1.14. Image Process Control Reference¶
The Image Process control class is intended for low-level control of
image processing functions. Unlike
controls in this class affect processing the image, and do not control
capturing of it.
1.14.1. Image Process Control IDs¶
- The IMAGE_PROC class descriptor.
V4L2_CID_LINK_FREQ (integer menu)
- Data bus frequency. Together with the media bus pixel code, bus type
(clock cycles per sample), the data bus frequency defines the pixel
V4L2_CID_PIXEL_RATE) in the pixel array (or possibly elsewhere, if the device is not an image sensor). The frame rate can be calculated from the pixel clock, image width and height and horizontal and vertical blanking. While the pixel rate control may be defined elsewhere than in the subdev containing the pixel array, the frame rate cannot be obtained from that information. This is because only on the pixel array it can be assumed that the vertical and horizontal blanking information is exact: no other blanking is allowed in the pixel array. The selection of frame rate is performed by selecting the desired horizontal and vertical blanking. The unit of this control is Hz.
V4L2_CID_PIXEL_RATE (64-bit integer)
- Pixel rate in the source pads of the subdev. This control is read-only and its unit is pixels / second.
- Some capture/display/sensor devices have the capability to generate test pattern images. These hardware specific test patterns can be used to test if a device is working properly.
- The video deinterlacing mode (such as Bob, Weave, …). The menu items are driver specific and are documented in Video4Linux (V4L) driver-specific documentation.
- Digital gain is the value by which all colour components are multiplied by. Typically the digital gain applied is the control value divided by e.g. 0x100, meaning that to get no digital gain the control value needs to be 0x100. The no-gain configuration is also typically the default.