mirror of https://gitee.com/openkylin/linux.git
media: dt-bindings: video-interface: Replace 'rotation' description
Replace the 'rotation' property description by providing a definition relative to the camera sensor pixel array coordinate system and the captured scene. Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Jacopo Mondi
Mauro Carvalho Chehab
parent
cabc918e5b
commit
915bd31ce9
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@ -85,9 +85,362 @@ Optional properties
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- lens-focus: A phandle to the node of the focus lens controller.
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- rotation: The device, typically an image sensor, is not mounted upright,
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but a number of degrees counter clockwise. Typical values are 0 and 180
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(upside down).
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- rotation: The camera rotation is expressed as the angular difference in
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degrees between two reference systems, one relative to the camera module, and
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one defined on the external world scene to be captured when projected on the
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image sensor pixel array.
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A camera sensor has a 2-dimensional reference system 'Rc' defined by
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its pixel array read-out order. The origin is set to the first pixel
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being read out, the X-axis points along the column read-out direction
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towards the last columns, and the Y-axis along the row read-out
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direction towards the last row.
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A typical example for a sensor with a 2592x1944 pixel array matrix
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observed from the front is:
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2591 X-axis 0
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<------------------------+ 0
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.......... ... ..........!
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.......... ... ..........! Y-axis
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... !
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.......... ... ..........!
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.......... ... ..........! 1943
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V
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The external world scene reference system 'Rs' is a 2-dimensional
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reference system on the focal plane of the camera module. The origin is
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placed on the top-left corner of the visible scene, the X-axis points
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towards the right, and the Y-axis points towards the bottom of the
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scene. The top, bottom, left and right directions are intentionally not
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defined and depend on the environment in which the camera is used.
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A typical example of a (very common) picture of a shark swimming from
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left to right, as seen from the camera, is:
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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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with the reference system 'Rs' placed on the camera focal plane:
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¸.·˙!
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¸.·˙ !
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_ ¸.·˙ !
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+-/ \-+¸.·˙ !
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| (o) | ! Camera focal plane
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+-----+˙·.¸ !
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˙·.¸ !
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˙·.¸ !
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˙·.¸!
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When projected on the sensor's pixel array, the image and the associated
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reference system 'Rs' are typically (but not always) inverted, due to
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the camera module's lens optical inversion effect.
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Assuming the above represented scene of the swimming shark, the lens
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inversion projects the scene and its reference system onto the sensor
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pixel array, seen from the front of the camera sensor, as follows:
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Y-axis
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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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0 +------------------------------------->
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0 X-axis
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Note the shark being upside-down.
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The resulting projected reference system is named 'Rp'.
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The camera rotation property is then defined as the angular difference
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in the counter-clockwise direction between the camera reference system
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'Rc' and the projected scene reference system 'Rp'. It is expressed in
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degrees as a number in the range [0, 360[.
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Examples
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0 degrees camera rotation:
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Y-Rp
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^
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Y-Rc !
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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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! 0 +------------------------------------->
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! 0 X-Rp
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0 +------------------------------------->
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0 X-Rc
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X-Rc 0
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<------------------------------------+ 0
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X-Rp 0 !
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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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! V
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! Y-Rc
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V
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Y-Rp
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90 degrees camera rotation:
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0 Y-Rc
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0 +-------------------->
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! Y-Rp
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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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! 0 +------------------------------------->
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! 0 X-Rp
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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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X-Rc
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180 degrees camera rotation:
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0
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<------------------------------------+ 0
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X-Rc !
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Y-Rp !
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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-Rc
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0 +------------------------------------->
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0 X-Rp
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270 degrees camera rotation:
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0 Y-Rc
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0 +-------------------->
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! 0
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! <-----------------------------------+ 0
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! X-Rp !
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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-Rp
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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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X-Rc
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Example one - Webcam
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A camera module installed on the user facing part of a laptop screen
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casing used for video calls. The captured images are meant to be
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displayed in landscape mode (width > height) on the laptop screen.
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The camera is typically mounted upside-down to compensate the lens
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optical inversion effect:
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Y-Rp
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Y-Rc ^
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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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! 0 +------------------------------------->
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! 0 X-Rp
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0 +------------------------------------->
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0 X-Rc
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The two reference systems are aligned, the resulting camera rotation is
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0 degrees, no rotation correction needs to be applied to the resulting
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image once captured to memory buffers to correctly display it to users:
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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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If the camera sensor is not mounted upside-down to compensate for the
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lens optical inversion, the two reference systems will not be aligned,
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with 'Rp' being rotated 180 degrees relatively to 'Rc':
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X-Rc 0
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<------------------------------------+ 0
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!
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Y-Rp !
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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-Rc
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0 +------------------------------------->
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0 X-Rp
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The image once captured to memory will then be rotated by 180 degrees:
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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 should be applied to
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correctly display the image:
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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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A camera installed on the back side of a mobile device facing away from
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the user. The captured images are meant to be displayed in portrait mode
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(height > width) to match the device screen orientation and the device
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usage orientation used when taking the picture.
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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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0 Y-Rc
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0 +-------------------->
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! Y-Rp
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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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! 0 +------------------------------------->
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! 0 X-Rp
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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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X-Rc
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The two reference systems are not aligned and the 'Rp' reference
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system is rotated by 90 degrees in the counter-clockwise direction
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relatively to the 'Rc' reference system.
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The image once captured to memory will be rotated:
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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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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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- orientation: The orientation of a device (typically an image sensor or a flash
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LED) describing its mounting position relative to the usage orientation of the
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