1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/media/uapi/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _camera-controls: 11 12************************ 13Camera Control Reference 14************************ 15 16The Camera class includes controls for mechanical (or equivalent 17digital) features of a device such as controllable lenses or sensors. 18 19 20.. _camera-control-id: 21 22Camera Control IDs 23================== 24 25``V4L2_CID_CAMERA_CLASS (class)`` 26 The Camera class descriptor. Calling 27 :ref:`VIDIOC_QUERYCTRL` for this control will 28 return a description of this control class. 29 30.. _v4l2-exposure-auto-type: 31 32``V4L2_CID_EXPOSURE_AUTO`` 33 (enum) 34 35enum v4l2_exposure_auto_type - 36 Enables automatic adjustments of the exposure time and/or iris 37 aperture. The effect of manual changes of the exposure time or iris 38 aperture while these features are enabled is undefined, drivers 39 should ignore such requests. Possible values are: 40 41 42 43.. flat-table:: 44 :header-rows: 0 45 :stub-columns: 0 46 47 * - ``V4L2_EXPOSURE_AUTO`` 48 - Automatic exposure time, automatic iris aperture. 49 * - ``V4L2_EXPOSURE_MANUAL`` 50 - Manual exposure time, manual iris. 51 * - ``V4L2_EXPOSURE_SHUTTER_PRIORITY`` 52 - Manual exposure time, auto iris. 53 * - ``V4L2_EXPOSURE_APERTURE_PRIORITY`` 54 - Auto exposure time, manual iris. 55 56 57 58``V4L2_CID_EXPOSURE_ABSOLUTE (integer)`` 59 Determines the exposure time of the camera sensor. The exposure time 60 is limited by the frame interval. Drivers should interpret the 61 values as 100 µs units, where the value 1 stands for 1/10000th of a 62 second, 10000 for 1 second and 100000 for 10 seconds. 63 64``V4L2_CID_EXPOSURE_AUTO_PRIORITY (boolean)`` 65 When ``V4L2_CID_EXPOSURE_AUTO`` is set to ``AUTO`` or 66 ``APERTURE_PRIORITY``, this control determines if the device may 67 dynamically vary the frame rate. By default this feature is disabled 68 (0) and the frame rate must remain constant. 69 70``V4L2_CID_AUTO_EXPOSURE_BIAS (integer menu)`` 71 Determines the automatic exposure compensation, it is effective only 72 when ``V4L2_CID_EXPOSURE_AUTO`` control is set to ``AUTO``, 73 ``SHUTTER_PRIORITY`` or ``APERTURE_PRIORITY``. It is expressed in 74 terms of EV, drivers should interpret the values as 0.001 EV units, 75 where the value 1000 stands for +1 EV. 76 77 Increasing the exposure compensation value is equivalent to 78 decreasing the exposure value (EV) and will increase the amount of 79 light at the image sensor. The camera performs the exposure 80 compensation by adjusting absolute exposure time and/or aperture. 81 82.. _v4l2-exposure-metering: 83 84``V4L2_CID_EXPOSURE_METERING`` 85 (enum) 86 87enum v4l2_exposure_metering - 88 Determines how the camera measures the amount of light available for 89 the frame exposure. Possible values are: 90 91.. tabularcolumns:: |p{8.7cm}|p{8.8cm}| 92 93.. flat-table:: 94 :header-rows: 0 95 :stub-columns: 0 96 97 * - ``V4L2_EXPOSURE_METERING_AVERAGE`` 98 - Use the light information coming from the entire frame and average 99 giving no weighting to any particular portion of the metered area. 100 * - ``V4L2_EXPOSURE_METERING_CENTER_WEIGHTED`` 101 - Average the light information coming from the entire frame giving 102 priority to the center of the metered area. 103 * - ``V4L2_EXPOSURE_METERING_SPOT`` 104 - Measure only very small area at the center of the frame. 105 * - ``V4L2_EXPOSURE_METERING_MATRIX`` 106 - A multi-zone metering. The light intensity is measured in several 107 points of the frame and the results are combined. The algorithm of 108 the zones selection and their significance in calculating the 109 final value is device dependent. 110 111 112 113``V4L2_CID_PAN_RELATIVE (integer)`` 114 This control turns the camera horizontally by the specified amount. 115 The unit is undefined. A positive value moves the camera to the 116 right (clockwise when viewed from above), a negative value to the 117 left. A value of zero does not cause motion. This is a write-only 118 control. 