel = in sync here (export thread)
+	 */
+	pthread_mutex_lock (&_freewheel_mutex);
+	while (_run) {
+		// check if we should run,
+		if (_freewheeling != _freewheel) {
+			if (!_freewheeling) {
+				// prepare leaving freewheeling mode
+				_freewheel = false; // first mark as disabled
+				_reinit_thread_callback = true; // hand over _main_thread
+				_freewheel_ack = false; // prepare next handshake
+#if 0 // TODO disable hadrware MIDI threads during freewheeling
+				_midiio->set_enabled(true);
+#endif
+			} else {
+				first_run = true;
+				_freewheel = true;
+			}
+		}
+
+		if (!_freewheel || !_freewheel_ack) {
+			// wait for a change, we use a timed wait to
+			// terminate early in case some error sets _run = 0
+			struct timeval tv;
+			struct timespec ts;
+			gettimeofday (&tv, NULL);
+			ts.tv_sec = tv.tv_sec + 3;
+			ts.tv_nsec = 0;
+			pthread_cond_timedwait (&_freewheel_signal, &_freewheel_mutex, &ts);
+			continue;
+		}
+
+		if (first_run) {
+			// tell the engine we're ready to GO.
+			engine.freewheel_callback (_freewheeling);
+			first_run = false;
+			_main_thread = pthread_self();
+			AudioEngine::thread_init_callback (this);
+#if 0 // TODO
+			_midiio->set_enabled(false);
+#endif
+		}
+
+		// process port updates first in every cycle.
+		pre_process();
+
+		// prevent device changes
+		pthread_mutex_lock (&_process_callback_mutex);
+
+		/* Freewheelin' */
+		
+		// clear input buffers
+		for (std::vector<ASIOBackendPort*>::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<ASIOBackendPort*>::const_iterator it = _system_midi_in.begin (); it != _system_midi_in.end (); ++it) {
+			static_cast<WindowsMidiBuffer*>((*it)->get_buffer(0))->clear ();
+		}
+
+		_last_process_start = 0;
+		if (engine.process_callback (_samples_per_period)) {
+			pthread_mutex_unlock (&_process_callback_mutex);
+			break;
+		}
+
+		pthread_mutex_unlock (&_process_callback_mutex);
+		_dsp_load = 1.0;
+		Glib::usleep (100); // don't hog cpu
+	}
+
+	pthread_mutex_unlock (&_freewheel_mutex);
+
+	_active_fw = false;
+
+	if (_run) {
+		// engine.process_callback() returner error
+		engine.halted_callback("ASIO Freehweeling aborted.");
+	}
+	return 0;
+}
+
+int
+ASIOBackend::process_callback (const uint32_t n_samples, const uint64_t host_time)
+{
+	uint32_t i = 0;
+	uint64_t clock1, clock2;
+
+	_active_cb = true;
+
+	if (_run && _freewheel && !_freewheel_ack) {
+		// acknowledge freewheeling; hand-over thread ID
+		pthread_mutex_lock (&_freewheel_mutex);
+		if (_freewheel) _freewheel_ack = true;
+		pthread_cond_signal (&_freewheel_signal);
+		pthread_mutex_unlock (&_freewheel_mutex);
+	}
+
+	if (!_run || _freewheel || _preinit) {
+		// NB if we return 1, the output is
+		// zeroed by the asio callback
+		return 1;
+	}
+
+	if (_reinit_thread_callback || _main_thread != pthread_self()) {
+		_reinit_thread_callback = false;
+		_main_thread = pthread_self();
+		AudioEngine::thread_init_callback (this);
+	}
+
+	if (pthread_mutex_trylock (&_process_callback_mutex)) {
+		// block while devices are added/removed
+#ifndef NDEBUG
+		printf("Xrun due to device change\n");
+#endif
+		engine.Xrun();
+		return 1;
+	}
+	/* port-connection change */
+	pre_process();
+
+	// cycle-length in usec
+	const double nominal_time = 1e6 * n_samples / _samplerate;
+
+	clock1 = g_get_monotonic_time();
+
+	/* get midi */
