merge with master and fix 2 conflicts

10 files changed, 451 insertions, 64 deletions

diff --git a/libs/backends/jack/jack_api.cc b/libs/backends/jack/jack_api.cc
index 836acfda11..c8859a1fc9 100644
--- a/libs/backends/jack/jack_api.cc
+++ b/libs/backends/jack/jack_api.cc
@@ -63,7 +63,7 @@ deinstantiate ()
 static bool
 already_configured ()
 {
-	return JackConnection::server_running ();
+	return !JackConnection::in_control ();
 }
 
 static ARDOUR::AudioBackendInfo _descriptor = {
diff --git a/libs/backends/jack/jack_audiobackend.cc b/libs/backends/jack/jack_audiobackend.cc
index 1e7cb9d8d5..ff76486bad 100644
--- a/libs/backends/jack/jack_audiobackend.cc
+++ b/libs/backends/jack/jack_audiobackend.cc
@@ -37,6 +37,7 @@
 #include "jack_audiobackend.h"
 #include "jack_connection.h"
 #include "jack_utils.h"
+#include "jack_session.h"
 
 #include "i18n.h"
 
@@ -45,6 +46,7 @@ using namespace PBD;
 using std::string;
 using std::vector;
 
+
 #define GET_PRIVATE_JACK_POINTER(localvar)  jack_client_t* localvar = _jack_connection->jack(); if (!(localvar)) { return; }
 #define GET_PRIVATE_JACK_POINTER_RET(localvar,r) jack_client_t* localvar = _jack_connection->jack(); if (!(localvar)) { return r; }
 
@@ -63,6 +65,7 @@ JACKAudioBackend::JACKAudioBackend (AudioEngine& e, boost::shared_ptr<JackConnec
 	, _target_systemic_output_latency (0)
 	, _current_sample_rate (0)
 	, _current_buffer_size (0)
+	, _session (0)
 {
 	_jack_connection->Connected.connect_same_thread (jack_connection_connection, boost::bind (&JACKAudioBackend::when_connected_to_jack, this));
 	_jack_connection->Disconnected.connect_same_thread (disconnect_connection, boost::bind (&JACKAudioBackend::disconnected, this, _1));
@@ -406,6 +409,12 @@ JACKAudioBackend::interleaved () const
 	return false;
 }
 
+string
+JACKAudioBackend::midi_option () const
+{
+	return _target_midi_option;
+}
+
 uint32_t
 JACKAudioBackend::input_channels () const
 {
@@ -462,7 +471,7 @@ JACKAudioBackend::raw_buffer_size(DataType t)
 }
 
 void
-JACKAudioBackend::setup_jack_startup_command ()
+JACKAudioBackend::setup_jack_startup_command (bool for_latency_measurement)
 {
 	/* first we map the parameters that have been set onto a
 	 * JackCommandLineOptions object.
@@ -487,6 +496,8 @@ JACKAudioBackend::setup_jack_startup_command ()
 	options.realtime = true;
 	options.ports_max = 2048;
 	
+	ARDOUR::set_midi_option (options, _target_midi_option);
+
 	/* this must always be true for any server instance we start ourselves
 	 */
 
@@ -494,7 +505,7 @@ JACKAudioBackend::setup_jack_startup_command ()
 
 	string cmdline;
 
-	if (!get_jack_command_line_string (options, cmdline)) {
+	if (!get_jack_command_line_string (options, cmdline, for_latency_measurement)) {
 		/* error, somehow - we will still try to start JACK
 		 * automatically but it will be without our preferred options
 		 */
@@ -509,12 +520,15 @@ JACKAudioBackend::setup_jack_startup_command ()
 /* ---- BASIC STATE CONTROL API: start/stop/pause/freewheel --- */
 
 int
-JACKAudioBackend::start ()
+JACKAudioBackend::_start (bool for_latency_measurement)
 {
 	if (!available()) {
 
-		if (!_jack_connection->server_running()) {
-			setup_jack_startup_command ();
+		if (_jack_connection->in_control()) {
+			/* we will be starting JACK, so set up the 
+			   command that JACK will use when it (auto-)starts
+			*/
+			setup_jack_startup_command (for_latency_measurement);
 		}
 
 		if (_jack_connection->open ()) {
@@ -591,7 +605,7 @@ JACKAudioBackend::freewheel (bool onoff)
 	}
 
 	if (jack_set_freewheel (_priv_jack, onoff) == 0) {
-		_freewheeling = true;
+		_freewheeling = onoff;
 		return 0;
 	}
 
