diff -r 567bb019e3e3 -r 7e817e7e631c gst_plugins_base/ext/alsa/gstalsamixer.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gst_plugins_base/ext/alsa/gstalsamixer.c	Wed Sep 01 12:16:41 2010 +0100
@@ -0,0 +1,887 @@
+/* ALSA mixer implementation.
+ * Copyright (C) 2003 Leif Johnson <leif@ambient.2y.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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/**
+ * SECTION:element-alsamixer
+ * @short_description: control properties of an audio device
+ * @see_also: alsasink, alsasrc
+ *
+ * <refsect2>
+ * <para>
+ * This element controls various aspects such as the volume and balance
+ * of an audio device using the ALSA api.
+ * </para>
+ * <para>
+ * The application should query and use the interfaces provided by this 
+ * element to control the device.
+ * </para>
+ * </refsect2>
+ *
+ * Last reviewed on 2006-03-01 (0.10.4)
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstalsamixer.h"
+
+static void gst_alsa_mixer_update_option (GstAlsaMixer * mixer,
+    GstAlsaMixerOptions * alsa_opts);
+static void gst_alsa_mixer_update_track (GstAlsaMixer * mixer,
+    GstAlsaMixerTrack * alsa_track);
+static int gst_alsa_mixer_handle_callback (snd_mixer_t * handle,
+    unsigned int mask, snd_mixer_elem_t * elem);
+
+/* First some utils, then the mixer implementation */
+static gboolean
+gst_alsa_mixer_open (GstAlsaMixer * mixer)
+{
+  gint err;
+  snd_ctl_t *ctl;
+  snd_ctl_card_info_t *card_info;
+
+  g_return_val_if_fail (mixer->handle == NULL, FALSE);
+
+  /* open and initialize the mixer device */
+  err = snd_mixer_open (&mixer->handle, 0);
+  if (err < 0 || mixer->handle == NULL)
+    goto open_failed;
+
+  if ((err = snd_mixer_attach (mixer->handle, mixer->device)) < 0) {
+    GST_WARNING ("Cannot open mixer for sound device '%s': %s", mixer->device,
+        snd_strerror (err));
+    goto error;
+  }
+
+  if ((err = snd_mixer_selem_register (mixer->handle, NULL, NULL)) < 0) {
+    GST_WARNING ("Cannot register mixer elements: %s", snd_strerror (err));
+    goto error;
+  }
+
+  if ((err = snd_mixer_load (mixer->handle)) < 0) {
+    GST_WARNING ("Cannot load mixer settings: %s", snd_strerror (err));
+    goto error;
+  }
+
+  snd_mixer_set_callback_private (mixer->handle, mixer);
+  snd_mixer_set_callback (mixer->handle, gst_alsa_mixer_handle_callback);
+
+  /* now get the device name, any of this is not fatal */
+  g_free (mixer->cardname);
+  if ((err = snd_ctl_open (&ctl, mixer->device, 0)) < 0) {
+    GST_WARNING ("Cannot open CTL: %s", snd_strerror (err));
+    goto no_card_name;
+  }
+
+  snd_ctl_card_info_malloc (&card_info);
+  if ((err = snd_ctl_card_info (ctl, card_info)) < 0) {
+    GST_WARNING ("Cannot get card info: %s", snd_strerror (err));
+    snd_ctl_close (ctl);
+    goto no_card_name;
+  }
+
+  mixer->cardname = g_strdup (snd_ctl_card_info_get_name (card_info));
+  GST_DEBUG ("Card name = %s", GST_STR_NULL (mixer->cardname));
+  snd_ctl_card_info_free (card_info);
+  snd_ctl_close (ctl);
+
+no_card_name:
+  if (mixer->cardname == NULL) {
+    mixer->cardname = g_strdup ("Unknown");
+    GST_DEBUG ("Cannot find card name");
+  }
+
+  GST_INFO ("Successfully opened mixer for device '%s'.", mixer->device);
+
+  return TRUE;
+
+  /* ERROR */
+open_failed:
+  {
+    GST_WARNING ("Cannot open mixer: %s", snd_strerror (err));
+    mixer->handle = NULL;
+    return FALSE;
+  }
+error:
+  {
+    snd_mixer_close (mixer->handle);
+    mixer->handle = NULL;
+    return FALSE;
+  }
+}
+
+static snd_mixer_elem_t *
+gst_alsa_mixer_find_master_mixer (GstAlsaMixer * mixer, snd_mixer_t * handle)
+{
+  snd_mixer_elem_t *element;
+  gint i, count;
+
+  count = snd_mixer_get_count (handle);
+
+  /* Check if we have a playback mixer labelled as 'Master' */
+  element = snd_mixer_first_elem (handle);
