media: vivid.rst: document HDMI Video Guard Band control

Document this new vivid test control.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/Documentation/admin-guide/media/vivid.rst b/Documentation/admin-guide/media/vivid.rst
index 6d7175f96f74c26a13944e467aa959ab584aac34..4f680dc9661cba0eaae7c258d3e955f2e9e80da0 100644 (file)
--- a/Documentation/admin-guide/media/vivid.rst
+++ b/Documentation/admin-guide/media/vivid.rst
@@ -714,6 +714,20 @@ The Test Pattern Controls are all specific to video capture.
 
        does the same for the EAV (End of Active Video) code.
 
+- Insert Video Guard Band
+
+       adds 4 columns of pixels with the HDMI Video Guard Band code at the
+       left hand side of the image. This only works with 3 or 4 byte RGB pixel
+       formats. The RGB pixel value 0xab/0x55/0xab turns out to be equivalent
+       to the HDMI Video Guard Band code that precedes each active video line
+       (see section 5.2.2.1 in the HDMI 1.3 Specification). To test if a video
+       receiver has correct HDMI Video Guard Band processing, enable this
+       control and then move the image to the left hand side of the screen.
+       That will result in video lines that start with multiple pixels that
+       have the same value as the Video Guard Band that precedes them.
+       Receivers that will just keep skipping Video Guard Band values will
+       now fail and either loose sync or these video lines will shift.
+
 
 Capture Feature Selection Controls
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^