Puls der Zeit

Prototype a basic stereo-playback only pulseaudio backend.

5 files changed, 2272 insertions, 1 deletions

diff --git a/gtk2_ardour/ardev_common.sh.in b/gtk2_ardour/ardev_common.sh.in
index 9966e61c17..fdc48e50c0 100644
--- a/gtk2_ardour/ardev_common.sh.in
+++ b/gtk2_ardour/ardev_common.sh.in
@@ -19,7 +19,7 @@ export ARDOUR_DATA_PATH=$TOP:$TOP/build:$TOP/gtk2_ardour:$TOP/build/gtk2_ardour:
 export ARDOUR_MIDIMAPS_PATH=$TOP/midi_maps:.
 export ARDOUR_EXPORT_FORMATS_PATH=$TOP/export:.
 export ARDOUR_THEMES_PATH=$TOP/gtk2_ardour/themes:.
-export ARDOUR_BACKEND_PATH=$libs/backends/jack:$libs/backends/dummy:$libs/backends/alsa:$libs/backends/coreaudio:$libs/backends/portaudio
+export ARDOUR_BACKEND_PATH=$libs/backends/jack:$libs/backends/dummy:$libs/backends/alsa:$libs/backends/coreaudio:$libs/backends/portaudio:$libs/backends/pulseaudio
 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/pulseaudio/pulseaudio_backend.cc b/libs/backends/pulseaudio/pulseaudio_backend.cc
new file mode 100644
index 0000000000..0c3d6c8a01
--- /dev/null
+++ b/libs/backends/pulseaudio/pulseaudio_backend.cc
@@ -0,0 +1,1799 @@
+/*
+ * Copyright (C) 2014,2019 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 <math.h>
+#include <regex.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+
+#include <glibmm.h>
+
+#include "pbd/compose.h"
+#include "pbd/error.h"
+#include "pbd/pthread_utils.h"
+
+#include "ardour/port_manager.h"
+
+#include "pulseaudio_backend.h"
+
+#include "pbd/i18n.h"
+
+using namespace ARDOUR;
+
+static std::string s_instance_name;
+
+const size_t PulseAudioBackend::_max_buffer_size = 8192;
+
+#define N_CHANNELS (2)
+
+PulseAudioBackend::PulseAudioBackend (AudioEngine& e, AudioBackendInfo& info)
+	: AudioBackend (e, info)
+	, p_stream (0)
+	, p_context (0)
+	, p_mainloop (0)
+	, _run (false)
+	, _active (false)
+	, _freewheel (false)
+	, _freewheeling (false)
+	, _last_process_start (0)
+	, _samplerate (48000)
+	, _samples_per_period (1024)
+	, _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);
+}
+
+PulseAudioBackend::~PulseAudioBackend ()
+{
+	pthread_mutex_destroy (&_port_callback_mutex);
+}
+
+/* Pulseaudio */
+void
+PulseAudioBackend::close_pulse (bool unlock)
+{
+	if (p_mainloop) {
+		if (unlock) {
+			pa_threaded_mainloop_unlock (p_mainloop);
+		}
+		pa_threaded_mainloop_stop (p_mainloop);
+	}
+
+	if (p_stream) {
+		pa_stream_disconnect (p_stream);
+		pa_stream_unref (p_stream);
+		p_stream = NULL;
+	}
+
+	if (p_context) {
+		pa_context_disconnect (p_context);
+		pa_context_unref (p_context);
+		p_context = NULL;
+	}
+
+	if (p_mainloop) {
+		pa_threaded_mainloop_free (p_mainloop);
+		p_mainloop = NULL;
+	}
+}
+
+int
+PulseAudioBackend::sync_pulse (pa_operation* op)
+{
+	/* wait for async operation to complete */
+	if (!op) {
+		pa_threaded_mainloop_unlock (p_mainloop);
+		return 0;
+	}
+
+	pa_operation_state_t state = pa_operation_get_state (op);
+
+	while (PA_OPERATION_RUNNING == state) {
+		pa_threaded_mainloop_wait (p_mainloop);
+		state = pa_operation_get_state (op);
+	}
+
+	pa_operation_unref (op);
+
+	pa_threaded_mainloop_unlock (p_mainloop);
+	return PA_OPERATION_DONE == state;
+}
+
+bool
+PulseAudioBackend::cork_pulse (bool pause)
+{
+	pa_threaded_mainloop_lock (p_mainloop);
+	_operation_succeeded = false;
+	return sync_pulse (pa_stream_cork (p_stream, pause ? 1 : 0, stream_operation_cb, this)) && _operation_succeeded;
+}
+
+void
+PulseAudioBackend::context_state_cb (pa_context* c, void* arg)
+{
+	PulseAudioBackend* d = static_cast<PulseAudioBackend*> (arg);
+	switch (pa_context_get_state (c)) {
+		case PA_CONTEXT_READY:
+		case PA_CONTEXT_TERMINATED:
+		case PA_CONTEXT_FAILED:
+			pa_threaded_mainloop_signal (d->p_mainloop, 0);
+			break;
+		case PA_CONTEXT_UNCONNECTED:
+		case PA_CONTEXT_CONNECTING:
+		case PA_CONTEXT_AUTHORIZING:
+		case PA_CONTEXT_SETTING_NAME:
+			break;
+	}
+}
+
+void
+PulseAudioBackend::stream_state_cb (pa_stream* s, void* arg)
+{
+	PulseAudioBackend* d = static_cast<PulseAudioBackend*> (arg);
+	switch (pa_stream_get_state (s)) {
+		case PA_STREAM_READY:
+		case PA_STREAM_FAILED:
+		case PA_STREAM_TERMINATED:
+			pa_threaded_mainloop_signal (d->p_mainloop, 0);
+			break;
+		case PA_STREAM_UNCONNECTED:
+		case PA_STREAM_CREATING:
+			break;
+	}
+}
+
+void
+PulseAudioBackend::stream_operation_cb (pa_stream*, int ok, void* arg)
+{
+	PulseAudioBackend* d    = static_cast<PulseAudioBackend*> (arg);
+	d->_operation_succeeded = ok;
+	pa_threaded_mainloop_signal (d->p_mainloop, 0);
+}
+
+void
+PulseAudioBackend::stream_request_cb (pa_stream*, size_t length, void* arg)
+{
+	PulseAudioBackend* d = static_cast<PulseAudioBackend*> (arg);
+	pa_threaded_mainloop_signal (d->p_mainloop, 0);
+	// XXX perhaps do processing here instead of waking up main callback thread.
