摄像头应用编程（三）：多平面视频采集

文章目录 1、前言2、环境介绍3、步骤4、应用程序编写5、测试5.1、编译应用程序5.2、运行应用程序 6、总结

1、前言

在查看摄像头类型时，大致可以分为两类：Video Capture 和 Video Capture Multiplanar。

本次应用程序主要针对类型为Video Capture Multiplanar的相机。

2、环境介绍

rk3566 + ov8858

3、步骤

应用程序编写主要分为以下几个步骤：

1、打开设备节点。

2、查询设备能力。

3、枚举支持的视频格式。

4、设置格式。

5、请求buffer。

6、buffer入队列。

7、打开相机。

8、buffer出队列。

9、保存为yuv文件。

10、buffer重新入队列。

11、关闭相机。

4、应用程序编写

完整的应用程序如下：

#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <sys/ioctl.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <linux/types.h> #include <linux/videodev2.h> #include <poll.h> #include <sys/mman.h> #include <jpeglib.h> #include <linux/fb.h> #define FRAME_SIZE_X 640 #define FRAME_SIZE_Y 480 int main(int argc, char **argv) { int fd; int ret; void *buffers[VIDEO_MAX_FRAME][VIDEO_MAX_PLANES]; int type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; int buffer_cnt; struct pollfd fds[1]; int i; int num_planes; char filename[32]; int file_cnt = 0; if (argc != 2) { printf("Usage: %s </dev/videoX>\n", argv[0]); return -1; } /* 1. open /dev/video* */ fd = open(argv[1], O_RDWR); if (fd < 0) { printf("can not open %s\n", argv[1]); goto _err; } /* 2. query capability */ struct v4l2_capability cap; memset(&cap, 0, sizeof(struct v4l2_capability)); if (0 == ioctl(fd, VIDIOC_QUERYCAP, &cap)) { if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE_MPLANE) == 0) { fprintf(stderr, "Error opening device %s: video capture mplane not supported.\n", argv[1]); goto _ioc_querycap_err; } if(!(cap.capabilities & V4L2_CAP_STREAMING)) { fprintf(stderr, "%s does not support streaming i/o\n", argv[1]); goto _ioc_querycap_err; } } else { printf("can not get capability\n"); goto _ioc_querycap_err; } /* 3. enum formt */ struct v4l2_fmtdesc fmtdesc; struct v4l2_frmsizeenum fsenum; int fmt_index = 0; int frame_index = 0; while (1) { fmtdesc.index = fmt_index; fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; if (0 != ioctl(fd, VIDIOC_ENUM_FMT, &fmtdesc)) break; // printf("format %s:\n", fmtdesc.description); frame_index = 0; while (1) { memset(&fsenum, 0, sizeof(struct v4l2_frmsizeenum)); fsenum.pixel_format = fmtdesc.pixelformat; fsenum.index = frame_index; if (ioctl(fd, VIDIOC_ENUM_FRAMESIZES, &fsenum) == 0) { // printf("\t%d: %d x %d\n", frame_index, fsenum.discrete.width, fsenum.discrete.height); } else { break; } frame_index++; } fmt_index++; } /* 4. set formt */ struct v4l2_format fmt; memset(&fmt, 0, sizeof(struct v4l2_format)); fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; fmt.fmt.pix.width = FRAME_SIZE_X; fmt.fmt.pix.height = FRAME_SIZE_Y; fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_NV21; fmt.fmt.pix.field = V4L2_FIELD_ANY; if (0 == ioctl(fd, VIDIOC_S_FMT, &fmt)) { num_planes = fmt.fmt.pix_mp.num_planes; printf("the final frame-size has been set : %d x %d\n", fmt.fmt.pix.width, fmt.fmt.pix.height); } else { printf("can not set format\n"); goto _ioc_sfmt_err; } /* 5. require buffer */ struct v4l2_requestbuffers rb; memset(&rb, 0, sizeof(struct v4l2_requestbuffers)); rb.count = 32; rb.