gstreamer/sys/v4l/v4l_calls.c

/* GStreamer
 *
 * v4l_calls.c: generic V4L calls
 *
 * Copyright (C) 2001-2002 Ronald Bultje <rbultje@ronald.bitfreak.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.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include <gst/gst.h>
#include <gst/interfaces/tuner.h>
#include <gst/interfaces/colorbalance.h>

#include "v4l_calls.h"
#include "gstv4ltuner.h"
#include "gstv4lcolorbalance.h"

#include "gstv4lsrc.h"
/* #include "gstv4lmjpegsrc.h" */
/* #include "gstv4lmjpegsink.h" */

GST_DEBUG_CATEGORY_EXTERN (v4l_debug);
#define GST_CAT_DEFAULT v4l_debug

static const char *picture_name[] = {
  "Hue",
  "Brightness",
  "Contrast",
  "Saturation",
  NULL
};

G_GNUC_UNUSED static const char *audio_name[] = {
  "Volume",
  "Mute",
  "Mode",
  NULL
};

static const char *norm_name[] = {
  "PAL",
  "NTSC",
  "SECAM",
  NULL
};

/******************************************************
 * gst_v4l_get_capabilities():
 *   get the device's capturing capabilities
 * sets v4lelement->vcap and v4lelement->vwin
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_get_capabilities (GstV4lElement * v4lelement)
{
  GST_DEBUG_OBJECT (v4lelement, "getting capabilities");
  GST_V4L_CHECK_OPEN (v4lelement);

  if (ioctl (v4lelement->video_fd, VIDIOCGCAP, &(v4lelement->vcap)) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("error getting capabilities %s of from device %s",
            g_strerror (errno), v4lelement->videodev));
    return FALSE;
  }

  if (ioctl (v4lelement->video_fd, VIDIOCGWIN, &(v4lelement->vwin)) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("error getting window properties %s of from device %s",
            g_strerror (errno), v4lelement->videodev));
    return FALSE;
  }

  return TRUE;
}

/******************************************************
 * gst_v4l_set_window_properties():
 *   set the device's capturing parameters (vwin)
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_set_window_properties (GstV4lElement * v4lelement)
{
  struct video_window vwin;

  GST_DEBUG_OBJECT (v4lelement, "setting window flags 0x%x to device %s",
      v4lelement->vwin.flags, v4lelement->videodev);
  GST_V4L_CHECK_OPEN (v4lelement);

  if (ioctl (v4lelement->video_fd, VIDIOCSWIN, &(v4lelement->vwin)) < 0) {
    GST_DEBUG_OBJECT (v4lelement,
        "could not ioctl window properties 0x%x to device %s",
        v4lelement->vwin.flags, v4lelement->videodev);
    return FALSE;
  }

  /* get it again to make sure we have it correctly */
  if (ioctl (v4lelement->video_fd, VIDIOCGWIN, &(vwin)) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("error getting window properties %s of from device %s",
            g_strerror (errno), v4lelement->videodev));
    return FALSE;
  }
  if (vwin.flags != v4lelement->vwin.flags) {
    GST_DEBUG_OBJECT (v4lelement, "set 0x%x but got 0x%x back",
        v4lelement->vwin.flags, vwin.flags);
    return FALSE;
  }

  return TRUE;
}

/******************************************************
 * gst_v4l_open():
 *   open the video device (v4lelement->videodev)
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_open (GstV4lElement * v4lelement)
{
  int num;

  GST_DEBUG_OBJECT (v4lelement, "opening device %s", v4lelement->videodev);
  GST_V4L_CHECK_NOT_OPEN (v4lelement);
  GST_V4L_CHECK_NOT_ACTIVE (v4lelement);

  /* be sure we have a device */
  if (!v4lelement->videodev) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, NOT_FOUND,
        (_("No device specified.")), (NULL));
    return FALSE;
  }

  /* open the device */
  v4lelement->video_fd = open (v4lelement->videodev, O_RDWR);
  if (!GST_V4L_IS_OPEN (v4lelement)) {
    if (errno == ENODEV || errno == ENOENT) {
      GST_ELEMENT_ERROR (v4lelement, RESOURCE, NOT_FOUND,
          (_("Device \"%s\" does not exist."), v4lelement->videodev), (NULL));
      return FALSE;
    }
    if (errno == EBUSY) {
      GST_ELEMENT_ERROR (v4lelement, RESOURCE, BUSY,
          (_("Device \"%s\" is already being used."), v4lelement->videodev),
          (NULL));
      return FALSE;
    }
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, OPEN_READ_WRITE,
        (_("Could not open device \"%s\" for reading and writing."),
            v4lelement->videodev), GST_ERROR_SYSTEM);
    return FALSE;
  }