+	// compare to coreaudio backend
+}
+
+void
+PulseAudioBackend::stream_latency_update_cb (pa_stream* s, void* arg)
+{
+	PulseAudioBackend* d = static_cast<PulseAudioBackend*> (arg);
+	pa_usec_t          latency;
+	int                negative;
+	// XXX this needs PA_STREAM_AUTO_TIMING_UPDATE
+	if (0 == pa_stream_get_latency (s, &latency, &negative)) {
+		if (negative) {
+			d->_systemic_audio_output_latency = 0;
+		} else {
+			d->_systemic_audio_output_latency = floorf (latency * d->_samplerate / 1000000.f);
+		}
+		// XXX garbage value
+		printf ("Pulse latency update %d\n", d->_systemic_audio_output_latency);
+		d->update_latencies ();
+	}
+	pa_threaded_mainloop_signal (d->p_mainloop, 0);
+}
+
+void
+PulseAudioBackend::stream_xrun_cb (pa_stream*, void* arg)
+{
+	PulseAudioBackend* d = static_cast<PulseAudioBackend*> (arg);
+	d->engine.Xrun ();
+}
+
+int
+PulseAudioBackend::init_pulse ()
+{
+	pa_sample_spec ss;
+	pa_buffer_attr ba;
+
+	ss.channels = N_CHANNELS;
+	ss.rate     = _samplerate;
+	ss.format   = PA_SAMPLE_FLOAT32LE;
+
+	/* https://freedesktop.org/software/pulseaudio/doxygen/structpa__buffer__attr.html */
+	ba.minreq    = _samples_per_period * N_CHANNELS * sizeof (float);
+	ba.maxlength = 2 * ba.minreq;
+	ba.prebuf    = (uint32_t)-1;
+	ba.tlength   = (uint32_t)-1;
+	ba.fragsize  = 0; // capture only
+
+	if (!pa_sample_spec_valid (&ss)) {
+		return AudioDeviceInvalidError;
+	}
+
+	if (!(p_mainloop = pa_threaded_mainloop_new ())) {
+		PBD::error << _("PulseAudioBackend: Failed to allocate main loop") << endmsg;
+		close_pulse ();
+		return BackendInitializationError;
+	}
+
+	if (!(p_context = pa_context_new (pa_threaded_mainloop_get_api (p_mainloop), PROGRAM_NAME))) {
+		PBD::error << _("PulseAudioBackend: Failed to allocate context") << endmsg;
+		close_pulse ();
+		return BackendInitializationError;
+	}
+
+	pa_context_set_state_callback (p_context, PulseAudioBackend::context_state_cb, this);
+
+	if (pa_context_connect (p_context, NULL, PA_CONTEXT_NOFLAGS, NULL) < 0) {
+		PBD::error << _("PulseAudioBackend: Failed to allocate context") << endmsg;
+		close_pulse ();
+		return AudioDeviceOpenError;
+	}
+
+	pa_threaded_mainloop_lock (p_mainloop);
+
+	if (pa_threaded_mainloop_start (p_mainloop) < 0) {
+		PBD::error << _("PulseAudioBackend: Failed to start main loop") << endmsg;
+		close_pulse (true);
+		return AudioDeviceOpenError;
+	}
+
+	/* Wait until the context is ready, context_state_cb will trigger this */
+	pa_threaded_mainloop_wait (p_mainloop);
+	if (pa_context_get_state (p_context) != PA_CONTEXT_READY) {
+		PBD::error << _("PulseAudioBackend: Failed to create context") << endmsg;
+		close_pulse (true);
+		return AudioDeviceOpenError;
+	}
+
+	if (!(p_stream = pa_stream_new (p_context, "master", &ss, NULL))) {
+		PBD::error << _("PulseAudioBackend: Failed to create new stream") << endmsg;
+		close_pulse (true);
+		return AudioDeviceOpenError;
+	}
+
+	pa_stream_set_state_callback (p_stream, PulseAudioBackend::stream_state_cb, this);
+	pa_stream_set_write_callback (p_stream, PulseAudioBackend::stream_request_cb, this);
+	pa_stream_set_latency_update_callback (p_stream, stream_latency_update_cb, this);
+	pa_stream_set_underflow_callback (p_stream, PulseAudioBackend::stream_xrun_cb, this);
+	pa_stream_set_overflow_callback (p_stream, PulseAudioBackend::stream_xrun_cb, this);
+
+	/* https://freedesktop.org/software/pulseaudio/doxygen/def_8h.html#a6966d809483170bc6d2e6c16188850fc */
+	pa_stream_flags_t sf = (pa_stream_flags_t) (
+			  (int)PA_STREAM_START_CORKED
+			| (int)PA_STREAM_FAIL_ON_SUSPEND
+			/*
+			| (int)PA_STREAM_ADJUST_LATENCY
+			| (int)PA_STREAM_AUTO_TIMING_UPDATE
+			| (int)PA_STREAM_INTERPOLATE_TIMING
+			*/
+			);
+
+	if (pa_stream_connect_playback (p_stream, NULL, &ba, sf, NULL, NULL) < 0) {
+		PBD::error << _("PulseAudioBackend: Failed to connect playback stream") << endmsg;
+		close_pulse (true);
+		return AudioDeviceOpenError;
+	}
+
+	/* Wait until the stream is ready */
+	pa_threaded_mainloop_wait (p_mainloop);
+
+	if (pa_stream_get_state (p_stream) != PA_STREAM_READY) {
+		PBD::error << _("PulseAudioBackend: Failed to start stream") << endmsg;
+		close_pulse (true);
+		return AudioDeviceOpenError;
+	}
+
+	pa_threaded_mainloop_unlock (p_mainloop);
+	return 0;
+}
+
+/* AUDIOBACKEND API */
+
+std::string
+PulseAudioBackend::name () const
+{
+	return X_("Pulseaudio");
+}
+
+bool
+PulseAudioBackend::is_realtime () const
+{
+	return true;
+}
+
+std::vector<AudioBackend::DeviceStatus>
+PulseAudioBackend::enumerate_devices () const
+{
+	std::vector<AudioBackend::DeviceStatus> devices;
+	devices.push_back (DeviceStatus (_("Default Playback"), true));
+	return devices;
+}
+
+std::vector<float>
+PulseAudioBackend::available_sample_rates (const std::string&) const
+{
+	std::vector<float> sr;
+	sr.push_back (8000.0);
+	sr.push_back (22050.0);
+	sr.push_back (24000.0);
+	sr.push_back (44100.0);
+	sr.push_back (48000.0);
+	sr.push_back (88200.0);
+	sr.push_back (96000.0);
+	sr.push_back (176400.0);
+	sr.push_back (192000.0);
+	return sr;
+}
+
+std::vector<uint32_t>
+PulseAudioBackend::available_buffer_sizes (const std::string&) const
+{
+	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);
+	bs.push_back (8192);
+	return bs;
+}
+
+uint32_t
+PulseAudioBackend::available_input_channel_count (const std::string&) const
+{
+	return 0;
+}
+
+uint32_t
+PulseAudioBackend::available_output_channel_count (const std::string&) const
+{
+	return N_CHANNELS;
+}
+
+bool
+PulseAudioBackend::can_change_sample_rate_when_running () const
+{
+	return false;
+}
+
+bool
+PulseAudioBackend::can_change_buffer_size_when_running () const
+{
+	return false;
+}
+
+int
+PulseAudioBackend::set_device_name (const std::string& d)
+{
+	return 0;
+}
+
+int
+PulseAudioBackend::set_sample_rate (float sr)
+{
+	if (sr <= 0) {
+		return -1;
+	}
+	_samplerate = sr;
+	engine.sample_rate_change (sr);
+	return 0;
+}
+
+int
+PulseAudioBackend::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
+PulseAudioBackend::set_interleaved (bool yn)
+{
+	if (!yn) {
+		return 0;
+	}
+	return -1;
+}
+
+int
+PulseAudioBackend::set_input_channels (uint32_t cc)
+{
+	return 0;
+}
+
+int
+PulseAudioBackend::set_output_channels (uint32_t cc)
+{
+	return 0;
+}
+
+int
+PulseAudioBackend::set_systemic_input_latency (uint32_t sl)
+{
+	return 0;
+}
+
+int
+PulseAudioBackend::set_systemic_output_latency (uint32_t sl)
+{
+	return 0;
+}
+
+/* Retrieving parameters */
+std::string
+PulseAudioBackend::device_name () const
+{
+	return _("Default Playback");
+}
+
+float
