From 05834fcf58fe77b0519a8dc40e3c4a5a28dfc88d Mon Sep 17 00:00:00 2001 From: Hans Verkuil 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 Signed-off-by: Mauro Carvalho Chehab --- .../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 93817f337033..7c63815e7afd 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. V4L2_FBUF_FLAG_OVERLAY 0x0002 - The frame buffer is an overlay surface the same -size as the capture. [?] - - - The purpose of -V4L2_FBUF_FLAG_OVERLAY was never quite clear. -Most drivers seem to ignore this flag. For compatibility with the -bttv driver applications should set the -V4L2_FBUF_FLAG_OVERLAY flag. + 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. + V4L2_FBUF_FLAG_CHROMAKEY -- GitLab