Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Oct 31, 2020 Here are some troubleshooting tips you can try to fix your webcam. Related: How to Disable an Integrated Webcam in Windows. Windows 10 Camera Not Working in Zoom. A problem that’s been manifesting itself in recent months is the Windows 10 camera not working for popular video-calling apps like Zoom, Skype, Hangouts, Messenger and so on. New camera driver interfaces for Windows 10.; 2 minutes to read; b; In this article. The following sections contain information about new camera driver interfaces for Windows 10. New camera driver controls for Windows 10. New camera driver enumerations for Windows 10. New camera driver functions for Windows 10.
32.1. Terminology¶
- camera / camera device / camera sensor - a video-camera sensor chip, capableof connecting to a variety of systems and interfaces, typically uses i2c forcontrol and configuration, and a parallel or a serial bus for data.
- camera host - an interface, to which a camera is connected. Typically aspecialised interface, present on many SoCs, e.g. PXA27x and PXA3xx, SuperH,i.MX27, i.MX31.
- camera host bus - a connection between a camera host and a camera. Can beparallel or serial, consists of data and control lines, e.g. clock, verticaland horizontal synchronization signals.
32.2. Purpose of the soc-camera subsystem¶
The soc-camera subsystem initially provided a unified API between camera hostdrivers and camera sensor drivers. Later the soc-camera sensor API has beenreplaced with the V4L2 standard subdev API. This also made camera driver re-usewith non-soc-camera hosts possible. The camera host API to the soc-camera corehas been preserved.
Soc-camera implements a V4L2 interface to the user, currently only the “mmap”method is supported by host drivers. However, the soc-camera core also providessupport for the “read” method.
The subsystem has been designed to support multiple camera host interfaces andmultiple cameras per interface, although most applications have only one camerasensor. Xlntidea driver download for windows 10 free.
32.3. Existing drivers¶
As of 3.7 there are seven host drivers in the mainline: atmel-isi.c,mx1_camera.c (broken, scheduled for removal), mx2_camera.c, mx3_camera.c,omap1_camera.c, pxa_camera.c, sh_mobile_ceu_camera.c, and multiple sensordrivers under drivers/media/i2c/soc_camera/.
32.4. Camera host API¶
A host camera driver is registered using the
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function. The host object can be initialized as follows:
All camera host methods are passed in a struct soc_camera_host_ops:
.add and .remove methods are called when a sensor is attached to or detachedfrom the host. .set_bus_param is used to configure physical connectionparameters between the host and the sensor. .init_videobuf2 is called bysoc-camera core when a video-device is opened, the host driver would typicallycall vb2_queue_init() in this method. Further video-buffer management isimplemented completely by the specific camera host driver. If the host driversupports non-standard pixel format conversion, it should implement a.get_formats and, possibly, a .put_formats operations. See below for moredetails about format conversion. The rest of the methods are called fromrespective V4L2 operations.
32.5. Camera API¶
Sensor drivers can use struct soc_camera_link, typically provided by theplatform, and used to specify to which camera host bus the sensor is connected,and optionally provide platform .power and .reset methods for the camera. Thisstruct is provided to the camera driver via the I2C client device platform dataand can be obtained, using the soc_camera_i2c_to_link() macro. Care should betaken, when using soc_camera_vdev_to_subdev() and when accessing structsoc_camera_device, using v4l2_get_subdev_hostdata(): both only work, whenrunning on an soc-camera host. The actual camera driver operation is implementedusing the V4L2 subdev API. Additionally soc-camera camera drivers can useauxiliary soc-camera helper functions like soc_camera_power_on() andsoc_camera_power_off(), which switch regulators, provided by the platform and callboard-specific power switching methods. soc_camera_apply_board_flags() takescamera bus configuration capability flags and applies any board transformations,e.g. signal polarity inversion. soc_mbus_get_fmtdesc() can be used to obtain apixel format descriptor, corresponding to a certain media-bus pixel format code.soc_camera_limit_side() can be used to restrict beginning and length of a frameside, based on camera capabilities.
32.6. VIDIOC_S_CROP and VIDIOC_S_FMT behaviour¶
Above user ioctls modify image geometry as follows:
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VIDIOC_S_CROP: sets location and sizes of the sensor window. Unit is one sensorpixel. Changing sensor window sizes preserves any scaling factors, thereforeuser window sizes change as well.
VIDIOC_S_FMT: sets user window. Should preserve previously set sensor window asmuch as possible by modifying scaling factors. If the sensor window cannot bepreserved precisely, it may be changed too.
In soc-camera there are two locations, where scaling and cropping can takeplace: in the camera driver and in the host driver. User ioctls are first passedto the host driver, which then generally passes them down to the camera driver.It is more efficient to perform scaling and cropping in the camera driver tosave camera bus bandwidth and maximise the framerate. However, if the cameradriver failed to set the required parameters with sufficient precision, the hostdriver may decide to also use its own scaling and cropping to fulfill the user’srequest.
Camera drivers are interfaced to the soc-camera core and to host drivers overthe v4l2-subdev API, which is completely functional, it doesn’t pass any data.Therefore all camera drivers shall reply to .g_fmt() requests with their currentoutput geometry. This is necessary to correctly configure the camera bus.s_fmt() and .try_fmt() have to be implemented too. Sensor window and scalingfactors have to be maintained by camera drivers internally. Tsd laptops & desktops driver download. According to theV4L2 API all capture drivers must support the VIDIOC_CROPCAP ioctl, hence werely on camera drivers implementing .cropcap(). If the camera driver does notsupport cropping, it may choose to not implement .s_crop(), but to enablecropping support by the camera host driver at least the .g_crop method must beimplemented.
User window geometry is kept in .user_width and .user_height fields in structsoc_camera_device and used by the soc-camera core and host drivers. The coreupdates these fields upon successful completion of a .s_fmt() call, but if thesefields change elsewhere, e.g. during .s_crop() processing, the host driver isresponsible for updating them.
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32.7. Format conversion¶
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V4L2 distinguishes between pixel formats, as they are stored in memory, and asthey are transferred over a media bus. Soc-camera provides support toconveniently manage these formats. A table of standard transformations ismaintained by soc-camera core, which describes, what FOURCC pixel format willbe obtained, if a media-bus pixel format is stored in memory according tocertain rules. E.g. if MEDIA_BUS_FMT_YUYV8_2X8 data is sampled with 8 bits persample and stored in memory in the little-endian order with no gaps betweenbytes, data in memory will represent the V4L2_PIX_FMT_YUYV FOURCC format. Thesestandard transformations will be used by soc-camera or by camera host drivers toconfigure camera drivers to produce the FOURCC format, requested by the user,using the VIDIOC_S_FMT ioctl(). Apart from those standard format conversions,host drivers can also provide their own conversion rules by implementing a.get_formats and, if required, a .put_formats methods.