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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _camera-controls:
+
+************************
+Camera Control Reference
+************************
+
+The Camera class includes controls for mechanical (or equivalent
+digital) features of a device such as controllable lenses or sensors.
+
+
+.. _camera-control-id:
+
+Camera Control IDs
+==================
+
+``V4L2_CID_CAMERA_CLASS (class)``
+ The Camera class descriptor. Calling
+ :ref:`VIDIOC_QUERYCTRL` for this control will
+ return a description of this control class.
+
+.. _v4l2-exposure-auto-type:
+
+``V4L2_CID_EXPOSURE_AUTO``
+ (enum)
+
+enum v4l2_exposure_auto_type -
+ Enables automatic adjustments of the exposure time and/or iris
+ aperture. The effect of manual changes of the exposure time or iris
+ aperture while these features are enabled is undefined, drivers
+ should ignore such requests. Possible values are:
+
+
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_EXPOSURE_AUTO``
+ - Automatic exposure time, automatic iris aperture.
+ * - ``V4L2_EXPOSURE_MANUAL``
+ - Manual exposure time, manual iris.
+ * - ``V4L2_EXPOSURE_SHUTTER_PRIORITY``
+ - Manual exposure time, auto iris.
+ * - ``V4L2_EXPOSURE_APERTURE_PRIORITY``
+ - Auto exposure time, manual iris.
+
+
+
+``V4L2_CID_EXPOSURE_ABSOLUTE (integer)``
+ Determines the exposure time of the camera sensor. The exposure time
+ is limited by the frame interval. Drivers should interpret the
+ values as 100 µs units, where the value 1 stands for 1/10000th of a
+ second, 10000 for 1 second and 100000 for 10 seconds.
+
+``V4L2_CID_EXPOSURE_AUTO_PRIORITY (boolean)``
+ When ``V4L2_CID_EXPOSURE_AUTO`` is set to ``AUTO`` or
+ ``APERTURE_PRIORITY``, this control determines if the device may
+ dynamically vary the frame rate. By default this feature is disabled
+ (0) and the frame rate must remain constant.
+
+``V4L2_CID_AUTO_EXPOSURE_BIAS (integer menu)``
+ Determines the automatic exposure compensation, it is effective only
+ when ``V4L2_CID_EXPOSURE_AUTO`` control is set to ``AUTO``,
+ ``SHUTTER_PRIORITY`` or ``APERTURE_PRIORITY``. It is expressed in
+ terms of EV, drivers should interpret the values as 0.001 EV units,
+ where the value 1000 stands for +1 EV.
+
+ Increasing the exposure compensation value is equivalent to
+ decreasing the exposure value (EV) and will increase the amount of
+ light at the image sensor. The camera performs the exposure
+ compensation by adjusting absolute exposure time and/or aperture.
+
+.. _v4l2-exposure-metering:
+
+``V4L2_CID_EXPOSURE_METERING``
+ (enum)
+
+enum v4l2_exposure_metering -
+ Determines how the camera measures the amount of light available for
+ the frame exposure. Possible values are:
+
+.. tabularcolumns:: |p{8.7cm}|p{8.8cm}|
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_EXPOSURE_METERING_AVERAGE``
+ - Use the light information coming from the entire frame and average
+ giving no weighting to any particular portion of the metered area.
+ * - ``V4L2_EXPOSURE_METERING_CENTER_WEIGHTED``
+ - Average the light information coming from the entire frame giving
+ priority to the center of the metered area.
+ * - ``V4L2_EXPOSURE_METERING_SPOT``
+ - Measure only very small area at the center of the frame.
+ * - ``V4L2_EXPOSURE_METERING_MATRIX``
+ - A multi-zone metering. The light intensity is measured in several
+ points of the frame and the results are combined. The algorithm of
+ the zones selection and their significance in calculating the
+ final value is device dependent.
+
+
+
+``V4L2_CID_PAN_RELATIVE (integer)``
+ This control turns the camera horizontally by the specified amount.
+ The unit is undefined. A positive value moves the camera to the
+ right (clockwise when viewed from above), a negative value to the
+ left. A value of zero does not cause motion. This is a write-only
+ control.
+
+``V4L2_CID_TILT_RELATIVE (integer)``
+ This control turns the camera vertically by the specified amount.
