实现 V4L2视频采集与 FFMPEG 编码YUYV 数据为H264 （1）

今天入职。公司给我分配了一个新的活，前期准备工作有两步：

1：实现 V4L2视频采集保存文件成为yuyv格式

2：FFMPEG 编码YUYV 数据为h264

因为之前没有接触过这些，所以在网上找了一些资料，这里记录一下也是自己的成长经验。

本文章写的是如何实现第一步实现 V4L2视频采集保存文件成为yuyv格式
我用的是USB2.0 UVC Camera免驱摄像头，首先确定摄像头是好的
1、直接插入win机器，然后打开相机功能看看有没有画面，相机启动时在搜索里面打“相机”然后回车
2、将摄像头插入Ubuntu中，在/dev/video0或者/dev/video0有的话说明成功识别了。
3、然后安装一个luvcview.tar.gz

4、执行luvcview如果出画面说明摄像头在Ubuntu中是好用的。

5、代码实现yuyv数据存储。这里说明一下代码是在网上找的自己稍加修改。

程序执行以后生成mytest.yuyv文件

相关包下载地址：http://download.youkuaiyun.com/download/u011186256/10246003

代码参考链接：

http://blog.youkuaiyun.com/zgyulongfei/article/details/7526249

http://blog.youkuaiyun.com/li_wen01/article/details/53557949

  
#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
#include <assert.h>  
  
#include <getopt.h>             /* getopt_long() */  
  
#include <fcntl.h>              /* low-level i/o */  
#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>          /* for videodev2.h */  
  
#include <linux/videodev2.h>  
  
#define CLEAR(x) memset (&(x), 0, sizeof (x))  
  
typedef enum {  
    IO_METHOD_READ, IO_METHOD_MMAP, IO_METHOD_USERPTR,  
} io_method;  
  
struct buffer {  
    void * start;  
    size_t length;  
};  
  
static char * dev_name = NULL;  
static io_method io = IO_METHOD_MMAP;  
static int fd = -1;  
struct buffer * buffers = NULL;  
static unsigned int n_buffers = 0;  
  
FILE *fp;  
char *filename = "mytest.yuyv";  
  
static void errno_exit(const char * s) {  
    fprintf(stderr, "%s error %d, %s/n", s, errno, strerror(errno));  
  
    exit(EXIT_FAILURE);  
}  
  
static int xioctl(int fd, int request, void * arg) {  
    int r;  
  
    do {  
        r = ioctl(fd, request, arg);  
    } while (-1 == r && EINTR == errno);  
  
    return r;  
}  
  
static void process_image(const void * p, int size) {  
    fwrite(p, size, 1, fp);  
}  
  
static int read_frame(void) {  
    struct v4l2_buffer buf;  
    unsigned int i;  
  
    switch (io) {  
    case IO_METHOD_READ:  
        if (-1 == read(fd, buffers[0].start, buffers[0].length)) {  
            switch (errno) {  
            case EAGAIN:  
                return 0;  
  
            case EIO:  
                /* Could ignore EIO, see spec. */  
                /* fall through */  
            default:  
                errno_exit("read");  
            }  
        }  
  
        process_image(buffers[0].start, buffers[0].length);  
  
        break;  
  
    case IO_METHOD_MMAP:  
        CLEAR(buf);  
  
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
        buf.memory = V4L2_MEMORY_MMAP;  
  
        if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {  
            switch (errno) {  
            case EAGAIN:  
                return 0;  
  
            case EIO:  
                /* Could ignore EIO, see spec. */  
  
                /* fall through */  
  
            default:  
                errno_exit("VIDIOC_DQBUF");  
            }  
        }  
  
        assert(buf.index < n_buffers);  
  
        process_image(buffers[buf.index].start, buf.length);  
  
        if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))  
            errno_exit("VIDIOC_QBUF");  
  
        break;  
  
    case IO_METHOD_USERPTR:  
        CLEAR(buf);  
  
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
        buf.memory = V4L2_MEMORY_USERPTR;  
  
        if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {  
            switch (errno) {  
            case EAGAIN:  
                return 0;  
  
            case EIO:  
                /* Could ignore EIO, see spec. */  
  
                /* fall through */  
  
            default:  
                errno_exit("VIDIOC_DQBUF");  
            }  
        }  
  
        for (i = 0; i < n_buffers; ++i)  
            if (buf.m.userptr == (unsigned long) buffers[i].start  
                    && buf.length == buffers[i].length)  
                break;  
  
        assert(i < n_buffers);  
  
        process_image((void *) buf.m.userptr, buf.length);  
  
        if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))  
            errno_exit("VIDIOC_QBUF");  
  
        break;  
    }  
  
    return 1;  
}  
  
static void mainloop(void) {  
    unsigned int count;  
  
    count = 500;  
  
    while (count-- > 0) {  
        for (;;) {  
            fd_set fds;  
            struct timeval tv;  
            int r;  
  
            FD_ZERO(&fds);  
            FD_SET(fd, &fds);  
  
            /* Timeout. */  
            tv.tv_sec = 2;  
            tv.tv_usec = 0;  
  
            r = select(fd + 1, &fds, NULL, NULL, &tv);  
  
            if (-1 == r) {  
                if (EINTR == errno)  
                    continue;  
  
                errno_exit("select");  
            }  
  
            if (0 == r) {  
                fprintf(stderr, "select timeout/n");  
                exit(EXIT_FAILURE);  
            }  
  
            if (read_frame())  
                break;  
  