+	i=0;
+	for (std::vector<ASIOBackendPort*>::const_iterator it = _system_midi_in.begin (); it != _system_midi_in.end (); ++it, ++i) {
+		WindowsMidiBuffer* mbuf = static_cast<WindowsMidiBuffer*>((*it)->get_buffer(0));
+		mbuf->clear();
+#if 0 // TODO
+		uint64_t time_ns;
+		uint8_t data[128];
+		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);
+		}
+#endif
+	}
+
+	/* get audio */
+	i = 0;
+	for (std::vector<ASIOBackendPort*>::const_iterator it = _system_inputs.begin (); it != _system_inputs.end (); ++it, ++i) {
+#if 0 // TODO
+		_pcmio->get_capture_channel (i, (float*)((*it)->get_buffer(n_samples)), n_samples);
+#else
+		memset ((*it)->get_buffer (n_samples), 0, n_samples * sizeof (Sample));
+#endif
+	}
+
+	/* clear output buffers */
+	for (std::vector<ASIOBackendPort*>::const_iterator it = _system_outputs.begin (); it != _system_outputs.end (); ++it) {
+		memset ((*it)->get_buffer (n_samples), 0, n_samples * sizeof (Sample));
+	}
+
+#if 0 // TODO; sync Audio + midi
+	_midiio->start_cycle();
+#endif
+	_last_process_start = host_time;
+
+	if (engine.process_callback (n_samples)) {
+		fprintf(stderr, "ENGINE PROCESS ERROR\n");
+		_active_cb = false;
+		pthread_mutex_unlock (&_process_callback_mutex);
+		return -1;
+	}
+
+	/* mixdown midi */
+	for (std::vector<ASIOBackendPort*>::const_iterator it = _system_midi_out.begin (); it != _system_midi_out.end (); ++it) {
+		static_cast<WindowsMidiPort*>(*it)->get_buffer(0);
+	}
+
+	/* queue outgoing midi */
+#if 0 // TODO
+	i = 0;
+	for (std::vector<ASIOBackendPort*>::const_iterator it = _system_midi_out.begin (); it != _system_midi_out.end (); ++it, ++i) {
+#if 0 // something's still b0rked with WindowsMidiIo::send_events()
+		const WindowsMidiBuffer *src = static_cast<const WindowsMidiPort*>(*it)->const_buffer();
+		_midiio->send_events (i, nominal_time, (void*)src);
+#else // works..
+		const WindowsMidiBuffer *src = static_cast<const WindowsMidiPort*>(*it)->const_buffer();
+		for (WindowsMidiBuffer::const_iterator mit = src->begin (); mit != src->end (); ++mit) {
+			_midiio->send_event (i, (*mit)->timestamp() / nominal_time, (*mit)->data(), (*mit)->size());
+		}
+#endif
+	}
+#endif
+
+	/* write back audio */
+#if 0 // TODO
+	i = 0;
+	for (std::vector<ASIOBackendPort*>::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);
+	}
+#endif
+
+	_processed_samples += n_samples;
+
+	/* calc DSP load. */
+	clock2 = g_get_monotonic_time();
+	const int64_t elapsed_time = clock2 - clock1;
+	_dsp_load = elapsed_time / nominal_time;
+
+	pthread_mutex_unlock (&_process_callback_mutex);
+	return 0;
+}
+
+void
+ASIOBackend::error_callback ()
+{
+#if 0 // TODO
+	_pcmio->set_error_callback (NULL, NULL);
+	_pcmio->set_sample_rate_callback (NULL, NULL);
+	_pcmio->set_xrun_callback (NULL, NULL);
+	_midiio->set_port_changed_callback(NULL, NULL);
+#endif
+	engine.halted_callback("ASIO Process aborted.");
+	_active_cb = false;
+}
+
+void
+ASIOBackend::xrun_callback ()
+{
+	engine.Xrun ();
+}
+
+void
+ASIOBackend::buffer_size_callback ()
+{
+#if 0 // TODO
+	uint32_t bs = _pcmio->samples_per_period();
+	if (bs == _samples_per_period) {
+		return;
+	}
+	_samples_per_period = bs;
+	engine.buffer_size_change (_samples_per_period);
+#endif
+}
+
+void
+ASIOBackend::sample_rate_callback ()
+{
+#if 0  // TODO
+	_pcmio->set_error_callback (NULL, NULL);
