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: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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@ -918,8 +918,8 @@ order</emphasis>.</para>
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<para>When the driver provides or accepts images field by field
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<para>When the driver provides or accepts images field by field
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rather than interleaved, it is also important applications understand
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rather than interleaved, it is also important applications understand
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how the fields combine to frames. We distinguish between top and
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how the fields combine to frames. We distinguish between top (aka odd) and
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bottom fields, the <emphasis>spatial order</emphasis>: The first line
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bottom (aka even) fields, the <emphasis>spatial order</emphasis>: The first line
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of the top field is the first line of an interlaced frame, the first
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of the top field is the first line of an interlaced frame, the first
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line of the bottom field is the second line of that frame.</para>
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line of the bottom field is the second line of that frame.</para>
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@ -972,12 +972,12 @@ between <constant>V4L2_FIELD_TOP</constant> and
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<row>
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<row>
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<entry><constant>V4L2_FIELD_TOP</constant></entry>
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<entry><constant>V4L2_FIELD_TOP</constant></entry>
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<entry>2</entry>
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<entry>2</entry>
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<entry>Images consist of the top field only.</entry>
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<entry>Images consist of the top (aka odd) field only.</entry>
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</row>
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</row>
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<row>
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<row>
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<entry><constant>V4L2_FIELD_BOTTOM</constant></entry>
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<entry><constant>V4L2_FIELD_BOTTOM</constant></entry>
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<entry>3</entry>
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<entry>3</entry>
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<entry>Images consist of the bottom field only.
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<entry>Images consist of the bottom (aka even) field only.
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Applications may wish to prevent a device from capturing interlaced
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Applications may wish to prevent a device from capturing interlaced
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images because they will have "comb" or "feathering" artefacts around
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images because they will have "comb" or "feathering" artefacts around
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moving objects.</entry>
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moving objects.</entry>
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