video-info: Add optional field-order caps field for interlaced-mode=interleaved

Usually this information is static for the whole stream, and various
container formats store this information inside the headers for the
whole stream.

Having it inside the caps for these cases simplifies code and makes it
possible to express these requirements more explicitly with the caps.

https://bugzilla.gnome.org/show_bug.cgi?id=771376

docs/libs/gst-plugins-base-libs-sections.txt

@@ -2479,6 +2479,7 @@ GST_TYPE_VIDEO_COLOR_PRIMARIES
 <SUBSECTION>
 GstVideoInfo
 GstVideoInterlaceMode
+GstVideoFieldOrder
 GstVideoMultiviewMode
 GstVideoMultiviewFramePacking
 GstVideoMultiviewFlags
@@ -2491,6 +2492,7 @@ GST_VIDEO_INFO_IS_GRAY
 GST_VIDEO_INFO_HAS_ALPHA
 GST_VIDEO_INFO_INTERLACE_MODE
 GST_VIDEO_INFO_IS_INTERLACED
+GST_VIDEO_INFO_FIELD_ORDER
 GST_VIDEO_INFO_FLAGS
 GST_VIDEO_INFO_WIDTH
 GST_VIDEO_INFO_HEIGHT
@@ -2533,6 +2535,8 @@ gst_video_info_align
 <SUBSECTION Standard>
 gst_video_interlace_mode_get_type
 GST_TYPE_VIDEO_INTERLACE_MODE
+gst_video_field_order_get_type
+GST_TYPE_VIDEO_FIELD_ORDER
 gst_video_flags_get_type
 GST_TYPE_VIDEO_FLAGS
 GST_TYPE_VIDEO_MULTIVIEW_FLAGS

gst-libs/gst/video/video-info.c

@@ -274,6 +274,54 @@ gst_video_interlace_mode_from_string (const gchar * mode)
   return GST_VIDEO_INTERLACE_MODE_PROGRESSIVE;
 }
 
+static const gchar *field_order[] = {
+  "unknown",
+  "top-field-first",
+  "bottom-field-first"
+};
+
+/**
+ * gst_video_field_order_to_string:
+ * @order: a #GstVideoFieldOrder
+ *
+ * Convert @order to its string representation.
+ *
+ * Returns: @order as a string or NULL if @order in invalid.
+ *
+ * Since: 1.12
+ */
+const gchar *
+gst_video_field_order_to_string (GstVideoFieldOrder order)
+{
+  if (((guint) order) >= G_N_ELEMENTS (field_order))
+    return NULL;
+
+  return field_order[order];
+}
+
+/**
+ * gst_video_field_order_from_string:
+ * @order: a field order
+ *
+ * Convert @order to a #GstVideoFieldOrder
+ *
+ * Returns: the #GstVideoFieldOrder of @order or
+ *    #GST_VIDEO_FIELD_ORDER_UNKNOWN when @order is not a valid
+ *    string representation for a #GstVideoFieldOrder.
+ *
+ * Since: 1.12
+ */
+GstVideoFieldOrder
+gst_video_field_order_from_string (const gchar * order)
+{
+  gint i;
+  for (i = 0; i < G_N_ELEMENTS (field_order); i++) {
+    if (g_str_equal (field_order[i], order))
+      return i;
+  }
+  return GST_VIDEO_FIELD_ORDER_UNKNOWN;
+}
+
 /**
  * gst_video_info_from_caps:
  * @info: a #GstVideoInfo
@@ -359,6 +407,13 @@ gst_video_info_from_caps (GstVideoInfo * info, const GstCaps * caps)
   else
     info->interlace_mode = GST_VIDEO_INTERLACE_MODE_PROGRESSIVE;
 
+  if (info->interlace_mode == GST_VIDEO_INTERLACE_MODE_INTERLEAVED &&
+      (s = gst_structure_get_string (structure, "field-order"))) {
+    GST_VIDEO_INFO_FIELD_ORDER (info) = gst_video_field_order_from_string (s);
+  } else {
+    GST_VIDEO_INFO_FIELD_ORDER (info) = GST_VIDEO_FIELD_ORDER_UNKNOWN;
+  }
+
   {
     if ((s = gst_structure_get_string (structure, "multiview-mode")))
       GST_VIDEO_INFO_MULTIVIEW_MODE (info) =
@@ -531,6 +586,13 @@ gst_video_info_to_caps (GstVideoInfo * info)
   gst_caps_set_simple (caps, "interlace-mode", G_TYPE_STRING,
       gst_video_interlace_mode_to_string (info->interlace_mode), NULL);
 