+	_pcmio->set_sample_rate_callback (NULL, NULL);
+	_pcmio->set_xrun_callback (NULL, NULL);
+	_midiio->set_port_changed_callback(NULL, NULL);
+	engine.halted_callback("Sample Rate Changed.");
+	stop();
+#endif
+}
+
+void
+ASIOBackend::hw_changed_callback ()
+{
+#if 0 // TODO
+	_reinit_thread_callback = true;
+	engine.request_device_list_update();
+#endif
+}
+
+/******************************************************************************/
+
+static boost::shared_ptr<ASIOBackend> _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 = {
+	"ASIO",
+	instantiate,
+	deinstantiate,
+	backend_factory,
+	already_configured,
+	available
+};
+
+static boost::shared_ptr<AudioBackend>
+backend_factory (AudioEngine& e)
+{
+	if (!_instance) {
+		_instance.reset (new ASIOBackend (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;
+}
+
+
+/******************************************************************************/
+ASIOBackendPort::ASIOBackendPort (ASIOBackend &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;
+}
+
+ASIOBackendPort::~ASIOBackendPort () {
+	disconnect_all ();
+}
+
+
+int ASIOBackendPort::connect (ASIOBackendPort *port)
+{
+	if (!port) {
+		PBD::error << _("ASIOBackendPort::connect (): invalid (null) port") << endmsg;
+		return -1;
+	}
+
+	if (type () != port->type ()) {
+		PBD::error << _("ASIOBackendPort::connect (): wrong port-type") << endmsg;
+		return -1;
+	}
+
+	if (is_output () && port->is_output ()) {
+		PBD::error << _("ASIOBackendPort::connect (): cannot inter-connect output ports.") << endmsg;
+		return -1;
+	}
+
+	if (is_input () && port->is_input ()) {
+		PBD::error << _("ASIOBackendPort::connect (): cannot inter-connect input ports.") << endmsg;
+		return -1;
+	}
+
+	if (this == port) {
+		PBD::error << _("ASIOBackendPort::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 << _("ASIOBackendPort::connect (): ports are already connected:")
+			<< " (" << name () << ") -> (" << port->name () << ")"
+			<< endmsg;
+#endif
+		return -1;
+	}
+
+	_connect (port, true);
+	return 0;
+}
+
+
+void ASIOBackendPort::_connect (ASIOBackendPort *port, bool callback)
+{
+	_connections.push_back (port);
+	if (callback) {
+		port->_connect (this, false);
+		_osx_backend.port_connect_callback (name(),  port->name(), true);
+	}
+}
+
+int ASIOBackendPort::disconnect (ASIOBackendPort *port)
+{
+	if (!port) {
+		PBD::error << _("ASIOBackendPort::disconnect (): invalid (null) port") << endmsg;
+		return -1;
+	}
+
+	if (!is_connected (port)) {
+		PBD::error << _("ASIOBackendPort::disconnect (): ports are not connected:")
+			<< " (" << name () << ") -> (" << port->name () << ")"
+			<< endmsg;
+		return -1;
+	}
+	_disconnect (port, true);
+	return 0;
+}
+
+void ASIOBackendPort::_disconnect (ASIOBackendPort *port, bool callback)
+{
+	std::vector<ASIOBackendPort*>::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 ASIOBackendPort::disconnect_all ()
+{
+	while (!_connections.empty ()) {
+		_connections.back ()->_disconnect (this, false);
+		_osx_backend.port_connect_callback (name(),  _connections.back ()->name(), false);
+		_connections.pop_back ();
+	}
+}
+
+bool
+ASIOBackendPort::is_connected (const ASIOBackendPort *port) const
+{
+	return std::find (_connections.begin (), _connections.end (), port) != _connections.end ();
+}
+
+bool ASIOBackendPort::is_physically_connected () const
