gstreamer/sys/v4l2/gstv4l2object.c

/* GStreamer
 *
 * Copyright (C) 2001-2002 Ronald Bultje <rbultje@ronald.bitfreak.net>
 *               2006 Edgard Lima <edgard.lima@indt.org.br>
 *
 * gstv4l2object.c: base class for V4L2 elements
 *
 * 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/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#ifdef HAVE_GUDEV
#include <gudev/gudev.h>
#endif

#include "v4l2_calls.h"
#include "gstv4l2tuner.h"
#if 0                           /* overlay is still not implemented #ifdef HAVE_XVIDEO */
#include "gstv4l2xoverlay.h"
#endif
#include "gstv4l2colorbalance.h"

#include "gst/gst-i18n-plugin.h"


GST_DEBUG_CATEGORY_EXTERN (v4l2_debug);
#define GST_CAT_DEFAULT v4l2_debug


#define DEFAULT_PROP_DEVICE_NAME 	NULL
#define DEFAULT_PROP_DEVICE_FD          -1
#define DEFAULT_PROP_FLAGS              0
#define DEFAULT_PROP_NORM               NULL
#define DEFAULT_PROP_CHANNEL            NULL
#define DEFAULT_PROP_FREQUENCY          0

enum
{
  PROP_0,
  V4L2_STD_OBJECT_PROPS,
};

const GList *
gst_v4l2_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) {
    list = g_list_append (NULL, g_object_class_find_property (klass, "device"));
  }

  GST_CLASS_UNLOCK (GST_OBJECT_CLASS (klass));

  return list;
}

static gboolean init = FALSE;
static GList *devices = NULL;

#ifdef HAVE_GUDEV
static gboolean
gst_v4l2_class_probe_devices_with_udev (GstElementClass * klass, gboolean check,
    GList ** klass_devices)
{
  GUdevClient *client = NULL;
  GList *item;

  if (!check) {
    while (devices) {
      gchar *device = devices->data;
      devices = g_list_remove (devices, device);
      g_free (device);
    }

    GST_INFO ("Enumerating video4linux devices from udev");
    client = g_udev_client_new (NULL);
    if (!client) {
      GST_WARNING ("Failed to initialize gudev client");
      goto finish;
    }

    item = g_udev_client_query_by_subsystem (client, "video4linux");
    while (item) {
      GUdevDevice *device = item->data;
      gchar *devnode = g_strdup (g_udev_device_get_device_file (device));
      gint api = g_udev_device_get_property_as_int (device, "ID_V4L_VERSION");
      GST_INFO ("Found new device: %s, API: %d", devnode, api);
      /* Append v4l2 devices only. If api is 0 probably v4l_id has
         been stripped out of the current udev installation, append
         anyway */
      if (api == 0) {
        GST_WARNING
            ("Couldn't retrieve ID_V4L_VERSION, silly udev installation?");
      }
      if ((api == 2 || api == 0)) {
        devices = g_list_append (devices, devnode);
      } else {
        g_free (devnode);
      }
      g_object_unref (device);
      item = item->next;
    }
    g_list_free (item);
    init = TRUE;
  }

finish:
  if (client) {
    g_object_unref (client);
  }

  *klass_devices = devices;

  return init;
}
#endif /* HAVE_GUDEV */

static gboolean
gst_v4l2_class_probe_devices (GstElementClass * klass, gboolean check,
    GList ** klass_devices)
{
  if (!check) {
    const gchar *dev_base[] = { "/dev/video", "/dev/v4l2/video", NULL };
    gint base, n, fd;

    while (devices) {
      gchar *device = devices->data;
      devices = g_list_remove (devices, device);
      g_free (device);
    }

    /*
     * detect /dev entries
     */
    for (n = 0; n < 64; n++) {
      for (base = 0; dev_base[base] != NULL; base++) {
        struct stat s;
        gchar *device = g_strdup_printf ("%s%d",
            dev_base[base],
            n);

        /*
         * does the /dev/ entry exist at all?
         */
        if (stat (device, &s) == 0) {
          /*
           * yes: is a device attached?
           */
          if (S_ISCHR (s.st_mode)) {

            if ((fd = open (device, O_RDWR | O_NONBLOCK)) > 0 || errno == EBUSY) {
              if (fd > 0)
                close (fd);

              devices = g_list_append (devices, device);
              break;
            }
          }
        }
        g_free (device);
      }
    }
    init = TRUE;
  }

  *klass_devices = devices;

  return init;
}

void
gst_v4l2_probe_probe_property (GstPropertyProbe * probe,
    guint prop_id, const GParamSpec * pspec, GList ** klass_devices)
{
  GstElementClass *klass = GST_ELEMENT_GET_CLASS (probe);

  switch (prop_id) {
    case PROP_DEVICE:
#ifdef HAVE_GUDEV
      if (!gst_v4l2_class_probe_devices_with_udev (klass, FALSE, klass_devices))
        gst_v4l2_class_probe_devices (klass, FALSE, klass_devices);
#else /* !HAVE_GUDEV */
      gst_v4l2_class_probe_devices (klass, FALSE, klass_devices);
#endif /* HAVE_GUDEV */
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
      break;
  }
}

gboolean
gst_v4l2_probe_needs_probe (GstPropertyProbe * probe,
    guint prop_id, const GParamSpec * pspec, GList ** klass_devices)
{
  GstElementClass *klass = GST_ELEMENT_GET_CLASS (probe);
  gboolean ret = FALSE;

  switch (prop_id) {
    case PROP_DEVICE:
#ifdef HAVE_GUDEV
      ret =
          !gst_v4l2_class_probe_devices_with_udev (klass, FALSE, klass_devices);
#else /* !HAVE_GUDEV */
      ret = !gst_v4l2_class_probe_devices (klass, TRUE, klass_devices);
#endif /* HAVE_GUDEV */
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
      break;
  }
  return ret;
}

static GValueArray *
gst_v4l2_class_list_devices (GstElementClass * klass, GList ** klass_devices)
{
  GValueArray *array;
  GValue value = { 0 };
  GList *item;

  if (!*klass_devices)
    return NULL;

  array = g_value_array_new (g_list_length (*klass_devices));
  item = *klass_devices;
  g_value_init (&value, G_TYPE_STRING);
  while (item) {
    gchar *device = item->data;

    g_value_set_string (&value, device);
    g_value_array_append (array, &value);

    item = item->next;
  }
  g_value_unset (&value);

  return array;
}

GValueArray *
gst_v4l2_probe_get_values (GstPropertyProbe * probe,
    guint prop_id, const GParamSpec * pspec, GList ** klass_devices)
{
  GstElementClass *klass = GST_ELEMENT_GET_CLASS (probe);
  GValueArray *array = NULL;

  switch (prop_id) {
    case PROP_DEVICE:
      array = gst_v4l2_class_list_devices (klass, klass_devices);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
      break;
  }

  return array;
}

#define GST_TYPE_V4L2_DEVICE_FLAGS (gst_v4l2_device_get_type ())
static GType
gst_v4l2_device_get_type (void)
{
  static GType v4l2_device_type = 0;

  if (v4l2_device_type == 0) {
    static const GFlagsValue values[] = {
      {V4L2_CAP_VIDEO_CAPTURE, "Device supports video capture", "capture"},
      {V4L2_CAP_VIDEO_OUTPUT, "Device supports video playback", "output"},
      {V4L2_CAP_VIDEO_OVERLAY, "Device supports video overlay", "overlay"},

      {V4L2_CAP_VBI_CAPTURE, "Device supports the VBI capture", "vbi-capture"},
      {V4L2_CAP_VBI_OUTPUT, "Device supports the VBI output", "vbi-output"},

      {V4L2_CAP_TUNER, "Device has a tuner or modulator", "tuner"},
      {V4L2_CAP_AUDIO, "Device has audio inputs or outputs", "audio"},

      {0, NULL, NULL}
    };

    v4l2_device_type =
        g_flags_register_static ("GstV4l2DeviceTypeFlags", values);
  }

  return v4l2_device_type;
}

void
gst_v4l2_object_install_properties_helper (GObjectClass * gobject_class,
    const char *default_device)
{
  g_object_class_install_property (gobject_class, PROP_DEVICE,
      g_param_spec_string ("device", "Device", "Device location",
          default_device, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_DEVICE_NAME,
      g_param_spec_string ("device-name", "Device name",
          "Name of the device", DEFAULT_PROP_DEVICE_NAME,
          G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_DEVICE_FD,
      g_param_spec_int ("device-fd", "File descriptor",
          "File descriptor of the device", -1, G_MAXINT, DEFAULT_PROP_DEVICE_FD,
          G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_FLAGS,
      g_param_spec_flags ("flags", "Flags", "Device type flags",
          GST_TYPE_V4L2_DEVICE_FLAGS, DEFAULT_PROP_FLAGS,
          G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
}

