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Commit 37089368 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
Browse files

V4L/DVB: v4l spec: document what odd and even fields are 



Document that odd == top and even == bottom. I can never remember this,
so it is probably worth documenting.

Signed-off-by: default avatarHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 09250193

Documentation/DocBook/v4l/io.xml

+4 −4
Original line number Diff line number Diff line
@@ -918,8 +918,8 @@ order</emphasis>.</para> 


    <para>When the driver provides or accepts images field by field

rather than interleaved, it is also important applications understand

how the fields combine to frames. We distinguish between top and

bottom fields, the <emphasis>spatial order</emphasis>: The first line

how the fields combine to frames. We distinguish between top (aka odd) and

bottom (aka even) fields, the <emphasis>spatial order</emphasis>: The first line

of the top field is the first line of an interlaced frame, the first

line of the bottom field is the second line of that frame.</para>
@@ -972,12 +972,12 @@ between <constant>V4L2_FIELD_TOP</constant> and 
	  <row>

	    <entry><constant>V4L2_FIELD_TOP</constant></entry>

	    <entry>2</entry>

	    <entry>Images consist of the top field only.</entry>

	    <entry>Images consist of the top (aka odd) field only.</entry>

	  </row>

	  <row>

	    <entry><constant>V4L2_FIELD_BOTTOM</constant></entry>

	    <entry>3</entry>

	    <entry>Images consist of the bottom field only.

	    <entry>Images consist of the bottom (aka even) field only.

Applications may wish to prevent a device from capturing interlaced

images because they will have "comb" or "feathering" artefacts around

moving objects.</entry>