+  for (i = 0; i < count; i++) {
+    if (snd_mixer_selem_has_playback_volume (element) &&
+        strcmp (snd_mixer_selem_get_name (element), "Master") == 0) {
+      return element;
+    }
+    element = snd_mixer_elem_next (element);
+  }
+
+  /* If not, check if we have a playback mixer labelled as 'Front' */
+  element = snd_mixer_first_elem (handle);
+  for (i = 0; i < count; i++) {
+    if (snd_mixer_selem_has_playback_volume (element) &&
+        strcmp (snd_mixer_selem_get_name (element), "Front") == 0) {
+      return element;
+    }
+    element = snd_mixer_elem_next (element);
+  }
+
+  /* If not, check if we have a playback mixer labelled as 'PCM' */
+  element = snd_mixer_first_elem (handle);
+  for (i = 0; i < count; i++) {
+    if (snd_mixer_selem_has_playback_volume (element) &&
+        strcmp (snd_mixer_selem_get_name (element), "PCM") == 0) {
+      return element;
+    }
+    element = snd_mixer_elem_next (element);
+  }
+
+  /* If not, check if we have a playback mixer with both volume and switch */
+  element = snd_mixer_first_elem (handle);
+  for (i = 0; i < count; i++) {
+    if (snd_mixer_selem_has_playback_volume (element) &&
+        snd_mixer_selem_has_playback_switch (element)) {
+      return element;
+    }
+    element = snd_mixer_elem_next (element);
+  }
+
+  /* If not, take any playback mixer with a volume control */
+  element = snd_mixer_first_elem (handle);
+  for (i = 0; i < count; i++) {
+    if (snd_mixer_selem_has_playback_volume (element)) {
+      return element;
+    }
+    element = snd_mixer_elem_next (element);
+  }
+
+  /* Looks like we're out of luck ... */
+  return NULL;
+}
+
+static void
+gst_alsa_mixer_update (GstAlsaMixer * mixer, snd_mixer_elem_t * elem)
+{
+  GList *item;
+
+  g_return_if_fail (mixer != NULL);
+
+  g_static_rec_mutex_lock (mixer->rec_mutex);
+
+  for (item = mixer->tracklist; item != NULL; item = item->next) {
+    if (GST_IS_ALSA_MIXER_TRACK (item->data)) {
+      if (elem && (GST_ALSA_MIXER_TRACK (item->data)->element != elem))
+        continue;
+
+      gst_alsa_mixer_update_track (mixer, GST_ALSA_MIXER_TRACK (item->data));
+    } else if (GST_IS_ALSA_MIXER_OPTIONS (item->data)) {
+      if (elem && (GST_ALSA_MIXER_OPTIONS (item->data)->element != elem))
+        continue;
+
+      gst_alsa_mixer_update_option (mixer, GST_ALSA_MIXER_OPTIONS (item->data));
+    }
+  }
+
+  g_static_rec_mutex_unlock (mixer->rec_mutex);
+}
+
+static int
+gst_alsa_mixer_elem_handle_callback (snd_mixer_elem_t * elem, unsigned int mask)
+{
+  GstAlsaMixer *mixer =
+      (GstAlsaMixer *) snd_mixer_elem_get_callback_private (elem);
+
+  GST_LOG ("ALSA elem cb");
+
+  g_return_val_if_fail (mixer != NULL, 1);
+
+  gst_alsa_mixer_update (mixer, elem);
+
+  return 0;
+}
+
+static int
+gst_alsa_mixer_handle_callback (snd_mixer_t * handle, unsigned int mask,
+    snd_mixer_elem_t * elem)
+{
+  GstAlsaMixer *mixer =
+      (GstAlsaMixer *) snd_mixer_get_callback_private (handle);
+
+  GST_LOG ("ALSA cb");
+
+  g_return_val_if_fail (mixer != NULL, 1);
+
+  /* Hopefully won't be call recursively and will handle pending elem events */
+  snd_mixer_handle_events (mixer->handle);
+
+  gst_alsa_mixer_update (mixer, elem);
+
+  return 0;
+}
+
+static void
+gst_alsa_mixer_ensure_track_list (GstAlsaMixer * mixer)
+{
+  gint i, count;
+  snd_mixer_elem_t *element, *master;
+  GList *item;
+
+  g_return_if_fail (mixer->handle != NULL);
+
+  if (mixer->tracklist)
+    return;
+
+  g_static_rec_mutex_lock (mixer->rec_mutex);
+
+  master = gst_alsa_mixer_find_master_mixer (mixer, mixer->handle);
+
+  count = snd_mixer_get_count (mixer->handle);
+  element = snd_mixer_first_elem (mixer->handle);
+
+  /* build track list
+   *
+   * Some ALSA tracks may have playback and capture capabilities.