+ The unit is undefined. A positive value moves the camera up, a
+ negative value down. A value of zero does not cause motion. This is
+ a write-only control.
+
+``V4L2_CID_PAN_RESET (button)``
+ When this control is set, the camera moves horizontally to the
+ default position.
+
+``V4L2_CID_TILT_RESET (button)``
+ When this control is set, the camera moves vertically to the default
+ position.
+
+``V4L2_CID_PAN_ABSOLUTE (integer)``
+ This control turns the camera horizontally to the specified
+ position. Positive values move the camera to the right (clockwise
+ when viewed from above), negative values to the left. Drivers should
+ interpret the values as arc seconds, with valid values between -180
+ * 3600 and +180 * 3600 inclusive.
+
+``V4L2_CID_TILT_ABSOLUTE (integer)``
+ This control turns the camera vertically to the specified position.
+ Positive values move the camera up, negative values down. Drivers
+ should interpret the values as arc seconds, with valid values
+ between -180 * 3600 and +180 * 3600 inclusive.
+
+``V4L2_CID_FOCUS_ABSOLUTE (integer)``
+ This control sets the focal point of the camera to the specified
+ position. The unit is undefined. Positive values set the focus
+ closer to the camera, negative values towards infinity.
+
+``V4L2_CID_FOCUS_RELATIVE (integer)``
+ This control moves the focal point of the camera by the specified
+ amount. The unit is undefined. Positive values move the focus closer
+ to the camera, negative values towards infinity. This is a
+ write-only control.
+
+``V4L2_CID_FOCUS_AUTO (boolean)``
+ Enables continuous automatic focus adjustments. The effect of manual
+ focus adjustments while this feature is enabled is undefined,
+ drivers should ignore such requests.
+
+``V4L2_CID_AUTO_FOCUS_START (button)``
+ Starts single auto focus process. The effect of setting this control
+ when ``V4L2_CID_FOCUS_AUTO`` is set to ``TRUE`` (1) is undefined,
+ drivers should ignore such requests.
+
+``V4L2_CID_AUTO_FOCUS_STOP (button)``
+ Aborts automatic focusing started with ``V4L2_CID_AUTO_FOCUS_START``
+ control. It is effective only when the continuous autofocus is
+ disabled, that is when ``V4L2_CID_FOCUS_AUTO`` control is set to
+ ``FALSE`` (0).
+
+.. _v4l2-auto-focus-status:
+
+``V4L2_CID_AUTO_FOCUS_STATUS (bitmask)``
+ The automatic focus status. This is a read-only control.
+
+ Setting ``V4L2_LOCK_FOCUS`` lock bit of the ``V4L2_CID_3A_LOCK``
+ control may stop updates of the ``V4L2_CID_AUTO_FOCUS_STATUS``
+ control value.
+
+.. tabularcolumns:: |p{6.7cm}|p{10.8cm}|
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_AUTO_FOCUS_STATUS_IDLE``
+ - Automatic focus is not active.
+ * - ``V4L2_AUTO_FOCUS_STATUS_BUSY``
+ - Automatic focusing is in progress.
+ * - ``V4L2_AUTO_FOCUS_STATUS_REACHED``
+ - Focus has been reached.
+ * - ``V4L2_AUTO_FOCUS_STATUS_FAILED``
+ - Automatic focus has failed, the driver will not transition from
+ this state until another action is performed by an application.
+
+
+
+.. _v4l2-auto-focus-range:
+
+``V4L2_CID_AUTO_FOCUS_RANGE``
+ (enum)
+
+enum v4l2_auto_focus_range -
+ Determines auto focus distance range for which lens may be adjusted.
+
+.. tabularcolumns:: |p{6.8cm}|p{10.7cm}|
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_AUTO_FOCUS_RANGE_AUTO``
+ - The camera automatically selects the focus range.
+ * - ``V4L2_AUTO_FOCUS_RANGE_NORMAL``
+ - Normal distance range, limited for best automatic focus
+ performance.
+ * - ``V4L2_AUTO_FOCUS_RANGE_MACRO``
+ - Macro (close-up) auto focus. The camera will use its minimum
+ possible distance for auto focus.
