-// "second_field_start" is only valid for interlaced modes; it signifies
-// how many lines from the very top of the frame there are before the second field
+// "second_field_start" is only valid for interlaced modes. If it is 1,
+// the two fields are actually stored interlaced (ie., every other line).
+// If not, each field is stored consecutively, and it signifies how many lines
+// from the very top of the frame there are before the second field