+   * Here we model them as two separate GStreamer tracks.
+   */
+
+  for (i = 0; i < count; i++) {
+    GstMixerTrack *play_track = NULL;
+    GstMixerTrack *cap_track = NULL;
+    const gchar *name;
+    GList *item;
+    gint samename = 0;
+
+    name = snd_mixer_selem_get_name (element);
+
+    /* prevent dup names */
+    for (item = mixer->tracklist; item != NULL; item = item->next) {
+      snd_mixer_elem_t *temp;
+
+      if (GST_IS_ALSA_MIXER_OPTIONS (item->data))
+        temp = GST_ALSA_MIXER_OPTIONS (item->data)->element;
+      else
+        temp = GST_ALSA_MIXER_TRACK (item->data)->element;
+
+      if (strcmp (name, snd_mixer_selem_get_name (temp)) == 0)
+        samename++;
+    }
+
+    GST_LOG ("[%s] probing element #%u, mixer->dir=%u", name, i, mixer->dir);
+
+    if (mixer->dir & GST_ALSA_MIXER_PLAYBACK) {
+      gboolean has_playback_switch, has_playback_volume;
+
+      has_playback_switch = snd_mixer_selem_has_playback_switch (element);
+      has_playback_volume = snd_mixer_selem_has_playback_volume (element);
+
+      GST_LOG ("[%s] PLAYBACK: has_playback_volume=%d, has_playback_switch=%d"
+          "%s", name, has_playback_volume, has_playback_switch,
+          (element == master) ? " MASTER" : "");
+
+      if (has_playback_volume) {
+        gint flags = GST_MIXER_TRACK_OUTPUT;
+
+        if (element == master)
+          flags |= GST_MIXER_TRACK_MASTER;
+
+        play_track = gst_alsa_mixer_track_new (element, samename, i,
+            flags, FALSE, NULL, FALSE);
+
+      } else if (has_playback_switch) {
+        /* simple mute switch */
+        play_track = gst_alsa_mixer_track_new (element, samename, i,
+            GST_MIXER_TRACK_OUTPUT, TRUE, NULL, FALSE);
+      }
+
+      if (snd_mixer_selem_is_enumerated (element)) {
+        GstMixerOptions *opts = gst_alsa_mixer_options_new (element, i);
+
+        GST_LOG ("[%s] is enumerated (%d)", name, i);
+        mixer->tracklist = g_list_append (mixer->tracklist, opts);
+      }
+    }
+
+    if (mixer->dir & GST_ALSA_MIXER_CAPTURE) {
+      gboolean has_capture_switch, has_common_switch;
+      gboolean has_capture_volume, has_common_volume;
+
+      has_capture_switch = snd_mixer_selem_has_capture_switch (element);
+      has_common_switch = snd_mixer_selem_has_common_switch (element);
+      has_capture_volume = snd_mixer_selem_has_capture_volume (element);
+      has_common_volume = snd_mixer_selem_has_common_volume (element);
+
+      GST_LOG ("[%s] CAPTURE: has_capture_volume=%d, has_common_volume=%d, "
+          "has_capture_switch=%d, has_common_switch=%d, play_track=%p", name,
+          has_capture_volume, has_common_volume, has_capture_switch,
+          has_common_switch, play_track);
+
+      if (has_capture_volume && !(play_track && has_common_volume)) {
+        cap_track = gst_alsa_mixer_track_new (element, samename, i,
+            GST_MIXER_TRACK_INPUT, FALSE, NULL, play_track != NULL);
+      } else if (has_capture_switch && !(play_track && has_common_switch)) {
