tag: Adds some basic photography tags

Adds the following basic photography tags.

API: GST_TAG_CAPTURING_SHUTTER_SPEED
API: GST_TAG_CAPTURING_FOCAL_RATIO
API: GST_TAG_CAPTURING_FOCAL_LENGTH
API: GST_TAG_CAPTURING_DIGITAL_ZOOM_RATIO
API: GST_TAG_CAPTURING_ISO_SPEED

Fixes #626651

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

@@ -1634,6 +1634,11 @@ GST_TAG_CDDA_TRACK_TAGS
 GST_TAG_CMML_CLIP
 GST_TAG_CMML_HEAD
 GST_TAG_CMML_STREAM
+GST_TAG_CAPTURING_SHUTTER_SPEED
+GST_TAG_CAPTURING_FOCAL_RATIO
+GST_TAG_CAPTURING_FOCAL_LENGTH
+GST_TAG_CAPTURING_DIGITAL_ZOOM_RATIO
+GST_TAG_CAPTURING_ISO_SPEED
 gst_tag_register_musicbrainz_tags
 gst_tag_freeform_string_to_utf8
 gst_tag_parse_extended_comment

gst-libs/gst/tag/tag.h

@@ -120,6 +120,53 @@ G_BEGIN_DECLS
  */
 #define GST_TAG_CDDA_MUSICBRAINZ_DISCID_FULL  "musicbrainz-discid-full"
 
+/**
+ * GST_TAG_CAPTURING_SHUTTER_SPEED:
+ *
+ * Shutter speed used when capturing an image, in seconds. (fraction)
+ *
+ * Since: 0.10.31
+ */
+#define GST_TAG_CAPTURING_SHUTTER_SPEED        "capturing-shutter-speed"
+
+/**
+ * GST_TAG_CAPTURING_FOCAL_RATIO:
+ *
+ * Focal ratio (f-number) used when capturing an image. (double)
+ *
+ * The value stored is the denominator of the focal ratio (f-number).
+ * For example, if this tag value is 2, the focal ratio is f/2.
+ *
+ * Since: 0.10.31
+ */
+#define GST_TAG_CAPTURING_FOCAL_RATIO          "capturing-focal-ratio"
+
+/**
+ * GST_TAG_CAPTURING_FOCAL_LENGTH:
+ *
+ * Focal length used when capturing an image, in mm. (double)
+ *
+ * Since: 0.10.31
+ */
+#define GST_TAG_CAPTURING_FOCAL_LENGTH         "capturing-focal-length"
+
+/**
+ * GST_TAG_CAPTURING_DIGITAL_ZOOM_RATIO:
+ *
+ * Digital zoom ratio used when capturing an image. (double)
+ *
+ * Since: 0.10.31
+ */
+#define GST_TAG_CAPTURING_DIGITAL_ZOOM_RATIO   "capturing-digital-zoom-ratio"
+
+/**
+ * GST_TAG_CAPTURING_ISO_SPEED:
+ *
+ * ISO speed used when capturing an image. (integer)
+ *
+ * Since: 0.10.31
+ */
+#define GST_TAG_CAPTURING_ISO_SPEED           "capturing-iso-speed"
 
 
 /* additional information for image tags */

gst-libs/gst/tag/tags.c

@@ -85,6 +85,27 @@ gst_tag_register_tags_internal (gpointer unused)
       "Musicbrainz discid for metadata retrieval (full)",
       gst_tag_merge_use_first);
 
+  /* photography tags */
+  gst_tag_register (GST_TAG_CAPTURING_SHUTTER_SPEED, GST_TAG_FLAG_META,
+      GST_TYPE_FRACTION, _("capturing shutter speed"),
+      _("Shutter speed used when capturing an image, in seconds"), NULL);
+
+  gst_tag_register (GST_TAG_CAPTURING_FOCAL_RATIO, GST_TAG_FLAG_META,
+      G_TYPE_DOUBLE, _("capturing focal ratio"),
+      _("Focal ratio (f-number) used when capturing the image"), NULL);
+
+  gst_tag_register (GST_TAG_CAPTURING_FOCAL_LENGTH, GST_TAG_FLAG_META,
+      G_TYPE_DOUBLE, _("capturing focal length"),
+      _("Focal length of the lens used capturing the image, in mm"), NULL);
+
+  gst_tag_register (GST_TAG_CAPTURING_DIGITAL_ZOOM_RATIO, GST_TAG_FLAG_META,
+      G_TYPE_DOUBLE, _("capturing digital zoom ratio"),
+      _("Digital zoom ratio used when capturing an image"), NULL);
+
+  gst_tag_register (GST_TAG_CAPTURING_ISO_SPEED, GST_TAG_FLAG_META,
+      G_TYPE_INT, _("capturing iso speed"),
+      _("The ISO speed used when capturing an image"), NULL);
+
   return NULL;
 }