path: root/Documentation/DocBook/media/v4l
diff options
authorHans Verkuil <hans.verkuil@cisco.com>2011-11-22 08:59:34 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2012-01-16 09:35:55 -0200
commit05834fcf58fe77b0519a8dc40e3c4a5a28dfc88d (patch)
tree5a73a2b0a534bdd2678d65eaa7df566fed2369ce /Documentation/DocBook/media/v4l
parent0cb64f02b8c8f8181d6eaa6d1931fe0bc4195a25 (diff)
[media] v4l2 spec: clarify usage of V4L2_FBUF_FLAG_OVERLAY
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation/DocBook/media/v4l')
1 files changed, 14 insertions, 9 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml b/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
index 93817f33703..7c63815e7af 100644
--- a/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
@@ -364,15 +364,20 @@ capability and it is cleared otherwise.</entry>
- <entry>The frame buffer is an overlay surface the same
-size as the capture. [?]</entry>
- </row>
- <row>
- <entry spanname="hspan">The purpose of
-<constant>V4L2_FBUF_FLAG_OVERLAY</constant> was never quite clear.
-Most drivers seem to ignore this flag. For compatibility with the
-<wordasword>bttv</wordasword> driver applications should set the
-<constant>V4L2_FBUF_FLAG_OVERLAY</constant> flag.</entry>
+ <entry>If this flag is set for a video capture device, then the
+driver will set the initial overlay size to cover the full framebuffer size,
+otherwise the existing overlay size (as set by &VIDIOC-S-FMT;) will be used.
+Only one video capture driver (bttv) supports this flag. The use of this flag
+for capture devices is deprecated. There is no way to detect which drivers
+support this flag, so the only reliable method of setting the overlay size is
+through &VIDIOC-S-FMT;.
+If this flag is set for a video output device, then the video output overlay
+window is relative to the top-left corner of the framebuffer and restricted
+to the size of the framebuffer. If it is cleared, then the video output
+overlay window is relative to the video output display.
+ </entry>