119 120``V4L2_CID_TILT_RELATIVE (integer)`` 121 This control turns the camera vertically by the specified amount. 122 The unit is undefined. A positive value moves the camera up, a 123 negative value down. A value of zero does not cause motion. This is 124 a write-only control. 125 126``V4L2_CID_PAN_RESET (button)`` 127 When this control is set, the camera moves horizontally to the 128 default position. 129 130``V4L2_CID_TILT_RESET (button)`` 131 When this control is set, the camera moves vertically to the default 132 position. 133 134``V4L2_CID_PAN_ABSOLUTE (integer)`` 135 This control turns the camera horizontally to the specified 136 position. Positive values move the camera to the right (clockwise 137 when viewed from above), negative values to the left. Drivers should 138 interpret the values as arc seconds, with valid values between -180 139 * 3600 and +180 * 3600 inclusive. 140 141``V4L2_CID_TILT_ABSOLUTE (integer)`` 142 This control turns the camera vertically to the specified position. 143 Positive values move the camera up, negative values down. Drivers 144 should interpret the values as arc seconds, with valid values 145 between -180 * 3600 and +180 * 3600 inclusive. 146 147``V4L2_CID_FOCUS_ABSOLUTE (integer)`` 148 This control sets the focal point of the camera to the specified 149 position. The unit is undefined. Positive values set the focus 150 closer to the camera, negative values towards infinity. 151 152``V4L2_CID_FOCUS_RELATIVE (integer)`` 153 This control moves the focal point of the camera by the specified 154 amount. The unit is undefined. Positive values move the focus closer 155 to the camera, negative values towards infinity. This is a 156 write-only control. 157 158``V4L2_CID_FOCUS_AUTO (boolean)`` 159 Enables continuous automatic focus adjustments. The effect of manual 160 focus adjustments while this feature is enabled is undefined, 161 drivers should ignore such requests. 162 163``V4L2_CID_AUTO_FOCUS_START (button)`` 164 Starts single auto focus process. The effect of setting this control 165 when ``V4L2_CID_FOCUS_AUTO`` is set to ``TRUE`` (1) is undefined, 166 drivers should ignore such requests. 167 168``V4L2_CID_AUTO_FOCUS_STOP (button)`` 169 Aborts automatic focusing started with ``V4L2_CID_AUTO_FOCUS_START`` 170 control. It is effective only when the continuous autofocus is 171 disabled, that is when ``V4L2_CID_FOCUS_AUTO`` control is set to 172 ``FALSE`` (0). 173 174.. _v4l2-auto-focus-status: 175 176``V4L2_CID_AUTO_FOCUS_STATUS (bitmask)`` 177 The automatic focus status. This is a read-only control. 178 179 Setting ``V4L2_LOCK_FOCUS`` lock bit of the ``V4L2_CID_3A_LOCK`` 180 control may stop updates of the ``V4L2_CID_AUTO_FOCUS_STATUS`` 181 control value. 182 183.. tabularcolumns:: |p{6.7cm}|p{10.8cm}| 184 185.. flat-table:: 186 :header-rows: 0 187 :stub-columns: 0 188 189 * - ``V4L2_AUTO_FOCUS_STATUS_IDLE`` 190 - Automatic focus is not active. 191 * - ``V4L2_AUTO_FOCUS_STATUS_BUSY`` 192 - Automatic focusing is in progress. 193 * - ``V4L2_AUTO_FOCUS_STATUS_REACHED`` 194 - Focus has been reached. 195 * - ``V4L2_AUTO_FOCUS_STATUS_FAILED`` 196 - Automatic focus has failed, the driver will not transition from 197 this state until another action is performed by an application. 198 199 200 201.. _v4l2-auto-focus-range: 202 203``V4L2_CID_AUTO_FOCUS_RANGE`` 204 (enum) 205 206enum v4l2_auto_focus_range - 207 Determines auto focus distance range for which lens may be adjusted. 208 209.. tabularcolumns:: |p{6.8cm}|p{10.7cm}| 210 211.. flat-table:: 212 :header-rows: 0 213 :stub-columns: 0 214 215 * - ``V4L2_AUTO_FOCUS_RANGE_AUTO`` 216 - The camera automatically selects the focus range. 217 * - ``V4L2_AUTO_FOCUS_RANGE_NORMAL`` 218 - Normal distance range, limited for best automatic focus 219 performance. 220 * - ``V4L2_AUTO_FOCUS_RANGE_MACRO`` 221 - Macro (close-up) auto focus. The camera will use its minimum 222 possible distance for auto focus. 223 * - ``V4L2_AUTO_FOCUS_RANGE_INFINITY`` 224 - The lens is set to focus on an object at infinite distance. 225 226 227 228``V4L2_CID_ZOOM_ABSOLUTE (integer)`` 229 Specify the objective lens focal length as an absolute value. The 230 zoom unit is driver-specific and its value should be a positive 231 integer. 