C++ GST_V4L2SRC函数代码示例

static GstCaps *
gst_v4l2src_get_caps (GstBaseSrc * src, GstCaps * filter)
{
  GstV4l2Src *v4l2src;
  GstV4l2Object *obj;
  GstCaps *ret;
  GSList *walk;
  GSList *formats;

  v4l2src = GST_V4L2SRC (src);
  obj = v4l2src->v4l2object;

  if (!GST_V4L2_IS_OPEN (obj)) {
    return gst_pad_get_pad_template_caps (GST_BASE_SRC_PAD (v4l2src));
  }

  if (v4l2src->probed_caps)
    return gst_caps_ref (v4l2src->probed_caps);

  formats = gst_v4l2_object_get_format_list (obj);

  ret = gst_caps_new_empty ();

  for (walk = formats; walk; walk = walk->next) {
    struct v4l2_fmtdesc *format;
    GstStructure *template;

static gboolean
gst_v4l2src_set_caps (GstBaseSrc * src, GstCaps * caps)
{
  GstV4l2Src *v4l2src;
  GstV4l2Object *obj;

  v4l2src = GST_V4L2SRC (src);
  obj = v4l2src->v4l2object;

  /* make sure the caps changed before doing anything */
  if (gst_v4l2_object_caps_equal (obj, caps))
    return TRUE;

  /* make sure we stop capturing and dealloc buffers */
  if (!gst_v4l2_object_stop (obj))
    return FALSE;

  g_signal_emit (v4l2src, gst_v4l2_signals[SIGNAL_PRE_SET_FORMAT], 0,
      v4l2src->v4l2object->video_fd, caps);

  if (!gst_v4l2_object_set_format (obj, caps))
    /* error already posted */
    return FALSE;

  return TRUE;
}

static GstCaps *
gst_v4l2src_get_caps (GstBaseSrc * src)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (src);
  GstCaps *ret;
  GSList *walk;
  GSList *formats;

  if (!GST_V4L2_IS_OPEN (v4l2src->v4l2object)) {
    /* FIXME: copy? */
    return
        gst_caps_copy (gst_pad_get_pad_template_caps (GST_BASE_SRC_PAD
            (v4l2src)));
  }

  if (v4l2src->probed_caps)
    return gst_caps_ref (v4l2src->probed_caps);

  formats = gst_v4l2_object_get_format_list (v4l2src->v4l2object);

  ret = gst_caps_new_empty ();

  for (walk = formats; walk; walk = walk->next) {
    struct v4l2_fmtdesc *format;

    GstStructure *template;

static gboolean
gst_v4l2src_iface_supported (GstImplementsInterface * iface, GType iface_type)
{
  GstV4l2Object *v4l2object = GST_V4L2SRC (iface)->v4l2object;

#ifdef HAVE_XVIDEO
  g_assert (iface_type == GST_TYPE_TUNER ||
      iface_type == GST_TYPE_X_OVERLAY ||
      iface_type == GST_TYPE_COLOR_BALANCE ||
      iface_type == GST_TYPE_VIDEO_ORIENTATION);
#else
  g_assert (iface_type == GST_TYPE_TUNER ||
      iface_type == GST_TYPE_COLOR_BALANCE ||
      iface_type == GST_TYPE_VIDEO_ORIENTATION);
#endif

  if (v4l2object->video_fd == -1)
    return FALSE;

#ifdef HAVE_XVIDEO
  if (iface_type == GST_TYPE_X_OVERLAY && !GST_V4L2_IS_OVERLAY (v4l2object))
    return FALSE;
#endif

  return TRUE;
}

static gboolean
gst_v4l2src_set_caps (GstBaseSrc * src, GstCaps * caps)
{
  GstV4l2Src *v4l2src;
  GstV4l2Object *obj;

  v4l2src = GST_V4L2SRC (src);
  obj = v4l2src->v4l2object;