GstV4l2Object *
gst_v4l2_object_new (GstElement * element,
    enum v4l2_buf_type type,
    const char *default_device,
    GstV4l2GetInOutFunction get_in_out_func,
    GstV4l2SetInOutFunction set_in_out_func,
    GstV4l2UpdateFpsFunction update_fps_func)
{
  GstV4l2Object *v4l2object;

  /*
   * some default values
   */
  v4l2object = g_new0 (GstV4l2Object, 1);

  v4l2object->type = type;
  v4l2object->formats = NULL;

  v4l2object->element = element;
  v4l2object->get_in_out_func = get_in_out_func;
  v4l2object->set_in_out_func = set_in_out_func;
  v4l2object->update_fps_func = update_fps_func;

  v4l2object->video_fd = -1;
  v4l2object->poll = gst_poll_new (TRUE);
  v4l2object->buffer = NULL;
  v4l2object->videodev = g_strdup (default_device);

  v4l2object->norms = NULL;
  v4l2object->channels = NULL;
  v4l2object->colors = NULL;

  v4l2object->xwindow_id = 0;

  return v4l2object;
}

static gboolean gst_v4l2_object_clear_format_list (GstV4l2Object * v4l2object);


void
gst_v4l2_object_destroy (GstV4l2Object * v4l2object)
{
  g_return_if_fail (v4l2object != NULL);

  if (v4l2object->videodev)
    g_free (v4l2object->videodev);

  if (v4l2object->poll)
    gst_poll_free (v4l2object->poll);

  if (v4l2object->channel)
    g_free (v4l2object->channel);

  if (v4l2object->norm)
    g_free (v4l2object->norm);

  if (v4l2object->formats) {
    gst_v4l2_object_clear_format_list (v4l2object);
  }

  g_free (v4l2object);
}


static gboolean
gst_v4l2_object_clear_format_list (GstV4l2Object * v4l2object)
{
  g_slist_foreach (v4l2object->formats, (GFunc) g_free, NULL);
  g_slist_free (v4l2object->formats);
  v4l2object->formats = NULL;

  return TRUE;
}


gboolean
gst_v4l2_object_set_property_helper (GstV4l2Object * v4l2object,
    guint prop_id, const GValue * value, GParamSpec * pspec)
{
  switch (prop_id) {
    case PROP_DEVICE:
      g_free (v4l2object->videodev);
      v4l2object->videodev = g_value_dup_string (value);
      break;
#if 0
    case PROP_NORM:
      if (GST_V4L2_IS_OPEN (v4l2object)) {
        GstTuner *tuner = GST_TUNER (v4l2object->element);
        GstTunerNorm *norm = gst_tuner_find_norm_by_name (tuner,
            (gchar *) g_value_get_string (value));

        if (norm) {
          /* like gst_tuner_set_norm (tuner, norm)
             without g_object_notify */
          gst_v4l2_tuner_set_norm (v4l2object, norm);
        }
      } else {
        g_free (v4l2object->norm);
        v4l2object->norm = g_value_dup_string (value);
      }
      break;
    case PROP_CHANNEL:
      if (GST_V4L2_IS_OPEN (v4l2object)) {
        GstTuner *tuner = GST_TUNER (v4l2object->element);
        GstTunerChannel *channel = gst_tuner_find_channel_by_name (tuner,
            (gchar *) g_value_get_string (value));

        if (channel) {
          /* like gst_tuner_set_channel (tuner, channel)
             without g_object_notify */
          gst_v4l2_tuner_set_channel (v4l2object, channel);
        }
      } else {
        g_free (v4l2object->channel);
        v4l2object->channel = g_value_dup_string (value);
      }
      break;
    case PROP_FREQUENCY:
      if (GST_V4L2_IS_OPEN (v4l2object)) {
        GstTuner *tuner = GST_TUNER (v4l2object->element);
        GstTunerChannel *channel = gst_tuner_get_channel (tuner);

        if (channel &&
            GST_TUNER_CHANNEL_HAS_FLAG (channel, GST_TUNER_CHANNEL_FREQUENCY)) {
          /* like
             gst_tuner_set_frequency (tuner, channel, g_value_get_ulong (value))
             without g_object_notify */
          gst_v4l2_tuner_set_frequency (v4l2object, channel,
              g_value_get_ulong (value));
        }
      } else {
        v4l2object->frequency = g_value_get_ulong (value);
      }
      break;
#endif
    default:
      return FALSE;
      break;
  }
  return TRUE;
}


gboolean
gst_v4l2_object_get_property_helper (GstV4l2Object * v4l2object,
    guint prop_id, GValue * value, GParamSpec * pspec)
{
  switch (prop_id) {
    case PROP_DEVICE:
      g_value_set_string (value, v4l2object->videodev);
      break;
    case PROP_DEVICE_NAME:
    {
      const guchar *new = NULL;

      if (GST_V4L2_IS_OPEN (v4l2object)) {
        new = v4l2object->vcap.card;
      } else if (gst_v4l2_open (v4l2object)) {
        new = v4l2object->vcap.card;
        gst_v4l2_close (v4l2object);
      }
      g_value_set_string (value, (gchar *) new);
      break;
    }
    case PROP_DEVICE_FD:
    {
      if (GST_V4L2_IS_OPEN (v4l2object))
        g_value_set_int (value, v4l2object->video_fd);
      else
        g_value_set_int (value, DEFAULT_PROP_DEVICE_FD);
      break;
    }
    case PROP_FLAGS:
    {
      guint flags = 0;

      if (GST_V4L2_IS_OPEN (v4l2object)) {
        flags |= v4l2object->vcap.capabilities &
            (V4L2_CAP_VIDEO_CAPTURE |
            V4L2_CAP_VIDEO_OUTPUT |
            V4L2_CAP_VIDEO_OVERLAY |
            V4L2_CAP_VBI_CAPTURE |
            V4L2_CAP_VBI_OUTPUT | V4L2_CAP_TUNER | V4L2_CAP_AUDIO);
      }
      g_value_set_flags (value, flags);
      break;
    }
    default:
      return FALSE;
      break;
  }
  return TRUE;
}

static void
gst_v4l2_set_defaults (GstV4l2Object * v4l2object)
{
  GstTunerNorm *norm = NULL;
  GstTunerChannel *channel = NULL;
  GstTuner *tuner;

  if (!GST_IS_TUNER (v4l2object->element))
    return;

  tuner = GST_TUNER (v4l2object->element);

  if (v4l2object->norm)
    norm = gst_tuner_find_norm_by_name (tuner, v4l2object->norm);
  if (norm) {
    gst_tuner_set_norm (tuner, norm);
  } else {
    norm =
        GST_TUNER_NORM (gst_tuner_get_norm (GST_TUNER (v4l2object->element)));
    if (norm) {
      g_free (v4l2object->norm);
      v4l2object->norm = g_strdup (norm->label);
      gst_tuner_norm_changed (tuner, norm);
    }
  }

  if (v4l2object->channel)
    channel = gst_tuner_find_channel_by_name (tuner, v4l2object->channel);
  if (channel) {
    gst_tuner_set_channel (tuner, channel);
  } else {
    channel =
        GST_TUNER_CHANNEL (gst_tuner_get_channel (GST_TUNER
            (v4l2object->element)));
    if (channel) {
      g_free (v4l2object->channel);
      v4l2object->channel = g_strdup (channel->label);
      gst_tuner_channel_changed (tuner, channel);
    }
  }

  if (channel
      && GST_TUNER_CHANNEL_HAS_FLAG (channel, GST_TUNER_CHANNEL_FREQUENCY)) {
    if (v4l2object->frequency != 0) {
      gst_tuner_set_frequency (tuner, channel, v4l2object->frequency);
    } else {
      v4l2object->frequency = gst_tuner_get_frequency (tuner, channel);
      if (v4l2object->frequency == 0) {
        /* guess */
        gst_tuner_set_frequency (tuner, channel, 1000);
      } else {
      }
    }
  }
}

gboolean
gst_v4l2_object_start (GstV4l2Object * v4l2object)
{
  if (gst_v4l2_open (v4l2object))
    gst_v4l2_set_defaults (v4l2object);
  else
    return FALSE;