+  if (info->interlace_mode == GST_VIDEO_INTERLACE_MODE_INTERLEAVED &&
+      GST_VIDEO_INFO_FIELD_ORDER (info) != GST_VIDEO_FIELD_ORDER_UNKNOWN) {
+    gst_caps_set_simple (caps, "field-order", G_TYPE_STRING,
+        gst_video_field_order_to_string (GST_VIDEO_INFO_FIELD_ORDER (info)),
+        NULL);
+  }
+
   if (GST_VIDEO_INFO_MULTIVIEW_MODE (info) != GST_VIDEO_MULTIVIEW_MODE_NONE) {
     const gchar *caps_str = NULL;
 

gst-libs/gst/video/video-info.h

@@ -227,6 +227,29 @@ typedef enum {
   GST_VIDEO_FLAG_PREMULTIPLIED_ALPHA = (1 << 1)
 } GstVideoFlags;
 
+/**
+ * GstVideoFieldOrder:
+ * @GST_VIDEO_FIELD_ORDER_UNKNOWN: unknown field order for interlaced content.
+ *     The actual field order is signalled via buffer flags.
+ * @GST_VIDEO_FIELD_ORDER_TOP_FIELD_FIRST: top field is first
+ * @GST_VIDEO_FIELD_ORDER_BOTTOM_FIELD_FIRST: bottom field is first
+ *
+ * Field order of interlaced content. This is only valid for
+ * interlaced-mode=interleaved and not interlaced-mode=mixed. In the case of
+ * mixed or GST_VIDEO_FIELD_ORDER_UNKOWN, the field order is signalled via
+ * buffer flags.
+ *
+ * Since: 1.12
+ */
+typedef enum {
+  GST_VIDEO_FIELD_ORDER_UNKNOWN            = 0,
+  GST_VIDEO_FIELD_ORDER_TOP_FIELD_FIRST    = 1,
+  GST_VIDEO_FIELD_ORDER_BOTTOM_FIELD_FIRST = 2,
+} GstVideoFieldOrder;
+
+const gchar *      gst_video_field_order_to_string    (GstVideoFieldOrder order);
+GstVideoFieldOrder gst_video_field_order_from_string  (const gchar * order);
+
 /**
  * GstVideoInfo:
  * @finfo: the format info of the video
@@ -281,6 +304,7 @@ struct _GstVideoInfo {
     struct {
       GstVideoMultiviewMode     multiview_mode;
       GstVideoMultiviewFlags    multiview_flags;
+      GstVideoFieldOrder        field_order;
     } abi;
     /*< private >*/
     gpointer _gst_reserved[GST_PADDING];
@@ -300,6 +324,7 @@ GType gst_video_info_get_type            (void);
 
 #define GST_VIDEO_INFO_INTERLACE_MODE(i) ((i)->interlace_mode)
 #define GST_VIDEO_INFO_IS_INTERLACED(i)  ((i)->interlace_mode != GST_VIDEO_INTERLACE_MODE_PROGRESSIVE)
+#define GST_VIDEO_INFO_FIELD_ORDER(i)    ((i)->ABI.abi.field_order)
 #define GST_VIDEO_INFO_FLAGS(i)          ((i)->flags)
 #define GST_VIDEO_INFO_WIDTH(i)          ((i)->width)
 #define GST_VIDEO_INFO_HEIGHT(i)         ((i)->height)

gst-libs/gst/video/videoorientation.c

@@ -41,8 +41,8 @@
 
 G_DEFINE_INTERFACE (GstVideoOrientation, gst_video_orientation, 0)
 
-static void
-gst_video_orientation_default_init (GstVideoOrientationInterface *
+     static void
+         gst_video_orientation_default_init (GstVideoOrientationInterface *
     iface)
 {
   /* default virtual functions */

win32/common/libgstvideo.def

@@ -166,6 +166,9 @@ EXPORTS
 	gst_video_event_parse_downstream_force_key_unit
 	gst_video_event_parse_still_frame
 	gst_video_event_parse_upstream_force_key_unit
+	gst_video_field_order_from_string
+	gst_video_field_order_get_type
+	gst_video_field_order_to_string
 	gst_video_filter_get_type
 	gst_video_flags_get_type
 	gst_video_format_flags_get_type