Lines Matching +full:image +full:- +full:sensor
1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
6 Sub-device Interface
13 components as software blocks called sub-devices.
15 V4L2 sub-devices are usually kernel-only objects. If the V4L2 driver
17 media entities. Applications will be able to enumerate the sub-devices
21 In addition to make sub-devices discoverable, drivers can also choose to
23 sub-device driver and the V4L2 device driver support this, sub-devices
26 - query, read and write sub-devices controls
28 - subscribe and unsubscribe to events and retrieve them
30 - negotiate image formats on individual pads
32 Sub-device character device nodes, conventionally named
33 ``/dev/v4l-subdev*``, use major number 81.
35 Drivers may opt to limit the sub-device character devices to only expose
36 operations that do not modify the device state. In such a case the sub-devices
37 are referred to as ``read-only`` in the rest of this documentation, and the
44 Most V4L2 controls are implemented by sub-device hardware. Drivers
46 Applications can control all sub-devices through a single interface.
50 sensors and image processing hardware implement identical functions,
55 Applications can access those hidden controls through the sub-device
59 sub-device.
68 V4L2 sub-devices can notify applications of events as described in
71 the sub-device. Depending on the driver, those events might also be
75 .. _pad-level-formats:
77 Pad-level Formats
82 Pad-level formats are only applicable to very complex devices that
83 need to expose low-level format configuration to user space. Generic
92 Image formats are typically negotiated on video capture and output
99 image sizes at the output of a pipeline can be achieved using different
101 :ref:`pipeline-scaling`, where image scaling can be performed on both
102 the video sensor and the host image processing hardware.
105 .. _pipeline-scaling:
107 .. kernel-figure:: pipeline.dot
111 Image Format Negotiation on Pipelines
117 The sensor scaler is usually of less quality than the host scaler, but
118 scaling on the sensor is required to achieve higher frame rates.
123 Drivers that implement the :ref:`media API <media-controller-intro>`
124 can expose pad-level image format configuration to applications. When
128 negotiate formats on a per-pad basis.
136 Pad-level image format configuration support can be tested by calling
138 0. If the driver returns an ``EINVAL`` error code pad-level format
139 configuration is not supported by the sub-device.
143 ------------------
162 the sub-device file handles. A
164 the last try format set *on the same sub-device file handle*. Several
165 applications querying the same sub-device at the same time will thus not
179 to an :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` call as-is
183 Drivers automatically propagate formats inside sub-devices. When a try
185 the same sub-device can be modified by the driver. Drivers are free to
189 - Formats should be propagated from sink pads to source pads. Modifying
193 - Sub-devices that scale frames using variable scaling factors should
199 propagating them from one sub-device file handle to another.
205 :ref:`sample-pipeline-config` shows a sample configuration sequence
206 for the pipeline described in :ref:`pipeline-scaling` (table columns
216 .. _sample-pipeline-config:
218 .. flat-table:: Sample Pipeline Configuration
219 :header-rows: 1
220 :stub-columns: 0
223 * -
224 - Sensor/0
227 - Frontend/0
230 - Frontend/1
233 - Scaler/0
236 - Scaler/0
239 - Scaler/1
242 * - Initial state
243 - 2048x1536
246 - (default)
247 - (default)
248 - (default)
249 - (default)
250 - (default)
251 * - Configure frontend sink format
252 - 2048x1536
255 - *2048x1536*
258 - *2046x1534*
261 - (default)
262 - (default)
263 - (default)
264 * - Configure scaler sink format
265 - 2048x1536
268 - 2048x1536
271 - 2046x1534
274 - *2046x1534*
277 - *0,0/2046x1534*
278 - *2046x1534*
281 * - Configure scaler sink compose selection
282 - 2048x1536
285 - 2048x1536
288 - 2046x1534
291 - 2046x1534
294 - *0,0/1280x960*
295 - *1280x960*
303 1. Initial state. The sensor source pad format is set to its native 3MP
330 be applied as-is by the driver without being modified.
333 .. _v4l2-subdev-selections:
336 ---------------------------------------------
338 Many sub-devices support cropping frames on their input or output pads
340 interest in an image, typically on an image sensor or a video decoder.
342 the area of the image that will be scaled up.
350 selection targets :ref:`v4l2-selections-common`.
353 The pad format represents the image size as received by the sub-device
355 represents the sub-image that will be transmitted further inside the
356 sub-device for processing.
358 The scaling operation changes the size of the image by scaling it to new
360 from the original and scaled image sizes. Both sizes are represented by
374 crop rectangle must be entirely contained inside the source image size
380 the image size either up or down. :ref:`v4l2-selection-flags`
384 --------------------------
400 as the BOUNDS rectangle, however. This may be because e.g. a sensor's
401 pixel array is not rectangular but cross-shaped or round. The maximum
406 ---------------------------------------------
408 Inside subdevs, the order of image processing steps will always be from
419 rectangle, which refers to the sink compose bounds rectangle --- if it
423 defines the parameters of the image the entity receives through the
436 performed to the image in the sink compose bounds rectangle.
440 exception of the image width and height. Width and height are defined
450 .. _subdev-image-processing-crop:
452 .. kernel-figure:: subdev-image-processing-crop.svg
453 :alt: subdev-image-processing-crop.svg
456 **Figure 4.5. Image processing in subdevs: simple crop example**
460 pad. Now the actual crop rectangle can be set on the sink pad --- the
467 .. _subdev-image-processing-scaling-multi-source:
469 .. kernel-figure:: subdev-image-processing-scaling-multi-source.svg
470 :alt: subdev-image-processing-scaling-multi-source.svg
473 **Figure 4.6. Image processing in subdevs: scaling with multiple sources**
477 scaled image. The location of the scaled image in the cropped image is
483 .. _subdev-image-processing-full:
485 .. kernel-figure:: subdev-image-processing-full.svg
486 :alt: subdev-image-processing-full.svg
489 …**Figure 4.7. Image processing in subdevs: scaling and composition with multiple sinks and sources…
501 subdev-formats