+{
+	for (std::vector<ASIOBackendPort*>::const_iterator it = _connections.begin (); it != _connections.end (); ++it) {
+		if ((*it)->is_physical ()) {
+			return true;
+		}
+	}
+	return false;
+}
+
+/******************************************************************************/
+
+ASIOPort::ASIOPort (ASIOBackend &b, const std::string& name, PortFlags flags)
+	: ASIOBackendPort (b, name, flags)
+{
+	memset (_buffer, 0, sizeof (_buffer));
+	mlock(_buffer, sizeof (_buffer));
+}
+
+ASIOPort::~ASIOPort () { }
+
+void* ASIOPort::get_buffer (pframes_t n_samples)
+{
+	if (is_input ()) {
+		std::vector<ASIOBackendPort*>::const_iterator it = get_connections ().begin ();
+		if (it == get_connections ().end ()) {
+			memset (_buffer, 0, n_samples * sizeof (Sample));
+		} else {
+			ASIOPort const * source = static_cast<const ASIOPort*>(*it);
+			assert (source && source->is_output ());
+			memcpy (_buffer, source->const_buffer (), n_samples * sizeof (Sample));
+			while (++it != get_connections ().end ()) {
+				source = static_cast<const ASIOPort*>(*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;
+}
+
+
+WindowsMidiPort::WindowsMidiPort (ASIOBackend &b, const std::string& name, PortFlags flags)
+	: ASIOBackendPort (b, name, flags)
+	, _n_periods (1)
+	, _bufperiod (0)
+{
+	_buffer[0].clear ();
+	_buffer[1].clear ();
+}
+
+WindowsMidiPort::~WindowsMidiPort () { }
+
+struct MidiEventSorter {
+	bool operator() (const boost::shared_ptr<WindowsMidiEvent>& a, const boost::shared_ptr<WindowsMidiEvent>& b) {
+		return *a < *b;
+	}
+};
+
+void* WindowsMidiPort::get_buffer (pframes_t /* nframes */)
+{
+	if (is_input ()) {
+		(_buffer[_bufperiod]).clear ();
+		for (std::vector<ASIOBackendPort*>::const_iterator i = get_connections ().begin ();
+				i != get_connections ().end ();
+				++i) {
+			const WindowsMidiBuffer * src = static_cast<const WindowsMidiPort*>(*i)->const_buffer ();
+			for (WindowsMidiBuffer::const_iterator it = src->begin (); it != src->end (); ++it) {
+				(_buffer[_bufperiod]).push_back (boost::shared_ptr<WindowsMidiEvent>(new WindowsMidiEvent (**it)));
+			}
+		}
+		std::sort ((_buffer[_bufperiod]).begin (), (_buffer[_bufperiod]).end (), MidiEventSorter());
+	}
+	return &(_buffer[_bufperiod]);
+}
+
+WindowsMidiEvent::WindowsMidiEvent (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);
+	}
+}
+
+WindowsMidiEvent::WindowsMidiEvent (const WindowsMidiEvent& 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 ());
+	}
+};
+
+WindowsMidiEvent::~WindowsMidiEvent () {
+	free (_data);
+};
diff --git a/libs/backends/asio/asio_backend.h b/libs/backends/asio/asio_backend.h
new file mode 100644
index 0000000000..bef158953b
--- /dev/null
+++ b/libs/backends/asio/asio_backend.h
@@ -0,0 +1,434 @@
+/*
+ * 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_asio_backend_h__
+#define __libbackend_asio_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"
+
+namespace ARDOUR {
+
+class ASIOBackend;
+
+class WindowsMidiEvent {
+	public:
+		WindowsMidiEvent (const pframes_t timestamp, const uint8_t* data, size_t size);
+		WindowsMidiEvent (const WindowsMidiEvent& other);
+		~WindowsMidiEvent ();
+		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 WindowsMidiEvent &other) const { return timestamp () < other.timestamp (); };
+	private:
+		size_t _size;