+ * - ``V4L2_AUTO_FOCUS_RANGE_INFINITY``
+ - The lens is set to focus on an object at infinite distance.
+
+
+
+``V4L2_CID_ZOOM_ABSOLUTE (integer)``
+ Specify the objective lens focal length as an absolute value. The
+ zoom unit is driver-specific and its value should be a positive
+ integer.
+
+``V4L2_CID_ZOOM_RELATIVE (integer)``
+ Specify the objective lens focal length relatively to the current
+ value. Positive values move the zoom lens group towards the
+ telephoto direction, negative values towards the wide-angle
+ direction. The zoom unit is driver-specific. This is a write-only
+ control.
+
+``V4L2_CID_ZOOM_CONTINUOUS (integer)``
+ Move the objective lens group at the specified speed until it
+ reaches physical device limits or until an explicit request to stop
+ the movement. A positive value moves the zoom lens group towards the
+ telephoto direction. A value of zero stops the zoom lens group
+ movement. A negative value moves the zoom lens group towards the
+ wide-angle direction. The zoom speed unit is driver-specific.
+
+``V4L2_CID_IRIS_ABSOLUTE (integer)``
+ This control sets the camera's aperture to the specified value. The
+ unit is undefined. Larger values open the iris wider, smaller values
+ close it.
+
+``V4L2_CID_IRIS_RELATIVE (integer)``
+ This control modifies the camera's aperture by the specified amount.
+ The unit is undefined. Positive values open the iris one step
+ further, negative values close it one step further. This is a
+ write-only control.
+
+``V4L2_CID_PRIVACY (boolean)``
+ Prevent video from being acquired by the camera. When this control
+ is set to ``TRUE`` (1), no image can be captured by the camera.
+ Common means to enforce privacy are mechanical obturation of the
+ sensor and firmware image processing, but the device is not
+ restricted to these methods. Devices that implement the privacy
+ control must support read access and may support write access.
+
+``V4L2_CID_BAND_STOP_FILTER (integer)``
+ Switch the band-stop filter of a camera sensor on or off, or specify
+ its strength. Such band-stop filters can be used, for example, to
+ filter out the fluorescent light component.
+
+.. _v4l2-auto-n-preset-white-balance:
+
+``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE``
+ (enum)
+
+enum v4l2_auto_n_preset_white_balance -
+ Sets white balance to automatic, manual or a preset. The presets
+ determine color temperature of the light as a hint to the camera for
+ white balance adjustments resulting in most accurate color
+ representation. The following white balance presets are listed in
+ order of increasing color temperature.
+
+.. tabularcolumns:: |p{7.2 cm}|p{10.3cm}|
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_WHITE_BALANCE_MANUAL``
+ - Manual white balance.
+ * - ``V4L2_WHITE_BALANCE_AUTO``
+ - Automatic white balance adjustments.
+ * - ``V4L2_WHITE_BALANCE_INCANDESCENT``
+ - White balance setting for incandescent (tungsten) lighting. It
+ generally cools down the colors and corresponds approximately to
+ 2500...3500 K color temperature range.
+ * - ``V4L2_WHITE_BALANCE_FLUORESCENT``
+ - White balance preset for fluorescent lighting. It corresponds
+ approximately to 4000...5000 K color temperature.
+ * - ``V4L2_WHITE_BALANCE_FLUORESCENT_H``
+ - With this setting the camera will compensate for fluorescent H
+ lighting.
+ * - ``V4L2_WHITE_BALANCE_HORIZON``
+ - White balance setting for horizon daylight. It corresponds
+ approximately to 5000 K color temperature.
+ * - ``V4L2_WHITE_BALANCE_DAYLIGHT``
+ - White balance preset for daylight (with clear sky). It corresponds
+ approximately to 5000...6500 K color temperature.
+ * - ``V4L2_WHITE_BALANCE_FLASH``
+ - With this setting the camera will compensate for the flash light.
+ It slightly warms up the colors and corresponds roughly to
+ 5000...5500 K color temperature.
+ * - ``V4L2_WHITE_BALANCE_CLOUDY``
+ - White balance preset for moderately overcast sky. This option
+ corresponds approximately to 6500...8000 K color temperature
+ range.