+PulseAudioBackend::sample_rate () const
+{
+	return _samplerate;
+}
+
+uint32_t
+PulseAudioBackend::buffer_size () const
+{
+	return _samples_per_period;
+}
+
+bool
+PulseAudioBackend::interleaved () const
+{
+	return false;
+}
+
+uint32_t
+PulseAudioBackend::input_channels () const
+{
+	return 0;
+}
+
+uint32_t
+PulseAudioBackend::output_channels () const
+{
+	return N_CHANNELS;
+}
+
+uint32_t
+PulseAudioBackend::systemic_input_latency () const
+{
+	return 0;
+}
+
+uint32_t
+PulseAudioBackend::systemic_output_latency () const
+{
+	return _systemic_audio_output_latency;
+}
+
+/* MIDI */
+std::vector<std::string>
+PulseAudioBackend::enumerate_midi_options () const
+{
+	std::vector<std::string> midi_options;
+	midi_options.push_back (get_standard_device_name (DeviceNone));
+	return midi_options;
+}
+
+std::vector<AudioBackend::DeviceStatus>
+PulseAudioBackend::enumerate_midi_devices () const
+{
+	return std::vector<AudioBackend::DeviceStatus> ();
+}
+
+int
+PulseAudioBackend::set_midi_option (const std::string& opt)
+{
+	return 0;
+}
+
+std::string
+PulseAudioBackend::midi_option () const
+{
+	return get_standard_device_name (DeviceNone);
+}
+
+/* State Control */
+
+static void*
+pthread_process (void* arg)
+{
+	PulseAudioBackend* d = static_cast<PulseAudioBackend*> (arg);
+	d->main_process_thread ();
+	pthread_exit (0);
+	return 0;
+}
+
+int
+PulseAudioBackend::_start (bool /*for_latency_measurement*/)
+{
+	if (!_active && _run) {
+		PBD::error << _("PulseAudioBackend: already active.") << endmsg;
+		/* recover from 'halted', reap threads */
+		stop ();
+	}
+
+	if (_active || _run) {
+		PBD::info << _("PulseAudioBackend: already active.") << endmsg;
+		return BackendReinitializationError;
+	}
+
+	if (_ports.size () || _portmap.size ()) {
+		PBD::warning << _("PulseAudioBackend: recovering from unclean shutdown, port registry is not empty.") << endmsg;
+		_system_outputs.clear ();
+		_ports.clear ();
+		_portmap.clear ();
+	}
+
+	/* reset internal state */
+	_dsp_load                      = 0;
+	_freewheeling                  = false;
+	_freewheel                     = false;
+	_last_process_start            = 0;
+	_systemic_audio_output_latency = 0;
+
+	/* connect to pulse-server and prepare stream */
+	int err = init_pulse ();
+	if (err) {
+		return err;
+	}
+
+	if (register_system_ports ()) {
+		PBD::error << _("PulseAudioBackend: failed to register system ports.") << endmsg;
+		close_pulse ();
+		return PortRegistrationError;
+	}
+
+	engine.sample_rate_change (_samplerate);
+	engine.buffer_size_change (_samples_per_period);
+
+	if (engine.reestablish_ports ()) {
+		PBD::error << _("PulseAudioBackend: Could not re-establish ports.") << endmsg;
+		close_pulse ();
+		return PortReconnectError;
+	}
+
+	engine.reconnect_ports ();
+
+	_run = true;
+	_port_change_flag = false;
+
+	if (pbd_realtime_pthread_create (PBD_SCHED_FIFO, -20, 100000,
+	                                 &_main_thread, pthread_process, this)) {
+		if (pthread_create (&_main_thread, NULL, pthread_process, this)) {
+			PBD::error << _("PulseAudioBackend: failed to create process thread.") << endmsg;
+			stop ();
+			_run = false;
+			return ProcessThreadStartError;
+		} else {
+			PBD::warning << _("PulseAudioBackend: cannot acquire realtime permissions.") << endmsg;
+		}
+	}
+
+	int timeout = 5000;
+	while (!_active && --timeout > 0) {
+		Glib::usleep (1000);
+	}
+
+	if (timeout == 0 || !_active) {
+		PBD::error << _("PulseAudioBackend: failed to start process thread.") << endmsg;
+		_run = false;
+		close_pulse ();
+		return ProcessThreadStartError;
+	}
+
+	return NoError;
+}
+
+int
+PulseAudioBackend::stop ()
+{
+	void* status;
+	if (!_run) {
+		return 0;
+	}
+
+	_run = false;
+	if (pthread_join (_main_thread, &status)) {
+		PBD::error << _("PulseAudioBackend: failed to terminate.") << endmsg;
+		return -1;
+	}
+	unregister_ports ();
+	close_pulse ();
+	return (_active == false) ? 0 : -1;
+}
+
+int
+PulseAudioBackend::freewheel (bool onoff)
+{
+	_freewheeling = onoff;
+	return 0;
+}
+
+float
+PulseAudioBackend::dsp_load () const
+{
+	return 100.f * _dsp_load;
+}
+
+size_t
+PulseAudioBackend::raw_buffer_size (DataType t)
+{
+	switch (t) {
+		case DataType::AUDIO:
+			return _samples_per_period * sizeof (Sample);
+		case DataType::MIDI:
+			return _max_buffer_size;
+	}
+	return 0;
+}
+
+/* Process time */
+samplepos_t
+PulseAudioBackend::sample_time ()
+{
+	return _processed_samples;
+}
+
+samplepos_t
+PulseAudioBackend::sample_time_at_cycle_start ()
+{
+	return _processed_samples;
+}
+
+pframes_t
+PulseAudioBackend::samples_since_cycle_start ()
+{
+	if (!_active || !_run || _freewheeling || _freewheel) {
+		return 0;
+	}
+	if (_last_process_start == 0) {
+		return 0;
+	}
+
+	const int64_t elapsed_time_us = g_get_monotonic_time () - _last_process_start;
+	return std::max ((pframes_t)0, (pframes_t)rint (1e-6 * elapsed_time_us * _samplerate));
+}
+
+void*
+PulseAudioBackend::pulse_process_thread (void* arg)
+{
+	ThreadData*             td = reinterpret_cast<ThreadData*> (arg);
+	boost::function<void()> f  = td->f;
+	delete td;
+	f ();
+	return 0;
+}
+
+int
+PulseAudioBackend::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 (pbd_realtime_pthread_create (PBD_SCHED_FIFO, -22, stacksize,
+	                                 &thread_id, pulse_process_thread, td)) {
+		pthread_attr_init (&attr);
+		pthread_attr_setstacksize (&attr, stacksize);
+		if (pthread_create (&thread_id, &attr, pulse_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
+PulseAudioBackend::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
+PulseAudioBackend::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
+PulseAudioBackend::process_thread_count ()
+{
+	return _threads.size ();
+}
+
+void
+PulseAudioBackend::update_latencies ()
+{
+	/* trigger latency callback in RT thread (locked graph) */
+	port_connect_add_remove_callback ();
+}
+
+/* PORTENGINE API */
+
+void*
+PulseAudioBackend::private_handle () const
+{
+	return NULL;
+}
+
+const std::string&
+PulseAudioBackend::my_name () const
+{
+	return _instance_name;
+}
+
+uint32_t
+PulseAudioBackend::port_name_size () const
+{
+	return 256;
+}
+
+int
+PulseAudioBackend::set_port_name (PortEngine::PortHandle port, const std::string& name)
+{
+	std::string newname (_instance_name + ":" + name);
+
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::set_port_name: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+
+	if (find_port (newname)) {
+		PBD::error << _("PulseBackend::set_port_name: Port with given name already exists") << endmsg;