232 233``V4L2_CID_ZOOM_RELATIVE (integer)`` 234 Specify the objective lens focal length relatively to the current 235 value. Positive values move the zoom lens group towards the 236 telephoto direction, negative values towards the wide-angle 237 direction. The zoom unit is driver-specific. This is a write-only 238 control. 239 240``V4L2_CID_ZOOM_CONTINUOUS (integer)`` 241 Move the objective lens group at the specified speed until it 242 reaches physical device limits or until an explicit request to stop 243 the movement. A positive value moves the zoom lens group towards the 244 telephoto direction. A value of zero stops the zoom lens group 245 movement. A negative value moves the zoom lens group towards the 246 wide-angle direction. The zoom speed unit is driver-specific. 247 248``V4L2_CID_IRIS_ABSOLUTE (integer)`` 249 This control sets the camera's aperture to the specified value. The 250 unit is undefined. Larger values open the iris wider, smaller values 251 close it. 252 253``V4L2_CID_IRIS_RELATIVE (integer)`` 254 This control modifies the camera's aperture by the specified amount. 255 The unit is undefined. Positive values open the iris one step 256 further, negative values close it one step further. This is a 257 write-only control. 258 259``V4L2_CID_PRIVACY (boolean)`` 260 Prevent video from being acquired by the camera. When this control 261 is set to ``TRUE`` (1), no image can be captured by the camera. 262 Common means to enforce privacy are mechanical obturation of the 263 sensor and firmware image processing, but the device is not 264 restricted to these methods. Devices that implement the privacy 265 control must support read access and may support write access. 266 267``V4L2_CID_BAND_STOP_FILTER (integer)`` 268 Switch the band-stop filter of a camera sensor on or off, or specify 269 its strength. Such band-stop filters can be used, for example, to 270 filter out the fluorescent light component. 271 272.. _v4l2-auto-n-preset-white-balance: 273 274``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE`` 275 (enum) 276 277enum v4l2_auto_n_preset_white_balance - 278 Sets white balance to automatic, manual or a preset. The presets 279 determine color temperature of the light as a hint to the camera for 280 white balance adjustments resulting in most accurate color 281 representation. The following white balance presets are listed in 282 order of increasing color temperature. 283 284.. tabularcolumns:: |p{7.2 cm}|p{10.3cm}| 285 286.. flat-table:: 287 :header-rows: 0 288 :stub-columns: 0 289 290 * - ``V4L2_WHITE_BALANCE_MANUAL`` 291 - Manual white balance. 292 * - ``V4L2_WHITE_BALANCE_AUTO`` 293 - Automatic white balance adjustments. 294 * - ``V4L2_WHITE_BALANCE_INCANDESCENT`` 295 - White balance setting for incandescent (tungsten) lighting. It 296 generally cools down the colors and corresponds approximately to 297 2500...3500 K color temperature range. 298 * - ``V4L2_WHITE_BALANCE_FLUORESCENT`` 299 - White balance preset for fluorescent lighting. It corresponds 300 approximately to 4000...5000 K color temperature. 301 * - ``V4L2_WHITE_BALANCE_FLUORESCENT_H`` 302 - With this setting the camera will compensate for fluorescent H 303 lighting. 304 * - ``V4L2_WHITE_BALANCE_HORIZON`` 305 - White balance setting for horizon daylight. It corresponds 306 approximately to 5000 K color temperature. 307 * - ``V4L2_WHITE_BALANCE_DAYLIGHT`` 308 - White balance preset for daylight (with clear sky). It corresponds 309 approximately to 5000...6500 K color temperature. 310 * - ``V4L2_WHITE_BALANCE_FLASH`` 311 - With this setting the camera will compensate for the flash light. 312 It slightly warms up the colors and corresponds roughly to 313 5000...5500 K color temperature. 314 * - ``V4L2_WHITE_BALANCE_CLOUDY`` 315 - White balance preset for moderately overcast sky. This option 316 corresponds approximately to 6500...8000 K color temperature 317 range. 318 * - ``V4L2_WHITE_BALANCE_SHADE`` 319 - White balance preset for shade or heavily overcast sky. It 320 corresponds approximately to 9000...10000 K color temperature. 