+ * - ``V4L2_WHITE_BALANCE_SHADE``
+ - White balance preset for shade or heavily overcast sky. It
+ corresponds approximately to 9000...10000 K color temperature.
+
+
+
+.. _v4l2-wide-dynamic-range:
+
+``V4L2_CID_WIDE_DYNAMIC_RANGE (boolean)``
+ Enables or disables the camera's wide dynamic range feature. This
+ feature allows to obtain clear images in situations where intensity
+ of the illumination varies significantly throughout the scene, i.e.
+ there are simultaneously very dark and very bright areas. It is most
+ commonly realized in cameras by combining two subsequent frames with
+ different exposure times. [#f1]_
+
+.. _v4l2-image-stabilization:
+
+``V4L2_CID_IMAGE_STABILIZATION (boolean)``
+ Enables or disables image stabilization.
+
+``V4L2_CID_ISO_SENSITIVITY (integer menu)``
+ Determines ISO equivalent of an image sensor indicating the sensor's
+ sensitivity to light. The numbers are expressed in arithmetic scale,
+ as per :ref:`iso12232` standard, where doubling the sensor
+ sensitivity is represented by doubling the numerical ISO value.
+ Applications should interpret the values as standard ISO values
+ multiplied by 1000, e.g. control value 800 stands for ISO 0.8.
+ Drivers will usually support only a subset of standard ISO values.
+ The effect of setting this control while the
+ ``V4L2_CID_ISO_SENSITIVITY_AUTO`` control is set to a value other
+ than ``V4L2_CID_ISO_SENSITIVITY_MANUAL`` is undefined, drivers
+ should ignore such requests.
+
+.. _v4l2-iso-sensitivity-auto-type:
+
+``V4L2_CID_ISO_SENSITIVITY_AUTO``
+ (enum)
+
+enum v4l2_iso_sensitivity_type -
+ Enables or disables automatic ISO sensitivity adjustments.
+
+
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_CID_ISO_SENSITIVITY_MANUAL``
+ - Manual ISO sensitivity.
+ * - ``V4L2_CID_ISO_SENSITIVITY_AUTO``
+ - Automatic ISO sensitivity adjustments.
+
+
+
+.. _v4l2-scene-mode:
+
+``V4L2_CID_SCENE_MODE``
+ (enum)
+
+enum v4l2_scene_mode -
+ This control allows to select scene programs as the camera automatic
+ modes optimized for common shooting scenes. Within these modes the
+ camera determines best exposure, aperture, focusing, light metering,
+ white balance and equivalent sensitivity. The controls of those
+ parameters are influenced by the scene mode control. An exact
+ behavior in each mode is subject to the camera specification.
+
+ When the scene mode feature is not used, this control should be set
+ to ``V4L2_SCENE_MODE_NONE`` to make sure the other possibly related
+ controls are accessible. The following scene programs are defined:
+
+.. raw:: latex
+
+ \small
+
+.. tabularcolumns:: |p{5.9cm}|p{11.5cm}|
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_SCENE_MODE_NONE``
+ - The scene mode feature is disabled.
+ * - ``V4L2_SCENE_MODE_BACKLIGHT``
+ - Backlight. Compensates for dark shadows when light is coming from
+ behind a subject, also by automatically turning on the flash.
+ * - ``V4L2_SCENE_MODE_BEACH_SNOW``
+ - Beach and snow. This mode compensates for all-white or bright
+ scenes, which tend to look gray and low contrast, when camera's
+ automatic exposure is based on an average scene brightness. To
+ compensate, this mode automatically slightly overexposes the
+ frames. The white balance may also be adjusted to compensate for
+ the fact that reflected snow looks bluish rather than white.
+ * - ``V4L2_SCENE_MODE_CANDLELIGHT``
+ - Candle light. The camera generally raises the ISO sensitivity and
+ lowers the shutter speed. This mode compensates for relatively
+ close subject in the scene. The flash is disabled in order to
+ preserve the ambiance of the light.
+ * - ``V4L2_SCENE_MODE_DAWN_DUSK``
+ - Dawn and dusk. Preserves the colors seen in low natural light
+ before dusk and after down. The camera may turn off the flash, and
+ automatically focus at infinity. It will usually boost saturation
+ and lower the shutter speed.