+		return -1;
+	}
+
+	PulsePort* p = static_cast<PulsePort*> (port);
+	_portmap.erase (p->name ());
+	_portmap.insert (make_pair (newname, p));
+	return p->set_name (newname);
+}
+
+std::string
+PulseAudioBackend::get_port_name (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::get_port_name: Invalid Port(s)") << endmsg;
+		return std::string ();
+	}
+	return static_cast<PulsePort*> (port)->name ();
+}
+
+PortFlags
+PulseAudioBackend::get_port_flags (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::get_port_flags: Invalid Port(s)") << endmsg;
+		return PortFlags (0);
+	}
+	return static_cast<PulsePort*> (port)->flags ();
+}
+
+int
+PulseAudioBackend::get_port_property (PortHandle port, const std::string& key, std::string& value, std::string& type) const
+{
+	if (!valid_port (port)) {
+		PBD::warning << _("PulseBackend::get_port_property: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	if (key == "http://jackaudio.org/metadata/pretty-name") {
+		type  = "";
+		value = static_cast<PulsePort*> (port)->pretty_name ();
+		if (!value.empty ()) {
+			return 0;
+		}
+	}
+	return -1;
+}
+
+int
+PulseAudioBackend::set_port_property (PortHandle port, const std::string& key, const std::string& value, const std::string& type)
+{
+	if (!valid_port (port)) {
+		PBD::warning << _("PulseBackend::set_port_property: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	if (key == "http://jackaudio.org/metadata/pretty-name" && type.empty ()) {
+		static_cast<PulsePort*> (port)->set_pretty_name (value);
+		return 0;
+	}
+	return -1;
+}
+
+PortEngine::PortHandle
+PulseAudioBackend::get_port_by_name (const std::string& name) const
+{
+	PortHandle port = (PortHandle)find_port (name);
+	return port;
+}
+
+int
+PulseAudioBackend::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 (PortIndex::const_iterator i = _ports.begin (); i != _ports.end (); ++i) {
+		PulsePort* port = *i;
+		if ((port->type () == type) && flags == (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
+PulseAudioBackend::port_data_type (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		return DataType::NIL;
+	}
+	return static_cast<PulsePort*> (port)->type ();
+}
+
+PortEngine::PortHandle
+PulseAudioBackend::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
+PulseAudioBackend::add_port (
+    const std::string& name,
+    ARDOUR::DataType   type,
+    ARDOUR::PortFlags  flags)
+{
+	assert (name.size ());
+	if (find_port (name)) {
+		PBD::error << _("PulseBackend::register_port: Port already exists:")
+		           << " (" << name << ")" << endmsg;
+		return 0;
+	}
+	PulsePort* port = NULL;
+	switch (type) {
+		case DataType::AUDIO:
+			port = new PulseAudioPort (*this, name, flags);
+			break;
+		case DataType::MIDI:
+			port = new PulseMidiPort (*this, name, flags);
+			break;
+		default:
+			PBD::error << _("PulseBackend::register_port: Invalid Data Type.") << endmsg;
+			return 0;
+	}
+
+	_ports.insert (port);
+	_portmap.insert (make_pair (name, port));
+
+	return port;
+}
+
+void
+PulseAudioBackend::unregister_port (PortEngine::PortHandle port_handle)
+{
+	if (!_run) {
+		return;
+	}
+	PulsePort*          port = static_cast<PulsePort*> (port_handle);
+	PortIndex::iterator i    = std::find (_ports.begin (), _ports.end (), static_cast<PulsePort*> (port_handle));
+	if (i == _ports.end ()) {
+		PBD::error << _("PulseBackend::unregister_port: Failed to find port") << endmsg;
+		return;
+	}
+	disconnect_all (port_handle);
+	_portmap.erase (port->name ());
+	_ports.erase (i);
+	delete port;
+}
+
+int
+PulseAudioBackend::register_system_ports ()
+{
+	LatencyRange lr;
+	/* audio ports */
+	lr.min = lr.max = _systemic_audio_output_latency;
+	for (int i = 1; i <= N_CHANNELS; ++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);
+		PulsePort* ap = static_cast<PulsePort*> (p);
+		//ap->set_pretty_name ("")
+		_system_outputs.push_back (ap);
+	}
+	return 0;
+}
+
+void
+PulseAudioBackend::unregister_ports (bool system_only)
+{
+	_system_outputs.clear ();
+
+	for (PortIndex::iterator i = _ports.begin (); i != _ports.end ();) {
+		PortIndex::iterator cur  = i++;
+		PulsePort*          port = *cur;
+		if (!system_only || (port->is_physical () && port->is_terminal ())) {
+			port->disconnect_all ();
+			_portmap.erase (port->name ());
+			delete port;
+			_ports.erase (cur);
+		}
+	}
+}
+
+void
+PulseAudioBackend::update_system_port_latecies ()
+{
+	for (std::vector<PulsePort*>::const_iterator it = _system_outputs.begin (); it != _system_outputs.end (); ++it) {
+		(*it)->update_connected_latency (false);
+	}
+}
+
+int
+PulseAudioBackend::connect (const std::string& src, const std::string& dst)
+{
+	PulsePort* src_port = find_port (src);
+	PulsePort* dst_port = find_port (dst);
+
+	if (!src_port) {
+		PBD::error << _("PulseBackend::connect: Invalid Source port:")
+		           << " (" << src << ")" << endmsg;
+		return -1;
+	}
+	if (!dst_port) {
+		PBD::error << _("PulseBackend::connect: Invalid Destination port:")
+		           << " (" << dst << ")" << endmsg;
+		return -1;
+	}
+	return src_port->connect (dst_port);
+}
+
+int
+PulseAudioBackend::disconnect (const std::string& src, const std::string& dst)
+{
+	PulsePort* src_port = find_port (src);
+	PulsePort* dst_port = find_port (dst);
+
+	if (!src_port || !dst_port) {
+		PBD::error << _("PulseBackend::disconnect: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return src_port->disconnect (dst_port);
+}
+
+int
+PulseAudioBackend::connect (PortEngine::PortHandle src, const std::string& dst)
+{
+	PulsePort* dst_port = find_port (dst);
+	if (!valid_port (src)) {
+		PBD::error << _("PulseBackend::connect: Invalid Source Port Handle") << endmsg;
+		return -1;
+	}
+	if (!dst_port) {
+		PBD::error << _("PulseBackend::connect: Invalid Destination Port")
+		           << " (" << dst << ")" << endmsg;
+		return -1;
+	}
+	return static_cast<PulsePort*> (src)->connect (dst_port);
+}
+
+int
+PulseAudioBackend::disconnect (PortEngine::PortHandle src, const std::string& dst)
+{
+	PulsePort* dst_port = find_port (dst);
+	if (!valid_port (src) || !dst_port) {
+		PBD::error << _("PulseBackend::disconnect: Invalid Port(s)") << endmsg;
+		return -1;
+	}
+	return static_cast<PulsePort*> (src)->disconnect (dst_port);
+}
+
+int
+PulseAudioBackend::disconnect_all (PortEngine::PortHandle port)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::disconnect_all: Invalid Port") << endmsg;
+		return -1;
+	}
+	static_cast<PulsePort*> (port)->disconnect_all ();
+	return 0;
+}
+
+bool