@@ -744,7 +758,8 @@ JACKAudioBackend::jack_timebase_callback (jack_transport_state_t state, pframes_
 	ARDOUR::Session* session = engine.session();
 
 	if (session) {
-		session->jack_timebase_callback (state, nframes, pos, new_position);
+		JACKSession jsession (session);
+		jsession.timebase_callback (state, nframes, pos, new_position);
 	}
 }
 
@@ -789,7 +804,6 @@ JACKAudioBackend::_xrun_callback (void *arg)
 	return 0;
 }
 
-#ifdef HAVE_JACK_SESSION
 void
 JACKAudioBackend::_session_callback (jack_session_event_t *event, void *arg)
 {
@@ -797,10 +811,10 @@ JACKAudioBackend::_session_callback (jack_session_event_t *event, void *arg)
 	ARDOUR::Session* session = jab->engine.session();
 
 	if (session) {
-		session->jack_session_event (event);
+		JACKSession jsession (session);
+		jsession.session_event (event);
 	}
 }
-#endif
 
 void
 JACKAudioBackend::_freewheel_callback (int onoff, void *arg)
@@ -822,25 +836,72 @@ JACKAudioBackend::_latency_callback (jack_latency_callback_mode_t mode, void* ar
 }
 
 int
-JACKAudioBackend::create_process_thread (boost::function<void()> f, pthread_t* thread, size_t stacksize)
+JACKAudioBackend::create_process_thread (boost::function<void()> f)
 {
         GET_PRIVATE_JACK_POINTER_RET (_priv_jack, -1);
-        ThreadData* td = new ThreadData (this, f, stacksize);
 
-        if (jack_client_create_thread (_priv_jack, thread, jack_client_real_time_priority (_priv_jack),
+	jack_native_thread_t thread_id;
+        ThreadData* td = new ThreadData (this, f, thread_stack_size());
+
+        if (jack_client_create_thread (_priv_jack, &thread_id, jack_client_real_time_priority (_priv_jack),
                                        jack_is_realtime (_priv_jack), _start_process_thread, td)) {
                 return -1;
         }
 
-        return 0;
+	_jack_threads.push_back(thread_id);
+	return 0;
 }
 
 int
-JACKAudioBackend::wait_for_process_thread_exit (AudioBackendNativeThread thr)
+JACKAudioBackend::join_process_threads ()
+{
+        GET_PRIVATE_JACK_POINTER_RET (_priv_jack, -1);
+
+	int ret = 0;
+
+	for (std::vector<jack_native_thread_t>::const_iterator i = _jack_threads.begin ();
+	     i != _jack_threads.end(); i++) {
+
+#if defined(USING_JACK2_EXPANSION_OF_JACK_API) || defined(PLATFORM_WINDOWS)
+		if (jack_client_stop_thread (_priv_jack, *i) != 0) {
+#else
+		void* status;
+		if (pthread_join (*i, &status) != 0) {
+#endif
+			error << "AudioEngine: cannot stop process thread" << endmsg;
+			ret += -1;
+		}
+	}
+
+	_jack_threads.clear();
+
+	return ret;
+}
+
+bool
+JACKAudioBackend::in_process_thread ()
+{
+	for (std::vector<jack_native_thread_t>::const_iterator i = _jack_threads.begin ();
+	     i != _jack_threads.end(); i++) {
+
+#ifdef COMPILER_MINGW
+		if (*i == GetCurrentThread()) {
+			return true;
+		}
+#else // pthreads
+		if (pthread_equal (*i, pthread_self()) != 0) {
+			return true;
+		}
+#endif
+	}
+
+	return false;
+}
+
+uint32_t
+JACKAudioBackend::process_thread_count ()
 {
-	void* status;
-	/* this doesn't actively try to stop the thread, it just waits till it exits */
-	return pthread_join (thr, &status);
+	return _jack_threads.size();
 }
 
