1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _camera-controls: 5 6************************ 7Camera Control Reference 8************************ 9 10The Camera class includes controls for mechanical (or equivalent 11digital) features of a device such as controllable lenses or sensors. 12 13 14.. _camera-control-id: 15 16Camera Control IDs 17================== 18 19``V4L2_CID_CAMERA_CLASS (class)`` 20 The Camera class descriptor. Calling 21 :ref:`VIDIOC_QUERYCTRL` for this control will 22 return a description of this control class. 23 24.. _v4l2-exposure-auto-type: 25 26``V4L2_CID_EXPOSURE_AUTO`` 27 (enum) 28 29enum v4l2_exposure_auto_type - 30 Enables automatic adjustments of the exposure time and/or iris 31 aperture. The effect of manual changes of the exposure time or iris 32 aperture while these features are enabled is undefined, drivers 33 should ignore such requests. Possible values are: 34 35 36.. tabularcolumns:: |p{7.1cm}|p{10.4cm}| 37 38.. flat-table:: 39 :header-rows: 0 40 :stub-columns: 0 41 42 * - ``V4L2_EXPOSURE_AUTO`` 43 - Automatic exposure time, automatic iris aperture. 44 * - ``V4L2_EXPOSURE_MANUAL`` 45 - Manual exposure time, manual iris. 46 * - ``V4L2_EXPOSURE_SHUTTER_PRIORITY`` 47 - Manual exposure time, auto iris. 48 * - ``V4L2_EXPOSURE_APERTURE_PRIORITY`` 49 - Auto exposure time, manual iris. 50 51 52 53``V4L2_CID_EXPOSURE_ABSOLUTE (integer)`` 54 Determines the exposure time of the camera sensor. The exposure time 55 is limited by the frame interval. Drivers should interpret the 56 values as 100 µs units, where the value 1 stands for 1/10000th of a 57 second, 10000 for 1 second and 100000 for 10 seconds. 58 59``V4L2_CID_EXPOSURE_AUTO_PRIORITY (boolean)`` 60 When ``V4L2_CID_EXPOSURE_AUTO`` is set to ``AUTO`` or 61 ``APERTURE_PRIORITY``, this control determines if the device may 62 dynamically vary the frame rate. By default this feature is disabled 63 (0) and the frame rate must remain constant. 64 65``V4L2_CID_AUTO_EXPOSURE_BIAS (integer menu)`` 66 Determines the automatic exposure compensation, it is effective only 67 when ``V4L2_CID_EXPOSURE_AUTO`` control is set to ``AUTO``, 68 ``SHUTTER_PRIORITY`` or ``APERTURE_PRIORITY``. It is expressed in 69 terms of EV, drivers should interpret the values as 0.001 EV units, 70 where the value 1000 stands for +1 EV. 71 72 Increasing the exposure compensation value is equivalent to 73 decreasing the exposure value (EV) and will increase the amount of 74 light at the image sensor. The camera performs the exposure 75 compensation by adjusting absolute exposure time and/or aperture. 76 77.. _v4l2-exposure-metering: 78 79``V4L2_CID_EXPOSURE_METERING`` 80 (enum) 81 82enum v4l2_exposure_metering - 83 Determines how the camera measures the amount of light available for 84 the frame exposure. Possible values are: 85 86.. tabularcolumns:: |p{8.7cm}|p{8.7cm}| 87 88.. flat-table:: 89 :header-rows: 0 90 :stub-columns: 0 91 92 * - ``V4L2_EXPOSURE_METERING_AVERAGE`` 93 - Use the light information coming from the entire frame and average 94 giving no weighting to any particular portion of the metered area. 95 * - ``V4L2_EXPOSURE_METERING_CENTER_WEIGHTED`` 96 - Average the light information coming from the entire frame giving 97 priority to the center of the metered area. 98 * - ``V4L2_EXPOSURE_METERING_SPOT`` 99 - Measure only very small area at the center of the frame. 100 * - ``V4L2_EXPOSURE_METERING_MATRIX`` 101 - A multi-zone metering. The light intensity is measured in several 102 points of the frame and the results are combined. The algorithm of 103 the zones selection and their significance in calculating the 104 final value is device dependent. 