#if 0                           /* overlay is still not implemented #ifdef HAVE_XVIDEO */
  gst_v4l2_xoverlay_start (v4l2object);
#endif

  return TRUE;
}

gboolean
gst_v4l2_object_stop (GstV4l2Object * v4l2object)
{
#if 0                           /* overlay is still not implemented #ifdef HAVE_XVIDEO */
  gst_v4l2_xoverlay_stop (v4l2object);
#endif

  if (!gst_v4l2_close (v4l2object))
    return FALSE;

  if (v4l2object->formats) {
    gst_v4l2_object_clear_format_list (v4l2object);
  }

  return TRUE;
}


/*
 * common format / caps utilities:
 */
typedef struct
{
  guint32 format;
  gboolean dimensions;
} GstV4L2FormatDesc;

static const GstV4L2FormatDesc gst_v4l2_formats[] = {
  /* from Linux 2.6.15 videodev2.h */
  {V4L2_PIX_FMT_RGB332, TRUE},
  {V4L2_PIX_FMT_RGB555, TRUE},
  {V4L2_PIX_FMT_RGB565, TRUE},
  {V4L2_PIX_FMT_RGB555X, TRUE},
  {V4L2_PIX_FMT_RGB565X, TRUE},
  {V4L2_PIX_FMT_BGR24, TRUE},
  {V4L2_PIX_FMT_RGB24, TRUE},
  {V4L2_PIX_FMT_BGR32, TRUE},
  {V4L2_PIX_FMT_RGB32, TRUE},
  {V4L2_PIX_FMT_GREY, TRUE},
  {V4L2_PIX_FMT_YVU410, TRUE},
  {V4L2_PIX_FMT_YVU420, TRUE},
  {V4L2_PIX_FMT_YUYV, TRUE},
  {V4L2_PIX_FMT_UYVY, TRUE},
  {V4L2_PIX_FMT_YUV422P, TRUE},
  {V4L2_PIX_FMT_YUV411P, TRUE},
  {V4L2_PIX_FMT_Y41P, TRUE},

  /* two planes -- one Y, one Cr + Cb interleaved  */
  {V4L2_PIX_FMT_NV12, TRUE},
  {V4L2_PIX_FMT_NV21, TRUE},

  /*  The following formats are not defined in the V4L2 specification */
  {V4L2_PIX_FMT_YUV410, TRUE},
  {V4L2_PIX_FMT_YUV420, TRUE},
  {V4L2_PIX_FMT_YYUV, TRUE},
  {V4L2_PIX_FMT_HI240, TRUE},

  /* see http://www.siliconimaging.com/RGB%20Bayer.htm */
#ifdef V4L2_PIX_FMT_SBGGR8
  {V4L2_PIX_FMT_SBGGR8, TRUE},
#endif

  /* compressed formats */
  {V4L2_PIX_FMT_MJPEG, TRUE},
  {V4L2_PIX_FMT_JPEG, TRUE},
  {V4L2_PIX_FMT_DV, TRUE},
  {V4L2_PIX_FMT_MPEG, FALSE},

  /*  Vendor-specific formats   */
  {V4L2_PIX_FMT_WNVA, TRUE},

#ifdef V4L2_PIX_FMT_SN9C10X
  {V4L2_PIX_FMT_SN9C10X, TRUE},
#endif
#ifdef V4L2_PIX_FMT_PWC1
  {V4L2_PIX_FMT_PWC1, TRUE},
#endif
#ifdef V4L2_PIX_FMT_PWC2
  {V4L2_PIX_FMT_PWC2, TRUE},
#endif
#ifdef V4L2_PIX_FMT_YVYU
  {V4L2_PIX_FMT_YVYU, TRUE},
#endif
};

#define GST_V4L2_FORMAT_COUNT (G_N_ELEMENTS (gst_v4l2_formats))


static struct v4l2_fmtdesc *
gst_v4l2_object_get_format_from_fourcc (GstV4l2Object * v4l2object,
    guint32 fourcc)
{
  struct v4l2_fmtdesc *fmt;
  GSList *walk;

  if (fourcc == 0)
    return NULL;

  walk = gst_v4l2_object_get_format_list (v4l2object);
  while (walk) {
    fmt = (struct v4l2_fmtdesc *) walk->data;
    if (fmt->pixelformat == fourcc)
      return fmt;
    /* special case for jpeg */
    if ((fmt->pixelformat == V4L2_PIX_FMT_MJPEG && fourcc == V4L2_PIX_FMT_JPEG)
        || (fmt->pixelformat == V4L2_PIX_FMT_JPEG
            && fourcc == V4L2_PIX_FMT_MJPEG)) {
      return fmt;
    }
    walk = g_slist_next (walk);
  }

  return NULL;
}



/* complete made up ranking, the values themselves are meaningless */
#define YUV_BASE_RANK     1000
#define JPEG_BASE_RANK     500
#define DV_BASE_RANK       200
#define RGB_BASE_RANK      100
#define YUV_ODD_BASE_RANK   50
#define RGB_ODD_BASE_RANK   25
#define BAYER_BASE_RANK     15
#define S910_BASE_RANK      10
#define GREY_BASE_RANK       5
#define PWC_BASE_RANK        1

/* This flag is already used by libv4l2 although
 * it was added to the Linux kernel in 2.6.32
 */
#ifndef V4L2_FMT_FLAG_EMULATED
#define V4L2_FMT_FLAG_EMULATED 0x0002
#endif

static gint
gst_v4l2_object_format_get_rank (const struct v4l2_fmtdesc *fmt)
{
  guint32 fourcc = fmt->pixelformat;
  gboolean emulated = ((fmt->flags & V4L2_FMT_FLAG_EMULATED) != 0);
  gint rank = 0;

  switch (fourcc) {
    case V4L2_PIX_FMT_MJPEG:
      rank = JPEG_BASE_RANK;
      break;
    case V4L2_PIX_FMT_JPEG:
      rank = JPEG_BASE_RANK + 1;
      break;
    case V4L2_PIX_FMT_MPEG:    /* MPEG          */
      rank = JPEG_BASE_RANK + 2;
      break;

    case V4L2_PIX_FMT_RGB332:
    case V4L2_PIX_FMT_RGB555:
    case V4L2_PIX_FMT_RGB555X:
    case V4L2_PIX_FMT_RGB565:
    case V4L2_PIX_FMT_RGB565X:
      rank = RGB_ODD_BASE_RANK;
      break;

    case V4L2_PIX_FMT_RGB24:
    case V4L2_PIX_FMT_BGR24:
      rank = RGB_BASE_RANK - 1;
      break;

    case V4L2_PIX_FMT_RGB32:
    case V4L2_PIX_FMT_BGR32:
      rank = RGB_BASE_RANK;
      break;

    case V4L2_PIX_FMT_GREY:    /*  8  Greyscale     */
      rank = GREY_BASE_RANK;
      break;

    case V4L2_PIX_FMT_NV12:    /* 12  Y/CbCr 4:2:0  */
    case V4L2_PIX_FMT_NV21:    /* 12  Y/CrCb 4:2:0  */
    case V4L2_PIX_FMT_YYUV:    /* 16  YUV 4:2:2     */
    case V4L2_PIX_FMT_HI240:   /*  8  8-bit color   */
      rank = YUV_ODD_BASE_RANK;
      break;

    case V4L2_PIX_FMT_YVU410:  /* YVU9,  9 bits per pixel */
      rank = YUV_BASE_RANK + 3;
      break;
    case V4L2_PIX_FMT_YUV410:  /* YUV9,  9 bits per pixel */
      rank = YUV_BASE_RANK + 2;
      break;
    case V4L2_PIX_FMT_YUV420:  /* I420, 12 bits per pixel */
      rank = YUV_BASE_RANK + 7;
      break;
    case V4L2_PIX_FMT_YUYV:    /* YUY2, 16 bits per pixel */
      rank = YUV_BASE_RANK + 10;
      break;
    case V4L2_PIX_FMT_YVU420:  /* YV12, 12 bits per pixel */
      rank = YUV_BASE_RANK + 6;
      break;
    case V4L2_PIX_FMT_UYVY:    /* UYVY, 16 bits per pixel */
      rank = YUV_BASE_RANK + 9;
      break;
    case V4L2_PIX_FMT_Y41P:    /* Y41P, 12 bits per pixel */
      rank = YUV_BASE_RANK + 5;
      break;
    case V4L2_PIX_FMT_YUV411P: /* Y41B, 12 bits per pixel */
      rank = YUV_BASE_RANK + 4;
      break;
    case V4L2_PIX_FMT_YUV422P: /* Y42B, 16 bits per pixel */
      rank = YUV_BASE_RANK + 8;
      break;

    case V4L2_PIX_FMT_DV:
      rank = DV_BASE_RANK;
      break;

    case V4L2_PIX_FMT_WNVA:    /* Winnov hw compres */
      rank = 0;
      break;

#ifdef V4L2_PIX_FMT_SBGGR8
    case V4L2_PIX_FMT_SBGGR8:
      rank = BAYER_BASE_RANK;
      break;
#endif

#ifdef V4L2_PIX_FMT_SN9C10X
    case V4L2_PIX_FMT_SN9C10X:
      rank = S910_BASE_RANK;
      break;
#endif

#ifdef V4L2_PIX_FMT_PWC1
    case V4L2_PIX_FMT_PWC1:
      rank = PWC_BASE_RANK;
      break;
#endif
#ifdef V4L2_PIX_FMT_PWC2
    case V4L2_PIX_FMT_PWC2:
      rank = PWC_BASE_RANK;
      break;
#endif

    default:
      rank = 0;
      break;
  }

  /* All ranks are below 1<<15 so a shift by 15
   * will a) make all non-emulated formats larger
   * than emulated and b) will not overflow
   */
  if (!emulated)
    rank <<= 15;

  return rank;
}



static gint
format_cmp_func (gconstpointer a, gconstpointer b)
{
  const struct v4l2_fmtdesc *fa = a;
  const struct v4l2_fmtdesc *fb = b;

  if (fa->pixelformat == fb->pixelformat)
    return 0;

  return gst_v4l2_object_format_get_rank (fa) -
      gst_v4l2_object_format_get_rank (fb);
}