  /* make sure the caps changed before doing anything */
  if (gst_v4l2_object_caps_equal (obj, caps))
    return TRUE;

  if (GST_V4L2_IS_ACTIVE (obj)) {
    /* Just check if the format is acceptable, once we know
     * no buffers should be outstanding we try S_FMT.
     *
     * Basesrc will do an allocation query that
     * should indirectly reclaim buffers, after that we can
     * set the format and then configure our pool */
    if (gst_v4l2_object_try_format (obj, caps)) {
      v4l2src->renegotiation_adjust = v4l2src->offset + 1;
      v4l2src->pending_set_fmt = TRUE;
    } else
      return FALSE;
  } else {
    /* make sure we stop capturing and dealloc buffers */
    if (!gst_v4l2_object_stop (obj))
      return FALSE;

    return gst_v4l2src_set_format (v4l2src, caps);
  }

  return TRUE;
}

static GstStateChangeReturn
gst_v4l2src_change_state (GstElement * element, GstStateChange transition)
{
  GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
  GstV4l2Src *v4l2src = GST_V4L2SRC (element);
  GstV4l2Object *obj = v4l2src->v4l2object;

  switch (transition) {
    case GST_STATE_CHANGE_NULL_TO_READY:
      /* open the device */
      if (!gst_v4l2_object_open (obj))
        return GST_STATE_CHANGE_FAILURE;
      break;
    default:
      break;
  }

  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);

  switch (transition) {
    case GST_STATE_CHANGE_READY_TO_NULL:
      /* close the device */
      if (!gst_v4l2_object_close (obj))
        return GST_STATE_CHANGE_FAILURE;

      break;
    default:
      break;
  }

  return ret;
}

static gboolean
gst_v4l2src_unlock_stop (GstBaseSrc * src)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (src);

  v4l2src->last_timestamp = 0;

  return gst_v4l2_object_unlock_stop (v4l2src->v4l2object);
}

static void
gst_v4l2src_dispose (GObject * object)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (object);

  if (v4l2src->probed_caps) {
    gst_caps_unref (v4l2src->probed_caps);
  }

  G_OBJECT_CLASS (parent_class)->dispose (object);
}

static gchar *
gst_v4l2src_uri_get_uri (GstURIHandler * handler)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (handler);

  if (v4l2src->v4l2object->videodev != NULL) {
    return g_strdup_printf ("v4l2://%s", v4l2src->v4l2object->videodev);
  }

  return g_strdup ("v4l2://");
}

static gboolean
gst_v4l2src_stop (GstBaseSrc * src)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (src);
  GstV4l2Object *obj = v4l2src->v4l2object;

  if (GST_V4L2_IS_ACTIVE (obj)) {
    if (!gst_v4l2_object_stop (obj))
      return FALSE;
  }
  return TRUE;
}

/* start and stop are not symmetric -- start will open the device, but not start
 * capture. it's setcaps that will start capture, which is called via basesrc's
 * negotiate method. stop will both stop capture and close the device.
 */
static gboolean
gst_v4l2src_start (GstBaseSrc * src)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (src);

  v4l2src->offset = 0;

  /* activate settings for first frame */
  v4l2src->ctrl_time = 0;
  gst_object_sync_values (GST_OBJECT (src), v4l2src->ctrl_time);

  return TRUE;
}

/* this is somewhat of a hack.. but better to keep the hack in
 * one place than copy/pasting it around..
 */
static GstV4l2Object *
get_v4l2_object (GstElement * v4l2elem)
{
  GstV4l2Object *v4l2object = NULL;
  if (GST_IS_V4L2SRC (v4l2elem)) {
    v4l2object = (GST_V4L2SRC (v4l2elem))->v4l2object;
  } else if (GST_IS_V4L2SINK (v4l2elem)) {
    v4l2object = (GST_V4L2SINK (v4l2elem))->v4l2object;
  } else {
    GST_ERROR_OBJECT (v4l2elem, "unknown v4l2 element");
  }
  return v4l2object;
}

static gboolean
gst_v4l2src_uri_set_uri (GstURIHandler * handler, const gchar * uri,
    GError ** error)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (handler);
  const gchar *device = DEFAULT_PROP_DEVICE;

  if (strcmp (uri, "v4l2://") != 0) {
    device = uri + 7;
  }
  g_object_set (v4l2src, "device", device, NULL);

  return TRUE;
}

static GstCaps *
gst_v4l2src_get_caps (GstBaseSrc * src, GstCaps * filter)
{
  GstV4l2Src *v4l2src;
  GstV4l2Object *obj;

  v4l2src = GST_V4L2SRC (src);
  obj = v4l2src->v4l2object;

  if (!GST_V4L2_IS_OPEN (obj)) {
    return gst_pad_get_pad_template_caps (GST_BASE_SRC_PAD (v4l2src));
  }

  return gst_v4l2_object_get_caps (obj, filter);
}

static void
gst_v4l2src_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec)
{
  GstV4l2Src *v4l2src = GST_V4L2SRC (object);

  if (!gst_v4l2_object_get_property_helper (v4l2src->v4l2object,
          prop_id, value, pspec)) {
    switch (prop_id) {
      default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
        break;
    }
  }
}