105 106 107 108``V4L2_CID_PAN_RELATIVE (integer)`` 109 This control turns the camera horizontally by the specified amount. 110 The unit is undefined. A positive value moves the camera to the 111 right (clockwise when viewed from above), a negative value to the 112 left. A value of zero does not cause motion. This is a write-only 113 control. 114 115``V4L2_CID_TILT_RELATIVE (integer)`` 116 This control turns the camera vertically by the specified amount. 117 The unit is undefined. A positive value moves the camera up, a 118 negative value down. A value of zero does not cause motion. This is 119 a write-only control. 120 121``V4L2_CID_PAN_RESET (button)`` 122 When this control is set, the camera moves horizontally to the 123 default position. 124 125``V4L2_CID_TILT_RESET (button)`` 126 When this control is set, the camera moves vertically to the default 127 position. 128 129``V4L2_CID_PAN_ABSOLUTE (integer)`` 130 This control turns the camera horizontally to the specified 131 position. Positive values move the camera to the right (clockwise 132 when viewed from above), negative values to the left. Drivers should 133 interpret the values as arc seconds, with valid values between -180 134 * 3600 and +180 * 3600 inclusive. 135 136``V4L2_CID_TILT_ABSOLUTE (integer)`` 137 This control turns the camera vertically to the specified position. 138 Positive values move the camera up, negative values down. Drivers 139 should interpret the values as arc seconds, with valid values 140 between -180 * 3600 and +180 * 3600 inclusive. 141 142``V4L2_CID_FOCUS_ABSOLUTE (integer)`` 143 This control sets the focal point of the camera to the specified 144 position. The unit is undefined. Positive values set the focus 145 closer to the camera, negative values towards infinity. 146 147``V4L2_CID_FOCUS_RELATIVE (integer)`` 148 This control moves the focal point of the camera by the specified 149 amount. The unit is undefined. Positive values move the focus closer 150 to the camera, negative values towards infinity. This is a 151 write-only control. 152 153``V4L2_CID_FOCUS_AUTO (boolean)`` 154 Enables continuous automatic focus adjustments. The effect of manual 155 focus adjustments while this feature is enabled is undefined, 156 drivers should ignore such requests. 157 158``V4L2_CID_AUTO_FOCUS_START (button)`` 159 Starts single auto focus process. The effect of setting this control 160 when ``V4L2_CID_FOCUS_AUTO`` is set to ``TRUE`` (1) is undefined, 161 drivers should ignore such requests. 162 163``V4L2_CID_AUTO_FOCUS_STOP (button)`` 164 Aborts automatic focusing started with ``V4L2_CID_AUTO_FOCUS_START`` 165 control. It is effective only when the continuous autofocus is 166 disabled, that is when ``V4L2_CID_FOCUS_AUTO`` control is set to 167 ``FALSE`` (0). 168 169.. _v4l2-auto-focus-status: 170 171``V4L2_CID_AUTO_FOCUS_STATUS (bitmask)`` 172 The automatic focus status. This is a read-only control. 173 174 Setting ``V4L2_LOCK_FOCUS`` lock bit of the ``V4L2_CID_3A_LOCK`` 175 control may stop updates of the ``V4L2_CID_AUTO_FOCUS_STATUS`` 176 control value. 177 178.. tabularcolumns:: |p{6.8cm}|p{10.7cm}| 179 180.. flat-table:: 181 :header-rows: 0 182 :stub-columns: 0 183 184 * - ``V4L2_AUTO_FOCUS_STATUS_IDLE`` 185 - Automatic focus is not active. 186 * - ``V4L2_AUTO_FOCUS_STATUS_BUSY`` 187 - Automatic focusing is in progress. 188 * - ``V4L2_AUTO_FOCUS_STATUS_REACHED`` 189 - Focus has been reached. 190 * - ``V4L2_AUTO_FOCUS_STATUS_FAILED`` 191 - Automatic focus has failed, the driver will not transition from 192 this state until another action is performed by an application. 193 194 195 196.. _v4l2-auto-focus-range: 197 198``V4L2_CID_AUTO_FOCUS_RANGE`` 199 (enum) 200 201enum v4l2_auto_focus_range - 202 Determines auto focus distance range for which lens may be adjusted. 