/******************************************************
 * gst_v4l2_object_fill_format_list():
 *   create list of supported capture formats
 * return value: TRUE on success, FALSE on error
 ******************************************************/
static gboolean
gst_v4l2_object_fill_format_list (GstV4l2Object * v4l2object)
{
  gint n;
  struct v4l2_fmtdesc *format;

  GST_DEBUG_OBJECT (v4l2object->element, "getting src format enumerations");

  /* format enumeration */
  for (n = 0;; n++) {
    format = g_new0 (struct v4l2_fmtdesc, 1);

    format->index = n;
    format->type = v4l2object->type;

    if (v4l2_ioctl (v4l2object->video_fd, VIDIOC_ENUM_FMT, format) < 0) {
      if (errno == EINVAL) {
        g_free (format);
        break;                  /* end of enumeration */
      } else {
        goto failed;
      }
    }

    GST_LOG_OBJECT (v4l2object->element, "index:       %u", format->index);
    GST_LOG_OBJECT (v4l2object->element, "type:        %d", format->type);
    GST_LOG_OBJECT (v4l2object->element, "flags:       %08x", format->flags);
    GST_LOG_OBJECT (v4l2object->element, "description: '%s'",
        format->description);
    GST_LOG_OBJECT (v4l2object->element, "pixelformat: %" GST_FOURCC_FORMAT,
        GST_FOURCC_ARGS (format->pixelformat));

    /* sort formats according to our preference;  we do this, because caps
     * are probed in the order the formats are in the list, and the order of
     * formats in the final probed caps matters for things like fixation */
    v4l2object->formats = g_slist_insert_sorted (v4l2object->formats, format,
        (GCompareFunc) format_cmp_func);
  }

  GST_DEBUG_OBJECT (v4l2object->element, "got %d format(s)", n);

  return TRUE;

  /* ERRORS */
failed:
  {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, SETTINGS,
        (_("Failed to enumerate possible video formats device '%s' can work with"), v4l2object->videodev), ("Failed to get number %d in pixelformat enumeration for %s. (%d - %s)", n, v4l2object->videodev, errno, g_strerror (errno)));
    g_free (format);
    return FALSE;
  }
}

/*
 * Get the list of supported capture formats, a list of
 * <code>struct v4l2_fmtdesc</code>.
 */
GSList *
gst_v4l2_object_get_format_list (GstV4l2Object * v4l2object)
{
  if (!v4l2object->formats)
    gst_v4l2_object_fill_format_list (v4l2object);
  return v4l2object->formats;
}


GstStructure *
gst_v4l2_object_v4l2fourcc_to_structure (guint32 fourcc)
{
  GstStructure *structure = NULL;

  switch (fourcc) {
    case V4L2_PIX_FMT_MJPEG:   /* Motion-JPEG */
    case V4L2_PIX_FMT_JPEG:    /* JFIF JPEG */
      structure = gst_structure_new ("image/jpeg", NULL);
      break;
    case V4L2_PIX_FMT_RGB332:
    case V4L2_PIX_FMT_RGB555:
    case V4L2_PIX_FMT_RGB555X:
    case V4L2_PIX_FMT_RGB565:
    case V4L2_PIX_FMT_RGB565X:
    case V4L2_PIX_FMT_RGB24:
    case V4L2_PIX_FMT_BGR24:
    case V4L2_PIX_FMT_RGB32:
    case V4L2_PIX_FMT_BGR32:{
      guint depth = 0, bpp = 0;

      gint endianness = 0;

      guint32 r_mask = 0, b_mask = 0, g_mask = 0;

      switch (fourcc) {
        case V4L2_PIX_FMT_RGB332:
          bpp = depth = 8;
          endianness = G_BYTE_ORDER;    /* 'like, whatever' */
          r_mask = 0xe0;
          g_mask = 0x1c;
          b_mask = 0x03;
          break;
        case V4L2_PIX_FMT_RGB555:
        case V4L2_PIX_FMT_RGB555X:
          bpp = 16;
          depth = 15;
          endianness =
              fourcc == V4L2_PIX_FMT_RGB555X ? G_BIG_ENDIAN : G_LITTLE_ENDIAN;
          r_mask = 0x7c00;
          g_mask = 0x03e0;
          b_mask = 0x001f;
          break;
        case V4L2_PIX_FMT_RGB565:
        case V4L2_PIX_FMT_RGB565X:
          bpp = depth = 16;
          endianness =
              fourcc == V4L2_PIX_FMT_RGB565X ? G_BIG_ENDIAN : G_LITTLE_ENDIAN;
          r_mask = 0xf800;
          g_mask = 0x07e0;
          b_mask = 0x001f;
          break;
        case V4L2_PIX_FMT_RGB24:
          bpp = depth = 24;
          endianness = G_BIG_ENDIAN;
          r_mask = 0xff0000;
          g_mask = 0x00ff00;
          b_mask = 0x0000ff;
          break;
        case V4L2_PIX_FMT_BGR24:
          bpp = depth = 24;
          endianness = G_BIG_ENDIAN;
          r_mask = 0x0000ff;
          g_mask = 0x00ff00;
          b_mask = 0xff0000;
          break;
        case V4L2_PIX_FMT_RGB32:
          bpp = depth = 32;
          endianness = G_BIG_ENDIAN;
          r_mask = 0xff000000;
          g_mask = 0x00ff0000;
          b_mask = 0x0000ff00;
          break;
        case V4L2_PIX_FMT_BGR32:
          bpp = depth = 32;
          endianness = G_BIG_ENDIAN;
          r_mask = 0x000000ff;
          g_mask = 0x0000ff00;
          b_mask = 0x00ff0000;
          break;
        default:
          g_assert_not_reached ();
          break;
      }
      structure = gst_structure_new ("video/x-raw-rgb",
          "bpp", G_TYPE_INT, bpp,
          "depth", G_TYPE_INT, depth,
          "red_mask", G_TYPE_INT, r_mask,
          "green_mask", G_TYPE_INT, g_mask,
          "blue_mask", G_TYPE_INT, b_mask,
          "endianness", G_TYPE_INT, endianness, NULL);
      break;
    }
    case V4L2_PIX_FMT_GREY:    /*  8  Greyscale     */
      structure = gst_structure_new ("video/x-raw-gray",
          "bpp", G_TYPE_INT, 8, NULL);
      break;
    case V4L2_PIX_FMT_YYUV:    /* 16  YUV 4:2:2     */
    case V4L2_PIX_FMT_HI240:   /*  8  8-bit color   */
      /* FIXME: get correct fourccs here */
      break;
    case V4L2_PIX_FMT_NV12:    /* 12  Y/CbCr 4:2:0  */
    case V4L2_PIX_FMT_NV21:    /* 12  Y/CrCb 4:2:0  */
    case V4L2_PIX_FMT_YVU410:
    case V4L2_PIX_FMT_YUV410:
    case V4L2_PIX_FMT_YUV420:  /* I420/IYUV */
    case V4L2_PIX_FMT_YUYV:
    case V4L2_PIX_FMT_YVU420:
    case V4L2_PIX_FMT_UYVY:
    case V4L2_PIX_FMT_Y41P:
    case V4L2_PIX_FMT_YUV422P:
#ifdef V4L2_PIX_FMT_YVYU
    case V4L2_PIX_FMT_YVYU:
#endif
    case V4L2_PIX_FMT_YUV411P:{
      guint32 fcc = 0;