+        cap_track = gst_alsa_mixer_track_new (element, samename, i,
+            GST_MIXER_TRACK_INPUT, TRUE, NULL, play_track != NULL);
+      }
+    }
+
+
+    if (play_track && cap_track) {
+      GST_ALSA_MIXER_TRACK (play_track)->shared_mute =
+          GST_ALSA_MIXER_TRACK (cap_track);
+      GST_ALSA_MIXER_TRACK (cap_track)->shared_mute =
+          GST_ALSA_MIXER_TRACK (play_track);
+    }
+
+    if (play_track)
+      mixer->tracklist = g_list_append (mixer->tracklist, play_track);
+
+    if (cap_track)
+      mixer->tracklist = g_list_append (mixer->tracklist, cap_track);
+
+    element = snd_mixer_elem_next (element);
+  }
+
+  for (item = mixer->tracklist; item != NULL; item = item->next) {
+    snd_mixer_elem_t *temp;
+
+    if (GST_IS_ALSA_MIXER_OPTIONS (item->data))
+      temp = GST_ALSA_MIXER_OPTIONS (item->data)->element;
+    else
+      temp = GST_ALSA_MIXER_TRACK (item->data)->element;
+
+    snd_mixer_elem_set_callback (temp, gst_alsa_mixer_elem_handle_callback);
+    snd_mixer_elem_set_callback_private (temp, mixer);
+  }
+
+  g_static_rec_mutex_unlock (mixer->rec_mutex);
+}
+
+static void
+task_monitor_alsa (gpointer data)
+{
+  struct pollfd *pfds;
+  unsigned int nfds, rnfds;
+  unsigned short revents;
+  GstAlsaMixer *mixer = (GstAlsaMixer *) data;
+
+  g_static_rec_mutex_lock (mixer->rec_mutex);
+
+  nfds = snd_mixer_poll_descriptors_count (mixer->handle);
+  if (nfds <= 0) {
+    GST_ERROR ("snd_mixer_poll_descriptors_count <= 0: %d", nfds);
+    /* FIXME: sleep ? stop monitoring ? */
+    return;
+  }
+
+  pfds = g_newa (struct pollfd, nfds + 1);
+  rnfds = snd_mixer_poll_descriptors (mixer->handle, pfds, nfds);
+  g_assert (rnfds <= nfds);
+
+  pfds[rnfds].fd = mixer->pfd[0];
+  pfds[rnfds].events = POLLIN | POLLPRI | POLLHUP | POLLERR;
+  pfds[rnfds].revents = 0;
+
+  g_static_rec_mutex_unlock (mixer->rec_mutex);
+
+  GST_LOG ("task loop");
+  poll (pfds, rnfds + 1, -1);
+
+  g_static_rec_mutex_lock (mixer->rec_mutex);
+
+  snd_mixer_poll_descriptors_revents (mixer->handle, pfds, nfds, &revents);
+  if (revents & POLLIN || revents & POLLPRI) {
+    GST_DEBUG ("Handling events");
+    snd_mixer_handle_events (mixer->handle);
+  }
+
+  g_static_rec_mutex_unlock (mixer->rec_mutex);
+}
+
+/* API */
+
+GstAlsaMixer *
+gst_alsa_mixer_new (const char *device, GstAlsaMixerDirection dir)
+{
+  GstAlsaMixer *ret = NULL;
+
+  g_return_val_if_fail (device != NULL, NULL);
+
+  ret = g_new0 (GstAlsaMixer, 1);
+
+  if (pipe (ret->pfd) == -1)
+    goto error;
+
+  ret->rec_mutex = g_new (GStaticRecMutex, 1);
+  g_static_rec_mutex_init (ret->rec_mutex);
+
+  ret->task_mutex = g_new (GStaticRecMutex, 1);
+  g_static_rec_mutex_init (ret->task_mutex);
+
+  ret->task = gst_task_create (task_monitor_alsa, ret);
+  gst_task_set_lock (ret->task, ret->task_mutex);
+
+  ret->device = g_strdup (device);
+  ret->dir = dir;
+
+  if (!gst_alsa_mixer_open (ret))
+    goto error;
+
+  if (gst_task_start (ret->task) == FALSE) {
+    GST_WARNING ("Could not start alsamixer task");