203 204.. tabularcolumns:: |p{6.9cm}|p{10.6cm}| 205 206.. flat-table:: 207 :header-rows: 0 208 :stub-columns: 0 209 210 * - ``V4L2_AUTO_FOCUS_RANGE_AUTO`` 211 - The camera automatically selects the focus range. 212 * - ``V4L2_AUTO_FOCUS_RANGE_NORMAL`` 213 - Normal distance range, limited for best automatic focus 214 performance. 215 * - ``V4L2_AUTO_FOCUS_RANGE_MACRO`` 216 - Macro (close-up) auto focus. The camera will use its minimum 217 possible distance for auto focus. 218 * - ``V4L2_AUTO_FOCUS_RANGE_INFINITY`` 219 - The lens is set to focus on an object at infinite distance. 220 221 222 223``V4L2_CID_ZOOM_ABSOLUTE (integer)`` 224 Specify the objective lens focal length as an absolute value. The 225 zoom unit is driver-specific and its value should be a positive 226 integer. 227 228``V4L2_CID_ZOOM_RELATIVE (integer)`` 229 Specify the objective lens focal length relatively to the current 230 value. Positive values move the zoom lens group towards the 231 telephoto direction, negative values towards the wide-angle 232 direction. The zoom unit is driver-specific. This is a write-only 233 control. 234 235``V4L2_CID_ZOOM_CONTINUOUS (integer)`` 236 Move the objective lens group at the specified speed until it 237 reaches physical device limits or until an explicit request to stop 238 the movement. A positive value moves the zoom lens group towards the 239 telephoto direction. A value of zero stops the zoom lens group 240 movement. A negative value moves the zoom lens group towards the 241 wide-angle direction. The zoom speed unit is driver-specific. 242 243``V4L2_CID_IRIS_ABSOLUTE (integer)`` 244 This control sets the camera's aperture to the specified value. The 245 unit is undefined. Larger values open the iris wider, smaller values 246 close it. 247 248``V4L2_CID_IRIS_RELATIVE (integer)`` 249 This control modifies the camera's aperture by the specified amount. 250 The unit is undefined. Positive values open the iris one step 251 further, negative values close it one step further. This is a 252 write-only control. 253 254``V4L2_CID_PRIVACY (boolean)`` 255 Prevent video from being acquired by the camera. When this control 256 is set to ``TRUE`` (1), no image can be captured by the camera. 257 Common means to enforce privacy are mechanical obturation of the 258 sensor and firmware image processing, but the device is not 259 restricted to these methods. Devices that implement the privacy 260 control must support read access and may support write access. 261 262``V4L2_CID_BAND_STOP_FILTER (integer)`` 263 Switch the band-stop filter of a camera sensor on or off, or specify 264 its strength. Such band-stop filters can be used, for example, to 265 filter out the fluorescent light component. 266 267.. _v4l2-auto-n-preset-white-balance: 268 269``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE`` 270 (enum) 271 272enum v4l2_auto_n_preset_white_balance - 273 Sets white balance to automatic, manual or a preset. The presets 274 determine color temperature of the light as a hint to the camera for 275 white balance adjustments resulting in most accurate color 276 representation. The following white balance presets are listed in 277 order of increasing color temperature. 278 279.. tabularcolumns:: |p{7.4cm}|p{10.1cm}| 280 281.. flat-table:: 282 :header-rows: 0 283 :stub-columns: 0 284 285 * - ``V4L2_WHITE_BALANCE_MANUAL`` 286 - Manual white balance. 287 * - ``V4L2_WHITE_BALANCE_AUTO`` 288 - Automatic white balance adjustments. 289 * - ``V4L2_WHITE_BALANCE_INCANDESCENT`` 290 - White balance setting for incandescent (tungsten) lighting. It 291 generally cools down the colors and corresponds approximately to 292 2500...3500 K color temperature range. 