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：