+PulseAudioBackend::connected (PortEngine::PortHandle port, bool /* process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::disconnect_all: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<PulsePort*> (port)->is_connected ();
+}
+
+bool
+PulseAudioBackend::connected_to (PortEngine::PortHandle src, const std::string& dst, bool /*process_callback_safe*/)
+{
+	PulsePort* dst_port = find_port (dst);
+#ifndef NDEBUG
+	if (!valid_port (src) || !dst_port) {
+		PBD::error << _("PulseBackend::connected_to: Invalid Port") << endmsg;
+		return false;
+	}
+#endif
+	return static_cast<PulsePort*> (src)->is_connected (dst_port);
+}
+
+bool
+PulseAudioBackend::physically_connected (PortEngine::PortHandle port, bool /*process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::physically_connected: Invalid Port") << endmsg;
+		return false;
+	}
+	return static_cast<PulsePort*> (port)->is_physically_connected ();
+}
+
+int
+PulseAudioBackend::get_connections (PortEngine::PortHandle port, std::vector<std::string>& names, bool /*process_callback_safe*/)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulseBackend::get_connections: Invalid Port") << endmsg;
+		return -1;
+	}
+
+	assert (0 == names.size ());
+
+	const std::set<PulsePort*>& connected_ports = static_cast<PulsePort*> (port)->get_connections ();
+
+	for (std::set<PulsePort*>::const_iterator i = connected_ports.begin (); i != connected_ports.end (); ++i) {
+		names.push_back ((*i)->name ());
+	}
+
+	return (int)names.size ();
+}
+
+/* MIDI */
+int
+PulseAudioBackend::midi_event_get (
+    pframes_t& timestamp,
+    size_t& size, uint8_t const** buf, void* port_buffer,
+    uint32_t event_index)
+{
+	assert (buf && port_buffer);
+	PulseMidiBuffer& source = *static_cast<PulseMidiBuffer*> (port_buffer);
+	if (event_index >= source.size ()) {
+		return -1;
+	}
+	PulseMidiEvent* const event = source[event_index].get ();
+
+	timestamp = event->timestamp ();
+	size      = event->size ();
+	*buf      = event->data ();
+	return 0;
+}
+
+int
+PulseAudioBackend::midi_event_put (
+    void*          port_buffer,
+    pframes_t      timestamp,
+    const uint8_t* buffer, size_t size)
+{
+	assert (buffer && port_buffer);
+	PulseMidiBuffer& dst = *static_cast<PulseMidiBuffer*> (port_buffer);
+	dst.push_back (boost::shared_ptr<PulseMidiEvent> (new PulseMidiEvent (timestamp, buffer, size)));
+	return 0;
+}
+
+uint32_t
+PulseAudioBackend::get_midi_event_count (void* port_buffer)
+{
+	assert (port_buffer);
+	return static_cast<PulseMidiBuffer*> (port_buffer)->size ();
+}
+
+void
+PulseAudioBackend::midi_clear (void* port_buffer)
+{
+	assert (port_buffer);
+	PulseMidiBuffer* buf = static_cast<PulseMidiBuffer*> (port_buffer);
+	assert (buf);
+	buf->clear ();
+}
+
+/* Monitoring */
+
+bool
+PulseAudioBackend::can_monitor_input () const
+{
+	return false;
+}
+
+int
+PulseAudioBackend::request_input_monitoring (PortEngine::PortHandle, bool)
+{
+	return -1;
+}
+
+int
+PulseAudioBackend::ensure_input_monitoring (PortEngine::PortHandle, bool)
+{
+	return -1;
+}
+
+bool
+    PulseAudioBackend::monitoring_input (PortEngine::PortHandle)
+{
+	return false;
+}
+
+/* Latency management */
+
+void
+PulseAudioBackend::set_latency_range (PortEngine::PortHandle port, bool for_playback, LatencyRange latency_range)
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulsePort::set_latency_range (): invalid port.") << endmsg;
+	}
+	static_cast<PulsePort*> (port)->set_latency_range (latency_range, for_playback);
+}
+
+LatencyRange
+PulseAudioBackend::get_latency_range (PortEngine::PortHandle port, bool for_playback)
+{
+	LatencyRange r;
+	if (!valid_port (port)) {
+		PBD::error << _("PulsePort::get_latency_range (): invalid port.") << endmsg;
+		r.min = 0;
+		r.max = 0;
+		return r;
+	}
+	PulsePort* p = static_cast<PulsePort*> (port);
+	assert (p);
+
+	r = p->latency_range (for_playback);
+	if (p->is_physical () && p->is_terminal ()) {
+		if (p->is_input () && for_playback) {
+			r.min += _samples_per_period + _systemic_audio_output_latency;
+			r.max += _samples_per_period + _systemic_audio_output_latency;
+		}
+		if (p->is_output () && !for_playback) {
+			r.min += _samples_per_period;
+			r.max += _samples_per_period;
+		}
+	}
+	return r;
+}
+
+/* Discovering physical ports */
+
+bool
+PulseAudioBackend::port_is_physical (PortEngine::PortHandle port) const
+{
+	if (!valid_port (port)) {
+		PBD::error << _("PulsePort::port_is_physical (): invalid port.") << endmsg;
+		return false;
+	}
+	return static_cast<PulsePort*> (port)->is_physical ();
+}
+
+void
+PulseAudioBackend::get_physical_outputs (DataType type, std::vector<std::string>& port_names)
+{
+	for (PortIndex::iterator i = _ports.begin (); i != _ports.end (); ++i) {
+		PulsePort* port = *i;
+		if ((port->type () == type) && port->is_input () && port->is_physical ()) {
+			port_names.push_back (port->name ());
+		}
+	}
+}
+
+void
+PulseAudioBackend::get_physical_inputs (DataType type, std::vector<std::string>& port_names)
+{
+	for (PortIndex::iterator i = _ports.begin (); i != _ports.end (); ++i) {
+		PulsePort* port = *i;
+		if ((port->type () == type) && port->is_output () && port->is_physical ()) {
+			port_names.push_back (port->name ());
+		}
+	}
+	assert (port_names.size () == 0);
+}
+
+ChanCount
+PulseAudioBackend::n_physical_outputs () const
+{
+	int n_midi  = 0;
+	int n_audio = 0;
+	for (PortIndex::const_iterator i = _ports.begin (); i != _ports.end (); ++i) {
+		PulsePort* port = *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
+PulseAudioBackend::n_physical_inputs () const
+{
+	int n_midi  = 0;
+	int n_audio = 0;
+	for (PortIndex::const_iterator i = _ports.begin (); i != _ports.end (); ++i) {
+		PulsePort* port = *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*
+PulseAudioBackend::get_buffer (PortEngine::PortHandle port, pframes_t nframes)
+{
+	assert (port);
+	assert (valid_port (port));
+	return static_cast<PulsePort*> (port)->get_buffer (nframes);
+}
+
+/* Engine Process */
+void*
+PulseAudioBackend::main_process_thread ()
+{
+	AudioEngine::thread_init_callback (this);
+	_active            = true;
+	_processed_samples = 0;
+
+	manager.registration_callback ();
+	manager.graph_order_callback ();
+
+	manager.registration_callback ();
+	manager.graph_order_callback ();
+
+	/* flush stream */
+	pa_threaded_mainloop_lock (p_mainloop);
+	sync_pulse (pa_stream_flush (p_stream, stream_operation_cb, this));
+
+	/* begin streaming */
+	if (!cork_pulse (false)) {
+		_active = false;
+		if (_run) {
+			engine.halted_callback ("PulseAudio: cannot uncork stream");
+		}