      switch (fourcc) {
        case V4L2_PIX_FMT_NV12:
          fcc = GST_MAKE_FOURCC ('N', 'V', '1', '2');
          break;
        case V4L2_PIX_FMT_NV21:
          fcc = GST_MAKE_FOURCC ('N', 'V', '2', '1');
          break;
        case V4L2_PIX_FMT_YVU410:
          fcc = GST_MAKE_FOURCC ('Y', 'V', 'U', '9');
          break;
        case V4L2_PIX_FMT_YUV410:
          fcc = GST_MAKE_FOURCC ('Y', 'U', 'V', '9');
          break;
        case V4L2_PIX_FMT_YUV420:
          fcc = GST_MAKE_FOURCC ('I', '4', '2', '0');
          break;
        case V4L2_PIX_FMT_YUYV:
          fcc = GST_MAKE_FOURCC ('Y', 'U', 'Y', '2');
          break;
        case V4L2_PIX_FMT_YVU420:
          fcc = GST_MAKE_FOURCC ('Y', 'V', '1', '2');
          break;
        case V4L2_PIX_FMT_UYVY:
          fcc = GST_MAKE_FOURCC ('U', 'Y', 'V', 'Y');
          break;
        case V4L2_PIX_FMT_Y41P:
          fcc = GST_MAKE_FOURCC ('Y', '4', '1', 'P');
          break;
        case V4L2_PIX_FMT_YUV411P:
          fcc = GST_MAKE_FOURCC ('Y', '4', '1', 'B');
          break;
        case V4L2_PIX_FMT_YUV422P:
          fcc = GST_MAKE_FOURCC ('Y', '4', '2', 'B');
          break;
#ifdef V4L2_PIX_FMT_YVYU
        case V4L2_PIX_FMT_YVYU:
          fcc = GST_MAKE_FOURCC ('Y', 'V', 'Y', 'U');
          break;
#endif
        default:
          g_assert_not_reached ();
          break;
      }
      structure = gst_structure_new ("video/x-raw-yuv",
          "format", GST_TYPE_FOURCC, fcc, NULL);
      break;
    }
    case V4L2_PIX_FMT_DV:
      structure =
          gst_structure_new ("video/x-dv", "systemstream", G_TYPE_BOOLEAN, TRUE,
          NULL);
      break;
    case V4L2_PIX_FMT_MPEG:    /* MPEG          */
      structure = gst_structure_new ("video/mpegts", NULL);
      break;
    case V4L2_PIX_FMT_WNVA:    /* Winnov hw compres */
      break;
#ifdef V4L2_PIX_FMT_SBGGR8
    case V4L2_PIX_FMT_SBGGR8:
      structure = gst_structure_new ("video/x-raw-bayer", NULL);
      break;
#endif
#ifdef V4L2_PIX_FMT_SN9C10X
    case V4L2_PIX_FMT_SN9C10X:
      structure = gst_structure_new ("video/x-sonix", NULL);
      break;
#endif
#ifdef V4L2_PIX_FMT_PWC1
    case V4L2_PIX_FMT_PWC1:
      structure = gst_structure_new ("video/x-pwc1", NULL);
      break;
#endif
#ifdef V4L2_PIX_FMT_PWC2
    case V4L2_PIX_FMT_PWC2:
      structure = gst_structure_new ("video/x-pwc2", NULL);
      break;
#endif
    default:
      GST_DEBUG ("Unknown fourcc 0x%08x %" GST_FOURCC_FORMAT,
          fourcc, GST_FOURCC_ARGS (fourcc));
      break;
  }

  return structure;
}



GstCaps *
gst_v4l2_object_get_all_caps (void)
{
  static GstCaps *caps = NULL;

  if (caps == NULL) {
    GstStructure *structure;

    guint i;

    caps = gst_caps_new_empty ();
    for (i = 0; i < GST_V4L2_FORMAT_COUNT; i++) {
      structure =
          gst_v4l2_object_v4l2fourcc_to_structure (gst_v4l2_formats[i].format);
      if (structure) {
        if (gst_v4l2_formats[i].dimensions) {
          gst_structure_set (structure,
              "width", GST_TYPE_INT_RANGE, 1, GST_V4L2_MAX_SIZE,
              "height", GST_TYPE_INT_RANGE, 1, GST_V4L2_MAX_SIZE,
              "framerate", GST_TYPE_FRACTION_RANGE, 0, 1, 100, 1, NULL);
        }
        gst_caps_append_structure (caps, structure);
      }
    }
  }

  return gst_caps_ref (caps);
}


/* collect data for the given caps
 * @caps: given input caps
 * @format: location for the v4l format
 * @w/@h: location for width and height
 * @fps_n/@fps_d: location for framerate
 * @size: location for expected size of the frame or 0 if unknown
 */
gboolean
gst_v4l2_object_get_caps_info (GstV4l2Object * v4l2object, GstCaps * caps,
    struct v4l2_fmtdesc ** format, gint * w, gint * h, guint * fps_n,
    guint * fps_d, guint * size)
{
  GstStructure *structure;
  const GValue *framerate;
  guint32 fourcc;
  const gchar *mimetype;
  guint outsize;

  /* default unknown values */
  fourcc = 0;
  outsize = 0;

  structure = gst_caps_get_structure (caps, 0);

  mimetype = gst_structure_get_name (structure);

  if (strcmp (mimetype, "video/mpegts") == 0) {
    fourcc = V4L2_PIX_FMT_MPEG;
    outsize = 8192;
    *fps_n = 0;
    *fps_d = 1;
    goto done;
  }

  if (!gst_structure_get_int (structure, "width", w))
    return FALSE;

  if (!gst_structure_get_int (structure, "height", h))
    return FALSE;

  framerate = gst_structure_get_value (structure, "framerate");
  if (!framerate)
    return FALSE;

  *fps_n = gst_value_get_fraction_numerator (framerate);
  *fps_d = gst_value_get_fraction_denominator (framerate);

  if (!strcmp (mimetype, "video/x-raw-yuv")) {
    gst_structure_get_fourcc (structure, "format", &fourcc);

    switch (fourcc) {
      case GST_MAKE_FOURCC ('I', '4', '2', '0'):
      case GST_MAKE_FOURCC ('I', 'Y', 'U', 'V'):
        fourcc = V4L2_PIX_FMT_YUV420;
        outsize = GST_ROUND_UP_4 (*w) * GST_ROUND_UP_2 (*h);
        outsize += 2 * ((GST_ROUND_UP_8 (*w) / 2) * (GST_ROUND_UP_2 (*h) / 2));
        break;
      case GST_MAKE_FOURCC ('Y', 'U', 'Y', '2'):
        fourcc = V4L2_PIX_FMT_YUYV;
        outsize = (GST_ROUND_UP_2 (*w) * 2) * *h;
        break;
      case GST_MAKE_FOURCC ('Y', '4', '1', 'P'):
        fourcc = V4L2_PIX_FMT_Y41P;
        outsize = (GST_ROUND_UP_2 (*w) * 2) * *h;
        break;
      case GST_MAKE_FOURCC ('U', 'Y', 'V', 'Y'):
        fourcc = V4L2_PIX_FMT_UYVY;
        outsize = (GST_ROUND_UP_2 (*w) * 2) * *h;
        break;
      case GST_MAKE_FOURCC ('Y', 'V', '1', '2'):
        fourcc = V4L2_PIX_FMT_YVU420;
        outsize = GST_ROUND_UP_4 (*w) * GST_ROUND_UP_2 (*h);
        outsize += 2 * ((GST_ROUND_UP_8 (*w) / 2) * (GST_ROUND_UP_2 (*h) / 2));
        break;
      case GST_MAKE_FOURCC ('Y', '4', '1', 'B'):
        fourcc = V4L2_PIX_FMT_YUV411P;
        outsize = GST_ROUND_UP_4 (*w) * *h;
        outsize += 2 * ((GST_ROUND_UP_8 (*w) / 4) * *h);
        break;
      case GST_MAKE_FOURCC ('Y', '4', '2', 'B'):
        fourcc = V4L2_PIX_FMT_YUV422P;
        outsize = GST_ROUND_UP_4 (*w) * *h;
        outsize += 2 * ((GST_ROUND_UP_8 (*w) / 2) * *h);
        break;
      case GST_MAKE_FOURCC ('N', 'V', '1', '2'):
        fourcc = V4L2_PIX_FMT_NV12;
        outsize = GST_ROUND_UP_4 (*w) * GST_ROUND_UP_2 (*h);
        outsize += (GST_ROUND_UP_4 (*w) * *h) / 2;
        break;
      case GST_MAKE_FOURCC ('N', 'V', '2', '1'):
        fourcc = V4L2_PIX_FMT_NV21;
        outsize = GST_ROUND_UP_4 (*w) * GST_ROUND_UP_2 (*h);
        outsize += (GST_ROUND_UP_4 (*w) * *h) / 2;
        break;
#ifdef V4L2_PIX_FMT_YVYU
      case GST_MAKE_FOURCC ('Y', 'V', 'Y', 'U'):
        fourcc = V4L2_PIX_FMT_YVYU;
        outsize = (GST_ROUND_UP_2 (*w) * 2) * *h;
        break;
#endif
    }
  } else if (!strcmp (mimetype, "video/x-raw-rgb")) {
    gint depth, endianness, r_mask;

    gst_structure_get_int (structure, "depth", &depth);
    gst_structure_get_int (structure, "endianness", &endianness);
    gst_structure_get_int (structure, "red_mask", &r_mask);