 void*
@@ -960,6 +1021,7 @@ JACKAudioBackend::disconnected (const char* why)
 		engine.halted_callback (why); /* EMIT SIGNAL */
         }
 }
+
 float 
 JACKAudioBackend::cpu_load() const 
 {
@@ -1056,3 +1118,16 @@ JACKAudioBackend::launch_control_app ()
 	args.push_back (appname);
 	Glib::spawn_async ("", args, Glib::SPAWN_SEARCH_PATH);
 }
+
+vector<string>
+JACKAudioBackend::enumerate_midi_options () const
+{
+	return ARDOUR::enumerate_midi_options ();
+}
+
+int
+JACKAudioBackend::set_midi_option (const string& opt)
+{
+	_target_midi_option = opt;
+	return 0;
+}
diff --git a/libs/backends/jack/jack_audiobackend.h b/libs/backends/jack/jack_audiobackend.h
index 9ab545f3ee..3c48be5ead 100644
--- a/libs/backends/jack/jack_audiobackend.h
+++ b/libs/backends/jack/jack_audiobackend.h
@@ -30,15 +30,14 @@
 #include <boost/shared_ptr.hpp>
 
 #include <jack/jack.h>
-#ifdef HAVE_JACK_SESSION
 #include <jack/session.h>
-#endif
 
 #include "ardour/audio_backend.h"
 
 namespace ARDOUR {
 
 class JackConnection;
+class JACKSession;
 
 class JACKAudioBackend : public AudioBackend {
   public:
@@ -90,7 +89,7 @@ class JACKAudioBackend : public AudioBackend {
     std::string control_app_name () const;
     void launch_control_app ();
 
-    int start ();
+    int _start (bool for_latency_measurement);
     int stop ();
     int pause ();
     int freewheel (bool);
@@ -103,8 +102,10 @@ class JACKAudioBackend : public AudioBackend {
 
     size_t raw_buffer_size (DataType t);
 
-    int create_process_thread (boost::function<void()> func, AudioBackendNativeThread*, size_t stacksize);
-    int wait_for_process_thread_exit (AudioBackendNativeThread);
+    int create_process_thread (boost::function<void()> func);
+    int join_process_threads ();
+    bool in_process_thread ();
+    uint32_t process_thread_count ();
 
     void transport_start ();
     void transport_stop ();
@@ -148,6 +149,10 @@ class JACKAudioBackend : public AudioBackend {
     
     /* MIDI */
 
+    std::vector<std::string> enumerate_midi_options () const;
+    int set_midi_option (const std::string&);
+    std::string midi_option () const;
+
     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);
@@ -184,6 +189,8 @@ class JACKAudioBackend : public AudioBackend {
     bool            _freewheeling;
     std::map<DataType,size_t> _raw_buffer_sizes;
 
+    std::vector<jack_native_thread_t> _jack_threads;
+
     static int  _xrun_callback (void *arg);
     static void* _process_thread (void *arg);
     static int  _sample_rate_callback (pframes_t nframes, void *arg);
@@ -192,9 +199,7 @@ class JACKAudioBackend : public AudioBackend {
     static int  _jack_sync_callback (jack_transport_state_t, jack_position_t*, void *arg);
     static void _freewheel_callback (int , void *arg);
     static void _latency_callback (jack_latency_callback_mode_t, void*);
-#ifdef HAVE_JACK_SESSION
     static void _session_callback (jack_session_event_t *event, void *arg);
-#endif
     
     void jack_timebase_callback (jack_transport_state_t, pframes_t, jack_position_t*, int);
     int  jack_sync_callback (jack_transport_state_t, jack_position_t*);
@@ -220,7 +225,7 @@ class JACKAudioBackend : public AudioBackend {
     void*  process_thread ();
     static void* _start_process_thread (void*);
 
-    void setup_jack_startup_command ();
+    void setup_jack_startup_command (bool for_latency_measurement);
 
     /* pffooo */
 
@@ -236,6 +241,7 @@ class JACKAudioBackend : public AudioBackend {
     uint32_t     _target_systemic_output_latency;
     uint32_t     _current_sample_rate;
     uint32_t     _current_buffer_size;
+    std::string  _target_midi_option;
 
     typedef std::set<std::string> DeviceList;
     typedef std::map<std::string,DeviceList> DriverDeviceMap;
@@ -257,6 +263,12 @@ class JACKAudioBackend : public AudioBackend {
 
     void when_connected_to_jack ();
     PBD::ScopedConnection jack_connection_connection;
+
+    /* Object to manage interactions with Session in a way that 
+       keeps JACK out of libardour directly
+    */
+
+    JACKSession* _session;
 };
 
