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[media] v4l: v4l2_subdev userspace crop API

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This patch adds the VIDIOC_SUBDEV_S_CROP and G_CROP ioctls to the
userland API. CROPCAP is not implemented because it's redundant.

Signed-off-by: Antti Koskipaa <akoskipa@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Antti Koskipaa
2010-06-23 05:03:42 -03:00
committed by Mauro Carvalho Chehab
parent 35c3017a29
commit f6a5cb1be8
7 changed files with 238 additions and 0 deletions
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33
Documentation/DocBook/v4l/dev-subdev.xml
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@@ -275,6 +275,39 @@
</para>
</section>
<section>
<title>Cropping and scaling</title>
<para>Many sub-devices support cropping frames on their input or output
pads (or possible even on both). Cropping is used to select the area of
interest in an image, typically on a video sensor or video decoder. It can
also be used as part of digital zoom implementations to select the area of
the image that will be scaled up.</para>
<para>Crop settings are defined by a crop rectangle and represented in a
&v4l2-rect; by the coordinates of the top left corner and the rectangle
size. Both the coordinates and sizes are expressed in pixels.</para>
<para>The crop rectangle is retrieved and set using the
&VIDIOC-SUBDEV-G-CROP; and &VIDIOC-SUBDEV-S-CROP; ioctls. Like for pad
formats, drivers store try and active crop rectangles. The format
negotiation mechanism applies to crop settings as well.</para>
<para>On input pads, cropping is applied relatively to the current pad
format. The pad format represents the image size as received by the
sub-device from the previous block in the pipeline, and the crop rectangle
represents the sub-image that will be transmitted further inside the
sub-device for processing. The crop rectangle be entirely containted
inside the input image size.</para>
<para>Input crop rectangle are reset to their default value when the input
image format is modified. Drivers should use the input image size as the
crop rectangle default value, but hardware requirements may prevent this.
</para>
<para>Cropping behaviour on output pads is not defined.</para>
</section>
</section>
&sub-subdev-formats;