+  }
+
+  return ret;
+
+  /* ERRORS */
+error:
+  {
+    gst_alsa_mixer_free (ret);
+    return NULL;
+  }
+}
+
+void
+gst_alsa_mixer_free (GstAlsaMixer * mixer)
+{
+  g_return_if_fail (mixer != NULL);
+
+  if (mixer->task) {
+    if (write (mixer->pfd[1], "stop", 5) <= 0) {
+      GST_ERROR ("Cannot send " "stop" " to alsamixer task");
+      close (mixer->pfd[1]);
+      mixer->pfd[1] = -1;
+    }
+
+    if (gst_task_join (mixer->task) == FALSE) {
+      GST_ERROR ("Cannot join alsamixer task");
+    }
+
+    gst_object_unref (mixer->task);
+    mixer->task = NULL;
+  }
+
+  g_static_rec_mutex_free (mixer->task_mutex);
+  g_free (mixer->task_mutex);
+  mixer->task_mutex = NULL;
+
+  if (mixer->pfd[0] > 0) {
+    close (mixer->pfd[0]);
+    mixer->pfd[0] = -1;
+  }
+
+  if (mixer->pfd[1] > 0) {
+    close (mixer->pfd[1]);
+    mixer->pfd[1] = -1;
+  }
+
+  if (mixer->interface) {
+    g_object_unref (G_OBJECT (mixer->interface));
+    mixer->interface = NULL;
+  }
+
+  if (mixer->device) {
+    g_free (mixer->device);
+    mixer->device = NULL;
+  }
+
+  if (mixer->cardname) {
+    g_free (mixer->cardname);
+    mixer->cardname = NULL;
+  }
+
+  if (mixer->tracklist) {
+    g_list_foreach (mixer->tracklist, (GFunc) g_object_unref, NULL);
+    g_list_free (mixer->tracklist);
+    mixer->tracklist = NULL;
+  }
+
+  if (mixer->handle) {
+    snd_mixer_close (mixer->handle);
+    mixer->handle = NULL;
+  }
+
+  g_static_rec_mutex_free (mixer->rec_mutex);
+  g_free (mixer->rec_mutex);
+  mixer->rec_mutex = NULL;
+
+  g_free (mixer);
+}
+
+const GList *
+gst_alsa_mixer_list_tracks (GstAlsaMixer * mixer)
+{
+  g_return_val_if_fail (mixer->handle != NULL, NULL);
+
+  gst_alsa_mixer_ensure_track_list (mixer);
+
+  return (const GList *) mixer->tracklist;
+}
+
+void
+gst_alsa_mixer_get_volume (GstAlsaMixer * mixer, GstMixerTrack * track,
+    gint * volumes)
+{
+  gint i;
+  GstAlsaMixerTrack *alsa_track = GST_ALSA_MIXER_TRACK (track);
+
+  g_return_if_fail (mixer->handle != NULL);
+
+  gst_alsa_mixer_track_update (alsa_track);
+
+  if (track->flags & GST_MIXER_TRACK_OUTPUT) {  /* return playback volume */
+
+    /* Is emulated mute flag activated? */
+    if (track->flags & GST_MIXER_TRACK_MUTE &&
+        !(alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_PSWITCH)) {
+      for (i = 0; i < track->num_channels; i++)
+        volumes[i] = alsa_track->volumes[i];
+    } else {
+      for (i = 0; i < track->num_channels; i++) {
+        long tmp = 0;
+
+        snd_mixer_selem_get_playback_volume (alsa_track->element, i, &tmp);
+        alsa_track->volumes[i] = volumes[i] = (gint) tmp;
+      }
+    }
+
+  } else if (track->flags & GST_MIXER_TRACK_INPUT) {    /* return capture volume */
+
+    /* Is emulated record flag activated? */
+    if (alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_CSWITCH ||
+        track->flags & GST_MIXER_TRACK_RECORD) {
+      for (i = 0; i < track->num_channels; i++) {
+        long tmp = 0;
+
