gstvideo: Add gst_video_get_size_from_caps function

gst_video_get_size_from_caps () allows easy calculation of the raw video
buffer size from some fixed video caps.

API: gst_video_get_size_from_caps()

gst-libs/gst/video/video.c

@@ -325,7 +325,7 @@ gst_video_parse_caps_chroma_site (GstCaps * caps)
  * Returns: TRUE if @caps was parsed correctly.
  */
 gboolean
-gst_video_format_parse_caps (GstCaps * caps, GstVideoFormat * format,
+gst_video_format_parse_caps (const GstCaps * caps, GstVideoFormat * format,
     int *width, int *height)
 {
   GstStructure *structure;
@@ -2066,6 +2066,36 @@ gst_video_format_get_size (GstVideoFormat format, int width, int height)
   }
 }
 
+/**
+ * gst_video_get_size_from_caps:
+ * @caps: a pointer to #GstCaps
+ * @size: a pointer to a gint that will be assigned the size (in bytes) of a video frame with the given caps
+ *
+ * Calculates the total number of bytes in the raw video format for the given
+ * caps.  This number should be used when allocating a buffer for raw video.
+ *
+ * Since: 0.10.34
+ *
+ * Returns: %TRUE if the size could be calculated from the caps
+ */
+gboolean
+gst_video_get_size_from_caps (const GstCaps * caps, gint * size)
+{
+  GstVideoFormat format = 0;
+  gint width = 0, height = 0;
+
+  g_return_val_if_fail (gst_caps_is_fixed (caps), FALSE);
+  g_return_val_if_fail (size != NULL, FALSE);
+
+  if (gst_video_format_parse_caps (caps, &format, &width, &height) == FALSE) {
+    GST_WARNING ("Could not parse caps: %" GST_PTR_FORMAT, caps);
+    return FALSE;
+  }
+
+  *size = gst_video_format_get_size (format, width, height);
+  return TRUE;
+}
+
 /**
  * gst_video_format_convert:
  * @format: a #GstVideoFormat

gst-libs/gst/video/video.h

@@ -446,8 +446,8 @@ gboolean gst_video_calculate_display_ratio (guint *dar_n, guint *dar_d,
             guint video_par_n, guint video_par_d, 
             guint display_par_n, guint display_par_d);
 
-gboolean gst_video_format_parse_caps (GstCaps *caps, GstVideoFormat *format,
+gboolean gst_video_format_parse_caps (const GstCaps *caps,
-    int *width, int *height);
+    GstVideoFormat *format, int *width, int *height);
 gboolean gst_video_format_parse_caps_interlaced (GstCaps *caps, gboolean *interlaced);
 gboolean gst_video_parse_caps_framerate (GstCaps *caps,
     int *fps_n, int *fps_d);
@@ -480,6 +480,7 @@ int gst_video_format_get_component_height (GstVideoFormat format, int component,
 int gst_video_format_get_component_offset (GstVideoFormat format, int component,
     int width, int height);
 int gst_video_format_get_size (GstVideoFormat format, int width, int height);
+gboolean gst_video_get_size_from_caps (const GstCaps * caps, gint * size);
 gboolean gst_video_format_convert (GstVideoFormat format, int width, int height,
     int fps_n, int fps_d,
     GstFormat src_format, gint64 src_value,

tests/check/libs/video.c

@@ -748,6 +748,28 @@ GST_START_TEST (test_convert_frame_async)
 
 GST_END_TEST;
 
+GST_START_TEST (test_video_size_from_caps)
+{
+  gint size;
+  guint32 fourcc = GST_MAKE_FOURCC ('Y', 'V', '1', '2');
+  GstCaps *caps = gst_caps_new_simple ("video/x-raw-yuv",
+      "format", GST_TYPE_FOURCC, fourcc,
+      "width", G_TYPE_INT, 640,
+      "height", G_TYPE_INT, 480,
+      "framerate", GST_TYPE_FRACTION, 25, 1,
+      NULL);
+
+  fail_unless (gst_video_get_size_from_caps (caps, &size));
+  fail_unless (size ==
+      gst_video_format_get_size (gst_video_format_from_fourcc (fourcc), 640,
+          480));
+  fail_unless (size == (640 * 480 * 12 / 8));
+
+  gst_caps_unref (caps);
+}
+
+GST_END_TEST;
+
 static Suite *
 video_suite (void)
 {
@@ -763,6 +785,7 @@ video_suite (void)
   tcase_add_test (tc_chain, test_events);
   tcase_add_test (tc_chain, test_convert_frame);
   tcase_add_test (tc_chain, test_convert_frame_async);
+  tcase_add_test (tc_chain, test_video_size_from_caps);
 
   return s;
 }