293 * - ``V4L2_WHITE_BALANCE_FLUORESCENT`` 294 - White balance preset for fluorescent lighting. It corresponds 295 approximately to 4000...5000 K color temperature. 296 * - ``V4L2_WHITE_BALANCE_FLUORESCENT_H`` 297 - With this setting the camera will compensate for fluorescent H 298 lighting. 299 * - ``V4L2_WHITE_BALANCE_HORIZON`` 300 - White balance setting for horizon daylight. It corresponds 301 approximately to 5000 K color temperature. 302 * - ``V4L2_WHITE_BALANCE_DAYLIGHT`` 303 - White balance preset for daylight (with clear sky). It corresponds 304 approximately to 5000...6500 K color temperature. 305 * - ``V4L2_WHITE_BALANCE_FLASH`` 306 - With this setting the camera will compensate for the flash light. 307 It slightly warms up the colors and corresponds roughly to 308 5000...5500 K color temperature. 309 * - ``V4L2_WHITE_BALANCE_CLOUDY`` 310 - White balance preset for moderately overcast sky. This option 311 corresponds approximately to 6500...8000 K color temperature 312 range. 313 * - ``V4L2_WHITE_BALANCE_SHADE`` 314 - White balance preset for shade or heavily overcast sky. It 315 corresponds approximately to 9000...10000 K color temperature. 316 317 318 319.. _v4l2-wide-dynamic-range: 320 321``V4L2_CID_WIDE_DYNAMIC_RANGE (boolean)`` 322 Enables or disables the camera's wide dynamic range feature. This 323 feature allows to obtain clear images in situations where intensity 324 of the illumination varies significantly throughout the scene, i.e. 325 there are simultaneously very dark and very bright areas. It is most 326 commonly realized in cameras by combining two subsequent frames with 327 different exposure times. [#f1]_ 328 329.. _v4l2-image-stabilization: 330 331``V4L2_CID_IMAGE_STABILIZATION (boolean)`` 332 Enables or disables image stabilization. 333 334``V4L2_CID_ISO_SENSITIVITY (integer menu)`` 335 Determines ISO equivalent of an image sensor indicating the sensor's 336 sensitivity to light. The numbers are expressed in arithmetic scale, 337 as per :ref:`iso12232` standard, where doubling the sensor 338 sensitivity is represented by doubling the numerical ISO value. 339 Applications should interpret the values as standard ISO values 340 multiplied by 1000, e.g. control value 800 stands for ISO 0.8. 341 Drivers will usually support only a subset of standard ISO values. 342 The effect of setting this control while the 343 ``V4L2_CID_ISO_SENSITIVITY_AUTO`` control is set to a value other 344 than ``V4L2_CID_ISO_SENSITIVITY_MANUAL`` is undefined, drivers 345 should ignore such requests. 346 347.. _v4l2-iso-sensitivity-auto-type: 348 349``V4L2_CID_ISO_SENSITIVITY_AUTO`` 350 (enum) 351 352enum v4l2_iso_sensitivity_type - 353 Enables or disables automatic ISO sensitivity adjustments. 354 355 356 357.. flat-table:: 358 :header-rows: 0 359 :stub-columns: 0 360 361 * - ``V4L2_CID_ISO_SENSITIVITY_MANUAL`` 362 - Manual ISO sensitivity. 363 * - ``V4L2_CID_ISO_SENSITIVITY_AUTO`` 364 - Automatic ISO sensitivity adjustments. 365 366 367 368.. _v4l2-scene-mode: 369 370``V4L2_CID_SCENE_MODE`` 371 (enum) 372 373enum v4l2_scene_mode - 374 This control allows to select scene programs as the camera automatic 375 modes optimized for common shooting scenes. Within these modes the 376 camera determines best exposure, aperture, focusing, light metering, 377 white balance and equivalent sensitivity. The controls of those 378 parameters are influenced by the scene mode control. An exact 379 behavior in each mode is subject to the camera specification. 