    switch (depth) {
      case 8:
        fourcc = V4L2_PIX_FMT_RGB332;
        break;
      case 15:
        fourcc = (endianness == G_LITTLE_ENDIAN) ?
            V4L2_PIX_FMT_RGB555 : V4L2_PIX_FMT_RGB555X;
        break;
      case 16:
        fourcc = (endianness == G_LITTLE_ENDIAN) ?
            V4L2_PIX_FMT_RGB565 : V4L2_PIX_FMT_RGB565X;
        break;
      case 24:
        fourcc = (r_mask == 0xFF) ? V4L2_PIX_FMT_BGR24 : V4L2_PIX_FMT_RGB24;
        break;
      case 32:
        fourcc = (r_mask == 0xFF) ? V4L2_PIX_FMT_BGR32 : V4L2_PIX_FMT_RGB32;
        break;
    }
  } else if (strcmp (mimetype, "video/x-dv") == 0) {
    fourcc = V4L2_PIX_FMT_DV;
  } else if (strcmp (mimetype, "image/jpeg") == 0) {
    fourcc = V4L2_PIX_FMT_JPEG;
#ifdef V4L2_PIX_FMT_SBGGR8
  } else if (strcmp (mimetype, "video/x-raw-bayer") == 0) {
    fourcc = V4L2_PIX_FMT_SBGGR8;
#endif
#ifdef V4L2_PIX_FMT_SN9C10X
  } else if (strcmp (mimetype, "video/x-sonix") == 0) {
    fourcc = V4L2_PIX_FMT_SN9C10X;
#endif
#ifdef V4L2_PIX_FMT_PWC1
  } else if (strcmp (mimetype, "video/x-pwc1") == 0) {
    fourcc = V4L2_PIX_FMT_PWC1;
#endif
#ifdef V4L2_PIX_FMT_PWC2
  } else if (strcmp (mimetype, "video/x-pwc2") == 0) {
    fourcc = V4L2_PIX_FMT_PWC2;
#endif
  } else if (strcmp (mimetype, "video/x-raw-gray") == 0) {
    fourcc = V4L2_PIX_FMT_GREY;
  }

  if (fourcc == 0)
    return FALSE;

done:
  *format = gst_v4l2_object_get_format_from_fourcc (v4l2object, fourcc);
  *size = outsize;

  return TRUE;
}



/* The frame interval enumeration code first appeared in Linux 2.6.19. */
#ifdef VIDIOC_ENUM_FRAMEINTERVALS
static GstStructure *
gst_v4l2_object_probe_caps_for_format_and_size (GstV4l2Object * v4l2object,
    guint32 pixelformat,
    guint32 width, guint32 height, const GstStructure * template)
{
  gint fd = v4l2object->video_fd;
  struct v4l2_frmivalenum ival;
  guint32 num, denom;
  GstStructure *s;
  GValue rates = { 0, };

  memset (&ival, 0, sizeof (struct v4l2_frmivalenum));
  ival.index = 0;
  ival.pixel_format = pixelformat;
  ival.width = width;
  ival.height = height;

  GST_LOG_OBJECT (v4l2object->element,
      "get frame interval for %ux%u, %" GST_FOURCC_FORMAT, width, height,
      GST_FOURCC_ARGS (pixelformat));

  /* keep in mind that v4l2 gives us frame intervals (durations); we invert the
   * fraction to get framerate */
  if (v4l2_ioctl (fd, VIDIOC_ENUM_FRAMEINTERVALS, &ival) < 0)
    goto enum_frameintervals_failed;

  if (ival.type == V4L2_FRMIVAL_TYPE_DISCRETE) {
    GValue rate = { 0, };

    g_value_init (&rates, GST_TYPE_LIST);
    g_value_init (&rate, GST_TYPE_FRACTION);

    do {
      num = ival.discrete.numerator;
      denom = ival.discrete.denominator;

      if (num > G_MAXINT || denom > G_MAXINT) {
        /* let us hope we don't get here... */
        num >>= 1;
        denom >>= 1;
      }

      GST_LOG_OBJECT (v4l2object->element, "adding discrete framerate: %d/%d",
          denom, num);

      /* swap to get the framerate */
      gst_value_set_fraction (&rate, denom, num);
      gst_value_list_append_value (&rates, &rate);

      ival.index++;
    } while (v4l2_ioctl (fd, VIDIOC_ENUM_FRAMEINTERVALS, &ival) >= 0);
  } else if (ival.type == V4L2_FRMIVAL_TYPE_STEPWISE) {
    GValue min = { 0, };
    GValue step = { 0, };
    GValue max = { 0, };
    gboolean added = FALSE;
    guint32 minnum, mindenom;
    guint32 maxnum, maxdenom;

    g_value_init (&rates, GST_TYPE_LIST);

    g_value_init (&min, GST_TYPE_FRACTION);
    g_value_init (&step, GST_TYPE_FRACTION);
    g_value_init (&max, GST_TYPE_FRACTION);

    /* get the min */
    minnum = ival.stepwise.min.numerator;
    mindenom = ival.stepwise.min.denominator;
    if (minnum > G_MAXINT || mindenom > G_MAXINT) {
      minnum >>= 1;
      mindenom >>= 1;
    }
    GST_LOG_OBJECT (v4l2object->element, "stepwise min frame interval: %d/%d",
        minnum, mindenom);
    gst_value_set_fraction (&min, minnum, mindenom);

    /* get the max */
    maxnum = ival.stepwise.max.numerator;
    maxdenom = ival.stepwise.max.denominator;
    if (maxnum > G_MAXINT || maxdenom > G_MAXINT) {
      maxnum >>= 1;
      maxdenom >>= 1;
    }

    GST_LOG_OBJECT (v4l2object->element, "stepwise max frame interval: %d/%d",
        maxnum, maxdenom);
    gst_value_set_fraction (&max, maxnum, maxdenom);

    /* get the step */
    num = ival.stepwise.step.numerator;
    denom = ival.stepwise.step.denominator;
    if (num > G_MAXINT || denom > G_MAXINT) {
      num >>= 1;
      denom >>= 1;
    }

    if (num == 0 || denom == 0) {
      /* in this case we have a wrong fraction or no step, set the step to max
       * so that we only add the min value in the loop below */
      num = maxnum;
      denom = maxdenom;
    }

    /* since we only have gst_value_fraction_subtract and not add, negate the
     * numerator */
    GST_LOG_OBJECT (v4l2object->element, "stepwise step frame interval: %d/%d",
        num, denom);
    gst_value_set_fraction (&step, -num, denom);

    while (gst_value_compare (&min, &max) <= 0) {
      GValue rate = { 0, };

      num = gst_value_get_fraction_numerator (&min);
      denom = gst_value_get_fraction_denominator (&min);
      GST_LOG_OBJECT (v4l2object->element, "adding stepwise framerate: %d/%d",
          denom, num);

      /* invert to get the framerate */
      g_value_init (&rate, GST_TYPE_FRACTION);
      gst_value_set_fraction (&rate, denom, num);
      gst_value_list_append_value (&rates, &rate);
      added = TRUE;

      /* we're actually adding because step was negated above. This is because
       * there is no _add function... */
      if (!gst_value_fraction_subtract (&min, &min, &step)) {
        GST_WARNING_OBJECT (v4l2object->element, "could not step fraction!");
        break;
      }
    }
    if (!added) {
      /* no range was added, leave the default range from the template */
      GST_WARNING_OBJECT (v4l2object->element,
          "no range added, leaving default");
      g_value_unset (&rates);
    }
  } else if (ival.type == V4L2_FRMIVAL_TYPE_CONTINUOUS) {
    guint32 maxnum, maxdenom;

    g_value_init (&rates, GST_TYPE_FRACTION_RANGE);

    num = ival.stepwise.min.numerator;
    denom = ival.stepwise.min.denominator;
    if (num > G_MAXINT || denom > G_MAXINT) {
      num >>= 1;
      denom >>= 1;
    }

    maxnum = ival.stepwise.max.numerator;
    maxdenom = ival.stepwise.max.denominator;
    if (maxnum > G_MAXINT || maxdenom > G_MAXINT) {
      maxnum >>= 1;
      maxdenom >>= 1;
    }

    GST_LOG_OBJECT (v4l2object->element,
        "continuous frame interval %d/%d to %d/%d", maxdenom, maxnum, denom,
        num);

    gst_value_set_fraction_range_full (&rates, maxdenom, maxnum, denom, num);
  } else {
    goto unknown_type;
  }

return_data:
  s = gst_structure_copy (template);
  gst_structure_set (s, "width", G_TYPE_INT, (gint) width,
      "height", G_TYPE_INT, (gint) height, NULL);

  if (G_IS_VALUE (&rates)) {
    /* only change the framerate on the template when we have a valid probed new
     * value */
    gst_structure_set_value (s, "framerate", &rates);
    g_value_unset (&rates);
  } else {
    gst_structure_set (s, "framerate", GST_TYPE_FRACTION_RANGE, 0, 1, 100, 1,
        NULL);
  }
  return s;

  /* ERRORS */
enum_frameintervals_failed:
  {
    GST_DEBUG_OBJECT (v4l2object->element,
        "Unable to enumerate intervals for %" GST_FOURCC_FORMAT "@%ux%u",
        GST_FOURCC_ARGS (pixelformat), width, height);
    goto return_data;
  }
unknown_type:
  {
    /* I don't see how this is actually an error, we ignore the format then */
    GST_WARNING_OBJECT (v4l2object->element,
        "Unknown frame interval type at %" GST_FOURCC_FORMAT "@%ux%u: %u",
        GST_FOURCC_ARGS (pixelformat), width, height, ival.type);
    return NULL;
  }
}
#endif /* defined VIDIOC_ENUM_FRAMEINTERVALS */