  /* get capabilities */
  if (!gst_v4l_get_capabilities (v4lelement)) {
    close (v4lelement->video_fd);
    v4lelement->video_fd = -1;
    return FALSE;
  }

  /* device type check */
  if ((GST_IS_V4LSRC (v4lelement) &&
          !(v4lelement->vcap.type & VID_TYPE_CAPTURE))) {
/*       (GST_IS_V4LMJPEGSRC (v4lelement) && */
/*           !(v4lelement->vcap.type & VID_TYPE_MJPEG_ENCODER)) || */
/*       (GST_IS_V4LMJPEGSINK (v4lelement) && */
/*           !(v4lelement->vcap.type & VID_TYPE_MJPEG_DECODER))) { */
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Device opened, but wrong type (0x%x)", v4lelement->vcap.type));
    close (v4lelement->video_fd);
    v4lelement->video_fd = -1;
    return FALSE;
  }

  GST_INFO_OBJECT (v4lelement, "Opened device \'%s\' (\'%s\') successfully",
      v4lelement->vcap.name, v4lelement->videodev);

  /* norms + inputs, for the tuner interface */
  for (num = 0; norm_name[num] != NULL; num++) {
    GstV4lTunerNorm *v4lnorm = g_object_new (GST_TYPE_V4L_TUNER_NORM,
        NULL);
    GstTunerNorm *norm = GST_TUNER_NORM (v4lnorm);

    norm->label = g_strdup (norm_name[num]);
    if (num == 1)
      gst_value_set_fraction (&norm->framerate, 30000, 1001);
    else
      gst_value_set_fraction (&norm->framerate, 25, 1);

    v4lnorm->index = num;
    v4lelement->norms = g_list_append (v4lelement->norms, (gpointer) norm);
  }
  v4lelement->channels = gst_v4l_get_chan_names (v4lelement);

  for (num = 0; picture_name[num] != NULL; num++) {
    GstV4lColorBalanceChannel *v4lchannel =
        g_object_new (GST_TYPE_V4L_COLOR_BALANCE_CHANNEL, NULL);
    GstColorBalanceChannel *channel = GST_COLOR_BALANCE_CHANNEL (v4lchannel);

    channel->label = g_strdup (picture_name[num]);
    channel->min_value = 0;
    channel->max_value = 65535;
    v4lchannel->index = num;
    v4lelement->colors = g_list_append (v4lelement->colors, channel);
  }

  GST_DEBUG_OBJECT (v4lelement, "Setting default norm/input");
  gst_v4l_set_chan_norm (v4lelement, 0, 0);

  return TRUE;
}


/******************************************************
 * gst_v4l_close():
 *   close the video device (v4lelement->video_fd)
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_close (GstV4lElement * v4lelement)
{
  GST_DEBUG_OBJECT (v4lelement, "closing device");
  GST_V4L_CHECK_OPEN (v4lelement);
  GST_V4L_CHECK_NOT_ACTIVE (v4lelement);

  close (v4lelement->video_fd);
  v4lelement->video_fd = -1;

  g_list_foreach (v4lelement->channels, (GFunc) g_object_unref, NULL);
  g_list_free (v4lelement->channels);
  v4lelement->channels = NULL;

  g_list_foreach (v4lelement->norms, (GFunc) g_object_unref, NULL);
  g_list_free (v4lelement->norms);
  v4lelement->norms = NULL;

  g_list_foreach (v4lelement->colors, (GFunc) g_object_unref, NULL);
  g_list_free (v4lelement->colors);
  v4lelement->colors = NULL;

  return TRUE;
}


/******************************************************
 * gst_v4l_get_num_chans()
 * return value: the number of video input channels
 ******************************************************/

static gint
gst_v4l_get_num_chans (GstV4lElement * v4lelement)
{
  GST_DEBUG_OBJECT (v4lelement, "getting number of channels");
  GST_V4L_CHECK_OPEN (v4lelement);

  return v4lelement->vcap.channels;
}


/******************************************************
 * gst_v4l_get_chan_names()
 * return value: a GList containing the channel names
 ******************************************************/