321 322 323 324.. _v4l2-wide-dynamic-range: 325 326``V4L2_CID_WIDE_DYNAMIC_RANGE (boolean)`` 327 Enables or disables the camera's wide dynamic range feature. This 328 feature allows to obtain clear images in situations where intensity 329 of the illumination varies significantly throughout the scene, i.e. 330 there are simultaneously very dark and very bright areas. It is most 331 commonly realized in cameras by combining two subsequent frames with 332 different exposure times. [#f1]_ 333 334.. _v4l2-image-stabilization: 335 336``V4L2_CID_IMAGE_STABILIZATION (boolean)`` 337 Enables or disables image stabilization. 338 339``V4L2_CID_ISO_SENSITIVITY (integer menu)`` 340 Determines ISO equivalent of an image sensor indicating the sensor's 341 sensitivity to light. The numbers are expressed in arithmetic scale, 342 as per :ref:`iso12232` standard, where doubling the sensor 343 sensitivity is represented by doubling the numerical ISO value. 344 Applications should interpret the values as standard ISO values 345 multiplied by 1000, e.g. control value 800 stands for ISO 0.8. 346 Drivers will usually support only a subset of standard ISO values. 347 The effect of setting this control while the 348 ``V4L2_CID_ISO_SENSITIVITY_AUTO`` control is set to a value other 349 than ``V4L2_CID_ISO_SENSITIVITY_MANUAL`` is undefined, drivers 350 should ignore such requests. 351 352.. _v4l2-iso-sensitivity-auto-type: 353 354``V4L2_CID_ISO_SENSITIVITY_AUTO`` 355 (enum) 356 357enum v4l2_iso_sensitivity_type - 358 Enables or disables automatic ISO sensitivity adjustments. 359 360 361 362.. flat-table:: 363 :header-rows: 0 364 :stub-columns: 0 365 366 * - ``V4L2_CID_ISO_SENSITIVITY_MANUAL`` 367 - Manual ISO sensitivity. 368 * - ``V4L2_CID_ISO_SENSITIVITY_AUTO`` 369 - Automatic ISO sensitivity adjustments. 370 371 372 373.. _v4l2-scene-mode: 374 375``V4L2_CID_SCENE_MODE`` 376 (enum) 377 378enum v4l2_scene_mode - 379 This control allows to select scene programs as the camera automatic 380 modes optimized for common shooting scenes. Within these modes the 381 camera determines best exposure, aperture, focusing, light metering, 382 white balance and equivalent sensitivity. The controls of those 383 parameters are influenced by the scene mode control. An exact 384 behavior in each mode is subject to the camera specification. 385 386 When the scene mode feature is not used, this control should be set 387 to ``V4L2_SCENE_MODE_NONE`` to make sure the other possibly related 388 controls are accessible. The following scene programs are defined: 389 390.. raw:: latex 391 392 \small 393 394.. tabularcolumns:: |p{5.9cm}|p{11.5cm}| 395 396.. flat-table:: 397 :header-rows: 0 398 :stub-columns: 0 399 400 * - ``V4L2_SCENE_MODE_NONE`` 401 - The scene mode feature is disabled. 402 * - ``V4L2_SCENE_MODE_BACKLIGHT`` 403 - Backlight. Compensates for dark shadows when light is coming from 404 behind a subject, also by automatically turning on the flash. 405 * - ``V4L2_SCENE_MODE_BEACH_SNOW`` 406 - Beach and snow. This mode compensates for all-white or bright 407 scenes, which tend to look gray and low contrast, when camera's 408 automatic exposure is based on an average scene brightness. To 409 compensate, this mode automatically slightly overexposes the 410 frames. The white balance may also be adjusted to compensate for 411 the fact that reflected snow looks bluish rather than white. 412 * - ``V4L2_SCENE_MODE_CANDLELIGHT`` 413 - Candle light. The camera generally raises the ISO sensitivity and 414 lowers the shutter speed. This mode compensates for relatively 415 close subject in the scene. The flash is disabled in order to 416 preserve the ambiance of the light. 417 * - ``V4L2_SCENE_MODE_DAWN_DUSK`` 418 - Dawn and dusk. Preserves the colors seen in low natural light 419 before dusk and after down. The camera may turn off the flash, and 420 automatically focus at infinity. It will usually boost saturation 421 and lower the shutter speed. 