 } // namespace
diff --git a/libs/backends/jack/jack_connection.cc b/libs/backends/jack/jack_connection.cc
index d5d25c747f..b3d7fcecc4 100644
--- a/libs/backends/jack/jack_connection.cc
+++ b/libs/backends/jack/jack_connection.cc
@@ -36,6 +36,8 @@ using std::vector;
 using std::cerr;
 using std::endl;
 
+bool JackConnection::_in_control = false;
+
 static void jack_halted_callback (void* arg)
 {
 	JackConnection* jc = static_cast<JackConnection*> (arg);
@@ -54,17 +56,9 @@ JackConnection::JackConnection (const std::string& arg1, const std::string& arg2
 	, _client_name (arg1)
 	, session_uuid (arg2)
 {
-	_in_control = !server_running();
-}
-
-JackConnection::~JackConnection ()
-{
-	close ();
-}
+	/* See if the server is already up 
+	 */
 
-bool
-JackConnection::server_running ()
-{
         EnvironmentalProtectionAgency* global_epa = EnvironmentalProtectionAgency::get_global_epa ();
         boost::scoped_ptr<EnvironmentalProtectionAgency> current_epa;
 
@@ -83,10 +77,15 @@ JackConnection::server_running ()
 
 	if (status == 0) {
 		jack_client_close (c);
-		return true;
+		_in_control = false;
+	} else {
+		_in_control = true;
 	}
+}
 
-	return false;
+JackConnection::~JackConnection ()
+{
+	close ();
 }
 
 int
@@ -106,19 +105,6 @@ JackConnection::open ()
                 global_epa->restore ();
         }
 
-	/* check to see if the server is already running so that we know if we
-	 * are starting it.
-	 */
-
-	jack_client_t* c = jack_client_open ("ardourprobe", JackNoStartServer, &status);
-
-	if (status == 0) {
-		_in_control = false;
-		jack_client_close (c);
-	} else {
-		_in_control = true;
-	}
-
 	/* ensure that PATH or equivalent includes likely locations of the JACK
 	 * server, in case the user's default does not.
 	 */
diff --git a/libs/backends/jack/jack_connection.h b/libs/backends/jack/jack_connection.h
index 229d9697d9..8d15be6e3a 100644
--- a/libs/backends/jack/jack_connection.h
+++ b/libs/backends/jack/jack_connection.h
@@ -27,15 +27,13 @@ class JackConnection {
     void halted_callback ();
     void halted_info_callback (jack_status_t, const char*);
 
-    bool in_control() const { return _in_control; }
+    static bool in_control() { return _in_control; }
 
-    static bool server_running();
-    
   private:
     jack_client_t* volatile _jack;
     std::string _client_name;
     std::string session_uuid;
-    bool _in_control;
+    static bool _in_control;
 };
 
