media: dt-bindings: video-interface: Replace 'rotation' description (915bd31c) · Commits · jan.koester / Linux

Documentation/devicetree/bindings/media/video-interfaces.txt

+356 −3

Original line number	Diff line number	Diff line
		@@ -85,9 +85,362 @@ Optional properties

		- lens-focus: A phandle to the node of the focus lens controller.

		- rotation: The device, typically an image sensor, is not mounted upright,
		but a number of degrees counter clockwise. Typical values are 0 and 180
		(upside down).
		- rotation: The camera rotation is expressed as the angular difference in
		degrees between two reference systems, one relative to the camera module, and
		one defined on the external world scene to be captured when projected on the
		image sensor pixel array.

		A camera sensor has a 2-dimensional reference system 'Rc' defined by
		its pixel array read-out order. The origin is set to the first pixel
		being read out, the X-axis points along the column read-out direction
		towards the last columns, and the Y-axis along the row read-out
		direction towards the last row.

		A typical example for a sensor with a 2592x1944 pixel array matrix
		observed from the front is:

		2591 X-axis 0
		<------------------------+ 0
		.......... ... ..........!
		.......... ... ..........! Y-axis
		... !
		.......... ... ..........!
		.......... ... ..........! 1943
		V

		The external world scene reference system 'Rs' is a 2-dimensional
		reference system on the focal plane of the camera module. The origin is
		placed on the top-left corner of the visible scene, the X-axis points
		towards the right, and the Y-axis points towards the bottom of the
		scene. The top, bottom, left and right directions are intentionally not
		defined and depend on the environment in which the camera is used.

		A typical example of a (very common) picture of a shark swimming from
		left to right, as seen from the camera, is:

		0 X-axis
		0 +------------------------------------->
		!
		!
		!
		! \|\____)\___
		! ) _____ __`<
		! \|/ )/
		!
		!
		!
		V
		Y-axis

		with the reference system 'Rs' placed on the camera focal plane:

		¸.·˙!
		¸.·˙ !
		_ ¸.·˙ !
		+-/ \-+¸.·˙ !
		\| (o) \| ! Camera focal plane
		+-----+˙·.¸ !
		˙·.¸ !
		˙·.¸ !
		˙·.¸!

		When projected on the sensor's pixel array, the image and the associated
		reference system 'Rs' are typically (but not always) inverted, due to
		the camera module's lens optical inversion effect.

		Assuming the above represented scene of the swimming shark, the lens
		inversion projects the scene and its reference system onto the sensor
		pixel array, seen from the front of the camera sensor, as follows:

		Y-axis
		^
		!
		!
		!
		! \|\_____)\__
		! ) ____ ___.<
		! \|/ )/
		!
		!
		!
		0 +------------------------------------->
		0 X-axis

		Note the shark being upside-down.

		The resulting projected reference system is named 'Rp'.

		The camera rotation property is then defined as the angular difference
		in the counter-clockwise direction between the camera reference system
		'Rc' and the projected scene reference system 'Rp'. It is expressed in
		degrees as a number in the range [0, 360[.

		Examples

		0 degrees camera rotation:


		Y-Rp
		^
		Y-Rc !
		^ !
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! 0 +------------------------------------->
		! 0 X-Rp
		0 +------------------------------------->
		0 X-Rc


		X-Rc 0
		<------------------------------------+ 0
		X-Rp 0 !
		<------------------------------------+ 0 !
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! V
		! Y-Rc
		V
		Y-Rp

		90 degrees camera rotation:

		0 Y-Rc
		0 +-------------------->
		! Y-Rp
		! ^
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! 0 +------------------------------------->
		! 0 X-Rp
		!
		!
		!
		!
		V
		X-Rc

		180 degrees camera rotation:

		0
		<------------------------------------+ 0
		X-Rc !
		Y-Rp !
		^ !
		! !
		! !
		! !
		! !
		! !
		! !
		! V
		! Y-Rc
		0 +------------------------------------->
		0 X-Rp

		270 degrees camera rotation:

		0 Y-Rc
		0 +-------------------->
		! 0
		! <-----------------------------------+ 0
		! X-Rp !
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! !
		! V
		! Y-Rp
		!
		!
		!
		!
		V
		X-Rc


		Example one - Webcam

		A camera module installed on the user facing part of a laptop screen
		casing used for video calls. The captured images are meant to be
		displayed in landscape mode (width > height) on the laptop screen.

