From 05834fcf58fe77b0519a8dc40e3c4a5a28dfc88d Mon Sep 17 00:00:00 2001 From: Hans Verkuil <hans.verkuil@cisco.com> Date: Tue, 22 Nov 2011 08:59:34 -0300 Subject: [PATCH] [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> --- .../DocBook/media/v4l/vidioc-g-fbuf.xml | 23 +++++++++++-------- 1 file 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 93817f3370330..7c63815e7afd0 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> <row> <entry><constant>V4L2_FBUF_FLAG_OVERLAY</constant></entry> <entry>0x0002</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> </row> <row> <entry><constant>V4L2_FBUF_FLAG_CHROMAKEY</constant></entry> -- GitLab