stl: add comment to validateVerticalPosition()

asticode · Sep 1, 2021 · 1c68b6c · 1c68b6c
1 parent ecffc0d
commit 1c68b6c
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/stl.go b/stl.go
@@ -735,6 +735,11 @@ func (t *ttiBlock) bytes(g *gsiBlock) (o []byte) {
 	return
 }
 
+// According to EBU 3264 (https://tech.ebu.ch/docs/tech/tech3264.pdf):
+// for teletext subtitles, VP contains a value in the range 1-23 decimal (01h-17h)
+// corresponding to theteletext row number of the first subtitle row.
+// Teletext ("closed") subtitles are indicated via the Display Standard Code
+// in the GSI block.
 func validateVerticalPosition(vp int, dsc string) byte {
 	closed := false
 	switch dsc {