+        snd_mixer_selem_get_capture_volume (alsa_track->element, i, &tmp);
+        alsa_track->volumes[i] = volumes[i] = (gint) tmp;
+      }
+    } else {
+      for (i = 0; i < track->num_channels; i++)
+        volumes[i] = alsa_track->volumes[i];
+    }
+  }
+}
+
+static gboolean
+check_if_volumes_are_the_same (guint num_channels, gint * volumes)
+{
+  guint i;
+
+  if (num_channels <= 1)
+    return TRUE;
+
+  for (i = 1; i < num_channels; i++) {
+    if (volumes[i] != volumes[0])
+      return FALSE;
+  }
+
+  return TRUE;
+}
+
+void
+gst_alsa_mixer_set_volume (GstAlsaMixer * mixer, GstMixerTrack * track,
+    gint * volumes)
+{
+  GstAlsaMixerTrack *alsa_track = GST_ALSA_MIXER_TRACK (track);
+  gint i;
+
+  g_return_if_fail (mixer->handle != NULL);
+
+  gst_alsa_mixer_track_update (alsa_track);
+
+  if (track->flags & GST_MIXER_TRACK_OUTPUT) {
+
+    /* Is emulated mute flag activated? */
+    if (track->flags & GST_MIXER_TRACK_MUTE &&
+        !(alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_PSWITCH)) {
+      for (i = 0; i < track->num_channels; i++)
+        alsa_track->volumes[i] = volumes[i];
+    } else {
+      if (check_if_volumes_are_the_same (track->num_channels, volumes)) {
+        snd_mixer_selem_set_playback_volume_all (alsa_track->element,
+            volumes[0]);
+        for (i = 0; i < track->num_channels; i++)
+          alsa_track->volumes[i] = volumes[0];
+      } else {
+        for (i = 0; i < track->num_channels; i++) {
+          alsa_track->volumes[i] = volumes[i];
+          snd_mixer_selem_set_playback_volume (alsa_track->element, i,
+              volumes[i]);
+        }
+      }
+    }
+
+  } else if (track->flags & GST_MIXER_TRACK_INPUT) {
+
+    /* Is emulated record flag activated? */
+    if (track->flags & GST_MIXER_TRACK_RECORD ||
+        alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_CSWITCH) {
+      if (check_if_volumes_are_the_same (track->num_channels, volumes)) {
+        snd_mixer_selem_set_capture_volume_all (alsa_track->element,
+            volumes[0]);
+        for (i = 0; i < track->num_channels; i++)
+          alsa_track->volumes[i] = volumes[0];
+      } else {
+        for (i = 0; i < track->num_channels; i++) {
+          alsa_track->volumes[i] = volumes[i];
+          snd_mixer_selem_set_capture_volume (alsa_track->element, i,
+              volumes[i]);
+        }
+      }
+    } else {
+      for (i = 0; i < track->num_channels; i++)
+        alsa_track->volumes[i] = volumes[i];
+    }
+  }
+}
+
+void
+gst_alsa_mixer_set_mute (GstAlsaMixer * mixer, GstMixerTrack * track,
+    gboolean mute)
+{
+  GstAlsaMixerTrack *alsa_track = GST_ALSA_MIXER_TRACK (track);
+
+  g_return_if_fail (mixer->handle != NULL);
+
+  gst_alsa_mixer_track_update (alsa_track);
+
+  if (!!(mute) == !!(track->flags & GST_MIXER_TRACK_MUTE))
+    return;
+
+  if (mute) {
+    track->flags |= GST_MIXER_TRACK_MUTE;
+
+    if (alsa_track->shared_mute)
+      ((GstMixerTrack *) (alsa_track->shared_mute))->flags |=