 } // namespace 
diff --git a/libs/backends/jack/jack_session.cc b/libs/backends/jack/jack_session.cc
new file mode 100644
index 0000000000..ca51dafccc
--- /dev/null
+++ b/libs/backends/jack/jack_session.cc
@@ -0,0 +1,193 @@
+/*
+  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 <time.h>
+
+#include <glibmm/miscutils.h>
+
+#include <jack/jack.h>
+
+#include "ardour/audioengine.h"
+#include "ardour/filename_extensions.h"
+#include "ardour/session.h"
+#include "ardour/session_directory.h"
+#include "ardour/tempo.h"
+
+#include "jack_session.h"
+
+using namespace ARDOUR;
+using std::string;
+
+JACKSession::JACKSession (Session* s)
+	: SessionHandlePtr (s)
+{
+}
+
+JACKSession::~JACKSession ()
+{
+}
+
+void
+JACKSession::session_event (jack_session_event_t* event)
+{
+        char timebuf[128], *tmp;
+        time_t n;
+        struct tm local_time;
+
+        time (&n);
+        localtime_r (&n, &local_time);
+        strftime (timebuf, sizeof(timebuf), "JS_%FT%T", &local_time);
+
+        while ((tmp = strchr(timebuf, ':'))) { *tmp = '.'; }
+
+        if (event->type == JackSessionSaveTemplate)
+        {
+                if (_session->save_template( timebuf )) {
+                        event->flags = JackSessionSaveError;
+                } else {
+                        string cmd ("ardour3 -P -U ");
+                        cmd += event->client_uuid;
+                        cmd += " -T ";
+                        cmd += timebuf;
+
+                        event->command_line = strdup (cmd.c_str());
+                }
+        }
+        else
+        {
+                if (_session->save_state (timebuf)) {
+                        event->flags = JackSessionSaveError;
+                } else {
+			std::string xml_path (_session->session_directory().root_path());
+			std::string legalized_filename = legalize_for_path (timebuf) + statefile_suffix;
+			xml_path = Glib::build_filename (xml_path, legalized_filename);
+
+                        string cmd ("ardour3 -P -U ");
+                        cmd += event->client_uuid;
+                        cmd += " \"";
+                        cmd += xml_path;
+                        cmd += '\"';
+
+                        event->command_line = strdup (cmd.c_str());
+                }
+        }
+
+	/* this won't be called if the port engine in use is not JACK, so we do 
+	   not have to worry about the type of PortEngine::private_handle()
+	*/
+
+	jack_client_t* jack_client = (jack_client_t*) AudioEngine::instance()->port_engine().private_handle();
+	
+	if (jack_client) {
+		jack_session_reply (jack_client, event);
+	}
+
+	if (event->type == JackSessionSaveAndQuit) {
+		_session->Quit (); /* EMIT SIGNAL */
+	}
+
+	jack_session_event_free (event);
+}
+
+void
+JACKSession::timebase_callback (jack_transport_state_t /*state*/,
+				 pframes_t /*nframes*/,
+				 jack_position_t* pos,
+				 int /*new_position*/)
+{
+	Timecode::BBT_Time bbt;
+	TempoMap& tempo_map (_session->tempo_map());
+	framepos_t tf = _session->transport_frame ();
+
+	/* BBT info */
+
+	TempoMetric metric (tempo_map.metric_at (tf));
+	
+	try {
+		tempo_map.bbt_time_rt (tf, bbt);
+		
+		pos->bar = bbt.bars;
+		pos->beat = bbt.beats;
+		pos->tick = bbt.ticks;
+		
+		// XXX still need to set bar_start_tick
+		
+		pos->beats_per_bar = metric.meter().divisions_per_bar();
+		pos->beat_type = metric.meter().note_divisor();
+		pos->ticks_per_beat = Timecode::BBT_Time::ticks_per_beat;
+		pos->beats_per_minute = metric.tempo().beats_per_minute();
+		
+		pos->valid = jack_position_bits_t (pos->valid | JackPositionBBT);
+		
+	} catch (...) {
+		/* no message */
+	}
+
+#ifdef HAVE_JACK_VIDEO_SUPPORT
+	//poke audio video ratio so Ardour can track Video Sync
+	pos->audio_frames_per_video_frame = _session->frame_rate() / _session->timecode_frames_per_second();
+	pos->valid = jack_position_bits_t (pos->valid | JackAudioVideoRatio);
+#endif
+
+#ifdef HAVE_JACK_TIMCODE_SUPPORT
+	/* This is not yet defined in JACK */
+
+	/* Timecode info */
+
+	pos->timecode_offset = _session->config.get_timecode_offset();
+	t.timecode_frame_rate = _session->timecode_frames_per_second();
+	pos->valid = jack_position_bits_t (pos->valid | JackPositionTimecode);
+#endif
+
+#ifdef HAVE_JACK_LOOPING_SUPPORT
+	/* This is not yet defined in JACK */
+	if (_transport_speed) {
+
+		if (play_loop) {
+
+			Location* location = _session->locations()->auto_loop_location();
+
+			if (location) {
+
+				t.transport_state = JackTransportLooping;
+				t.loop_start = location->start();
+				t.loop_end = location->end();
+				t.valid = jack_transport_bits_t (t.valid | JackTransportLoop);
+
+			} else {
+
+				t.loop_start = 0;
+				t.loop_end = 0;
+				t.transport_state = JackTransportRolling;
+
+			}
+
+		} else {
+
+			t.loop_start = 0;
+			t.loop_end = 0;
+			t.transport_state = JackTransportRolling;
+
+		}
+
+	}
+#endif
+}
+
diff --git a/libs/backends/jack/jack_session.h b/libs/backends/jack/jack_session.h
new file mode 100644
index 0000000000..c912b5f170
--- /dev/null
+++ b/libs/backends/jack/jack_session.h
@@ -0,0 +1,47 @@
+/*
+  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 __ardour_jack_audiobackend_jack_session_h__
+#define __ardour_jack_audiobackend_jack_session_h__
+
+#include <jack/session.h>
+#include <jack/transport.h>
+
+#include "ardour/types.h"
+#include "ardour/session_handle.h"
+
+namespace ARDOUR {
+	class Session;
+
+class JACKSession : public ARDOUR::SessionHandlePtr
+{
+  public:
+    JACKSession (ARDOUR::Session* s);
+    ~JACKSession ();
+    
+    void session_event (jack_session_event_t* event);
+    void timebase_callback (jack_transport_state_t /*state*/,
+			    ARDOUR::pframes_t /*nframes*/,
+			    jack_position_t* pos,
+			    int /*new_position*/);
+};
+
+} /* namespace */
+
+#endif /* __ardour_jack_audiobackend_jack_session_h__ */
diff --git a/libs/backends/jack/jack_utils.cc b/libs/backends/jack/jack_utils.cc
index 93fc3d440a..92f175d9cb 100644
--- a/libs/backends/jack/jack_utils.cc
+++ b/libs/backends/jack/jack_utils.cc
@@ -83,6 +83,8 @@ namespace {
 	const char * const dummy_driver_command_line_name = X_("dummy");
 
