说明：  在Linux下，所有外设都被看成一种特殊的文件，成为“设备文件”，可以象访问普通文件一样对其进行读写。一般来说，采用V4L2驱动的摄像头设备文件是/dev/v4l/video0。为了通用，可以建立一个到/dev/video0的链接。V4L2支持两种方式来采集图像：内存映射方式(mmap)和直接读取方式(read)。V4L2在include/linux/videodev.h文件中定义了一些重要的数据结构，在采集图像的过程中，就是通过对这些数据的操作来获得最终的图像数据。Linux系统V4L2的能力可在Linux内核编译阶段配置，默认情况下都有此开发接口。V4L2从Linux 2.5.x版本的内核中开始出现。
(Under Linux, all peripherals are regarded as a special kind of file, which can be read and written like ordinary files. Generally speaking, the camera device file driven by V4L2 is / dev / V4L / video0. For general purposes, you can create a link to / dev / video0. V4L2 supports two ways of collecting images: MMAP and read. V4L2 defines some important data structures in include/linux/videodev.h file. In the process of collecting images, it is through the operation of these data to obtain the final image data. The capabilities of Linux system V4L2 can be configured at the compilation stage of the Linux kernel, which is the development interface by default. V4L2 began to appear in the Linux 2.5.x version of the kernel.)