380 381 When the scene mode feature is not used, this control should be set 382 to ``V4L2_SCENE_MODE_NONE`` to make sure the other possibly related 383 controls are accessible. The following scene programs are defined: 384 385.. raw:: latex 386 387 \small 388 389.. tabularcolumns:: |p{5.9cm}|p{11.6cm}| 390 391.. cssclass:: longtable 392 393.. flat-table:: 394 :header-rows: 0 395 :stub-columns: 0 396 397 * - ``V4L2_SCENE_MODE_NONE`` 398 - The scene mode feature is disabled. 399 * - ``V4L2_SCENE_MODE_BACKLIGHT`` 400 - Backlight. Compensates for dark shadows when light is coming from 401 behind a subject, also by automatically turning on the flash. 402 * - ``V4L2_SCENE_MODE_BEACH_SNOW`` 403 - Beach and snow. This mode compensates for all-white or bright 404 scenes, which tend to look gray and low contrast, when camera's 405 automatic exposure is based on an average scene brightness. To 406 compensate, this mode automatically slightly overexposes the 407 frames. The white balance may also be adjusted to compensate for 408 the fact that reflected snow looks bluish rather than white. 409 * - ``V4L2_SCENE_MODE_CANDLELIGHT`` 410 - Candle light. The camera generally raises the ISO sensitivity and 411 lowers the shutter speed. This mode compensates for relatively 412 close subject in the scene. The flash is disabled in order to 413 preserve the ambiance of the light. 414 * - ``V4L2_SCENE_MODE_DAWN_DUSK`` 415 - Dawn and dusk. Preserves the colors seen in low natural light 416 before dusk and after down. The camera may turn off the flash, and 417 automatically focus at infinity. It will usually boost saturation 418 and lower the shutter speed. 419 * - ``V4L2_SCENE_MODE_FALL_COLORS`` 420 - Fall colors. Increases saturation and adjusts white balance for 421 color enhancement. Pictures of autumn leaves get saturated reds 422 and yellows. 423 * - ``V4L2_SCENE_MODE_FIREWORKS`` 424 - Fireworks. Long exposure times are used to capture the expanding 425 burst of light from a firework. The camera may invoke image 426 stabilization. 427 * - ``V4L2_SCENE_MODE_LANDSCAPE`` 428 - Landscape. The camera may choose a small aperture to provide deep 429 depth of field and long exposure duration to help capture detail 430 in dim light conditions. The focus is fixed at infinity. Suitable 431 for distant and wide scenery. 432 * - ``V4L2_SCENE_MODE_NIGHT`` 433 - Night, also known as Night Landscape. Designed for low light 434 conditions, it preserves detail in the dark areas without blowing 435 out bright objects. The camera generally sets itself to a 436 medium-to-high ISO sensitivity, with a relatively long exposure 437 time, and turns flash off. As such, there will be increased image 438 noise and the possibility of blurred image. 439 * - ``V4L2_SCENE_MODE_PARTY_INDOOR`` 440 - Party and indoor. Designed to capture indoor scenes that are lit 441 by indoor background lighting as well as the flash. The camera 442 usually increases ISO sensitivity, and adjusts exposure for the 443 low light conditions. 444 * - ``V4L2_SCENE_MODE_PORTRAIT`` 445 - Portrait. The camera adjusts the aperture so that the depth of 446 field is reduced, which helps to isolate the subject against a 447 smooth background. Most cameras recognize the presence of faces in 448 the scene and focus on them. The color hue is adjusted to enhance 449 skin tones. The intensity of the flash is often reduced. 450 * - ``V4L2_SCENE_MODE_SPORTS`` 451 - Sports. Significantly increases ISO and uses a fast shutter speed 452 to freeze motion of rapidly-moving subjects. Increased image noise 453 may be seen in this mode. 454 * - ``V4L2_SCENE_MODE_SUNSET`` 455 - Sunset. Preserves deep hues seen in sunsets and sunrises. It bumps 456 up the saturation. 457 * - ``V4L2_SCENE_MODE_TEXT`` 458 - Text. It applies extra contrast and sharpness, it is typically a 459 black-and-white mode optimized for readability. Automatic focus 460 may be switched to close-up mode and this setting may also involve 461 some lens-distortion correction. 