#ifdef VIDIOC_ENUM_FRAMESIZES
static gint
sort_by_frame_size (GstStructure * s1, GstStructure * s2)
{
  int w1, h1, w2, h2;

  gst_structure_get_int (s1, "width", &w1);
  gst_structure_get_int (s1, "height", &h1);
  gst_structure_get_int (s2, "width", &w2);
  gst_structure_get_int (s2, "height", &h2);

  /* I think it's safe to assume that this won't overflow for a while */
  return ((w2 * h2) - (w1 * h1));
}
#endif

static gboolean
gst_v4l2_object_get_nearest_size (GstV4l2Object * v4l2object,
    guint32 pixelformat, gint * width, gint * height);

GstCaps *
gst_v4l2_object_probe_caps_for_format (GstV4l2Object * v4l2object,
    guint32 pixelformat, const GstStructure * template)
{
  GstCaps *ret = gst_caps_new_empty ();
  GstStructure *tmp;

#ifdef VIDIOC_ENUM_FRAMESIZES
  gint fd = v4l2object->video_fd;
  struct v4l2_frmsizeenum size;
  GList *results = NULL;
  guint32 w, h;

  if (pixelformat == GST_MAKE_FOURCC ('M', 'P', 'E', 'G'))
    return gst_caps_new_simple ("video/mpegts", NULL);

  memset (&size, 0, sizeof (struct v4l2_frmsizeenum));
  size.index = 0;
  size.pixel_format = pixelformat;

  GST_DEBUG_OBJECT (v4l2object->element, "Enumerating frame sizes");

  if (v4l2_ioctl (fd, VIDIOC_ENUM_FRAMESIZES, &size) < 0)
    goto enum_framesizes_failed;

  if (size.type == V4L2_FRMSIZE_TYPE_DISCRETE) {
    do {
      GST_LOG_OBJECT (v4l2object->element, "got discrete frame size %dx%d",
          size.discrete.width, size.discrete.height);

      w = MIN (size.discrete.width, G_MAXINT);
      h = MIN (size.discrete.height, G_MAXINT);

      if (w && h) {
        tmp =
            gst_v4l2_object_probe_caps_for_format_and_size (v4l2object,
            pixelformat, w, h, template);

        if (tmp)
          results = g_list_prepend (results, tmp);
      }

      size.index++;
    } while (v4l2_ioctl (fd, VIDIOC_ENUM_FRAMESIZES, &size) >= 0);
    GST_DEBUG_OBJECT (v4l2object->element,
        "done iterating discrete frame sizes");
  } else if (size.type == V4L2_FRMSIZE_TYPE_STEPWISE) {
    GST_DEBUG_OBJECT (v4l2object->element, "we have stepwise frame sizes:");
    GST_DEBUG_OBJECT (v4l2object->element, "min width:   %d",
        size.stepwise.min_width);
    GST_DEBUG_OBJECT (v4l2object->element, "min height:  %d",
        size.stepwise.min_height);
    GST_DEBUG_OBJECT (v4l2object->element, "max width:   %d",
        size.stepwise.max_width);
    GST_DEBUG_OBJECT (v4l2object->element, "min height:  %d",
        size.stepwise.max_height);
    GST_DEBUG_OBJECT (v4l2object->element, "step width:  %d",
        size.stepwise.step_width);
    GST_DEBUG_OBJECT (v4l2object->element, "step height: %d",
        size.stepwise.step_height);

    for (w = size.stepwise.min_width, h = size.stepwise.min_height;
        w < size.stepwise.max_width && h < size.stepwise.max_height;
        w += size.stepwise.step_width, h += size.stepwise.step_height) {
      if (w == 0 || h == 0)
        continue;

      tmp =
          gst_v4l2_object_probe_caps_for_format_and_size (v4l2object,
          pixelformat, w, h, template);

      if (tmp)
        results = g_list_prepend (results, tmp);
    }
    GST_DEBUG_OBJECT (v4l2object->element,
        "done iterating stepwise frame sizes");
  } else if (size.type == V4L2_FRMSIZE_TYPE_CONTINUOUS) {
    guint32 maxw, maxh;

    GST_DEBUG_OBJECT (v4l2object->element, "we have continuous frame sizes:");
    GST_DEBUG_OBJECT (v4l2object->element, "min width:   %d",
        size.stepwise.min_width);
    GST_DEBUG_OBJECT (v4l2object->element, "min height:  %d",
        size.stepwise.min_height);
    GST_DEBUG_OBJECT (v4l2object->element, "max width:   %d",
        size.stepwise.max_width);
    GST_DEBUG_OBJECT (v4l2object->element, "min height:  %d",
        size.stepwise.max_height);

    w = MAX (size.stepwise.min_width, 1);
    h = MAX (size.stepwise.min_height, 1);
    maxw = MIN (size.stepwise.max_width, G_MAXINT);
    maxh = MIN (size.stepwise.max_height, G_MAXINT);

    tmp =
        gst_v4l2_object_probe_caps_for_format_and_size (v4l2object, pixelformat,
        w, h, template);
    if (tmp) {
      gst_structure_set (tmp, "width", GST_TYPE_INT_RANGE, (gint) w,
          (gint) maxw, "height", GST_TYPE_INT_RANGE, (gint) h, (gint) maxh,
          NULL);

      /* no point using the results list here, since there's only one struct */
      gst_caps_append_structure (ret, tmp);
    }
  } else {
    goto unknown_type;
  }

  /* we use an intermediary list to store and then sort the results of the
   * probing because we can't make any assumptions about the order in which
   * the driver will give us the sizes, but we want the final caps to contain
   * the results starting with the highest resolution and having the lowest
   * resolution last, since order in caps matters for things like fixation. */
  results = g_list_sort (results, (GCompareFunc) sort_by_frame_size);
  while (results != NULL) {
    gst_caps_append_structure (ret, GST_STRUCTURE (results->data));
    results = g_list_delete_link (results, results);
  }

  if (gst_caps_is_empty (ret))
    goto enum_framesizes_no_results;

  return ret;

  /* ERRORS */
enum_framesizes_failed:
  {
    /* I don't see how this is actually an error */
    GST_DEBUG_OBJECT (v4l2object->element,
        "Failed to enumerate frame sizes for pixelformat %" GST_FOURCC_FORMAT
        " (%s)", GST_FOURCC_ARGS (pixelformat), g_strerror (errno));
    goto default_frame_sizes;
  }
enum_framesizes_no_results:
  {
    /* it's possible that VIDIOC_ENUM_FRAMESIZES is defined but the driver in
     * question doesn't actually support it yet */
    GST_DEBUG_OBJECT (v4l2object->element,
        "No results for pixelformat %" GST_FOURCC_FORMAT
        " enumerating frame sizes, trying fallback",
        GST_FOURCC_ARGS (pixelformat));
    goto default_frame_sizes;
  }
unknown_type:
  {
    GST_WARNING_OBJECT (v4l2object->element,
        "Unknown frame sizeenum type for pixelformat %" GST_FOURCC_FORMAT
        ": %u", GST_FOURCC_ARGS (pixelformat), size.type);
    goto default_frame_sizes;
  }
default_frame_sizes:
#endif /* defined VIDIOC_ENUM_FRAMESIZES */
  {
    gint min_w, max_w, min_h, max_h, fix_num = 0, fix_denom = 0;

    /* This code is for Linux < 2.6.19 */
    min_w = min_h = 1;
    max_w = max_h = GST_V4L2_MAX_SIZE;
    if (!gst_v4l2_object_get_nearest_size (v4l2object, pixelformat, &min_w,
            &min_h)) {
      GST_WARNING_OBJECT (v4l2object->element,
          "Could not probe minimum capture size for pixelformat %"
          GST_FOURCC_FORMAT, GST_FOURCC_ARGS (pixelformat));
    }
    if (!gst_v4l2_object_get_nearest_size (v4l2object, pixelformat, &max_w,
            &max_h)) {
      GST_WARNING_OBJECT (v4l2object->element,
          "Could not probe maximum capture size for pixelformat %"
          GST_FOURCC_FORMAT, GST_FOURCC_ARGS (pixelformat));
    }