 	// should we provide more "pretty" names like above?
+	const char * const alsa_seq_midi_driver_name = X_("alsa");
+	const char * const alsa_raw_midi_driver_name = X_("alsarawmidi");
 	const char * const alsaseq_midi_driver_name = X_("seq");
 	const char * const alsaraw_midi_driver_name = X_("raw");
 	const char * const winmme_midi_driver_name = X_("winmme");
@@ -92,6 +94,8 @@ namespace {
 	const char * const default_device_name = X_("Default");
 }
 
+static ARDOUR::MidiOptions midi_options;
+
 std::string
 get_none_string ()
 {
@@ -682,7 +686,7 @@ ARDOUR::JackCommandLineOptions::JackCommandLineOptions ()
 }
 
 bool
-ARDOUR::get_jack_command_line_string (JackCommandLineOptions& options, string& command_line)
+ARDOUR::get_jack_command_line_string (JackCommandLineOptions& options, string& command_line, bool for_latency_measurement)
 {
 	vector<string> args;
 
@@ -740,6 +744,16 @@ ARDOUR::get_jack_command_line_string (JackCommandLineOptions& options, string& c
 	}
 #endif
 
+	if (options.driver == alsa_driver_name) {
+		if (options.midi_driver == alsa_seq_midi_driver_name) {
+			args.push_back ("-X");
+			args.push_back ("alsa_midi");
+		} else if (options.midi_driver == alsa_raw_midi_driver_name) {
+			args.push_back ("-X");
+			args.push_back ("alsarawmidi");
+		}
+	}
+
 	string command_line_driver_name;
 
 	if (!get_jack_command_line_audio_driver_name (options.driver, command_line_driver_name)) {
@@ -811,7 +825,7 @@ ARDOUR::get_jack_command_line_string (JackCommandLineOptions& options, string& c
 	args.push_back ("-p");
 	args.push_back (to_string (options.period_size, std::dec));
 
-	if (get_jack_audio_driver_supports_latency_adjustment (options.driver)) {
+	if (!for_latency_measurement && get_jack_audio_driver_supports_latency_adjustment (options.driver)) {
 		if (options.input_latency) {
 			args.push_back ("-I");
 			args.push_back (to_string (options.input_latency, std::dec));
@@ -846,10 +860,15 @@ ARDOUR::get_jack_command_line_string (JackCommandLineOptions& options, string& c
 		if (options.soft_mode) {
 			args.push_back ("-s");
 		}
+	}
 
-		if (!options.midi_driver.empty() && options.midi_driver != get_none_string ()) {
-			args.push_back ("-X");
-			args.push_back (options.midi_driver);
+	if (options.driver == alsa_driver_name || options.driver == coreaudio_driver_name) {
+
+		if (options.midi_driver != alsa_seq_midi_driver_name) {
+			if (!options.midi_driver.empty() && options.midi_driver != get_none_string ()) {
+				args.push_back ("-X");
+				args.push_back (options.midi_driver);
+			}
 		}
 	}
 
