gistfile1.cpp

static GstElement* findDeviceSource(GstElement* autoSrc)
{
    GstElement* deviceSrc;
    GstChildProxy* childProxy = GST_CHILD_PROXY(autoSrc);
    if (!childProxy)
        return deviceSrc;

    GstStateChangeReturn stateChangeResult = gst_element_set_state(autoSrc, GST_STATE_READY);
    if (stateChangeResult != GST_STATE_CHANGE_SUCCESS)
        return deviceSrc;

    if (gst_child_proxy_get_children_count(childProxy))
        deviceSrc = adoptGRef(GST_ELEMENT(gst_child_proxy_get_child_by_index(childProxy, 0)));

    gst_element_set_state(autoSrc, GST_STATE_NULL);
    return deviceSrc;
}