VIDIOC

VIDIOC is a term that often refers to the ioctl interface used by Video4Linux2 (V4L2), a device driver API for video capture devices on Linux systems. This interface allows user-space applications to interact with video devices, such as webcams or TV tuner cards, by sending control commands. The name "VIDIOC" is derived from the specific `ioctl` request codes that are used to communicate with these devices.

Through VIDIOC, applications can perform a variety of operations. These include enumerating supported video formats, setting resolution and frame rates, capturing video frames, and controlling device-specific features like brightness, contrast, and saturation. The ioctl system provides a standardized way to access these functionalities across different hardware manufacturers.

When an application needs to interact with a video device, it opens a file descriptor associated with that device. It then uses the `ioctl` system call, passing the file descriptor and a specific command code (prefixed with VIDIOC_) along with any necessary data structures. The kernel, in turn, directs this command to the appropriate V4L2 driver, which then executes the requested operation on the hardware. This mechanism is fundamental to how video capture and manipulation are handled in the Linux environment.