ext/alsa/: Helper functions to add device probing via the GstPropertyProbe interface to a class.

Original commit message from CVS:
* ext/alsa/Makefile.am:
* ext/alsa/gstalsadeviceprobe.c:
* ext/alsa/gstalsadeviceprobe.h:
Helper functions to add device probing via the GstPropertyProbe
interface to a class.
* ext/alsa/gstalsamixer.h:
Comment out GST_ALSA_MIXER, it returns a struct that's not
used.
* ext/alsa/gstalsamixer.c: (gst_alsa_mixer_open):
Add some debug info.
* ext/alsa/gstalsamixerelement.c:
(gst_alsa_mixer_element_interface_supported),
(gst_implements_interface_init),
(gst_alsa_mixer_element_init_interfaces),
(gst_alsa_mixer_element_class_init),
(gst_alsa_mixer_element_finalize), (gst_alsa_mixer_element_init),
(gst_alsa_mixer_element_set_property),
(gst_alsa_mixer_element_get_property),
(gst_alsa_mixer_element_change_state):
* ext/alsa/gstalsamixerelement.h:
Add 'device' and 'device-name' properties. Add GstPropertyProbe
for device handling (gnome-volume-control will need that).

8 files changed, 532 insertions, 21 deletions

diff --git a/ChangeLog b/ChangeLog
index e21bc2123..d85c606da 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,32 @@
-2005-12-12  Christian Schaller  <set EMAIL_ADDRESS environment variable>
+2005-12-14  Tim-Philipp Müller  <tim at centricular dot net>
 
+	* ext/alsa/Makefile.am:
+	* ext/alsa/gstalsadeviceprobe.c:
+	* ext/alsa/gstalsadeviceprobe.h:
+	  Helper functions to add device probing via the GstPropertyProbe
+	  interface to a class.
+
+	* ext/alsa/gstalsamixer.h:
+	  Comment out GST_ALSA_MIXER, it returns a struct that's not
+	  used.
+
+	* ext/alsa/gstalsamixer.c: (gst_alsa_mixer_open):
+	  Add some debug info. 
+
+	* ext/alsa/gstalsamixerelement.c:
+	(gst_alsa_mixer_element_interface_supported),
+	(gst_implements_interface_init),
+	(gst_alsa_mixer_element_init_interfaces),
+	(gst_alsa_mixer_element_class_init),
+	(gst_alsa_mixer_element_finalize), (gst_alsa_mixer_element_init),
+	(gst_alsa_mixer_element_set_property),
+	(gst_alsa_mixer_element_get_property),
+	(gst_alsa_mixer_element_change_state):
+	* ext/alsa/gstalsamixerelement.h:
+	  Add 'device' and 'device-name' properties. Add GstPropertyProbe
+	  for device handling (gnome-volume-control will need that).
+
+2005-12-12  Christian Schaller  <uraeus@gnome.org>
 
 	* ext/Makefile.am: fix cdparanoia entry
 	* gst-plugins-base.spec.in: add cdparanoia
diff --git a/ext/alsa/Makefile.am b/ext/alsa/Makefile.am
index a8bfdeda2..c34e112f8 100644
--- a/ext/alsa/Makefile.am
+++ b/ext/alsa/Makefile.am
@@ -1,11 +1,12 @@
 plugin_LTLIBRARIES = libgstalsa.la
 
 libgstalsa_la_SOURCES = \
-	gstalsaplugin.c \
+	gstalsadeviceprobe.c \
 	gstalsamixer.c	\
 	gstalsamixerelement.c \
 	gstalsamixertrack.c \
 	gstalsamixeroptions.c \
+	gstalsaplugin.c \
 	gstalsasink.c 	\
 	gstalsasrc.c
 
