L4V2框架下APP编写ioctl流程

本文主要是介绍L4V2框架下APP编写ioctl流程，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

摄像头L4V2框架编写APP，对获取数据的由抽象硬件到软件ioctl操作有具体流程。

查询设备能力属性

 struct v4l2_capability cap;ioctl(fd, VIDIOC_QUERYCAP, &cap);

枚举格式

struct v4l2_fmtdesc fmtdesc;fmtdesc.index = fmt_index; fmtdesc.type  = V4L2_BUF_TYPE_VIDEO_CAPTURE;  ioctl(fd, VIDIOC_ENUM_FMT, &fmtdesc);

枚举帧大小

struct v4l2_frmsizeenum fsenum;fsenum.pixel_format = fmtdesc.pixelformat;fsenum.index = frame_index;ioctl(fd, VIDIOC_ENUM_FRAMESIZES, &fsenum);

设置格式

struct v4l2_format fmt;fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;fmt.fmt.pix.width = 1024;fmt.fmt.pix.height = 768;fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;fmt.fmt.pix.field = V4L2_FIELD_ANY;ioctl(fd, VIDIOC_S_FMT, &fmt);

申请buffer

struct v4l2_requestbuffers rb;rb.count = 32;rb.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;rb.memory = V4L2_MEMORY_MMAP;ioctl(fd, VIDIOC_REQBUFS, &rb);

查询buffer是否申请成功

struct v4l2_buffer buf;buf.index = i;buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;ioctl(fd, VIDIOC_QUERYBUF, &buf);

buffer放入空闲链表

 struct v4l2_buffer buf;buf.index = i;buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;ioctl(fd, VIDIOC_QBUF, &buf);

启动摄像头

   type = V4L2_BUF_TYPE_VIDEO_CAPTURE;ioctl(fd, VIDIOC_STREAMON, &type);

buffer取出队列

struct v4l2_buffer buf;buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;ioctl(fd, VIDIOC_DQBUF, &buf);

使用id的 ioctrl命令

//查询设备支持的控制属性
struct v4l2_queryctrl   qctrl;qctrl.id = V4L2_CID_BRIGHTNESS; ioctl(fd, VIDIOC_QUERYCTRL, &qctrl);  
//获取当前的控制值
struct v4l2_control ctl;ctl.id = V4L2_CID_BRIGHTNESS;ioctl(fd, VIDIOC_G_CTRL, &ctl);     
//设置当前的控制值struct v4l2_control c;c.id = V4L2_CID_BRIGHTNESS; c.value = 99;ioctl(h->fd, VIDIOC_S_CTRL, &c);    

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