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; rb.memory = V4L2_MEMORY_MMAP; if (0 == ioctl(fd, VIDIOC_REQBUFS, &rb)) { buffer_cnt = rb.count; for(i = 0; i < rb.count; i++) { struct v4l2_buffer buf; struct v4l2_plane planes[num_planes]; memset(&buf, 0, sizeof(struct v4l2_buffer)); memset(&planes, 0, sizeof(planes)); buf.index = i; buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; buf.memory = V4L2_MEMORY_MMAP; buf.m.planes = planes; buf.length = num_planes; if (0 == ioctl(fd, VIDIOC_QUERYBUF, &buf)) { for (int j = 0; j < num_planes; j++) { buffers[i][j] = mmap(NULL, buf.m.planes[j].length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.planes[j].m.mem_offset); if (buffers[i][j] == MAP_FAILED) { printf("Unable to map buffer\n"); goto _err; } } } else { printf("can not query buffer\n"); goto _err; } } } else { printf("can not request buffers\n"); goto _ioc_reqbufs_err; } /* 6. queue buffer */ for(i = 0; i < buffer_cnt; ++i) { struct v4l2_buffer buf; struct v4l2_plane planes[num_planes]; memset(&buf, 0, sizeof(struct v4l2_buffer)); memset(&planes, 0, sizeof(planes)); buf.index = i; buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; buf.memory = V4L2_MEMORY_MMAP; buf.m.planes = planes; buf.length = num_planes; if (0 != ioctl(fd, VIDIOC_QBUF, &buf)) { perror("Unable to queue buffer"); goto _ioc_qbuf_err; } } /* start camera */ if (0 != ioctl(fd, VIDIOC_STREAMON, &type)) { printf("Unable to start capture\n"); goto _err; } printf("start camera ...\n"); while (1) { /* poll */ memset(fds, 0, sizeof(fds)); fds[0].fd = fd; fds[0].events = POLLIN; if (1 == poll(fds, 1, -1)) { /* dequeue buffer */ struct v4l2_buffer buf; struct v4l2_plane planes[num_planes]; memset(&buf, 0, sizeof(struct v4l2_buffer)); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE; buf.memory = V4L2_MEMORY_MMAP; buf.m.planes = planes; buf.length = num_planes; if (0 != ioctl(fd, VIDIOC_DQBUF, &buf)) { printf("Unable to dequeue buffer\n"); goto _ioc_dqbuf_err; } /* save as file */ sprintf(filename, "video_raw_data_%04d.yuv", file_cnt++); int fd_file = open(filename, O_RDWR | O_CREAT, 0666); if (fd_file < 0) { printf("can not create file : %s\n", filename); } printf("capture to %s\n", filename); for (int i = 0; i < num_planes; i++) write(fd_file, buffers[buf.index][i], buf.m.planes[i].bytesused); close(fd_file); /* queue buffer */ if (0 != ioctl(fd, VIDIOC_QBUF, &buf)) { printf("Unable to queue buffer"); goto _ioc_qbuf_err; } } } /* close camera */ if (0 != ioctl(fd, VIDIOC_STREAMOFF, &type)) { printf("Unable to stop capture\n"); goto _ioc_streamoff_err; } close(fd); return 0; _ioc_qbuf_err: _ioc_reqbufs_err: _ioc_sfmt_err: _ioc_querycap_err: _ioc_streamoff_err: _ioc_dqbuf_err: _err: return -1; } 5、测试 5.1、编译应用程序

如果你使用的buildroot系统，需要交叉编译。

这里测试所使用的板子跑的是ubuntu，执行如下命令直接编译：

sudo gcc -o mipi_to_yuv mipi_to_yuv.c 5.2、运行应用程序 sudo ./mipi_to_yuv /dev/video0

在windows下使用yuv播放器打开任意一张图片：

6、总结

参考文章：

Camera | 4.瑞芯微平台MIPI摄像头应用程序编写_瑞芯微-CSDN专栏

源码gitee仓库：

仓库主页： gitee /cattle_l/v4l2_app.git 直接拉取： git clone gitee /cattle_l/v4l2_app.git