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-rw-r--r--Documentation/DocBook/media/v4l/dev-sliced-vbi.xml9
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/DocBook/media/v4l/dev-sliced-vbi.xml b/Documentation/DocBook/media/v4l/dev-sliced-vbi.xml
index 548f8ea28dee..7a8bf3011ee9 100644
--- a/Documentation/DocBook/media/v4l/dev-sliced-vbi.xml
+++ b/Documentation/DocBook/media/v4l/dev-sliced-vbi.xml
@@ -185,7 +185,14 @@ tables, sigh. --></para></entry>
<entry></entry>
<entry spanname="hspan">Drivers must set
<structfield>service_lines</structfield>[0][0] and
-<structfield>service_lines</structfield>[1][0] to zero.</entry>
+<structfield>service_lines</structfield>[1][0] to zero.
+The <constant>V4L2_VBI_ITU_525_F1_START</constant>,
+<constant>V4L2_VBI_ITU_525_F2_START</constant>,
+<constant>V4L2_VBI_ITU_625_F1_START</constant> and
+<constant>V4L2_VBI_ITU_625_F2_START</constant> defines give the start
+line numbers for each field for each 525 or 625 line format as a
+convenience. Don't forget that ITU line numbering starts at 1, not 0.
+</entry>
</row>
<row>
<entry>__u32</entry>