@@ -18,9 +19,10 @@ libgstalsa_la_LIBADD = \
 
 noinst_HEADERS = \
 	gstalsa.h \
-	gstalsasink.h \
-	gstalsasrc.h \
+	gstalsadeviceprobe.h \
 	gstalsamixer.h \
 	gstalsamixerelement.h \
 	gstalsamixertrack.h \
-	gstalsamixeroptions.h
+	gstalsamixeroptions.h \
+	gstalsasrc.h \
+	gstalsasink.h
diff --git a/ext/alsa/gstalsadeviceprobe.c b/ext/alsa/gstalsadeviceprobe.c
new file mode 100644
index 000000000..606918c5b
--- /dev/null
+++ b/ext/alsa/gstalsadeviceprobe.c
@@ -0,0 +1,291 @@
+/* Copyright (C) 2001 CodeFactory AB
+ * Copyright (C) 2001 Thomas Nyberg <thomas@codefactory.se>
+ * Copyright (C) 2001-2002 Andy Wingo <apwingo@eos.ncsu.edu>
+ * Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
+ * Copyright (C) 2005 Tim-Philipp Müller <tim centricular net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstalsadeviceprobe.h"
+#include "gst/interfaces/propertyprobe.h"
+
+#define DATA_OFFSET_QUARK \
+    g_quark_from_static_string ("alsa-device-probe-data-offset-quark")
+
+#define DEVICE_PROPID_QUARK \
+    g_quark_from_static_string ("alsa-device-probe-device-propid-quark")
+
+static const GList *
+gst_alsa_device_property_probe_get_properties (GstPropertyProbe * probe)
+{
+  GObjectClass *klass = G_OBJECT_GET_CLASS (probe);
+  static GList *list = NULL;
+
+  /* well, not perfect, but better than no locking at all.
+   * In the worst case we leak a list node, so who cares? */
+  GST_CLASS_LOCK (GST_OBJECT_CLASS (klass));
+
+  if (!list) {
+    GParamSpec *pspec;
+
+    pspec = g_object_class_find_property (klass, "device");
+    list = g_list_append (NULL, pspec);
+  }
+
+  GST_CLASS_UNLOCK (GST_OBJECT_CLASS (klass));
+
+  return list;
+}
+
+/* yes, this is evil, but hey, it works */
+
+static gboolean
+gst_alsa_device_probe_get_data (GObject * obj, GstAlsaDeviceProbeData ** p_data,
+    guint * p_device_propid)
+{
+  gpointer klass;
+  guint devpropid;
+  guint offset;
+  GType type;
+
+  type = G_TYPE_FROM_INSTANCE (obj);
+
+  /* in case this is a derived class ... */
+  while (g_type_get_qdata (type, DATA_OFFSET_QUARK) == NULL) {
+    type = g_type_parent (type);
+    g_return_val_if_fail (G_TYPE_IS_FUNDAMENTAL (type) == FALSE, FALSE);
+  }
+
+  offset = GPOINTER_TO_UINT (g_type_get_qdata (type, DATA_OFFSET_QUARK));
+  devpropid = GPOINTER_TO_UINT (g_type_get_qdata (type, DEVICE_PROPID_QUARK));
+
+  g_return_val_if_fail (offset != 0, FALSE);
+  g_return_val_if_fail (devpropid != 0, FALSE);
+
+  klass = G_OBJECT_GET_CLASS (obj);
+
+  *p_data = (GstAlsaDeviceProbeData *) G_STRUCT_MEMBER_P (klass, offset);
+  *p_device_propid = devpropid;
+
+  return TRUE;
+}
+
+static void
+gst_alsa_add_device_list (GstAlsaDeviceProbeData * probe_data,
+    snd_pcm_stream_t stream)
+{
+  snd_ctl_t *handle;
+  int card, err, dev;
+  snd_ctl_card_info_t *info;
+  snd_pcm_info_t *pcminfo;
+  gboolean mixer = (stream == -1);
+
+  if (stream == -1)
+    stream = 0;
+
+  snd_ctl_card_info_alloca (&info);
+  snd_pcm_info_alloca (&pcminfo);
+  card = -1;
+
+  if (snd_card_next (&card) < 0 || card < 0) {
+    /* no soundcard found */
+    return;
+  }
+  while (card >= 0) {
+    gchar name[32];
+
+    g_snprintf (name, sizeof (name), "hw:%d", card);
+    if ((err = snd_ctl_open (&handle, name, 0)) < 0) {
+      goto next_card;
+    }
+    if ((err = snd_ctl_card_info (handle, info)) < 0) {
+      snd_ctl_close (handle);
+      goto next_card;
+    }
+
+    if (mixer) {
+      probe_data->devices = g_list_append (probe_data->devices,
+          g_strdup (name));
+    } else {
+      dev = -1;
+      while (1) {
+        gchar *gst_device;
+
+        snd_ctl_pcm_next_device (handle, &dev);
+
+        if (dev < 0)
+          break;
+        snd_pcm_info_set_device (pcminfo, dev);
+        snd_pcm_info_set_subdevice (pcminfo, 0);
+        snd_pcm_info_set_stream (pcminfo, stream);
+        if ((err = snd_ctl_pcm_info (handle, pcminfo)) < 0) {
+          continue;
+        }
+
+        gst_device = g_strdup_printf ("hw:%d,%d", card, dev);
+        probe_data->devices = g_list_append (probe_data->devices, gst_device);
+      }
+    }
+    snd_ctl_close (handle);
+  next_card:
+    if (snd_card_next (&card) < 0) {
+      break;
+    }
+  }
+}
+
+static gboolean
+gst_alsa_probe_devices (GstElementClass * klass,
+    GstAlsaDeviceProbeData * probe_data, gboolean check)
+{
+  static gboolean init = FALSE;
+
+  /* I'm pretty sure ALSA has a good way to do this. However, their cool
+   * auto-generated documentation is pretty much useless if you try to
+   * do function-wise look-ups. */
+
+  if (!init && !check) {
+    snd_pcm_stream_t mode = -1;
+    const GList *templates;
+
+    /* we assume one pad template at max [zero=mixer] */
+    templates = gst_element_class_get_pad_template_list (klass);
+    if (templates) {
