| .. Permission is granted to copy, distribute and/or modify this |
| .. document under the terms of the GNU Free Documentation License, |
| .. Version 1.1 or any later version published by the Free Software |
| .. Foundation, with no Invariant Sections, no Front-Cover Texts |
| .. and no Back-Cover Texts. A copy of the license is included at |
| .. Documentation/userspace-api/media/fdl-appendix.rst. |
| .. |
| .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections |
| |
| .. _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. |