462 463.. raw:: latex 464 465 \normalsize 466 467 468``V4L2_CID_3A_LOCK (bitmask)`` 469 This control locks or unlocks the automatic focus, exposure and 470 white balance. The automatic adjustments can be paused independently 471 by setting the corresponding lock bit to 1. The camera then retains 472 the settings until the lock bit is cleared. The following lock bits 473 are defined: 474 475 When a given algorithm is not enabled, drivers should ignore 476 requests to lock it and should return no error. An example might be 477 an application setting bit ``V4L2_LOCK_WHITE_BALANCE`` when the 478 ``V4L2_CID_AUTO_WHITE_BALANCE`` control is set to ``FALSE``. The 479 value of this control may be changed by exposure, white balance or 480 focus controls. 481 482 483 484.. flat-table:: 485 :header-rows: 0 486 :stub-columns: 0 487 488 * - ``V4L2_LOCK_EXPOSURE`` 489 - Automatic exposure adjustments lock. 490 * - ``V4L2_LOCK_WHITE_BALANCE`` 491 - Automatic white balance adjustments lock. 492 * - ``V4L2_LOCK_FOCUS`` 493 - Automatic focus lock. 494 495 496 497``V4L2_CID_PAN_SPEED (integer)`` 498 This control turns the camera horizontally at the specific speed. 499 The unit is undefined. A positive value moves the camera to the 500 right (clockwise when viewed from above), a negative value to the 501 left. A value of zero stops the motion if one is in progress and has 502 no effect otherwise. 503 504``V4L2_CID_TILT_SPEED (integer)`` 505 This control turns the camera vertically at the specified speed. The 506 unit is undefined. A positive value moves the camera up, a negative 507 value down. A value of zero stops the motion if one is in progress 508 and has no effect otherwise. 509 510.. _v4l2-camera-sensor-orientation: 511 512``V4L2_CID_CAMERA_ORIENTATION (menu)`` 513 This read-only control describes the camera orientation by reporting its 514 mounting position on the device where the camera is installed. The control 515 value is constant and not modifiable by software. This control is 516 particularly meaningful for devices which have a well defined orientation, 517 such as phones, laptops and portable devices since the control is expressed 518 as a position relative to the device's intended usage orientation. For 519 example, a camera installed on the user-facing side of a phone, a tablet or 520 a laptop device is said to be have ``V4L2_CAMERA_ORIENTATION_FRONT`` 521 orientation, while a camera installed on the opposite side of the front one 522 is said to be have ``V4L2_CAMERA_ORIENTATION_BACK`` orientation. Camera 523 sensors not directly attached to the device, or attached in a way that 524 allows them to move freely, such as webcams and digital cameras, are said to 525 have the ``V4L2_CAMERA_ORIENTATION_EXTERNAL`` orientation. 526 527 528.. tabularcolumns:: |p{7.7cm}|p{9.8cm}| 529 530.. flat-table:: 531 :header-rows: 0 532 :stub-columns: 0 533 534 * - ``V4L2_CAMERA_ORIENTATION_FRONT`` 535 - The camera is oriented towards the user facing side of the device. 536 * - ``V4L2_CAMERA_ORIENTATION_BACK`` 537 - The camera is oriented towards the back facing side of the device. 538 * - ``V4L2_CAMERA_ORIENTATION_EXTERNAL`` 539 - The camera is not directly attached to the device and is freely movable. 540 541 542.. _v4l2-camera-sensor-rotation: 543 544``V4L2_CID_CAMERA_SENSOR_ROTATION (integer)`` 545 This read-only control describes the rotation correction in degrees in the 546 counter-clockwise direction to be applied to the captured images once 547 captured to memory to compensate for the camera sensor mounting rotation. 