+ * - ``V4L2_SCENE_MODE_FALL_COLORS``
+ - Fall colors. Increases saturation and adjusts white balance for
+ color enhancement. Pictures of autumn leaves get saturated reds
+ and yellows.
+ * - ``V4L2_SCENE_MODE_FIREWORKS``
+ - Fireworks. Long exposure times are used to capture the expanding
+ burst of light from a firework. The camera may invoke image
+ stabilization.
+ * - ``V4L2_SCENE_MODE_LANDSCAPE``
+ - Landscape. The camera may choose a small aperture to provide deep
+ depth of field and long exposure duration to help capture detail
+ in dim light conditions. The focus is fixed at infinity. Suitable
+ for distant and wide scenery.
+ * - ``V4L2_SCENE_MODE_NIGHT``
+ - Night, also known as Night Landscape. Designed for low light
+ conditions, it preserves detail in the dark areas without blowing
+ out bright objects. The camera generally sets itself to a
+ medium-to-high ISO sensitivity, with a relatively long exposure
+ time, and turns flash off. As such, there will be increased image
+ noise and the possibility of blurred image.
+ * - ``V4L2_SCENE_MODE_PARTY_INDOOR``
+ - Party and indoor. Designed to capture indoor scenes that are lit
+ by indoor background lighting as well as the flash. The camera
+ usually increases ISO sensitivity, and adjusts exposure for the
+ low light conditions.
+ * - ``V4L2_SCENE_MODE_PORTRAIT``
+ - Portrait. The camera adjusts the aperture so that the depth of
+ field is reduced, which helps to isolate the subject against a
+ smooth background. Most cameras recognize the presence of faces in
+ the scene and focus on them. The color hue is adjusted to enhance
+ skin tones. The intensity of the flash is often reduced.
+ * - ``V4L2_SCENE_MODE_SPORTS``
+ - Sports. Significantly increases ISO and uses a fast shutter speed
+ to freeze motion of rapidly-moving subjects. Increased image noise
+ may be seen in this mode.
+ * - ``V4L2_SCENE_MODE_SUNSET``
+ - Sunset. Preserves deep hues seen in sunsets and sunrises. It bumps
+ up the saturation.
+ * - ``V4L2_SCENE_MODE_TEXT``
+ - Text. It applies extra contrast and sharpness, it is typically a
+ black-and-white mode optimized for readability. Automatic focus
+ may be switched to close-up mode and this setting may also involve
+ some lens-distortion correction.
+
+.. raw:: latex
+
+ \normalsize
+
+
+``V4L2_CID_3A_LOCK (bitmask)``
+ This control locks or unlocks the automatic focus, exposure and
+ white balance. The automatic adjustments can be paused independently
+ by setting the corresponding lock bit to 1. The camera then retains
+ the settings until the lock bit is cleared. The following lock bits
+ are defined:
+
+ When a given algorithm is not enabled, drivers should ignore
+ requests to lock it and should return no error. An example might be
+ an application setting bit ``V4L2_LOCK_WHITE_BALANCE`` when the
+ ``V4L2_CID_AUTO_WHITE_BALANCE`` control is set to ``FALSE``. The
+ value of this control may be changed by exposure, white balance or
+ focus controls.
+
+
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_LOCK_EXPOSURE``
+ - Automatic exposure adjustments lock.
+ * - ``V4L2_LOCK_WHITE_BALANCE``
+ - Automatic white balance adjustments lock.
+ * - ``V4L2_LOCK_FOCUS``
+ - Automatic focus lock.
+
+
+
+``V4L2_CID_PAN_SPEED (integer)``
+ This control turns the camera horizontally at the specific speed.
+ The unit is undefined. A positive value moves the camera to the
+ right (clockwise when viewed from above), a negative value to the
+ left. A value of zero stops the motion if one is in progress and has
+ no effect otherwise.
+
+``V4L2_CID_TILT_SPEED (integer)``
+ This control turns the camera vertically at the specified speed. The
+ unit is undefined. A positive value moves the camera up, a negative
+ value down. A value of zero stops the motion if one is in progress
+ and has no effect otherwise.