+	}
+
+	stream_latency_update_cb (p_stream, this);
+
+	while (_run) {
+		if (_freewheeling != _freewheel) {
+			_freewheel = _freewheeling;
+			engine.freewheel_callback (_freewheel);
+
+			/* drain stream freewheeling */
+			pa_threaded_mainloop_lock (p_mainloop);
+			_operation_succeeded = false;
+			sync_pulse (pa_stream_drain (p_stream, stream_operation_cb, this));
+			if (!_operation_succeeded) {
+				break;
+			}
+
+			/* suspend output while freewheeling, re-anable after */
+			if (!cork_pulse (_freewheel)) {
+				break;
+			}
+			if (!_freewheel) {
+				pa_threaded_mainloop_lock (p_mainloop);
+				_operation_succeeded = false;
+				sync_pulse (pa_stream_flush (p_stream, stream_operation_cb, this));
+				if (!_operation_succeeded) {
+					break;
+				}
+			}
+		}
+
+		if (!_freewheel) {
+			pa_threaded_mainloop_lock (p_mainloop);
+
+			size_t bytes_to_write = sizeof (float) * _samples_per_period * N_CHANNELS;
+			if (pa_stream_writable_size (p_stream) < bytes_to_write) {
+				/* wait until stream_request_cb triggers */
+				pa_threaded_mainloop_wait (p_mainloop);
+			}
+
+			if (pa_stream_get_state (p_stream) != PA_STREAM_READY) {
+				break;
+			}
+
+			int64_t clock1 = g_get_monotonic_time ();
+			/* call engine process callback */
+			_last_process_start = g_get_monotonic_time ();
+			if (engine.process_callback (_samples_per_period)) {
+				_active = false;
+				return 0;
+			}
+
+			/* write back audio */
+			uint32_t i = 0;
+			float    buf[_max_buffer_size * N_CHANNELS];
+			assert (_system_outputs.size () == N_CHANNELS);
+
+			/* interleave */
+			for (std::vector<PulsePort *>::const_iterator it = _system_outputs.begin (); it != _system_outputs.end (); ++it, ++i) {
+				const float* src = (const float*)(*it)->get_buffer (_samples_per_period);
+				for (size_t n = 0; n < _samples_per_period; ++n) {
+					buf[N_CHANNELS * n + i] = src[n];
+				}
+			}
+
+			if (pa_stream_write (p_stream, buf, bytes_to_write, NULL, 0, PA_SEEK_RELATIVE) < 0) {
+				break;
+			}
+			pa_threaded_mainloop_unlock (p_mainloop);
+
+			_processed_samples += _samples_per_period;
+
+			_dsp_load_calc.set_max_time (_samplerate, _samples_per_period);
+			_dsp_load_calc.set_start_timestamp_us (clock1);
+			_dsp_load_calc.set_stop_timestamp_us (g_get_monotonic_time ());
+			_dsp_load = _dsp_load_calc.get_dsp_load ();
+		} else {
+			/* Freewheelin' */
+			_last_process_start = 0;
+			if (engine.process_callback (_samples_per_period)) {
+				_active = false;
+				return 0;
+			}
+
+			_dsp_load = 1.0f;
+			Glib::usleep (100); // don't hog cpu
+		}
+
+		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) {
+			update_system_port_latecies ();
+			engine.latency_callback (false);
+			engine.latency_callback (true);
+		}
+	}
+
+	_active = false;
+	if (_run) {
+		engine.halted_callback ("PulseAudio I/O error.");
+	}
+	return 0;
+}
+
+/******************************************************************************/
+
+static boost::shared_ptr<PulseAudioBackend> _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 = {
+	_("Pulseaudio"),
+	instantiate,
+	deinstantiate,
+	backend_factory,
+	already_configured,
+	available
+};
+
+static boost::shared_ptr<AudioBackend>
+backend_factory (AudioEngine& e)
+{
+	if (!_instance) {
+		_instance.reset (new PulseAudioBackend (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;
+}
+
+/******************************************************************************/
+PulsePort::PulsePort (PulseAudioBackend& b, const std::string& name, PortFlags flags)
+    : _pulse_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;
+	_pulse_backend.port_connect_add_remove_callback (); // XXX -> RT
+}
+
+PulsePort::~PulsePort ()
+{
+	disconnect_all ();
+	_pulse_backend.port_connect_add_remove_callback (); // XXX -> RT
+}
+
+int
+PulsePort::connect (PulsePort* port)
+{
+	if (!port) {
+		PBD::error << _("PulsePort::connect (): invalid (null) port") << endmsg;
+		return -1;
+	}
+
+	if (type () != port->type ()) {
+		PBD::error << _("PulsePort::connect (): wrong port-type") << endmsg;
+		return -1;
+	}
+
+	if (is_output () && port->is_output ()) {
+		PBD::error << _("PulsePort::connect (): cannot inter-connect output ports.") << endmsg;
+		return -1;
+	}
+
+	if (is_input () && port->is_input ()) {
+		PBD::error << _("PulsePort::connect (): cannot inter-connect input ports.") << endmsg;
+		return -1;
+	}
+
+	if (this == port) {
+		PBD::error << _("PulsePort::connect (): cannot self-connect ports.") << endmsg;
+		return -1;
+	}
+
+	if (is_connected (port)) {
+		return -1;
+	}
+
+	_connect (port, true);
+	return 0;
+}
+
+void
+PulsePort::_connect (PulsePort* port, bool callback)
+{
+	_connections.insert (port);
+	if (callback) {
+		port->_connect (this, false);
+		_pulse_backend.port_connect_callback (name (), port->name (), true);
+	}
+}
+
+int
+PulsePort::disconnect (PulsePort* port)
+{
+	if (!port) {
+		PBD::error << _("PulsePort::disconnect (): invalid (null) port") << endmsg;
+		return -1;
+	}
+
+	if (!is_connected (port)) {
+		PBD::error << _("PulsePort::disconnect (): ports are not connected:")
+		           << " (" << name () << ") -> (" << port->name () << ")"
+		           << endmsg;
+		return -1;
+	}
+	_disconnect (port, true);
+	return 0;
+}
+
+void
+PulsePort::_disconnect (PulsePort* port, bool callback)
+{
+	std::set<PulsePort*>::iterator it = _connections.find (port);
+	assert (it != _connections.end ());
+	_connections.erase (it);
+	if (callback) {
+		port->_disconnect (this, false);
+		_pulse_backend.port_connect_callback (name (), port->name (), false);
+	}
+}
+
+void
+PulsePort::disconnect_all ()
+{
+	while (!_connections.empty ()) {
+		std::set<PulsePort*>::iterator it = _connections.begin ();
+		(*it)->_disconnect (this, false);
+		_pulse_backend.port_connect_callback (name (), (*it)->name (), false);
+		_connections.erase (it);
+	}
+}
+
+bool
+PulsePort::is_connected (const PulsePort* port) const
+{
+	return _connections.find (const_cast<PulsePort*> (port)) != _connections.end ();
+}
+
+bool
+PulsePort::is_physically_connected () const
+{
+	for (std::set<PulsePort*>::const_iterator it = _connections.begin (); it != _connections.end (); ++it) {
+		if ((*it)->is_physical ()) {
+			return true;
+		}
+	}
+	return false;
+}
+
+void
+PulsePort::set_latency_range (const LatencyRange& latency_range, bool for_playback)
+{
+	if (for_playback) {
+		_playback_latency_range = latency_range;
+	} else {
+		_capture_latency_range = latency_range;
+	}
+
+	for (std::set<PulsePort*>::const_iterator it = _connections.begin (); it != _connections.end (); ++it) {