422 * - ``V4L2_SCENE_MODE_FALL_COLORS`` 423 - Fall colors. Increases saturation and adjusts white balance for 424 color enhancement. Pictures of autumn leaves get saturated reds 425 and yellows. 426 * - ``V4L2_SCENE_MODE_FIREWORKS`` 427 - Fireworks. Long exposure times are used to capture the expanding 428 burst of light from a firework. The camera may invoke image 429 stabilization. 430 * - ``V4L2_SCENE_MODE_LANDSCAPE`` 431 - Landscape. The camera may choose a small aperture to provide deep 432 depth of field and long exposure duration to help capture detail 433 in dim light conditions. The focus is fixed at infinity. Suitable 434 for distant and wide scenery. 435 * - ``V4L2_SCENE_MODE_NIGHT`` 436 - Night, also known as Night Landscape. Designed for low light 437 conditions, it preserves detail in the dark areas without blowing 438 out bright objects. The camera generally sets itself to a 439 medium-to-high ISO sensitivity, with a relatively long exposure 440 time, and turns flash off. As such, there will be increased image 441 noise and the possibility of blurred image. 442 * - ``V4L2_SCENE_MODE_PARTY_INDOOR`` 443 - Party and indoor. Designed to capture indoor scenes that are lit 444 by indoor background lighting as well as the flash. The camera 445 usually increases ISO sensitivity, and adjusts exposure for the 446 low light conditions. 447 * - ``V4L2_SCENE_MODE_PORTRAIT`` 448 - Portrait. The camera adjusts the aperture so that the depth of 449 field is reduced, which helps to isolate the subject against a 450 smooth background. Most cameras recognize the presence of faces in 451 the scene and focus on them. The color hue is adjusted to enhance 452 skin tones. The intensity of the flash is often reduced. 453 * - ``V4L2_SCENE_MODE_SPORTS`` 454 - Sports. Significantly increases ISO and uses a fast shutter speed 455 to freeze motion of rapidly-moving subjects. Increased image noise 456 may be seen in this mode. 457 * - ``V4L2_SCENE_MODE_SUNSET`` 458 - Sunset. Preserves deep hues seen in sunsets and sunrises. It bumps 459 up the saturation. 460 * - ``V4L2_SCENE_MODE_TEXT`` 461 - Text. It applies extra contrast and sharpness, it is typically a 462 black-and-white mode optimized for readability. Automatic focus 463 may be switched to close-up mode and this setting may also involve 464 some lens-distortion correction. 465 466.. raw:: latex 467 468 \normalsize 469 470 471``V4L2_CID_3A_LOCK (bitmask)`` 472 This control locks or unlocks the automatic focus, exposure and 473 white balance. The automatic adjustments can be paused independently 474 by setting the corresponding lock bit to 1. The camera then retains 475 the settings until the lock bit is cleared. The following lock bits 476 are defined: 477 478 When a given algorithm is not enabled, drivers should ignore 479 requests to lock it and should return no error. An example might be 480 an application setting bit ``V4L2_LOCK_WHITE_BALANCE`` when the 481 ``V4L2_CID_AUTO_WHITE_BALANCE`` control is set to ``FALSE``. The 482 value of this control may be changed by exposure, white balance or 483 focus controls. 484 485 486 487.. flat-table:: 488 :header-rows: 0 489 :stub-columns: 0 490 491 * - ``V4L2_LOCK_EXPOSURE`` 492 - Automatic exposure adjustments lock. 493 * - ``V4L2_LOCK_WHITE_BALANCE`` 494 - Automatic white balance adjustments lock. 495 * - ``V4L2_LOCK_FOCUS`` 496 - Automatic focus lock. 497 498 499 500``V4L2_CID_PAN_SPEED (integer)`` 501 This control turns the camera horizontally at the specific speed. 502 The unit is undefined. A positive value moves the camera to the 503 right (clockwise when viewed from above), a negative value to the 504 left. A value of zero stops the motion if one is in progress and has 505 no effect otherwise. 506 507``V4L2_CID_TILT_SPEED (integer)`` 508 This control turns the camera vertically at the specified speed. The 509 unit is undefined. A positive value moves the camera up, a negative 510 value down. A value of zero stops the motion if one is in progress 511 and has no effect otherwise. 512 513.. [#f1] 514 This control may be changed to a menu control in the future, if more 515 options are required. 516