+		pframes_t _timestamp;
+		uint8_t *_data;
+};
+
+typedef std::vector<boost::shared_ptr<WindowsMidiEvent> > WindowsMidiBuffer;
+
+class ASIOBackendPort {
+	protected:
+		ASIOBackendPort (ASIOBackend &b, const std::string&, PortFlags);
+	public:
+		virtual ~ASIOBackendPort ();
+
+		const std::string& name () const { return _name; }
+		const std::string& pretty_name () const { return _pretty_name; }
+		PortFlags flags () const { return _flags; }
+
+		int set_name (const std::string &name) { _name = name; return 0; }
+		int set_pretty_name (const std::string &name) { _pretty_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 ASIOBackendPort *port) const;
+		bool is_physically_connected () const;
+
+		const std::vector<ASIOBackendPort *>& get_connections () const { return _connections; }
+
+		int connect (ASIOBackendPort *port);
+		int disconnect (ASIOBackendPort *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:
+		ASIOBackend &_osx_backend;
+		std::string _name;
+		std::string _pretty_name;
+		const PortFlags _flags;
+		LatencyRange _capture_latency_range;
+		LatencyRange _playback_latency_range;
+		std::vector<ASIOBackendPort*> _connections;
+
+		void _connect (ASIOBackendPort* , bool);
+		void _disconnect (ASIOBackendPort* , bool);
+
+}; // class ASIOBackendPort
+
+class ASIOPort : public ASIOBackendPort {
+	public:
+		ASIOPort (ASIOBackend &b, const std::string&, PortFlags);
+		~ASIOPort ();
+
+		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 ASIOPort
+
+class WindowsMidiPort : public ASIOBackendPort {
+	public:
+		WindowsMidiPort (ASIOBackend &b, const std::string&, PortFlags);
+		~WindowsMidiPort ();
+
+		DataType type () const { return DataType::MIDI; };
+
+		void* get_buffer (pframes_t nframes);
+		const WindowsMidiBuffer * 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:
+		WindowsMidiBuffer _buffer[2];
+		int _n_periods;
+		int _bufperiod;
+}; // class WindowsMidiPort
+
+class ASIOBackend : public AudioBackend {
+	friend class ASIOBackendPort;
+	public:
+		ASIOBackend (AudioEngine& e, AudioBackendInfo& info);
+		~ASIOBackend ();
+
+		/* 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) { return 0; }
+		int set_systemic_midi_output_latency (std::string const, uint32_t) { return 0; }
+
+		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 { return 0; }
+		uint32_t     systemic_midi_output_latency (std::string const) const { return 0; }
+
+		bool can_set_systemic_midi_latencies () const { return false; /* TODO */}
+
+		/* External control app - TODO */
+		std::string control_app_name () const { return std::string (); /* return std::string ("Windows"); */ }
+		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 {
+			return std::vector<AudioBackend::DeviceStatus> ();
+		}
+		int set_midi_device_enabled (std::string const, bool) {
+			return true;
+		}
+		bool midi_device_enabled (std::string const) const {
+			return false;
+		}
+
+		// really private, but needing static access:
+		int process_callback(uint32_t, uint64_t);
+		void error_callback();
+		void xrun_callback();
+		void buffer_size_callback();
+		void sample_rate_callback();
+		void hw_changed_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_port_property (PortHandle, const std::string& key, std::string& value, std::string& type) 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 pre_process ();