+          GST_MIXER_TRACK_MUTE;
+  } else {
+    track->flags &= ~GST_MIXER_TRACK_MUTE;
+
+    if (alsa_track->shared_mute)
+      ((GstMixerTrack *) (alsa_track->shared_mute))->flags &=
+          ~GST_MIXER_TRACK_MUTE;
+  }
+
+  if (alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_PSWITCH) {
+    snd_mixer_selem_set_playback_switch_all (alsa_track->element, mute ? 0 : 1);
+  } else {
+    gint i;
+    GstAlsaMixerTrack *ctrl_track;
+
+    if ((track->flags & GST_MIXER_TRACK_INPUT)
+        && alsa_track->shared_mute != NULL)
+      ctrl_track = alsa_track->shared_mute;
+    else
+      ctrl_track = alsa_track;
+
+    for (i = 0; i < ((GstMixerTrack *) ctrl_track)->num_channels; i++) {
+      long vol =
+          mute ? ((GstMixerTrack *) ctrl_track)->min_volume : ctrl_track->
+          volumes[i];
+      snd_mixer_selem_set_playback_volume (ctrl_track->element, i, vol);
+    }
+  }
+}
+
+void
+gst_alsa_mixer_set_record (GstAlsaMixer * mixer,
+    GstMixerTrack * track, gboolean record)
+{
+  GstAlsaMixerTrack *alsa_track = GST_ALSA_MIXER_TRACK (track);
+
+  g_return_if_fail (mixer->handle != NULL);
+
+  gst_alsa_mixer_track_update (alsa_track);
+
+  if (!!(record) == !!(track->flags & GST_MIXER_TRACK_RECORD))
+    return;
+
+  if (record) {
+    track->flags |= GST_MIXER_TRACK_RECORD;
+  } else {
+    track->flags &= ~GST_MIXER_TRACK_RECORD;
+  }
+
+  if (alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_CSWITCH) {
+    snd_mixer_selem_set_capture_switch_all (alsa_track->element,
+        record ? 1 : 0);
+
+    /* update all tracks in same exlusive cswitch group */
+    if (alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_CSWITCH_EXCL) {
+      GList *item;
+
+      for (item = mixer->tracklist; item != NULL; item = item->next) {
+
+        if (GST_IS_ALSA_MIXER_TRACK (item->data)) {
+          GstAlsaMixerTrack *item_alsa_track =
+              GST_ALSA_MIXER_TRACK (item->data);
+
+          if (item_alsa_track->alsa_flags & GST_ALSA_MIXER_TRACK_CSWITCH_EXCL &&
+              item_alsa_track->capture_group == alsa_track->capture_group) {
+            gst_alsa_mixer_track_update (item_alsa_track);
+          }
+        }
+      }
+    }
+  } else {
+    gint i;
+
+    for (i = 0; i < track->num_channels; i++) {
+      long vol = record ? alsa_track->volumes[i] : track->min_volume;
+
+      snd_mixer_selem_set_capture_volume (alsa_track->element, i, vol);
+    }
+  }
+}
+
+void
+gst_alsa_mixer_set_option (GstAlsaMixer * mixer,
+    GstMixerOptions * opts, gchar * value)
+{
+  gint idx = -1, n = 0;
+  GList *item;
+  GstAlsaMixerOptions *alsa_opts = GST_ALSA_MIXER_OPTIONS (opts);
+
+  g_return_if_fail (mixer->handle != NULL);
+
+  for (item = opts->values; item != NULL; item = item->next, n++) {
+    if (!strcmp (item->data, value)) {
+      idx = n;
+      break;
+    }
+  }
+  if (idx == -1)
+    return;
+
+  snd_mixer_selem_set_enum_item (alsa_opts->element, 0, idx);
+}
+
+const gchar *
+gst_alsa_mixer_get_option (GstAlsaMixer * mixer, GstMixerOptions * opts)
