152 lines
6.7 KiB
Diff
152 lines
6.7 KiB
Diff
From 00d84a43c7042b55e81d0818b0d1a6e44c6f79b5 Mon Sep 17 00:00:00 2001
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From: Jacopo Mondi <jacopo@jmondi.org>
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Date: Sat, 9 May 2020 11:04:47 +0200
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Subject: [PATCH] media: v4l2-ctrl: Document
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V4L2_CID_CAMERA_SENSOR_ROTATION
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Add documentation for the V4L2_CID_CAMERA_SENSOR_ROTATION camera
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control. The newly added read-only control reports the rotation
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correction to be applied to images before displaying them to the user.
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Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
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Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
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Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
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Commit 9926c2248740a632b0629fd8c07d0fc361dc15cc upstream
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Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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---
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.../media/uapi/v4l/ext-ctrls-camera.rst | 121 ++++++++++++++++++
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1 file changed, 121 insertions(+)
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--- a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst
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+++ b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst
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@@ -540,6 +540,127 @@ enum v4l2_scene_mode -
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+``V4L2_CID_CAMERA_SENSOR_ROTATION (integer)``
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+ This read-only control describes the rotation correction in degrees in the
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+ counter-clockwise direction to be applied to the captured images once
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+ captured to memory to compensate for the camera sensor mounting rotation.
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+
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+ For a precise definition of the sensor mounting rotation refer to the
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+ extensive description of the 'rotation' properties in the device tree
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+ bindings file 'video-interfaces.txt'.
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+
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+ A few examples are below reported, using a shark swimming from left to
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+ right in front of the user as the example scene to capture. ::
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+
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+ 0 X-axis
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+ 0 +------------------------------------->
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+ !
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+ !
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+ !
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+ ! |\____)\___
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+ ! ) _____ __`<
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+ ! |/ )/
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+ !
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+ !
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+ !
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+ V
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+ Y-axis
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+
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+ Example one - Webcam
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+
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+ Assuming you can bring your laptop with you while swimming with sharks,
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+ the camera module of the laptop is installed on the user facing part of a
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+ laptop screen casing, and is typically used for video calls. The captured
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+ images are meant to be displayed in landscape mode (width > height) on the
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+ laptop screen.
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+
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+ The camera is typically mounted upside-down to compensate the lens optical
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+ inversion effect. In this case the value of the
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+ V4L2_CID_CAMERA_SENSOR_ROTATION control is 0, no rotation is required to
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+ display images correctly to the user.
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+
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+ If the camera sensor is not mounted upside-down it is required to compensate
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+ the lens optical inversion effect and the value of the
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+ V4L2_CID_CAMERA_SENSOR_ROTATION control is 180 degrees, as images will
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+ result rotated when captured to memory. ::
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+
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+ +--------------------------------------+
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+ ! !
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+ ! !
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+ ! !
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+ ! __/(_____/| !
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+ ! >.___ ____ ( !
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+ ! \( \| !
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+ ! !
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+ ! !
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+ ! !
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+ +--------------------------------------+
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+
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+ A software rotation correction of 180 degrees has to be applied to correctly
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+ display the image on the user screen. ::
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+
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+ +--------------------------------------+
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+ ! !
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+ ! !
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+ ! !
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+ ! |\____)\___ !
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+ ! ) _____ __`< !
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+ ! |/ )/ !
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+ ! !
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+ ! !
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+ ! !
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+ +--------------------------------------+
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+
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+ Example two - Phone camera
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+
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+ It is more handy to go and swim with sharks with only your mobile phone
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+ with you and take pictures with the camera that is installed on the back
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+ side of the device, facing away from the user. The captured images are meant
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+ to be displayed in portrait mode (height > width) to match the device screen
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+ orientation and the device usage orientation used when taking the picture.
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+
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+ The camera sensor is typically mounted with its pixel array longer side
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+ aligned to the device longer side, upside-down mounted to compensate for
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+ the lens optical inversion effect.
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+
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+ The images once captured to memory will be rotated and the value of the
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+ V4L2_CID_CAMERA_SENSOR_ROTATION will report a 90 degree rotation. ::
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+
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+
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+ +-------------------------------------+
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+ | _ _ |
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+ | \ / |
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+ | | | |
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+ | | | |
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+ | | > |
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+ | < | |
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+ | | | |
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+ | . |
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+ | V |
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+ +-------------------------------------+
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+
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+ A correction of 90 degrees in counter-clockwise direction has to be
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+ applied to correctly display the image in portrait mode on the device
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+ screen. ::
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+
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+ +--------------------+
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+ | |
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+ | |
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+ | |
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+ | |
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+ | |
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+ | |
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+ | |\____)\___ |
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+ | ) _____ __`< |
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+ | |/ )/ |
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+ | |
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+ | |
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+ | |
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+ | |
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+ | |
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+ +--------------------+
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+
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+
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.. [#f1]
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This control may be changed to a menu control in the future, if more
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options are required.
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