+      if (GST_PAD_TEMPLATE_DIRECTION (templates->data) == GST_PAD_SRC)
+        mode = SND_PCM_STREAM_CAPTURE;
+      else
+        mode = SND_PCM_STREAM_PLAYBACK;
+    }
+
+    gst_alsa_add_device_list (probe_data, mode);
+
+    init = TRUE;
+  }
+
+  return init;
+}
+
+static void
+gst_alsa_device_property_probe_probe_property (GstPropertyProbe * probe,
+    guint prop_id, const GParamSpec * pspec)
+{
+  GstAlsaDeviceProbeData *probe_data;
+  guint devid;
+
+  if (!gst_alsa_device_probe_get_data (G_OBJECT (probe), &probe_data, &devid))
+    g_return_if_reached ();
+
+  if (prop_id == devid) {
+    gst_alsa_probe_devices (GST_ELEMENT_GET_CLASS (probe), probe_data, FALSE);
+  } else {
+    G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
+  }
+}
+
+static gboolean
+gst_alsa_device_property_probe_needs_probe (GstPropertyProbe * probe,
+    guint prop_id, const GParamSpec * pspec)
+{
+  GstAlsaDeviceProbeData *probe_data;
+  GstElementClass *klass;
+  guint devid;
+
+  if (!gst_alsa_device_probe_get_data (G_OBJECT (probe), &probe_data, &devid))
+    g_return_val_if_reached (FALSE);
+
+  if (prop_id != devid) {
+    G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
+    return FALSE;
+  }
+
+  klass = GST_ELEMENT_GET_CLASS (probe);
+  return !gst_alsa_probe_devices (klass, probe_data, TRUE);
+}
+
+static GValueArray *
+gst_alsa_device_probe_list_devices (GstAlsaDeviceProbeData * probe_data)
+{
+  GValueArray *array;
+  GValue value = { 0 };
+  GList *item;
+
+  if (!probe_data->devices)
+    return NULL;
+
+  array = g_value_array_new (g_list_length (probe_data->devices));
+  g_value_init (&value, G_TYPE_STRING);
+  for (item = probe_data->devices; item != NULL; item = item->next) {
+    g_value_set_string (&value, (const gchar *) item->data);
+    g_value_array_append (array, &value);
+  }
+  g_value_unset (&value);
+
+  return array;
+}
+
+static GValueArray *
+gst_alsa_device_property_probe_get_values (GstPropertyProbe * probe,
+    guint prop_id, const GParamSpec * pspec)
+{
+  GstAlsaDeviceProbeData *probe_data;
+  guint devid;
+
+  if (!gst_alsa_device_probe_get_data (G_OBJECT (probe), &probe_data, &devid))
+    g_return_val_if_reached (NULL);
+
+  if (prop_id != devid) {
+    G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
+    return NULL;
+  }
+
+  return gst_alsa_device_probe_list_devices (probe_data);
+}
+
+static void
+gst_alsa_property_probe_interface_init (GstPropertyProbeInterface * iface)
+{
+  iface->get_properties = gst_alsa_device_property_probe_get_properties;
+  iface->probe_property = gst_alsa_device_property_probe_probe_property;
+  iface->needs_probe = gst_alsa_device_property_probe_needs_probe;
+  iface->get_values = gst_alsa_device_property_probe_get_values;
+}
+
+void
+gst_alsa_type_add_device_property_probe_interface (GType type,
+    guint probe_data_klass_offset, guint device_prop_id)
+{
+  static const GInterfaceInfo probe_iface_info = {
+    (GInterfaceInitFunc) gst_alsa_property_probe_interface_init,
+    NULL,
+    NULL,
+  };
+
+  g_assert (probe_data_klass_offset != 0);
+  g_assert (device_prop_id != 0);
+
+  g_type_set_qdata (type, DATA_OFFSET_QUARK,
+      GUINT_TO_POINTER (probe_data_klass_offset));
+
+  g_type_set_qdata (type, DEVICE_PROPID_QUARK,
+      GUINT_TO_POINTER (device_prop_id));
+
+  g_type_add_interface_static (type, GST_TYPE_PROPERTY_PROBE,
+      &probe_iface_info);
+}
diff --git a/ext/alsa/gstalsadeviceprobe.h b/ext/alsa/gstalsadeviceprobe.h
new file mode 100644
index 000000000..3ad207658
--- /dev/null
+++ b/ext/alsa/gstalsadeviceprobe.h
@@ -0,0 +1,43 @@
+/* Copyright (C) 2001 CodeFactory AB
+ * Copyright (C) 2001 Thomas Nyberg <thomas@codefactory.se>
+ * Copyright (C) 2001-2002 Andy Wingo <apwingo@eos.ncsu.edu>
+ * Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __GST_ALSA_DEVICE_PROBE_H__
+#define __GST_ALSA_DEVICE_PROBE_H__
+
+#include "gstalsa.h"
+
+G_BEGIN_DECLS
+
+typedef struct _GstAlsaDeviceProbeData GstAlsaDeviceProbeData;
+
+struct _GstAlsaDeviceProbeData {
+  /* autodetected devices available */
+  GList *devices;
+};
+
+/* offset is the offset of the device probe data struct in the klass struct */
+void      gst_alsa_type_add_device_property_probe_interface (GType  type,
+                                                             guint  probe_data_offset,
+                                                             guint  device_prop_id);
+
+G_END_DECLS
+
+#endif /* __GST_ALSA_DEVICE_PROBE_H__ */
+
diff --git a/ext/alsa/gstalsamixer.c b/ext/alsa/gstalsamixer.c
index 15b25f93d..8656924d8 100644
--- a/ext/alsa/gstalsamixer.c
+++ b/ext/alsa/gstalsamixer.c
@@ -81,8 +81,11 @@ gst_alsa_mixer_open (GstAlsaMixer * mixer)
   if (sscanf (mixer->device, "hw:%d", &devicenum) == 1) {
     gchar *name;
 
