+ /** Interop and SMPTE use the same VAlign choices (top, center, bottom) but give them different
+ * meanings. This is the standard which should be used to interpret v_align() in this subtitle;
+ * valign_standard == SMPTE means:
+ * top - top of screen to top of subtitle
+ * center - centre of screen to center of subtitle
+ * bottom - bottom of screen to bottom of subtitle
+ * valign_standard == Interop means:
+ * top - top of screen to baseline of subtitle
+ * center - centre of screen to baseline of subtitle
+ * bottom - bottom of screen to baseline of subtitle
+ */
+ dcp::Standard valign_standard;