+{
+  gint ret;
+  guint idx;
+  GstAlsaMixerOptions *alsa_opts = GST_ALSA_MIXER_OPTIONS (opts);
+
+  g_return_val_if_fail (mixer->handle != NULL, NULL);
+
+  ret = snd_mixer_selem_get_enum_item (alsa_opts->element, 0, &idx);
+  if (ret == 0)
+    return g_list_nth_data (opts->values, idx);
+  else
+    return snd_strerror (ret);  /* feeble attempt at error handling */
+}
+
+GstMixerFlags
+gst_alsa_mixer_get_mixer_flags (GstAlsaMixer * mixer)
+{
+  g_return_val_if_fail (mixer != NULL, GST_MIXER_FLAG_NONE);
+
+  return GST_MIXER_FLAG_AUTO_NOTIFICATIONS;
+}
+
+static void
+gst_alsa_mixer_update_option (GstAlsaMixer * mixer,
+    GstAlsaMixerOptions * alsa_opts)
+{
+  gint ret;
+  guint idx;
+  /* const */ gchar *option;
+
+  if (mixer->interface == NULL) {
+    GST_WARNING ("Cannot send update notifications, no GstMixer * given");
+    return;
+  }
+
+  ret = snd_mixer_selem_get_enum_item (alsa_opts->element, 0, &idx);
+  if (ret == 0) {
+    option = g_list_nth_data (GST_MIXER_OPTIONS (alsa_opts)->values, idx);
+    gst_mixer_option_changed (mixer->interface, GST_MIXER_OPTIONS (alsa_opts),
+        option);
+  }
+}
+
+static void
+gst_alsa_mixer_update_track (GstAlsaMixer * mixer,
+    GstAlsaMixerTrack * alsa_track)
+{
+  GstMixerTrack *track = (GstMixerTrack *) alsa_track;
+  gboolean old_mute;
+  gboolean old_record;
+  gint i, n_channels;
+  gint *old_volumes;
+
+  GST_DEBUG ("Updating track %" GST_PTR_FORMAT, alsa_track);
+
+  if (mixer->interface == NULL) {
+    GST_WARNING ("Cannot send update notifications, no GstMixer * given");
+    return;
+  }
+
+  old_mute = !!(GST_MIXER_TRACK_HAS_FLAG (track, GST_MIXER_TRACK_MUTE));
+  old_record = !!(GST_MIXER_TRACK_HAS_FLAG (track, GST_MIXER_TRACK_RECORD));
+  old_volumes = g_new (gint, track->num_channels);
+  n_channels = track->num_channels;
+  memcpy (old_volumes, alsa_track->volumes,
+      sizeof (gint) * track->num_channels);
+
+  gst_alsa_mixer_track_update (alsa_track);
+
+  if (old_record !=
+      !!(GST_MIXER_TRACK_HAS_FLAG (track, GST_MIXER_TRACK_RECORD))) {
+    gst_mixer_record_toggled (mixer->interface, track,
+        !!GST_MIXER_TRACK_HAS_FLAG (track, GST_MIXER_TRACK_RECORD));
+  }
+  if (old_mute != !!(GST_MIXER_TRACK_HAS_FLAG (track, GST_MIXER_TRACK_MUTE))) {
+    gst_mixer_mute_toggled (mixer->interface, track,
+        !!GST_MIXER_TRACK_HAS_FLAG (track, GST_MIXER_TRACK_MUTE));
+  }
+
+  n_channels = MIN (n_channels, track->num_channels);
+  for (i = 0; i < n_channels; i++) {
+    if (old_volumes[i] != alsa_track->volumes[i]) {
+      gst_mixer_volume_changed (mixer->interface, track, alsa_track->volumes);
+      break;
+    }
+  }
+  g_free (old_volumes);
+}
+
+/* utility function for gstalsamixerelement to set the interface */
+void
+_gst_alsa_mixer_set_interface (GstAlsaMixer * mixer, GstMixer * interface)
+{
+  g_return_if_fail (mixer != NULL && mixer->interface == NULL);
+  g_return_if_fail (interface != NULL);
+
+  mixer->interface = g_object_ref (G_OBJECT (interface));
+}