-    if (!snd_card_get_name (devicenum, &name))
-      mixer->cardname = name;
+    if (!snd_card_get_name (devicenum, &name)) {
+      mixer->cardname = g_strdup (name);
+      free (name);
+      GST_DEBUG ("Card name = %s", GST_STR_NULL (mixer->cardname));
+    }
   }
 
   GST_INFO ("Successfully opened mixer for device `%s'.", mixer->device);
diff --git a/ext/alsa/gstalsamixer.h b/ext/alsa/gstalsamixer.h
index 49f71d5eb..971f8053d 100644
--- a/ext/alsa/gstalsamixer.h
+++ b/ext/alsa/gstalsamixer.h
@@ -30,8 +30,8 @@
 
 G_BEGIN_DECLS
 
-
-#define GST_ALSA_MIXER(obj)             ((GstAlsaMixer*)(obj))
+/* This does not get you what you think it does, use obj->mixer   */
+/* #define GST_ALSA_MIXER(obj)             ((GstAlsaMixer*)(obj)) */
 
 
 typedef enum {
diff --git a/ext/alsa/gstalsamixerelement.c b/ext/alsa/gstalsamixerelement.c
index 72a16650c..ae19035c8 100644
--- a/ext/alsa/gstalsamixerelement.c
+++ b/ext/alsa/gstalsamixerelement.c
@@ -23,6 +23,13 @@
 #endif
 