GList *
gst_v4l_get_chan_names (GstV4lElement * v4lelement)
{
  struct video_channel vchan;
  GList *list = NULL;
  gint i;

  GST_DEBUG_OBJECT (v4lelement, "getting channel names");

  if (!GST_V4L_IS_OPEN (v4lelement))
    return NULL;

  for (i = 0; i < gst_v4l_get_num_chans (v4lelement); i++) {
    GstV4lTunerChannel *v4lchannel = g_object_new (GST_TYPE_V4L_TUNER_CHANNEL,
        NULL);
    GstTunerChannel *channel = GST_TUNER_CHANNEL (v4lchannel);

    vchan.channel = i;
    if (ioctl (v4lelement->video_fd, VIDIOCGCHAN, &vchan) < 0)
      return NULL;              /* memleak... */
    channel->label = g_strdup (vchan.name);
    channel->flags = GST_TUNER_CHANNEL_INPUT;
    v4lchannel->index = i;
    if (vchan.flags & VIDEO_VC_TUNER) {
      struct video_tuner vtun;
      gint n;

      for (n = 0;; n++) {
        if (n >= vchan.tuners) {
          vtun.tuner = 0;       /* default */
        } else {
          vtun.tuner = n;
          if (ioctl (v4lelement->video_fd, VIDIOCGTUNER, &vtun) < 0)
            continue;           /* no more tuners */
          if (strcmp (vtun.name, vchan.name) != 0) {
            continue;           /* not this one */
          }
        }
        /* FIXME: in the case of n >= vchan.tuners the code below accesses
         * uninitialised fields in vtun
         * Not sure if the codeblock below should go into the else above, but
         * then setting vtun.tuner=0 is a bit pointless.
         */
        v4lchannel->tuner = n;
        channel->flags |= GST_TUNER_CHANNEL_FREQUENCY;
        channel->freq_multiplicator =
            62.5 * ((vtun.flags & VIDEO_TUNER_LOW) ? 1 : 1000);
        channel->min_frequency = vtun.rangelow * channel->freq_multiplicator;
        channel->max_frequency = vtun.rangehigh * channel->freq_multiplicator;
        channel->min_signal = 0;
        channel->max_signal = 0xffff;
        break;
      }

    }
    if (vchan.flags & VIDEO_VC_AUDIO) {
      struct video_audio vaud;
      gint n;

      for (n = 0; n < v4lelement->vcap.audios; n++) {
        vaud.audio = n;
        if (ioctl (v4lelement->video_fd, VIDIOCGAUDIO, &vaud) < 0)
          continue;
        if (!strcmp (vaud.name, vchan.name)) {
          v4lchannel->audio = n;
          channel->flags |= GST_TUNER_CHANNEL_AUDIO;
          break;
        }
      }
    }
    list = g_list_append (list, (gpointer) channel);
  }

  return list;
}


/******************************************************
 * gst_v4l_get_chan_norm():
 *   get the currently active video-channel and it's
 *   norm (VIDEO_MODE_{PAL|NTSC|SECAM|AUTO})
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_get_chan_norm (GstV4lElement * v4lelement, gint * channel, gint * norm)
{
  GST_DEBUG_OBJECT (v4lelement, "getting current channel and norm");
  GST_V4L_CHECK_OPEN (v4lelement);

  if (channel)
    *channel = v4lelement->vchan.channel;
  if (norm)
    *norm = v4lelement->vchan.norm;

  return TRUE;
}


/******************************************************
 * gst_v4l_set_chan_norm():
 *   set a new active channel and it's norm
 *   (VIDEO_MODE_{PAL|NTSC|SECAM|AUTO})
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_set_chan_norm (GstV4lElement * v4lelement, gint channel, gint norm)
{
  GST_DEBUG_OBJECT (v4lelement, "setting channel = %d, norm = %d (%s)",
      channel, norm, norm_name[norm]);
  GST_V4L_CHECK_OPEN (v4lelement);
  //GST_V4L_CHECK_NOT_ACTIVE (v4lelement);

  v4lelement->vchan.channel = channel;
  v4lelement->vchan.norm = norm;

  if (ioctl (v4lelement->video_fd, VIDIOCSCHAN, &(v4lelement->vchan)) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error setting the channel/norm settings: %s", g_strerror (errno)));
    return FALSE;
  }

  if (ioctl (v4lelement->video_fd, VIDIOCGCHAN, &(v4lelement->vchan)) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting the channel/norm settings: %s", g_strerror (errno)));
    return FALSE;
  }

  return TRUE;
}


/******************************************************
 * gst_v4l_get_signal():
 *   get the current signal
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_get_signal (GstV4lElement * v4lelement, gint tunernum, guint * signal)
{
  struct video_tuner tuner;