+
+``V4L2_CID_CAMERA_ORIENTATION (menu)``
+ This read-only control describes the camera orientation by reporting its
+ mounting position on the device where the camera is installed. The control
+ value is constant and not modifiable by software. This control is
+ particularly meaningful for devices which have a well defined orientation,
+ such as phones, laptops and portable devices since the control is expressed
+ as a position relative to the device's intended usage orientation. For
+ example, a camera installed on the user-facing side of a phone, a tablet or
+ a laptop device is said to be have ``V4L2_CAMERA_ORIENTATION_FRONT``
+ orientation, while a camera installed on the opposite side of the front one
+ is said to be have ``V4L2_CAMERA_ORIENTATION_BACK`` orientation. Camera
+ sensors not directly attached to the device, or attached in a way that
+ allows them to move freely, such as webcams and digital cameras, are said to
+ have the ``V4L2_CAMERA_ORIENTATION_EXTERNAL`` orientation.
+
+
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_CAMERA_ORIENTATION_FRONT``
+ - The camera is oriented towards the user facing side of the device.
+ * - ``V4L2_CAMERA_ORIENTATION_BACK``
+ - The camera is oriented towards the back facing side of the device.
+ * - ``V4L2_CAMERA_ORIENTATION_EXTERNAL``
+ - The camera is not directly attached to the device and is freely movable.
+
+
+
+``V4L2_CID_CAMERA_SENSOR_ROTATION (integer)``
+ This read-only control describes the rotation correction in degrees in the
+ counter-clockwise direction to be applied to the captured images once
+ captured to memory to compensate for the camera sensor mounting rotation.
+
+ For a precise definition of the sensor mounting rotation refer to the
+ extensive description of the 'rotation' properties in the device tree
+ bindings file 'video-interfaces.txt'.
+
+ A few examples are below reported, using a shark swimming from left to
+ right in front of the user as the example scene to capture. ::
+
+ 0 X-axis
+ 0 +------------------------------------->
+ !
+ !
+ !
+ ! |\____)\___
+ ! ) _____ __`<
+ ! |/ )/
+ !
+ !
+ !
+ V
+ Y-axis
+
+ Example one - Webcam
+
+ Assuming you can bring your laptop with you while swimming with sharks,
+ the camera module of the laptop is installed on the user facing part of a
+ laptop screen casing, and is typically 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. In this case the value of the
+ V4L2_CID_CAMERA_SENSOR_ROTATION control is 0, no rotation is required to
+ display images correctly to the user.
+
+ If the camera sensor is not mounted upside-down it is required to compensate
+ the lens optical inversion effect and the value of the
+ V4L2_CID_CAMERA_SENSOR_ROTATION control is 180 degrees, as images will
+ result rotated when captured to memory. ::
+
+ +--------------------------------------+
+ ! !
+ ! !
+ ! !
+ ! __/(_____/| !
+ ! >.___ ____ ( !
+ ! \( \| !
+ ! !
+ ! !
+ ! !
+ +--------------------------------------+
+
+ A software rotation correction of 180 degrees has to be applied to correctly
+ display the image on the user screen. ::
+
+ +--------------------------------------+
+ ! !
+ ! !
+ ! !
+ ! |\____)\___ !
+ ! ) _____ __`< !
+ ! |/ )/ !
+ ! !
+ ! !
+ ! !
+ +--------------------------------------+
+
+ Example two - Phone camera
+
+ It is more handy to go and swim with sharks with only your mobile phone
+ with you and take pictures with the camera that is installed on the back
+ side of the 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.
+
+ The images once captured to memory will be rotated and the value of the
+ V4L2_CID_CAMERA_SENSOR_ROTATION will report a 90 degree rotation. ::
+
+
+ +-------------------------------------+
+ | _ _ |
+ | \ / |
+ | | | |
+ | | | |
+ | | > |
+ | < | |
+ | | | |
+ | . |
+ | 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. ::
+
+ +--------------------+
+ | |
+ | |
+ | |
+ | |
+ | |
+ | |
+ | |\____)\___ |
+ | ) _____ __`< |
+ | |/ )/ |
+ | |
+ | |
+ | |
+ | |
+ | |
+ +--------------------+
+
+
+.. [#f1]
+ This control may be changed to a menu control in the future, if more
+ options are required.