[经验]

摄像头程序V4L2（如何显示到LCD屏幕上）

2013-12-22 16:45:16

6187 摄像头

这是一个V4L2的摄像头程序，驱动已经有了，这个驱动可以获取到一张图片并保持到根目录下，我如何就获取的摄像头数据实时的显示到LCD屏幕上去呢？求大神一起分析，我搞了很久了。谢谢

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include time.h>
#include
#include
#include
#include

#define CAMERA_DEVICE "/dev/video0"
#define CAPTURE_FILE "frame.avi"

#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;
VideoBuffer framebuf[BUFFER_COUNT];

int main()
{
int i, ret;

// 打开设备
int fd;
fd = open(CAMERA_DEVICE, O_RDWR, 0);
if (fd < 0) {
      printf("Open %s failedn", CAMERA_DEVICE);
      return -1;
}

// 获取驱动信息
struct v4l2_capability cap;
ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);
if (ret < 0) {
      printf("VIDIOC_QUERYCAP failed (%d)n", ret);
      return ret;
}
// Print capability infomations
printf("Capability Informations:n");
printf(" driver: %sn", cap.driver);
printf(" card: %sn", cap.card);
printf(" bus_info: %sn", cap.bus_info);
printf(" version: %08Xn", cap.version);
printf(" capabilities: %08Xn", cap.capabilities);

// 设置视频格式
struct v4l2_format fmt;
memset(&fmt, 0, sizeof(fmt));
fmt.type             = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width    = VIDEO_WIDTH;
fmt.fmt.pix.height    = VIDEO_HEIGHT;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field    = V4L2_FIELD_INTERLACED;
ret = ioctl(fd, VIDIOC_S_FMT, &fmt);
if (ret < 0) {
      printf("VIDIOC_S_FMT failed (%d)n", ret);
      return ret;
}

// 获取视频格式
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(" type: %dn", fmt.type);
printf(" width: %dn", fmt.fmt.pix.width);
printf(" height: %dn", fmt.fmt.pix.height);
char fmtstr[8];
memset(fmtstr, 0, 8);
memcpy(fmtstr, &fmt.fmt.pix.pixelformat, 4);
printf(" pixelformat: %sn", fmtstr);
printf(" field: %dn", fmt.fmt.pix.field);
printf(" bytesperline: %dn", fmt.fmt.pix.bytesperline);
printf(" sizeimage: %dn", fmt.fmt.pix.sizeimage);
printf(" colorspace: %dn", fmt.fmt.pix.colorspace);
printf(" priv: %dn", fmt.fmt.pix.priv);
printf(" raw_date: %sn", fmt.fmt.raw_data);

// 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) );
struct v4l2_buffer buf;

for (i = 0; i < reqbuf.count; i++)
{
      buf.index = i;
      buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      buf.memory = V4L2_MEMORY_MMAP;
//读取缓存
      ret = ioctl(fd , VIDIOC_QUERYBUF, &buf);
      if(ret < 0) {
         printf("VIDIOC_QUERYBUF (%d) failed (%d)n", i, ret);
         return ret;
      }

      // mmap buffer
      framebuf[i].length = buf.length;

   // 转换成相对地址
      framebuf[i].start = (char *) mmap(0, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
      if (framebuf[i].start == MAP_FAILED) {
         printf("mmap (%d) failed: %sn", i, strerror(errno));
         return -1;
      }

      // Queen buffer 放入缓存队列
      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=%dn", i, (unsigned int)framebuf[i].start, framebuf[i].length);
}

// 开始录制
enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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 failedn");
      return -1;
}
fwrite(framebuf[buf.index].start, 1, buf.length, fp);
fclose(fp);
printf("Capture one frame saved in %sn", 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(framebuf[i].start, framebuf[i].length);
}

close(fd);
printf("Camera test Done.n");
return 0;
}