  GST_DEBUG_OBJECT (v4lelement, "getting tuner signal");
  GST_V4L_CHECK_OPEN (v4lelement);

  tuner.tuner = tunernum;
  if (ioctl (v4lelement->video_fd, VIDIOCGTUNER, &tuner) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting tuner signal: %s", g_strerror (errno)));
    return FALSE;
  }

  *signal = tuner.signal;

  return TRUE;
}


/******************************************************
 * gst_v4l_get_frequency():
 *   get the current frequency
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_get_frequency (GstV4lElement * v4lelement,
    gint tunernum, gulong * frequency)
{
  struct video_tuner vtun;
  GstTunerChannel *channel;

  GST_DEBUG_OBJECT (v4lelement, "getting tuner frequency");
  GST_V4L_CHECK_OPEN (v4lelement);

  channel = gst_tuner_get_channel (GST_TUNER (v4lelement));

  /* check that this is the current input */
  vtun.tuner = tunernum;
  if (ioctl (v4lelement->video_fd, VIDIOCGTUNER, &vtun) < 0)
    return FALSE;
  if (strcmp (vtun.name, v4lelement->vchan.name))
    return FALSE;

  if (ioctl (v4lelement->video_fd, VIDIOCGFREQ, frequency) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting tuner frequency: %s", g_strerror (errno)));
    return FALSE;
  }

  *frequency = *frequency * channel->freq_multiplicator;

  return TRUE;
}


/******************************************************
 * gst_v4l_set_frequency():
 *   set frequency
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_set_frequency (GstV4lElement * v4lelement,
    gint tunernum, gulong frequency)
{
  struct video_tuner vtun;
  GstTunerChannel *channel;

  GST_DEBUG_OBJECT (v4lelement, "setting tuner frequency to %lu", frequency);
  GST_V4L_CHECK_OPEN (v4lelement);

  channel = gst_tuner_get_channel (GST_TUNER (v4lelement));

  /* check that this is the current input */
  vtun.tuner = tunernum;
  if (ioctl (v4lelement->video_fd, VIDIOCGTUNER, &vtun) < 0)
    return FALSE;
  if (strcmp (vtun.name, v4lelement->vchan.name))
    return FALSE;

  frequency = frequency / channel->freq_multiplicator;

  if (ioctl (v4lelement->video_fd, VIDIOCSFREQ, &frequency) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error setting tuner frequency: %s", g_strerror (errno)));
    return FALSE;
  }

  return TRUE;
}


/******************************************************
 * gst_v4l_get_picture():
 *   get a picture value
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_get_picture (GstV4lElement * v4lelement,
    GstV4lPictureType type, gint * value)
{
  struct video_picture vpic;

  GST_DEBUG_OBJECT (v4lelement, "getting picture property type %d (%s)", type,
      picture_name[type]);
  GST_V4L_CHECK_OPEN (v4lelement);

  if (ioctl (v4lelement->video_fd, VIDIOCGPICT, &vpic) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting picture parameters: %s", g_strerror (errno)));
    return FALSE;
  }

  switch (type) {
    case V4L_PICTURE_HUE:
      *value = vpic.hue;
      break;
    case V4L_PICTURE_BRIGHTNESS:
      *value = vpic.brightness;
      break;
    case V4L_PICTURE_CONTRAST:
      *value = vpic.contrast;
      break;
    case V4L_PICTURE_SATURATION:
      *value = vpic.colour;
      break;
    default:
      GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
          ("Error getting picture parameters: unknown type %d", type));
      return FALSE;
  }

  return TRUE;
}


/******************************************************
 * gst_v4l_set_picture():
 *   set a picture value
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_set_picture (GstV4lElement * v4lelement,
    GstV4lPictureType type, gint value)
{
  struct video_picture vpic;