548 549 For a precise definition of the sensor mounting rotation refer to the 550 extensive description of the 'rotation' properties in the device tree 551 bindings file 'video-interfaces.txt'. 552 553 A few examples are below reported, using a shark swimming from left to 554 right in front of the user as the example scene to capture. :: 555 556 0 X-axis 557 0 +-------------------------------------> 558 ! 559 ! 560 ! 561 ! |\____)\___ 562 ! ) _____ __`< 563 ! |/ )/ 564 ! 565 ! 566 ! 567 V 568 Y-axis 569 570 Example one - Webcam 571 572 Assuming you can bring your laptop with you while swimming with sharks, 573 the camera module of the laptop is installed on the user facing part of a 574 laptop screen casing, and is typically used for video calls. The captured 575 images are meant to be displayed in landscape mode (width > height) on the 576 laptop screen. 577 578 The camera is typically mounted upside-down to compensate the lens optical 579 inversion effect. In this case the value of the 580 V4L2_CID_CAMERA_SENSOR_ROTATION control is 0, no rotation is required to 581 display images correctly to the user. 582 583 If the camera sensor is not mounted upside-down it is required to compensate 584 the lens optical inversion effect and the value of the 585 V4L2_CID_CAMERA_SENSOR_ROTATION control is 180 degrees, as images will 586 result rotated when captured to memory. :: 587 588 +--------------------------------------+ 589 ! ! 590 ! ! 591 ! ! 592 ! __/(_____/| ! 593 ! >.___ ____ ( ! 594 ! \( \| ! 595 ! ! 596 ! ! 597 ! ! 598 +--------------------------------------+ 599 600 A software rotation correction of 180 degrees has to be applied to correctly 601 display the image on the user screen. :: 602 603 +--------------------------------------+ 604 ! ! 605 ! ! 606 ! ! 607 ! |\____)\___ ! 608 ! ) _____ __`< ! 609 ! |/ )/ ! 610 ! ! 611 ! ! 612 ! ! 613 +--------------------------------------+ 614 615 Example two - Phone camera 616 617 It is more handy to go and swim with sharks with only your mobile phone 618 with you and take pictures with the camera that is installed on the back 619 side of the device, facing away from the user. The captured images are meant 620 to be displayed in portrait mode (height > width) to match the device screen 621 orientation and the device usage orientation used when taking the picture. 622 623 The camera sensor is typically mounted with its pixel array longer side 624 aligned to the device longer side, upside-down mounted to compensate for 625 the lens optical inversion effect. 626 627 The images once captured to memory will be rotated and the value of the 628 V4L2_CID_CAMERA_SENSOR_ROTATION will report a 90 degree rotation. :: 629 630 631 +-------------------------------------+ 632 | _ _ | 633 | \ / | 634 | | | | 635 | | | | 636 | | > | 637 | < | | 638 | | | | 639 | . | 640 | V | 641 +-------------------------------------+ 642 643 A correction of 90 degrees in counter-clockwise direction has to be 644 applied to correctly display the image in portrait mode on the device 645 screen. :: 646 647 +--------------------+ 648 | | 649 | | 650 | | 651 | | 652 | | 653 | | 654 | |\____)\___ | 655 | ) _____ __`< | 656 | |/ )/ | 657 | | 658 | | 659 | | 660 | | 661 | | 662 +--------------------+ 663 664 665.. [#f1] 666 This control may be changed to a menu control in the future, if more 667 options are required. 668 669``V4L2_CID_HDR_SENSOR_MODE (menu)`` 670 Change the sensor HDR mode. A HDR picture is obtained by merging two 671 captures of the same scene using two different exposure periods. HDR mode 672 describes the way these two captures are merged in the sensor. 673 674 As modes differ for each sensor, menu items are not standardized by this 675 control and are left to the programmer. 676