adapt AudioEngine to new AudioBackend API

libs/ardour/ardour/audioengine.h

@@ -83,8 +83,8 @@ public:
      * just forward to a backend implementation.
      */
 
-    int            start ();
-    int            stop ();
+    int            start (bool for_latency_measurement=false);
+    int            stop (bool for_latency_measurement=false);
     int            pause ();
     int            freewheel (bool start_stop);
     float          get_cpu_load() const ;
@@ -194,7 +194,7 @@ public:
 
     MTDM* mtdm();
     int  prepare_for_latency_measurement ();
-    void start_latency_detection ();
+    int  start_latency_detection ();
     void stop_latency_detection ();
     void set_latency_input_port (const std::string&);
     void set_latency_output_port (const std::string&);
@@ -229,6 +229,7 @@ public:
     std::string               _latency_input_name;
     std::string               _latency_output_name;
     framecnt_t                _latency_signal_latency;
+    bool                      _stopped_for_latency;
     bool                      _started_for_latency;
     bool                      _in_destructor;
 

libs/ardour/audioengine.cc

@@ -80,7 +80,7 @@ AudioEngine::AudioEngine ()
 	, _latency_output_port (0)
 	, _latency_flush_frames (0)
 	, _latency_signal_latency (0)
-	, _started_for_latency (false)
+	, _stopped_for_latency (false)
 	, _in_destructor (false)
 {
 	g_atomic_int_set (&m_meter_exit, 0);
@@ -596,7 +596,7 @@ AudioEngine::set_backend (const std::string& name, const std::string& arg1, cons
 /* BACKEND PROXY WRAPPERS */
 
 int
-AudioEngine::start ()
+AudioEngine::start (bool for_latency)
 {
 	if (!_backend) {
 		return -1;
@@ -609,7 +609,7 @@ AudioEngine::start ()
 	_processed_frames = 0;
 	last_monitor_check = 0;
 	
-	if (_backend->start()) {
+	if (_backend->start (for_latency)) {
 		return -1;
 	}
 
@@ -625,7 +625,7 @@ AudioEngine::start ()
 	
 	start_metering_thread ();
 	
-	if (!_started_for_latency) {
+	if (!for_latency) {
 		Running(); /* EMIT SIGNAL */
 	}
 	
@@ -633,7 +633,7 @@ AudioEngine::start ()
 }
 
 int
-AudioEngine::stop ()
+AudioEngine::stop (bool for_latency)
 {
 	if (!_backend) {
 		return 0;
@@ -654,7 +654,10 @@ AudioEngine::stop ()
 	stop_metering_thread ();
 	
 	Port::PortDrop ();
-	Stopped (); /* EMIT SIGNAL */
+
+	if (!for_latency) {
+		Stopped (); /* EMIT SIGNAL */
+	}
 	
 	return 0;
 }
@@ -1018,7 +1021,10 @@ AudioEngine::halted_callback (const char* why)
 	_running = false;
 
 	Port::PortDrop (); /* EMIT SIGNAL */
-	Halted (why);      /* EMIT SIGNAL */
+
+	if (!_started_for_latency) {
+		Halted (why);      /* EMIT SIGNAL */
+	}
 }
 
 bool
@@ -1047,23 +1053,26 @@ AudioEngine::mtdm()
 int
 AudioEngine::prepare_for_latency_measurement ()
 {
-	if (!running()) {
-		_started_for_latency = true;
+	if (running()) {
+		_stopped_for_latency = true;
+		stop (true);
+	}
 
-		if (start()) {
-			_started_for_latency = false;
-			return -1;
-		}
+	if (start (true)) {
+		_started_for_latency = true;
+		return -1;
 	}
 
 	return 0;
 }
 
-void
+int
 AudioEngine::start_latency_detection ()
 {
-	if (prepare_for_latency_measurement ()) {
-		return;
+	if (!running()) {
+		if (prepare_for_latency_measurement ()) {
+			return -1;
+		}
 	}
 
 	PortEngine& pe (port_engine());
@@ -1077,27 +1086,32 @@ AudioEngine::start_latency_detection ()
 	PortEngine::PortHandle* in = pe.get_port_by_name (_latency_input_name);
 
 	if (!out || !in) {
-		return;
+		stop (true);
+		return -1;
 	}
 
 	/* create the ports we will use to read/write data */
 	
 	if ((_latency_output_port = pe.register_port ("latency_out", DataType::AUDIO, IsOutput)) == 0) {
-		return;
+		stop (true);
+		return -1;
 	}
 	if (pe.connect (_latency_output_port, _latency_output_name)) {
 		pe.unregister_port (_latency_output_port);
-		return;
+		stop (true);
+		return -1;
 	}
 
 	const string portname ("latency_in");
 	if ((_latency_input_port = pe.register_port (portname, DataType::AUDIO, IsInput)) == 0) {
 		pe.unregister_port (_latency_output_port);
-		return;
+		stop (true);
+		return -1;
 	}
 	if (pe.connect (_latency_input_name, make_port_name_non_relative (portname))) {
 		pe.unregister_port (_latency_output_port);
-		return;
+		stop (true);
+		return -1;
 	}
 
 	LatencyRange lr;
@@ -1113,6 +1127,7 @@ AudioEngine::start_latency_detection ()
 	_measuring_latency = true;
         _latency_flush_frames = samples_per_cycle();
 
+	return 0;
 }
 
 void
@@ -1128,9 +1143,15 @@ AudioEngine::stop_latency_detection ()
 		port_engine().unregister_port (_latency_input_port);
 		_latency_input_port = 0;
 	}
-	if (_started_for_latency) {
-		stop ();
+
+	stop (true);
+
+	if (_stopped_for_latency) {
+		start ();
 	}
+
+	_stopped_for_latency = false;
+	_started_for_latency = false;
 }
 
 void