HOWTO：linux下采集设想头图像并播放

听海拉拉 2010-10-11 09:44:43

Hi all，
在linux下实验一段程序，可以采集一祯图像，并保存，但想采集的同时播放并保存成视频文件，不知道怎么入手。
谢谢
BR

 #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 CLEAR(x) memset (&(x), 0, sizeof (x))



struct buffer {

    void *                  start;

    size_t                  length;

};



static char *           dev_name        = "/dev/video0";//摄像头设备名

static int              fd              = -1;

struct buffer *         buffers         = NULL;

static unsigned int     n_buffers       = 0;



FILE *file_fd;

static unsigned long file_length;

static unsigned char *file_name;

//////////////////////////////////////////////////////

//获取一帧数据

//////////////////////////////////////////////////////

static int read_frame (void)

{

    struct v4l2_buffer buf;

    unsigned int i;

    

    CLEAR (buf);

    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    buf.memory = V4L2_MEMORY_MMAP;

    int ff = ioctl (fd, VIDIOC_DQBUF, &buf);

    if(ff<0)

        printf("failture\n"); //出列采集的帧缓冲

    

    assert (buf.index < n_buffers);

    printf ("buf.index dq is %d,\n",buf.index);

    

    fwrite(buffers[buf.index].start, buffers[buf.index].length, 1, file_fd); //将其写入文件中

    

    ff=ioctl (fd, VIDIOC_QBUF, &buf); //再将其入列

    if(ff<0)

        printf("failture VIDIOC_QBUF\n"); 

    return 1;

}



int main (int argc,char ** argv)

{

    struct v4l2_capability cap; 

    struct v4l2_format fmt;

    unsigned int i;

    enum v4l2_buf_type type;

    

    file_fd = fopen("test-mmap.jpg", "w");//图片文件名

    

    fd = open (dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);//打开设备

    

    int ff=ioctl (fd, VIDIOC_QUERYCAP, &cap);//获取摄像头参数

    if(ff<0)

        printf("failture VIDIOC_QUERYCAP\n");

    

    struct v4l2_fmtdesc fmt1;

    int ret;

    memset(&fmt1, 0, sizeof(fmt1));

    fmt1.index = 0;

    fmt1.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    while ((ret = ioctl(fd, VIDIOC_ENUM_FMT, &fmt1)) == 0) 

    {

        fmt1.index++;

        printf("{ pixelformat = '%c%c%c%c', description = '%s' }\n",

               fmt1.pixelformat & 0xFF, (fmt1.pixelformat >> 8) & 0xFF,

               (fmt1.pixelformat >> 16) & 0xFF, (fmt1.pixelformat >> 24) & 0xFF,

               fmt1.description);

        

    }

    CLEAR (fmt);

    fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    fmt.fmt.pix.width       = 640; 

    fmt.fmt.pix.height      = 480;

    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;//V4L2_PIX_FMT_YUYV;//V4L2_PIX_FMT_YVU420;//V4L2_PIX_FMT_YUYV;

    fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;

    ff = ioctl (fd, VIDIOC_S_FMT, &fmt); //设置图像格式

    if(ff<0)

        printf("failture VIDIOC_S_FMT\n");

    file_length = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height; //计算图片大小

    

    struct v4l2_requestbuffers req;

    CLEAR (req);

    req.count               = 1;

    req.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    req.memory              = V4L2_MEMORY_MMAP;

    

    ioctl (fd, VIDIOC_REQBUFS, &req); //申请缓冲，count是申请的数量

    if(ff<0)

        printf("failture VIDIOC_REQBUFS\n");

    if (req.count < 1)

        printf("Insufficient buffer memory\n");

    

    buffers = calloc (req.count, sizeof (*buffers));//内存中建立对应空间

    

    for (n_buffers = 0; n_buffers < req.count; ++n_buffers) 

    {

        struct v4l2_buffer buf;   //驱动中的一帧

        CLEAR (buf);

        buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;

        buf.memory      = V4L2_MEMORY_MMAP;

        buf.index       = n_buffers;

        

        if (-1 == ioctl (fd, VIDIOC_QUERYBUF, &buf)) //映射用户空间

            printf ("VIDIOC_QUERYBUF error\n");

        

        buffers[n_buffers].length = buf.length;

        buffers[n_buffers].start =

                mmap (NULL /* start anywhere */,    //通过mmap建立映射关系

                      buf.length,

                      PROT_READ | PROT_WRITE /* required */,

                      MAP_SHARED /* recommended */,

                      fd, buf.m.offset);

        

        if (MAP_FAILED == buffers[n_buffers].start)

            printf ("mmap failed\n");

    }

    

    for (i = 0; i < n_buffers; ++i) 

    {

        struct v4l2_buffer buf;

        CLEAR (buf);

        

        buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;

        buf.memory      = V4L2_MEMORY_MMAP;

        buf.index       = i;

        

        if (-1 == ioctl (fd, VIDIOC_QBUF, &buf))//申请到的缓冲进入列队

            printf ("VIDIOC_QBUF failed\n");

    }

    

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    

    if (-1 == ioctl (fd, VIDIOC_STREAMON, &type)) //开始捕捉图像数据

        printf ("VIDIOC_STREAMON failed\n");

    

    for (;;) //这一段涉及到异步IO

    {

        fd_set fds;

        struct timeval tv;

        int r;

        

        FD_ZERO (&fds);//将指定的文件描述符集清空

        FD_SET (fd, &fds);//在文件描述符集合中增加一个新的文件描述符

        

        /* Timeout. */

        tv.tv_sec = 2;

        tv.tv_usec = 0;

        

        r = select (fd + 1, &fds, NULL, NULL, &tv);//判断是否可读（即摄像头是否准备好），tv是定时

        

        if (-1 == r) {

            if (EINTR == errno)

                continue;

            printf ("select err\n");

        }

        if (0 == r) {

            fprintf (stderr, "select timeout\n");

            exit (EXIT_FAILURE);

        }

        

        if (read_frame ())//如果可读，执行read_frame ()函数，并跳出循环

            break;

    }

    

    unmap:

    for (i = 0; i < n_buffers; ++i)

        if (-1 == munmap (buffers[i].start, buffers[i].length))

            printf ("munmap error");

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;   

    if (-1 == ioctl(fd, VIDIOC_STREAMOFF, &type))   

        printf("VIDIOC_STREAMOFF"); 

    close (fd);

    fclose (file_fd);

    exit (EXIT_SUCCESS);

    return 0;

}