+		if ((*it)->is_physical ()) {
+			(*it)->update_connected_latency (is_input ());
+		}
+	}
+}
+
+void
+PulsePort::update_connected_latency (bool for_playback)
+{
+	LatencyRange lr;
+	lr.min = lr.max = 0;
+	for (std::set<PulsePort*>::const_iterator it = _connections.begin (); it != _connections.end (); ++it) {
+		LatencyRange l;
+		l      = (*it)->latency_range (for_playback);
+		lr.min = std::max (lr.min, l.min);
+		lr.max = std::max (lr.max, l.max);
+	}
+	set_latency_range (lr, for_playback);
+}
+
+/******************************************************************************/
+
+PulseAudioPort::PulseAudioPort (PulseAudioBackend& b, const std::string& name, PortFlags flags)
+    : PulsePort (b, name, flags)
+{
+	memset (_buffer, 0, sizeof (_buffer));
+	mlock (_buffer, sizeof (_buffer));
+}
+
+PulseAudioPort::~PulseAudioPort ()
+{
+}
+
+void*
+PulseAudioPort::get_buffer (pframes_t n_samples)
+{
+	if (is_input ()) {
+		const std::set<PulsePort*>&          connections = get_connections ();
+		std::set<PulsePort*>::const_iterator it          = connections.begin ();
+		if (it == connections.end ()) {
+			memset (_buffer, 0, n_samples * sizeof (Sample));
+		} else {
+			PulseAudioPort* source = static_cast<PulseAudioPort*> (*it);
+			assert (source && source->is_output ());
+			memcpy (_buffer, source->const_buffer (), n_samples * sizeof (Sample));
+			while (++it != connections.end ()) {
+				source = static_cast<PulseAudioPort*> (*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;
+}
+
+PulseMidiPort::PulseMidiPort (PulseAudioBackend& b, const std::string& name, PortFlags flags)
+    : PulsePort (b, name, flags)
+{
+	_buffer.clear ();
+	_buffer.reserve (256);
+}
+
+PulseMidiPort::~PulseMidiPort ()
+{
+}
+
+struct MidiEventSorter {
+	bool
+	operator() (const boost::shared_ptr<PulseMidiEvent>& a, const boost::shared_ptr<PulseMidiEvent>& b)
+	{
+		return *a < *b;
+	}
+};
+
+void* PulseMidiPort::get_buffer (pframes_t /*n_samples*/)
+{
+	if (is_input ()) {
+		_buffer.clear ();
+		const std::set<PulsePort*>& connections = get_connections ();
+		for (std::set<PulsePort*>::const_iterator i = connections.begin ();
+		     i != connections.end ();
+		     ++i) {
+			const PulseMidiBuffer* src = static_cast<PulseMidiPort*> (*i)->const_buffer ();
+			for (PulseMidiBuffer::const_iterator it = src->begin (); it != src->end (); ++it) {
+				_buffer.push_back (*it);
+			}
+		}
+		std::stable_sort (_buffer.begin (), _buffer.end (), MidiEventSorter ());
+	}
+	return &_buffer;
+}
+
+PulseMidiEvent::PulseMidiEvent (const pframes_t timestamp, const uint8_t* data, size_t size)
+    : _size (size)
+    , _timestamp (timestamp)
+{
+	if (size > 0 && size < MaxPulseMidiEventSize) {
+		memcpy (_data, data, size);
+	}
+}
+
+PulseMidiEvent::PulseMidiEvent (const PulseMidiEvent& other)
+    : _size (other.size ())
+    , _timestamp (other.timestamp ())
+{
+	if (other.size () && other.const_data ()) {
+		assert (other._size < MaxPulseMidiEventSize);
+		memcpy (_data, other._data, other._size);
+	}
+};
diff --git a/libs/backends/pulseaudio/pulseaudio_backend.h b/libs/backends/pulseaudio/pulseaudio_backend.h
new file mode 100644
index 0000000000..d4eccf2bad
--- /dev/null
+++ b/libs/backends/pulseaudio/pulseaudio_backend.h
@@ -0,0 +1,427 @@
+/*
+ * Copyright (C) 2014,2019 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_pulse_audiobackend_h__
+#define __libbackend_pulse_audiobackend_h__
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+#include <pthread.h>
+#include <stdint.h>
+
+#include <pulse/pulseaudio.h>
+
+#include <boost/shared_ptr.hpp>
+
+#include "ardour/audio_backend.h"
+#include "ardour/dsp_load_calculator.h"
+#include "pbd/natsort.h"
+
+#define MaxPulseMidiEventSize (256)
+
+namespace ARDOUR {
+
+class PulseAudioBackend;
+
+class PulseMidiEvent
+{
+public:
+	PulseMidiEvent (const pframes_t timestamp, const uint8_t* data, size_t size);
+	PulseMidiEvent (const PulseMidiEvent& other);
+
+	size_t size () const { return _size; };
+	pframes_t timestamp () const { return _timestamp; };
+	const uint8_t* data () const { return _data; };
+	const uint8_t* const_data () const { return _data; };
+	bool operator< (const PulseMidiEvent& other) const { return timestamp () < other.timestamp (); };
+
+private:
+	size_t    _size;
+	pframes_t _timestamp;
+	uint8_t   _data[MaxPulseMidiEventSize];
+};
+
+typedef std::vector<boost::shared_ptr<PulseMidiEvent> > PulseMidiBuffer;
+
+class PulsePort
+{
+protected:
+	PulsePort (PulseAudioBackend& b, const std::string&, PortFlags);
+
+public:
+	virtual ~PulsePort ();
+
+	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;
+
+	virtual void* get_buffer (pframes_t nframes) = 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 PulsePort* port) const;
+	bool is_physically_connected () const;
+
+	int connect (PulsePort* port);
+	int disconnect (PulsePort* port);
+	void disconnect_all ();
+
+	const std::set<PulsePort*>&
+	get_connections () const
+	{
+		return _connections;
+	}
+
+	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);
+	void update_connected_latency (bool for_playback);
+
+private:
+	PulseAudioBackend&   _pulse_backend;
+	std::string          _name;
+	std::string          _pretty_name;
+	const PortFlags      _flags;
+	LatencyRange         _capture_latency_range;
+	LatencyRange         _playback_latency_range;
+	std::set<PulsePort*> _connections;
+
+	void _connect (PulsePort*, bool);
+	void _disconnect (PulsePort*, bool);
+}; // class PulsePort
+
+class PulseAudioPort : public PulsePort
+{
+public:
+	PulseAudioPort (PulseAudioBackend& b, const std::string&, PortFlags);
+	~PulseAudioPort ();
+
+	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 PulseAudioPort
+
+class PulseMidiPort : public PulsePort
+{
+public:
+	PulseMidiPort (PulseAudioBackend& b, const std::string&, PortFlags);
+	~PulseMidiPort ();
+
+	DataType type () const { return DataType::MIDI; };
+
+	void* get_buffer (pframes_t nframes);
+	const PulseMidiBuffer* const_buffer () const { return &_buffer; }
+
+private:
+	PulseMidiBuffer _buffer;
+}; // class PulseMidiPort
+
+class PulseAudioBackend : public AudioBackend
+{
+	friend class PulsePort;
+
+public:
+	PulseAudioBackend (AudioEngine& e, AudioBackendInfo& info);
+	~PulseAudioBackend ();
+
+	/* 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; }
+
+	/* 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;
+	std::vector<DeviceStatus> enumerate_midi_devices () const;
+	int                       set_midi_option (const std::string&);