 #include "gstalsamixerelement.h"
+#include "gstalsadeviceprobe.h"
+
+enum
+{
+  PROP_DEVICE = 1,
+  PROP_DEVICE_NAME
+};
 
 
 static GstElementDetails gst_alsa_mixer_element_details =
@@ -31,15 +38,62 @@ GST_ELEMENT_DETAILS ("Alsa Mixer",
     "Control sound input and output levels with ALSA",
     "Leif Johnson <leif@ambient.2y.net>");
 
+static void gst_alsa_mixer_element_init_interfaces (GType type);
+
+GST_BOILERPLATE_FULL (GstAlsaMixerElement, gst_alsa_mixer_element,
+    GstElement, GST_TYPE_ELEMENT, gst_alsa_mixer_element_init_interfaces)
+
+/* massive macro that takes care of all the GstMixer stuff */
+    GST_IMPLEMENT_ALSA_MIXER_METHODS (GstAlsaMixerElement, gst_alsa_mixer_element);
 
-GST_BOILERPLATE_WITH_INTERFACE (GstAlsaMixerElement, gst_alsa_mixer_element,
-    GstElement, GST_TYPE_ELEMENT, GstMixer, GST_TYPE_MIXER,
-    gst_alsa_mixer_element);
+     static void gst_alsa_mixer_element_get_property (GObject * object,
+    guint prop_id, GValue * value, GParamSpec * pspec);
+     static void gst_alsa_mixer_element_set_property (GObject * object,
+    guint prop_id, const GValue * value, GParamSpec * pspec);
+     static void gst_alsa_mixer_element_finalize (GObject * object);
 
-GST_IMPLEMENT_ALSA_MIXER_METHODS (GstAlsaMixerElement, gst_alsa_mixer_element);
+     static GstStateChangeReturn gst_alsa_mixer_element_change_state (GstElement
+    * element, GstStateChange transition);
+
+     static gboolean
+         gst_alsa_mixer_element_interface_supported (GstAlsaMixerElement * this,
+    GType interface_type)
+{
+  if (interface_type == GST_TYPE_MIXER) {
+    return gst_alsa_mixer_element_supported (this, interface_type);
+  }
+
+  g_return_val_if_reached (FALSE);
+}
+
+static void
+gst_implements_interface_init (GstImplementsInterfaceClass * klass)
+{
+  klass->supported = (gpointer) gst_alsa_mixer_element_interface_supported;
+}
 
-static GstStateChangeReturn gst_alsa_mixer_element_change_state (GstElement *
-    element, GstStateChange transition);
+static void
+gst_alsa_mixer_element_init_interfaces (GType type)
+{
+  static const GInterfaceInfo implements_iface_info = {
+    (GInterfaceInitFunc) gst_implements_interface_init,
+    NULL,
+    NULL,
+  };
+  static const GInterfaceInfo mixer_iface_info = {
+    (GInterfaceInitFunc) gst_alsa_mixer_element_interface_init,
+    NULL,
+    NULL,
+  };
+
+  g_type_add_interface_static (type, GST_TYPE_IMPLEMENTS_INTERFACE,
+      &implements_iface_info);
+  g_type_add_interface_static (type, GST_TYPE_MIXER, &mixer_iface_info);
+
+  gst_alsa_type_add_device_property_probe_interface (type,
+      G_STRUCT_OFFSET (GstAlsaMixerElementClass, device_probe_data),
+      PROP_DEVICE);
+}
 
 static void
 gst_alsa_mixer_element_base_init (gpointer klass)
@@ -52,10 +106,36 @@ static void
 gst_alsa_mixer_element_class_init (GstAlsaMixerElementClass * klass)
 {
   GstElementClass *element_class;
+  GObjectClass *gobject_class;
 
   element_class = (GstElementClass *) klass;
+  gobject_class = (GObjectClass *) klass;
+
+  gobject_class->finalize = gst_alsa_mixer_element_finalize;
+  gobject_class->get_property = gst_alsa_mixer_element_get_property;
+  gobject_class->set_property = gst_alsa_mixer_element_set_property;
 
