v4l2src: Add source-change / resolution-change support

This branch adds support for driver driven source changes along with DV_TIMING locking support. Effectively, drivers can emit SOURCE_CHANGE event, with the RESOLUTION_CHANGE flag in order to signal that something got changes at the input signal. In that situation, we need to reset (streamoff/on) as we may not get more data otherwise. While doing this, we now query for detected DV_TIMING (aka modes) and lock/set these. We also default to the link detected width/height/framerate.

As a bonus, v4l2src will now mimic decklinksrc when the signal is lost and recovered. A WARNING with RESSOURCE/READ will be emited when the signal is lost, and an INFO message again with RESSOURCE/READ for when it's recovered.

This has been tested with vivid test driver and an work in progress HDMI receiver driver.

sys/v4l2/gstv4l2object.h

@@ -65,7+65,7 @@
   GST_V4L2_IO_MMAP          = 2,
   GST_V4L2_IO_USERPTR       = 3,
   GST_V4L2_IO_DMABUF        = 4,
   GST_V4L2_IO_DMABUF_IMPORT = 5
 } GstV4l2IOMode;
 
 typedef gboolean  (*GstV4l2GetInOutFunction)  (GstV4l2Object * v4l2object, guint32 * input);
@@ -327,7+327,7 @@
 gboolean     gst_v4l2_set_norm       (GstV4l2Object * v4l2object, v4l2_std_id norm);
 gboolean     gst_v4l2_get_input      (GstV4l2Object * v4l2object, guint32 * input);
 gboolean     gst_v4l2_set_input      (GstV4l2Object * v4l2object, guint32 input);
+gboolean     gst_v4l2_query_input    (GstV4l2Object * v4l2object, struct v4l2_input * input);
 gboolean     gst_v4l2_get_output     (GstV4l2Object * v4l2object, guint32 * output);
 gboolean     gst_v4l2_set_output     (GstV4l2Object * v4l2object, guint32 output);
 
 /* frequency control */
 gboolean     gst_v4l2_get_frequency   (GstV4l2Object * v4l2object, gint tunernum, gulong * frequency);
 gboolean     gst_v4l2_set_frequency   (GstV4l2Object * v4l2object, gint tunernum, gulong frequency);
@@ -341,3+342,3 @@
 gboolean     gst_v4l2_set_string_attribute (GstV4l2Object * v4l2object, int attribute_num, const char *value);
 gboolean     gst_v4l2_set_controls    (GstV4l2Object * v4l2object, GstStructure * controls);
 
-
 /* events */
 gboolean     gst_v4l2_subscribe_event (GstV4l2Object * v4l2object, guint32 event);
 gboolean     gst_v4l2_dequeue_event   (GstV4l2Object * v4l2object, struct v4l2_event *event);