+	std::string               midi_option () const;
+
+	int set_midi_device_enabled (std::string const, bool) { return 0; }
+	bool midi_device_enabled (std::string const) const { return true; }
+	bool can_set_systemic_midi_latencies () const { return false; }
+
+	/* State Control */
+protected:
+	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 */
+	samplepos_t sample_time ();
+	samplepos_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;
+
+	uint32_t    port_name_size () const;
+	int         set_port_name (PortHandle, const std::string&);
+	std::string get_port_name (PortHandle) const;
+	PortFlags   get_port_flags (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 set_port_property (PortHandle, const std::string& key, const std::string& value, const std::string& type);
+
+	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 const** 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* main_process_thread ();
+
+private:
+	std::string _instance_name;
+
+	/* pulse */
+	struct pa_stream*            p_stream;
+	struct pa_context*           p_context;
+	struct pa_threaded_mainloop* p_mainloop;
+
+	int  init_pulse ();
+	void close_pulse (bool unlock = false);
+	int  sync_pulse (pa_operation*);
+	bool cork_pulse (bool);
+
+	static void context_state_cb (pa_context*, void*);
+	static void stream_state_cb (pa_stream*, void*);
+	static void stream_request_cb (pa_stream*, size_t, void*);
+	static void stream_latency_update_cb (pa_stream*, void*);
+	static void stream_xrun_cb (pa_stream*, void*);
+	static void stream_operation_cb (pa_stream*, int, void*);
+
+	bool _operation_succeeded;
+
+	bool _run;    /* keep going or stop, ardour thread */
+	bool _active; /* is running, process thread */
+	bool _freewheel;
+	bool _freewheeling;
+
+	uint64_t _last_process_start;
+
+	/* audio settings */
+	float    _samplerate;
+	size_t   _samples_per_period;
+	uint32_t _systemic_audio_output_latency;
+
+	static const size_t _max_buffer_size;
+
+	/* processing */
+	float                     _dsp_load;
+	ARDOUR::DSPLoadCalculator _dsp_load_calc;
+	samplecnt_t               _processed_samples;
+	pthread_t                 _main_thread;
+
+	/* process threads */
+	static void*           pulse_process_thread (void*);
+	std::vector<pthread_t> _threads;
+
+	struct ThreadData {
+		PulseAudioBackend*      engine;
+		boost::function<void()> f;
+		size_t                  stacksize;
+
+		ThreadData (PulseAudioBackend* 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_ports ();
+	void unregister_ports (bool system_only = false);
+	void update_system_port_latecies ();
+
+	std::vector<PulsePort*> _system_outputs;
+
+	struct SortByPortName {
+		bool operator() (const PulsePort* lhs, const PulsePort* rhs) const
+		{
+			return PBD::naturally_less (lhs->name ().c_str (), rhs->name ().c_str ());
+		}
+	};
+
+	typedef std::map<std::string, PulsePort*>    PortMap;   // fast lookup in _ports
+	typedef std::set<PulsePort*, SortByPortName> PortIndex; // fast lookup in _ports
+	PortMap   _portmap;
+	PortIndex _ports;
+
+	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 (), static_cast<PulsePort*> (port)) != _ports.end ();
+	}
+
+	PulsePort*
+	find_port (const std::string& port_name) const
+	{
+		PortMap::const_iterator it = _portmap.find (port_name);
+		if (it == _portmap.end ()) {
+			return NULL;
+		}
+		return (*it).second;
+	}
+}; // class PulseAudioBackend
+
+} // namespace
+
+#endif /* __libbackend_pulse_audiobackend_h__ */
diff --git a/libs/backends/pulseaudio/wscript b/libs/backends/pulseaudio/wscript
new file mode 100644
index 0000000000..73ebd5a4d6
--- /dev/null
+++ b/libs/backends/pulseaudio/wscript
@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+from waflib.extras import autowaf as autowaf
+import os
+import sys
+import re
+
+I18N_PACKAGE = 'pulse-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 = [
+            'pulseaudio_backend.cc',
+            ]
+    obj.includes = ['.']
+    obj.name     = 'pulseaudio_backend'
+    obj.target   = 'pulseaudio_backend'
+    obj.use      = 'libardour libpbd'
+    obj.uselib   = 'PULSEAUDIO GLIBMM XML'
+    obj.install_path  = os.path.join(bld.env['LIBDIR'], 'backends')
+    obj.defines = ['PACKAGE="' + I18N_PACKAGE + '"',
+                   'ARDOURBACKEND_DLL_EXPORTS'
+                  ]
diff --git a/wscript b/wscript
index 40ce25b290..3a90652701 100644
--- a/wscript
+++ b/wscript
@@ -1044,6 +1044,9 @@ def configure(conf):
     if re.search ("linux", sys.platform) != None and Options.options.dist_target != 'mingw':
         autowaf.check_pkg(conf, 'alsa', uselib_store='ALSA')
 
+    if re.search ("linux", sys.platform) != None and Options.options.dist_target != 'mingw':
+        autowaf.check_pkg(conf, 'libpulse', uselib_store='PULSEAUDIO', atleast_version='10.0', mandatory=False)
+
     if re.search ("openbsd", sys.platform) != None:
         conf.env.append_value('LDFLAGS', '-L/usr/X11R6/lib')
 
@@ -1229,6 +1232,7 @@ int main () { return 0; }
     conf.env['BUILD_DUMMYBACKEND'] = any('dummy' in b for b in backends)
     conf.env['BUILD_PABACKEND'] = any('portaudio' in b for b in backends)
     conf.env['BUILD_CORECRAPPITA'] = any('coreaudio' in b for b in backends)
+    conf.env['BUILD_PULSEAUDIO'] = any('pulseaudio' in b for b in backends)
 
     if re.search ("linux", sys.platform) != None and Options.options.dist_target != 'mingw' and conf.env['BUILD_PABACKEND']:
         print("PortAudio Backend is not for Linux")
@@ -1242,6 +1246,14 @@ int main () { return 0; }
         print("ALSA Backend is only available on Linux")
         sys.exit(1)
 
+    if re.search ("linux", sys.platform) == None and conf.env['BUILD_PULSEAUDIO']:
+        print("Pulseaudio Backend is only available on Linux")
+        sys.exit(1)
+
+    if conf.env['BUILD_PULSEAUDIO'] and not conf.is_defined('HAVE_PULSEAUDIO'):
+        print("Pulseaudio Backend requires libpulse-dev")
+        sys.exit(1)
+
     set_compiler_flags (conf, Options.options)
 
     if sys.platform == 'darwin':
@@ -1327,6 +1339,7 @@ const char* const ardour_config_info = "\\n\\
     write_config_text('ALSA Backend',          conf.env['BUILD_ALSABACKEND'])
     write_config_text('Dummy backend',         conf.env['BUILD_DUMMYBACKEND'])
     write_config_text('JACK Backend',          conf.env['BUILD_JACKBACKEND'])
+    write_config_text('Pulseaudio Backend',    conf.env['BUILD_PULSEAUDIO'])
     config_text.write("\\n\\\n")
     write_config_text('Buildstack', conf.env['DEPSTACK_REV'])
     write_config_text('Mac i386 Architecture', opts.generic)