-  element_class->change_state = gst_alsa_mixer_element_change_state;
+  g_object_class_install_property (gobject_class, PROP_DEVICE,
+      g_param_spec_string ("device", "Device",
+          "ALSA device, as defined in an asound configuration file",
+          "default", G_PARAM_READWRITE));
+
+  g_object_class_install_property (gobject_class, PROP_DEVICE_NAME,
+      g_param_spec_string ("device-name", "Device name",
+          "Human-readable name of the sound device", "", G_PARAM_READABLE));
+
+  element_class->change_state =
+      GST_DEBUG_FUNCPTR (gst_alsa_mixer_element_change_state);
+}
+
+static void
+gst_alsa_mixer_element_finalize (GObject * obj)
+{
+  GstAlsaMixerElement *this = GST_ALSA_MIXER_ELEMENT (obj);
+
+  g_free (this->device);
+
+  G_OBJECT_CLASS (parent_class)->finalize (obj);
 }
 
 static void
@@ -63,20 +143,84 @@ gst_alsa_mixer_element_init (GstAlsaMixerElement * this,
     GstAlsaMixerElementClass * klass)
 {
   this->mixer = NULL;
+  this->device = g_strdup ("default");
+}
+
+static void
+gst_alsa_mixer_element_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstAlsaMixerElement *this = GST_ALSA_MIXER_ELEMENT (object);
+
+  switch (prop_id) {
+    case PROP_DEVICE:{
+      GST_OBJECT_LOCK (this);
+      g_free (this->device);
+      this->device = g_value_dup_string (value);
+      GST_OBJECT_UNLOCK (this);
+      break;
+    }
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_alsa_mixer_element_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstAlsaMixerElement *this = GST_ALSA_MIXER_ELEMENT (object);
+
+  switch (prop_id) {
+    case PROP_DEVICE:{
+      GST_OBJECT_LOCK (this);
+      g_value_set_string (value, this->device);
+      GST_OBJECT_UNLOCK (this);
+      break;
+    }
+    case PROP_DEVICE_NAME:{
+      GST_OBJECT_LOCK (this);
+      if (this->mixer) {
+        g_value_set_string (value, this->mixer->cardname);
+      } else {
+        g_value_set_string (value, NULL);
+      }
+      GST_OBJECT_UNLOCK (this);
+      break;
+    }
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
 }
 
 static GstStateChangeReturn
 gst_alsa_mixer_element_change_state (GstElement * element,
     GstStateChange transition)
 {
+  GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
   GstAlsaMixerElement *this = GST_ALSA_MIXER_ELEMENT (element);
 
   switch (transition) {
     case GST_STATE_CHANGE_NULL_TO_READY:
       if (!this->mixer) {
-        this->mixer = gst_alsa_mixer_new ("hw:0", GST_ALSA_MIXER_ALL);
+        if (!this->device) {
+          this->mixer = gst_alsa_mixer_new ("default", GST_ALSA_MIXER_ALL);
+        } else {
+          this->mixer = gst_alsa_mixer_new (this->device, GST_ALSA_MIXER_ALL);
+        }
       }
       break;
+    default:
+      break;
+  }
+
+  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
+  if (ret == GST_STATE_CHANGE_FAILURE)
+    return ret;
+
+  switch (transition) {
     case GST_STATE_CHANGE_READY_TO_NULL:
       if (this->mixer) {
         gst_alsa_mixer_free (this->mixer);
@@ -87,8 +231,5 @@ gst_alsa_mixer_element_change_state (GstElement * element,
       break;
   }
 
-  if (GST_ELEMENT_CLASS (parent_class)->change_state)
-    return GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
-
-  return GST_STATE_CHANGE_SUCCESS;
+  return ret;
 }
diff --git a/ext/alsa/gstalsamixerelement.h b/ext/alsa/gstalsamixerelement.h
index e53380092..de9471cb7 100644
--- a/ext/alsa/gstalsamixerelement.h
+++ b/ext/alsa/gstalsamixerelement.h
@@ -23,6 +23,7 @@
 
 #include "gstalsa.h"
 #include "gstalsamixer.h"
+#include "gstalsadeviceprobe.h"
 
 
 G_BEGIN_DECLS
@@ -43,10 +44,13 @@ struct _GstAlsaMixerElement {
   GstElement            parent;
 
   GstAlsaMixer          *mixer;
+  gchar                 *device;
 };
 
 struct _GstAlsaMixerElementClass {
   GstElementClass       parent;
+
+  GstAlsaDeviceProbeData   device_probe_data;
 };