+
+	private:
+		std::string _instance_name;
+		//ASIOPCM *_pcmio; // TODO
+		//WindowsMidiIo *_midiio; // TODO
+
+		bool  _run; /* keep going or stop, ardour thread */
+		bool  _active_cb; /* is running, asio callback */
+		bool  _active_fw; /* is running, freewheel thread */
+		bool  _preinit;
+		bool  _freewheeling;
+		bool  _freewheel;
+		bool  _freewheel_ack;
+		bool  _reinit_thread_callback;
+		bool  _measure_latency;
+
+		uint64_t _last_process_start;
+
+		pthread_mutex_t _process_callback_mutex;
+
+		pthread_mutex_t _freewheel_mutex;
+		pthread_cond_t  _freewheel_signal;
+
+		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;
+
+		/* processing */
+		float  _dsp_load;
+		uint64_t _processed_samples;
+
+		pthread_t _main_thread;
+		pthread_t _freeewheel_thread;
+
+		/* process threads */
+		static void* asio_process_thread (void *);
+		std::vector<pthread_t> _threads;
+
+		struct ThreadData {
+			ASIOBackend* engine;
+			boost::function<void ()> f;
+			size_t stacksize;
+
+			ThreadData (ASIOBackend* 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 ();
+		void unregister_ports (bool system_only = false);
+
+		std::vector<ASIOBackendPort *> _ports;
+		std::vector<ASIOBackendPort *> _system_inputs;
+		std::vector<ASIOBackendPort *> _system_outputs;
+		std::vector<ASIOBackendPort *> _system_midi_in;
+		std::vector<ASIOBackendPort *> _system_midi_out;
+
+		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 (), (ASIOBackendPort*)port) != _ports.end ();
+		}
+
+		ASIOBackendPort * find_port (const std::string& port_name) const {
+			for (std::vector<ASIOBackendPort*>::const_iterator it = _ports.begin (); it != _ports.end (); ++it) {
+				if ((*it)->name () == port_name) {
+					return *it;
+				}
+			}
+			return NULL;
+		}
+
+		ASIOBackendPort * find_port_in (std::vector<ASIOBackendPort *> plist, const std::string& port_name) const {
+			for (std::vector<ASIOBackendPort*>::const_iterator it = plist.begin (); it != plist.end (); ++it) {
+				if ((*it)->name () == port_name) {
+					return *it;
+				}
+			}
+			return NULL;
+		}
+
+}; // class ASIOBackend
+
+} // namespace
+
+#endif /* __libbackend_asio_backend_h__ */
diff --git a/libs/backends/asio/rt_thread.h b/libs/backends/asio/rt_thread.h
new file mode 100644
index 0000000000..0535602bf2
--- /dev/null
+++ b/libs/backends/asio/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_portaudio_rthread_h__
+#define __libbackend_portaudio_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/asio/wscript b/libs/backends/asio/wscript
new file mode 100644
index 0000000000..fd122192af
--- /dev/null
+++ b/libs/backends/asio/wscript
@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+from waflib.extras import autowaf as autowaf
+from waflib import Options
+import os
+import sys
+import re
+
+I18N_PACKAGE = 'asio-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 = [ 'asio_backend.cc',
+#                  'asio_io.cc',
+#                  'mme_io.cc'
+                 ]
+    obj.includes = ['.']
+    obj.name     = 'asio_backend'
+    obj.target   = 'asio_backend'
+    obj.use      = 'libardour libpbd'
+    obj.install_path  = os.path.join(bld.env['LIBDIR'], 'backends')
+    obj.defines = ['PACKAGE="' + I18N_PACKAGE + '"',
+                   'ARDOURBACKEND_DLL_EXPORTS'
+                  ]