    /* Since we can't get framerate directly, try to use the current norm */
    if (v4l2object->norm && v4l2object->norms) {
      GList *norms;
      GstTunerNorm *norm = NULL;

      for (norms = v4l2object->norms; norms != NULL; norms = norms->next) {
        norm = (GstTunerNorm *) norms->data;
        if (!strcmp (norm->label, v4l2object->norm))
          break;
      }
      /* If it's possible, set framerate to that (discrete) value */
      if (norm) {
        fix_num = gst_value_get_fraction_numerator (&norm->framerate);
        fix_denom = gst_value_get_fraction_denominator (&norm->framerate);
      }
    }

    tmp = gst_structure_copy (template);
    if (fix_num) {
      gst_structure_set (tmp, "framerate", GST_TYPE_FRACTION, fix_num,
          fix_denom, NULL);
    } else {
      /* if norm can't be used, copy the template framerate */
      gst_structure_set (tmp, "framerate", GST_TYPE_FRACTION_RANGE, 0, 1,
          100, 1, NULL);
    }

    if (min_w == max_w)
      gst_structure_set (tmp, "width", G_TYPE_INT, max_w, NULL);
    else
      gst_structure_set (tmp, "width", GST_TYPE_INT_RANGE, min_w, max_w, NULL);

    if (min_h == max_h)
      gst_structure_set (tmp, "height", G_TYPE_INT, max_h, NULL);
    else
      gst_structure_set (tmp, "height", GST_TYPE_INT_RANGE, min_h, max_h, NULL);

    gst_caps_append_structure (ret, tmp);

    return ret;
  }
}

static gboolean
gst_v4l2_object_get_nearest_size (GstV4l2Object * v4l2object,
    guint32 pixelformat, gint * width, gint * height)
{
  struct v4l2_format fmt;
  int fd;
  int r;

  g_return_val_if_fail (width != NULL, FALSE);
  g_return_val_if_fail (height != NULL, FALSE);

  GST_LOG_OBJECT (v4l2object->element,
      "getting nearest size to %dx%d with format %" GST_FOURCC_FORMAT,
      *width, *height, GST_FOURCC_ARGS (pixelformat));

  fd = v4l2object->video_fd;

  /* get size delimiters */
  memset (&fmt, 0, sizeof (fmt));
  fmt.type = v4l2object->type;
  fmt.fmt.pix.width = *width;
  fmt.fmt.pix.height = *height;
  fmt.fmt.pix.pixelformat = pixelformat;
  fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;

  r = v4l2_ioctl (fd, VIDIOC_TRY_FMT, &fmt);
  if (r < 0 && errno == EINVAL) {
    /* try again with progressive video */
    fmt.fmt.pix.width = *width;
    fmt.fmt.pix.height = *height;
    fmt.fmt.pix.pixelformat = pixelformat;
    fmt.fmt.pix.field = V4L2_FIELD_NONE;
    r = v4l2_ioctl (fd, VIDIOC_TRY_FMT, &fmt);
  }

  if (r < 0) {
    /* The driver might not implement TRY_FMT, in which case we will try
       S_FMT to probe */
    if (errno != ENOTTY)
      return FALSE;

    /* Only try S_FMT if we're not actively capturing yet, which we shouldn't
       be, because we're still probing */
    if (GST_V4L2_IS_ACTIVE (v4l2object))
      return FALSE;

    GST_LOG_OBJECT (v4l2object->element,
        "Failed to probe size limit with VIDIOC_TRY_FMT, trying VIDIOC_S_FMT");

    fmt.fmt.pix.width = *width;
    fmt.fmt.pix.height = *height;

    r = v4l2_ioctl (fd, VIDIOC_S_FMT, &fmt);
    if (r < 0 && errno == EINVAL) {
      /* try again with progressive video */
      fmt.fmt.pix.width = *width;
      fmt.fmt.pix.height = *height;
      fmt.fmt.pix.pixelformat = pixelformat;
      fmt.fmt.pix.field = V4L2_FIELD_NONE;
      r = v4l2_ioctl (fd, VIDIOC_S_FMT, &fmt);
    }

    if (r < 0)
      return FALSE;
  }

  GST_LOG_OBJECT (v4l2object->element,
      "got nearest size %dx%d", fmt.fmt.pix.width, fmt.fmt.pix.height);

  *width = fmt.fmt.pix.width;
  *height = fmt.fmt.pix.height;

  return TRUE;
}


gboolean
gst_v4l2_object_set_format (GstV4l2Object * v4l2object, guint32 pixelformat,
    guint32 width, guint32 height)
{
  gint fd = v4l2object->video_fd;
  struct v4l2_format format;

  GST_DEBUG_OBJECT (v4l2object->element, "Setting format to %dx%d, format "
      "%" GST_FOURCC_FORMAT, width, height, GST_FOURCC_ARGS (pixelformat));

  GST_V4L2_CHECK_OPEN (v4l2object);
  GST_V4L2_CHECK_NOT_ACTIVE (v4l2object);

  if (pixelformat == GST_MAKE_FOURCC ('M', 'P', 'E', 'G'))
    return TRUE;

  memset (&format, 0x00, sizeof (struct v4l2_format));
  format.type = v4l2object->type;

  if (v4l2_ioctl (fd, VIDIOC_G_FMT, &format) < 0)
    goto get_fmt_failed;

  if (format.type == v4l2object->type &&
      format.fmt.pix.width == width &&
      format.fmt.pix.height == height &&
      format.fmt.pix.pixelformat == pixelformat) {
    /* Nothing to do. We want to succeed immediately
     * here because setting the same format back
     * can still fail due to EBUSY. By short-circuiting
     * here, we allow pausing and re-playing pipelines
     * with changed caps, as long as the changed caps
     * do not change the webcam's format. Otherwise,
     * any caps change would require us to go to NULL
     * state to close the device and set format.
     */
    return TRUE;
  }

  format.type = v4l2object->type;
  format.fmt.pix.width = width;
  format.fmt.pix.height = height;
  format.fmt.pix.pixelformat = pixelformat;
  /* FIXME: request whole frames; need to use gstreamer interlace support
   * (INTERLACED mode returns frames where the fields have already been
   *  combined, there are other modes for requesting fields individually) */
  format.fmt.pix.field = V4L2_FIELD_INTERLACED;

  if (v4l2_ioctl (fd, VIDIOC_S_FMT, &format) < 0) {
    /* we might also get EBUSY here */
    if (errno != EINVAL)
      goto set_fmt_failed;

    GST_DEBUG_OBJECT (v4l2object->element, "trying again...");

    /* try again with progressive video */
    format.fmt.pix.width = width;
    format.fmt.pix.height = height;
    format.fmt.pix.pixelformat = pixelformat;
    format.fmt.pix.field = V4L2_FIELD_NONE;
    if (v4l2_ioctl (fd, VIDIOC_S_FMT, &format) < 0)
      goto set_fmt_failed;
  }

  if (format.fmt.pix.width != width || format.fmt.pix.height != height)
    goto invalid_dimensions;

  if (format.fmt.pix.pixelformat != pixelformat)
    goto invalid_pixelformat;

  return TRUE;

  /* ERRORS */
get_fmt_failed:
  {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, SETTINGS,
        (_("Device '%s' does not support video capture"),
            v4l2object->videodev),
        ("Call to G_FMT failed: (%s)", g_strerror (errno)));
    return FALSE;
  }
set_fmt_failed:
  {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, SETTINGS,
        (_("Device '%s' cannot capture at %dx%d"),
            v4l2object->videodev, width, height),
        ("Call to S_FMT failed for %" GST_FOURCC_FORMAT " @ %dx%d: %s",
            GST_FOURCC_ARGS (pixelformat), width, height, g_strerror (errno)));
    return FALSE;
  }
invalid_dimensions:
  {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, SETTINGS,
        (_("Device '%s' cannot capture at %dx%d"),
            v4l2object->videodev, width, height),
        ("Tried to capture at %dx%d, but device returned size %dx%d",
            width, height, format.fmt.pix.width, format.fmt.pix.height));
    return FALSE;
  }
invalid_pixelformat:
  {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, SETTINGS,
        (_("Device '%s' cannot capture in the specified format"),
            v4l2object->videodev),
        ("Tried to capture in %" GST_FOURCC_FORMAT
            ", but device returned format" " %" GST_FOURCC_FORMAT,
            GST_FOURCC_ARGS (pixelformat),
            GST_FOURCC_ARGS (format.fmt.pix.pixelformat)));
    return FALSE;
  }
}

gboolean
gst_v4l2_object_start_streaming (GstV4l2Object * v4l2object)
{
  if (v4l2_ioctl (v4l2object->video_fd, VIDIOC_STREAMON,
          &(v4l2object->type)) < 0) {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, OPEN_READ,
        (_("Error starting streaming on device '%s'."), v4l2object->videodev),
        GST_ERROR_SYSTEM);
    return FALSE;
  }
  return TRUE;
}

gboolean
gst_v4l2_object_stop_streaming (GstV4l2Object * v4l2object)
{
  if (v4l2_ioctl (v4l2object->video_fd, VIDIOC_STREAMOFF,
          &(v4l2object->type)) < 0) {
    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, OPEN_READ,
        (_("Error stopping streaming on device '%s'."), v4l2object->videodev),
        GST_ERROR_SYSTEM);
    return FALSE;
  }
  return TRUE;
}