		The camera is typically mounted upside-down to compensate the lens
		optical inversion effect:

		Y-Rp
		Y-Rc ^
		^ !
		! !
		! ! \|\_____)\__
		! ! ) ____ ___.<
		! ! \|/ )/
		! !
		! !
		! !
		! 0 +------------------------------------->
		! 0 X-Rp
		0 +------------------------------------->
		0 X-Rc

		The two reference systems are aligned, the resulting camera rotation is
		0 degrees, no rotation correction needs to be applied to the resulting
		image once captured to memory buffers to correctly display it to users:

		+--------------------------------------+
		! !
		! !
		! !
		! \|\____)\___ !
		! ) _____ __`< !
		! \|/ )/ !
		! !
		! !
		! !
		+--------------------------------------+

		If the camera sensor is not mounted upside-down to compensate for the
		lens optical inversion, the two reference systems will not be aligned,
		with 'Rp' being rotated 180 degrees relatively to 'Rc':


		X-Rc 0
		<------------------------------------+ 0
		!
		Y-Rp !
		^ !
		! !
		! \|\_____)\__ !
		! ) ____ ___.< !
		! \|/ )/ !
		! !
		! !
		! V
		! Y-Rc
		0 +------------------------------------->
		0 X-Rp

		The image once captured to memory will then be rotated by 180 degrees:

		+--------------------------------------+
		! !
		! !
		! !
		! __/(_____/\| !
		! >.___ ____ ( !
		! \( \\| !
		! !
		! !
		! !
		+--------------------------------------+

		A software rotation correction of 180 degrees should be applied to
		correctly display the image:

		+--------------------------------------+
		! !
		! !
		! !
		! \|\____)\___ !
		! ) _____ __`< !
		! \|/ )/ !
		! !
		! !
		! !
		+--------------------------------------+

		Example two - Phone camera

		A camera installed on the back side of a mobile device facing away from
		the user. The captured images are meant to be displayed in portrait mode
		(height > width) to match the device screen orientation and the device
		usage orientation used when taking the picture.

		The camera sensor is typically mounted with its pixel array longer side
		aligned to the device longer side, upside-down mounted to compensate for
		the lens optical inversion effect:

		0 Y-Rc
		0 +-------------------->
		! Y-Rp
		! ^
		! !
		! !
		! !
		! ! \|\_____)\__
		! ! ) ____ ___.<
		! ! \|/ )/
		! !
		! !
		! !
		! 0 +------------------------------------->
		! 0 X-Rp
		!
		!
		!
		!
		V
		X-Rc

		The two reference systems are not aligned and the 'Rp' reference
		system is rotated by 90 degrees in the counter-clockwise direction
		relatively to the 'Rc' reference system.

		The image once captured to memory will be rotated:

		+-------------------------------------+
		\| _ _ \|
		\| \ / \|
		\| \| \| \|
		\| \| \| \|
		\| \| > \|
		\| < \| \|
		\| \| \| \|
		\| . \|
		\| V \|
		+-------------------------------------+

		A correction of 90 degrees in counter-clockwise direction has to be
		applied to correctly display the image in portrait mode on the device
		screen:

		+--------------------+
		\| \|
		\| \|
		\| \|
		\| \|
		\| \|
		\| \|
		\| \|\____)\___ \|
		\| ) _____ __`< \|
		\| \|/ )/ \|
		\| \|
		\| \|
		\| \|
		\| \|
		\| \|
		+--------------------+

		- orientation: The orientation of a device (typically an image sensor or a flash
		LED) describing its mounting position relative to the usage orientation of the