diff --git a/libs/ardouralsautil/ardouralsautil/devicelist.h b/libs/ardouralsautil/ardouralsautil/devicelist.h
index 2f8c2c4e90..b68a44c3ae 100644
--- a/libs/ardouralsautil/ardouralsautil/devicelist.h
+++ b/libs/ardouralsautil/ardouralsautil/devicelist.h
@@ -23,8 +23,13 @@
 #include <string>
 #include <map>
 namespace ARDOUR {
+	enum AlsaDuplex {
+		HalfDuplexIn  = 1,
+		HalfDuplexOut = 2,
+		FullDuplex    = 3,
+	};
 
-	void get_alsa_audio_device_names (std::map<std::string, std::string>& devices);
+	void get_alsa_audio_device_names (std::map<std::string, std::string>& devices, AlsaDuplex duplex = FullDuplex);
 	void get_alsa_rawmidi_device_names (std::map<std::string, std::string>& devices);
 	void get_alsa_sequencer_names (std::map<std::string, std::string>& devices);
 	int card_to_num(const char* device_name);
diff --git a/libs/ardouralsautil/devicelist.cc b/libs/ardouralsautil/devicelist.cc
index b20df100db..3fdb1401af 100644
--- a/libs/ardouralsautil/devicelist.cc
+++ b/libs/ardouralsautil/devicelist.cc
@@ -24,7 +24,7 @@
 using namespace std;
 
 void
-ARDOUR::get_alsa_audio_device_names (std::map<std::string, std::string>& devices)
+ARDOUR::get_alsa_audio_device_names (std::map<std::string, std::string>& devices, AlsaDuplex duplex)
 {
 	snd_ctl_t *handle;
 	snd_ctl_card_info_t *info;
@@ -35,6 +35,8 @@ ARDOUR::get_alsa_audio_device_names (std::map<std::string, std::string>& devices
 	int cardnum = -1;
 	int device = -1;
 
+	assert (duplex > 0);
+
 	while (snd_card_next (&cardnum) >= 0 && cardnum >= 0) {
 
 		devname = "hw:";
@@ -63,7 +65,7 @@ ARDOUR::get_alsa_audio_device_names (std::map<std::string, std::string>& devices
 				snd_pcm_info_set_subdevice (pcminfo, 0);
 				snd_pcm_info_set_stream (pcminfo, SND_PCM_STREAM_CAPTURE);
 
-				if (snd_ctl_pcm_info (handle, pcminfo) < 0) {
+				if (snd_ctl_pcm_info (handle, pcminfo) < 0 && (duplex & HalfDuplexIn)) {
 					continue;
 				}
 
@@ -71,7 +73,7 @@ ARDOUR::get_alsa_audio_device_names (std::map<std::string, std::string>& devices
 				snd_pcm_info_set_subdevice (pcminfo, 0);
 				snd_pcm_info_set_stream (pcminfo, SND_PCM_STREAM_PLAYBACK);
 
-				if (snd_ctl_pcm_info (handle, pcminfo) < 0) {
+				if (snd_ctl_pcm_info (handle, pcminfo) < 0 && (duplex & HalfDuplexOut)) {
 					continue;
 				}
 				devname += ',';