@@ -900,3 +919,54 @@ ARDOUR::write_jack_config_file (const std::string& config_file_path, const strin
 	jackdrc.close ();
 	return true;
 }
+
+vector<string>
+ARDOUR::enumerate_midi_options () 
+{
+	if (midi_options.empty()) {
+#ifdef HAVE_ALSA
+		midi_options.push_back (make_pair (_("(legacy) ALSA raw devices"), alsaraw_midi_driver_name));
+		midi_options.push_back (make_pair (_("(legacy) ALSA sequencer"), alsaseq_midi_driver_name));
+		midi_options.push_back (make_pair (_("ALSA (JACK1, 0.124 and later)"), alsa_seq_midi_driver_name));
+		midi_options.push_back (make_pair (_("ALSA (JACK2, 1.9.8 and later)"), alsa_raw_midi_driver_name));
+#endif
+#ifdef HAVE_PORTAUDIO
+		/* Windows folks: what name makes sense here? Are there other
+		   choices as well ?
+		*/
+		midi_options.push_back (make_pair (_("Multimedia Extension"), winmme_midi_driver_name));
+#endif
+#ifdef __APPLE__
+		midi_options.push_back (make_pair (_("CoreMIDI"), coremidi_midi_driver_name));
+#endif
+	}
+
+	vector<string> v;
+
+	v.push_back (get_none_string());
+
+	for (MidiOptions::const_iterator i = midi_options.begin(); i != midi_options.end(); ++i) {
+		v.push_back (i->first);
+	}
+
+	return v;
+}
+
+int
+ARDOUR::set_midi_option (ARDOUR::JackCommandLineOptions& options, const string& opt)
+{
+	if (opt.empty() || opt == get_none_string()) {
+		options.midi_driver = "";
+		return 0;
+	}
+
+	for (MidiOptions::const_iterator i = midi_options.begin(); i != midi_options.end(); ++i) {
+		if (i->first == opt) {
+			options.midi_driver = i->second;
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
diff --git a/libs/backends/jack/jack_utils.h b/libs/backends/jack/jack_utils.h
index a7521ad1c4..ee8575c5c8 100644
--- a/libs/backends/jack/jack_utils.h
+++ b/libs/backends/jack/jack_utils.h
@@ -180,6 +180,8 @@ namespace ARDOUR {
 	 */
 	bool get_jack_default_server_path (std::string& server_path);
 
+	typedef std::vector<std::pair<std::string,std::string> > MidiOptions;
+
 	/**
 	 * @return The name of the jack server config file
 	 */
@@ -228,8 +230,11 @@ namespace ARDOUR {
 		std::string      midi_driver;
 	};
 
+	std::vector<std::string> enumerate_midi_options ();
+	int set_midi_option (ARDOUR::JackCommandLineOptions&, const std::string& opt);
+
 	/**
 	 * @return true if able to build a valid command line based on options
 	 */
-	bool get_jack_command_line_string (JackCommandLineOptions& options, std::string& command_line);
+	bool get_jack_command_line_string (JackCommandLineOptions& options, std::string& command_line, bool for_latency_measurement);
 }
diff --git a/libs/backends/jack/wscript b/libs/backends/jack/wscript
index 2903abb641..111ecf3218 100644
--- a/libs/backends/jack/wscript
+++ b/libs/backends/jack/wscript
@@ -19,6 +19,7 @@ def options(opt):
     autowaf.set_options(opt)
 
 def configure(conf):
+    autowaf.check_pkg(conf, 'jack', uselib_store='JACK', atleast_version='0.121.0')
     autowaf.configure(conf)
 
 def build(bld):
@@ -28,10 +29,10 @@ def build(bld):
             'jack_connection.cc',
             'jack_audiobackend.cc',
             'jack_portengine.cc',
-            'jack_utils.cc'
+            'jack_utils.cc',
+            'jack_session.cc',
             ]
     obj.includes = ['.']
-    obj.cxxflags = [ '-fPIC' ]
     obj.name     = 'jack_audiobackend'
     obj.target   = 'jack_audiobackend'
     obj.uselib   = [ 'JACK' ]