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Commit 0fb6ec6b authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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[media] V4L2 Spec: clarify usage of V4L2_FBUF_FLAG_PRIMARY 



As per discussion during the 2011 V4L-DVB workshop.

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 146d35b0

Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml

+6 −4
Original line number Diff line number Diff line
@@ -295,7 +295,8 @@ set this field to zero.</entry> 
	    <entry>The device is capable of non-destructive overlays.

When the driver clears this flag, only destructive overlays are

supported. There are no drivers yet which support both destructive and

non-destructive overlays.</entry>

non-destructive overlays. Video Output Overlays are in practice always

non-destructive.</entry>

	  </row>

	  <row>

	    <entry><constant>V4L2_FBUF_CAP_CHROMAKEY</constant></entry>
@@ -356,7 +357,9 @@ with the chroma-key colors are replaced by video pixels, which is exactly opposi 
	    <entry><constant>V4L2_FBUF_FLAG_PRIMARY</constant></entry>

	    <entry>0x0001</entry>

	    <entry>The framebuffer is the primary graphics surface.

In other words, the overlay is destructive. [?]</entry>

In other words, the overlay is destructive. This flag is typically set by any

driver that doesn't have the <constant>V4L2_FBUF_CAP_EXTERNOVERLAY</constant>

capability and it is cleared otherwise.</entry>

	  </row>

	  <row>

	    <entry><constant>V4L2_FBUF_FLAG_OVERLAY</constant></entry>
@@ -366,9 +369,8 @@ size as the capture. [?]</entry> 
	  </row>

	  <row>

	    <entry spanname="hspan">The purpose of

<constant>V4L2_FBUF_FLAG_PRIMARY</constant> and

<constant>V4L2_FBUF_FLAG_OVERLAY</constant> was never quite clear.

Most drivers seem to ignore these flags. For compatibility with the

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>

	  </row>