一、内核设置
Linux内核中已经带有很完善的USB摄像头驱动，支持几乎所有的USB摄像头，我们只需要配置内核，选择上相应的Sensor型号即可。
配置内核，支持USB摄像头：
Device Drivers --->
<*> Multimedia support --->
<*> Video For Linux
[*] Enable Video For Linux API 1 (DEPRECATED)
[*] Video capture adapters --->
[*] V4L USB devices --->
<*> USB Video Class (UVC)
[*] UVC input events device support
[*] GSPCA based webcams --->
到这里，我们就可以选择所需要的USB摄像头驱动，当然也可以选择所有的USB摄像头驱动支持（这样编译出的内核会比较大）
GSPCA是一个万能摄像头驱动程序，进入GSPCA based webcams进行选择。
插入USB摄像头（我使用的UVC摄像头），会提示：
usb 1-1.1: new full speed USB device using s3c2410-ohci and address 3
usb 1-1.1: New USB device found, idVendor=0ac8, idProduct=3450
usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-1.1: Product: Deasy USB2.0 Camera
usb 1-1.1: Manufacturer: Vimicro Corp.
uvcvideo: Found UVC 1.00 device Deasy USB2.0 Camera (0ac8:3450)
input: Deasy USB2.0 Camera as
/devices/platform/s3c2410-ohci/usb1/1-1/1-1.1/1-1.1:1.0/input/input3
它的设备名称是：
/dev/video0
USB摄像头一般都是基于V4L2架构的，需要编写V4L2架构的程序来操作摄像头
二、编写V4L2的应用程序
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <getopt.h> #include <fcntl.h> #include <unistd.h> #include <errno.h> #include <malloc.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/time.h> #include <sys/mman.h> #include <sys/ioctl.h> #include <asm/types.h> #include <linux/videodev2.h> #define CAMERA_DEVICE "/dev/video0" #define CAPTURE_FILE "frame.jpg" #define VIDEO_WIDTH 640 #define VIDEO_HEIGHT 480 #define VIDEO_FORMAT V4L2_PIX_FMT_YUYV #define BUFFER_COUNT 4 typedef struct VideoBuffer { void *start; size_t length; }VideoBuffer; int fd; //摄像头文件描述符 void open_camera(char *path); void get_camera_info(); void get_vedio_info(); //打开设备 void open_camera(char *path) { fd = open(CAMERA_DEVICE, O_RDWR, 0); if(fd < 0) { printf("Open %s failed\n", CAMERA_DEVICE); exit(EXIT_FAILURE); } } //获取驱动信息 void get_camera_info() { struct v4l2_capability cap; ret = ioctl(fd, VIDIOC_QUERYCAP, &cap); if(ret < 0) { printf("VIDIOC_QUERYCAP failed (%d)\n", ret); return ret; } // Print capability informations printf("Capbility Informations:\n"); printf("*\tdriver: %s\n", cap.driver); printf("*\tcard: %s\n", cap.card); printf("*\tbus_info: %s\n", cap.bus_info); printf("*\tversion: %08X\n", cap.version); printf("*\tcapabilities: %08X\n", cap.capabilities); } //获取视频格式 void get_vedio_info() { struct v4l2_format fmt; memset(&fmt, 0, sizeof(fmt)); fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; ret = ioctl(fd, VIDIOC_G_FMT, &fmt); if(ret < 0) { printf("VIDIOC_G_FMT failed (%d)\n", ret); return ret; } // Print Stream Format printf("Stream Format Informations:\n"); printf("*\ttype: %d\n", fmt.type); printf("*\twidth: %d\n", fmt.fmt.pix.width); printf("*\theight: %d\n", fmt.fmt.pix.height); char fmtstr[8]; memset(fmtstr, 0, 8); memcpy(fmtstr, &fmt.fmt.pix.pixelformat, 4); printf("*\tpixelformat: %s\n", fmtstr); printf("*\tfield: %d\n", fmt.fmt.pix.field); printf("*\tbytesperline: %d\n", fmt.fmt.pix.bytesperline); printf("*\tsizeimage: %d\n", fmt.fmt.pix.sizeimage); printf("*\tcolorspace: %d\n", fmt.fmt.pix.colorspace); printf("*\tpriv: %d\n", fmt.fmt.pix.priv); // printf("*\traw_data: %s\n", fmt.fmt.raw_data); /* 显示所有支持的格式 */ struct v4l2_fmtdesc fmtdesc; fmtdesc.index = 0; fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; printf("Support format:\n"); while(ioctl(fd, VIDIOC_ENUM_FMT, &fmtdesc) != -1) { printf("\t%d.%s\n", fmtdesc.index+1, fmtdesc.description); fmtdesc.index++; } } int main() { int i, ret; open_camera(CAMERA_DEVICE); get_camera_info(); get_vedio_info(); //请求分配内存 struct v4l2_requestbuffers reqbuf; reqbuf.count = BUFFER_COUNT; reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; reqbuf.memory = V4L2_MEMORY_MMAP; ret = ioctl(fd, VIDIOC_REQBUFS, &reqbuf); if(ret < 0) { printf("VIDIOC_REQBUFS failed (%d)\n", ret); return ret; } //获取空间 VideoBuffer *buffers = calloc(reqbuf.count, sizeof(*buffers)); if(!buffers) { //映射 fprintf(stderr, "Out of memory\n"); exit(EXIT_FAILURE); } for(i=0;i<reqbuf.count;i++) { struct v4l2_buffer buf; memset(&buf, 0, sizeof(buf)); buf.index = i; buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; ret = ioctl(fd, VIDIOC_QUERYBUF, &buf); if(ret < 0) { printf("VIDIOC_QUERYBUF (%d) failed (%d)\n", i, ret); return ret; } // mmap buffer buffers[i].length = buf.length; buffers[i].start = (char *)mmap(0, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset); if(buffers[i].start == MAP_FAILED) { printf("mmap (%d) failed: %s\n", i, strerror(errno)); return -1; } // Queen buffer ret = ioctl(fd, VIDIOC_QBUF, &buf); if(ret < 0) { printf("VIDIOC_QBUF (%d) failed (%d)\n", i, ret); return -1; } printf("Frame buffer: %d: address=0x%x, length=%d\n", i, (unsigned int)buffers[i].start, buffers[i].length); } // 开始录制 struct v4l2_buffer buf; enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.index = 0; buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; ret = ioctl(fd, VIDIOC_STREAMON, &type); if (ret < 0) { printf("VIDIOC_STREAMON failed (%d)\n", ret); return ret; } // Get frame ret = ioctl(fd, VIDIOC_DQBUF, &buf); if (ret < 0) { printf("VIDIOC_DQBUF failed (%d)\n", ret); return ret; } // Process the frame FILE *fp = fopen(CAPTURE_FILE, "wb"); if (fp < 0) { printf("open frame data file failed\n"); return -1; } fwrite(buffers[buf.index].start, 1, buf.length, fp); fclose(fp); printf("Capture one frame saved in %s\n", CAPTURE_FILE); // Re-queen buffer ret = ioctl(fd, VIDIOC_QBUF, &buf); if (ret < 0) { printf("VIDIOC_QBUF failed (%d)\n", ret); return ret; } // Release the resource for(i=0;i<4;i++) { munmap(buffers[i].start, buffers[i].length); } close(fd); printf("Camera test Done.\n"); return 0; }
三、使用软件打开
不过要选择对应的格式：