  GST_DEBUG_OBJECT (v4lelement, "setting picture type %d (%s) to value %d",
      type, picture_name[type], value);
  GST_V4L_CHECK_OPEN (v4lelement);

  if (ioctl (v4lelement->video_fd, VIDIOCGPICT, &vpic) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting picture parameters: %s", g_strerror (errno)));
    return FALSE;
  }

  switch (type) {
    case V4L_PICTURE_HUE:
      vpic.hue = value;
      break;
    case V4L_PICTURE_BRIGHTNESS:
      vpic.brightness = value;
      break;
    case V4L_PICTURE_CONTRAST:
      vpic.contrast = value;
      break;
    case V4L_PICTURE_SATURATION:
      vpic.colour = value;
      break;
    default:
      GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
          ("Error setting picture parameters: unknown type %d", type));
      return FALSE;
  }

  if (ioctl (v4lelement->video_fd, VIDIOCSPICT, &vpic) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error setting picture parameters: %s", g_strerror (errno)));
    return FALSE;
  }

  return TRUE;
}


/******************************************************
 * gst_v4l_get_audio():
 *   get some audio value
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_get_audio (GstV4lElement * v4lelement,
    gint audionum, GstV4lAudioType type, gint * value)
{
  struct video_audio vau;

  GST_DEBUG_OBJECT (v4lelement, "getting audio parameter type %d (%s)", type,
      audio_name[type]);
  GST_V4L_CHECK_OPEN (v4lelement);

  vau.audio = audionum;
  if (ioctl (v4lelement->video_fd, VIDIOCGAUDIO, &vau) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting audio parameters: %s", g_strerror (errno)));
    return FALSE;
  }

  switch (type) {
    case V4L_AUDIO_MUTE:
      *value = (vau.flags & VIDEO_AUDIO_MUTE);
      break;
    case V4L_AUDIO_VOLUME:
      *value = vau.volume;
      break;
    case V4L_AUDIO_MODE:
      *value = vau.mode;
      break;
    default:
      GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
          ("Error getting audio parameters: unknown type %d", type));
      return FALSE;
  }

  return TRUE;
}


/******************************************************
 * gst_v4l_set_audio():
 *   set some audio value
 * return value: TRUE on success, FALSE on error
 ******************************************************/

gboolean
gst_v4l_set_audio (GstV4lElement * v4lelement,
    gint audionum, GstV4lAudioType type, gint value)
{
  struct video_audio vau;

  GST_DEBUG_OBJECT (v4lelement,
      "setting audio parameter type %d (%s) to value %d", type,
      audio_name[type], value);
  GST_V4L_CHECK_OPEN (v4lelement);

  vau.audio = audionum;
  if (ioctl (v4lelement->video_fd, VIDIOCGAUDIO, &vau) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error getting audio parameters: %s", g_strerror (errno)));
    return FALSE;
  }

  switch (type) {
    case V4L_AUDIO_MUTE:
      if (!(vau.flags & VIDEO_AUDIO_MUTABLE)) {
        GST_ELEMENT_ERROR (v4lelement, CORE, NOT_IMPLEMENTED, (NULL),
            ("Error setting audio mute: (un)setting mute is not supported"));
        return FALSE;
      }
      if (value)
        vau.flags |= VIDEO_AUDIO_MUTE;
      else
        vau.flags &= ~VIDEO_AUDIO_MUTE;
      break;
    case V4L_AUDIO_VOLUME:
      if (!(vau.flags & VIDEO_AUDIO_VOLUME)) {
        GST_ELEMENT_ERROR (v4lelement, CORE, NOT_IMPLEMENTED, (NULL),
            ("Error setting audio volume: setting volume is not supported"));
        return FALSE;
      }
      vau.volume = value;
      break;
    case V4L_AUDIO_MODE:
      vau.mode = value;
      break;
    default:
      GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
          ("Error setting audio parameters: unknown type %d", type));
      return FALSE;
  }

  if (ioctl (v4lelement->video_fd, VIDIOCSAUDIO, &vau) < 0) {
    GST_ELEMENT_ERROR (v4lelement, RESOURCE, SETTINGS, (NULL),
        ("Error setting audio parameters: %s", g_strerror (errno)));
    return FALSE;
  }

  return TRUE;
}