            /* EAGAIN - continue select loop. */  
        }  
    }  
}  
  
static void stop_capturing(void) {  
    enum v4l2_buf_type type;  
  
    switch (io) {  
    case IO_METHOD_READ:  
        /* Nothing to do. */  
        break;  
  
    case IO_METHOD_MMAP:  
    case IO_METHOD_USERPTR:  
        type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
  
        if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))  
            errno_exit("VIDIOC_STREAMOFF");  
  
        break;  
    }  
}  
  
static void start_capturing(void) {  
    unsigned int i;  
    enum v4l2_buf_type type;  
  
    switch (io) {  
    case IO_METHOD_READ:  
        /* Nothing to do. */  
        break;  
  
    case IO_METHOD_MMAP:  
        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 == xioctl(fd, VIDIOC_QBUF, &buf))  
                errno_exit("VIDIOC_QBUF");  
        }  
  
        type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
  
        if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))  
            errno_exit("VIDIOC_STREAMON");  
  
        break;  
  
    case IO_METHOD_USERPTR:  
        for (i = 0; i < n_buffers; ++i) {  
            struct v4l2_buffer buf;  
  
            CLEAR(buf);  
  
            buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
            buf.memory = V4L2_MEMORY_USERPTR;  
            buf.index = i;  
            buf.m.userptr = (unsigned long) buffers[i].start;  
            buf.length = buffers[i].length;  
  
            if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))  
                errno_exit("VIDIOC_QBUF");  
        }  
  
        type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
  
        if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))  
            errno_exit("VIDIOC_STREAMON");  
  
        break;  
    }  
}  
  
static void uninit_device(void) {  
    unsigned int i;  
  
    switch (io) {  
    case IO_METHOD_READ:  
        free(buffers[0].start);  
        break;  
  
    case IO_METHOD_MMAP:  
        for (i = 0; i < n_buffers; ++i)  
            if (-1 == munmap(buffers[i].start, buffers[i].length))  
                errno_exit("munmap");  
        break;  
  
    case IO_METHOD_USERPTR:  
        for (i = 0; i < n_buffers; ++i)  
            free(buffers[i].start);  
        break;  
    }  
  
    free(buffers);  
}  
  
static void init_read(unsigned int buffer_size) {  
    buffers = calloc(1, sizeof(*buffers));  
  
    if (!buffers) {  
        fprintf(stderr, "Out of memory/n");  
        exit(EXIT_FAILURE);  
    }  
  
    buffers[0].length = buffer_size;  
    buffers[0].start = malloc(buffer_size);  
  
    if (!buffers[0].start) {  
        fprintf(stderr, "Out of memory/n");  
        exit(EXIT_FAILURE);  
    }  
}  
  
static void init_mmap(void) {  
    struct v4l2_requestbuffers req;  
  
    CLEAR(req);  
  
    req.count = 4;  
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
    req.memory = V4L2_MEMORY_MMAP;  
  
    if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {  
        if (EINVAL == errno) {  
            fprintf(stderr, "%s does not support "  
                    "memory mapping/n", dev_name);  
            exit(EXIT_FAILURE);  
        } else {  
            errno_exit("VIDIOC_REQBUFS");  
        }  
    }  
  
    if (req.count < 2) {  
        fprintf(stderr, "Insufficient buffer memory on %s/n", dev_name);  
        exit(EXIT_FAILURE);  
    }  
  
    buffers = calloc(req.count, sizeof(*buffers));  
  
    if (!buffers) {  
        fprintf(stderr, "Out of memory/n");  
        exit(EXIT_FAILURE);  
    }  
  
    for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {  
        struct v4l2_buffer buf;  
  
        CLEAR(buf);  
  
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
        buf.memory = V4L2_MEMORY_MMAP;  
        buf.index = n_buffers;  
  
        if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))  
            errno_exit("VIDIOC_QUERYBUF");  
  
        buffers[n_buffers].length = buf.length;  
        buffers[n_buffers].start = mmap(NULL /* start anywhere */, buf.length,  
                PROT_READ | PROT_WRITE /* required */,  
                MAP_SHARED /* recommended */, fd, buf.m.offset);  
  
        if (MAP_FAILED == buffers[n_buffers].start)  
            errno_exit("mmap");  
    }  
}  
  
static void init_userp(unsigned int buffer_size) {  
    struct v4l2_requestbuffers req;  
    unsigned int page_size;  
  
    page_size = getpagesize();  
    buffer_size = (buffer_size + page_size - 1) & ~(page_size - 1);  
  
    CLEAR(req);  
  
    req.count = 4;  
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
    req.memory = V4L2_MEMORY_USERPTR;  
  
    if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {  
        if (EINVAL == errno) {  
            fprintf(stderr, "%s does not support "  
                    "user pointer i/o/n", dev_name);  
            exit(EXIT_FAILURE);  
        } else {  
            errno_exit("VIDIOC_REQBUFS");  
        }  
    }  
  
    buffers = calloc(4, sizeof(*buffers));  
  
    if (!buffers) {  
        fprintf(stderr, "Out of memory/n");  
        exit(EXIT_FAILURE);  
    }  
  
    for (n_buffers = 0; n_buffers < 4; ++n_buffers) {  
        buffers[n_buffers].length = buffer_size;  
        buffers[n_buffers].start = memalign(/* boundary */page_size,  
                buffer_size);  
  
        if (!buffers[n_buffers].start) {  
            fprintf(stderr, "Out of memory/n");  
            exit(EXIT_FAILURE);  
        }  
    }  
}  
  
static void init_device(void) {  
    struct v4l2_capability cap;  
    struct v4l2_cropcap cropcap;  
    struct v4l2_crop crop;  
    struct v4l2_format fmt;  
    unsigned int min;  
  
    if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {  
        if (EINVAL == errno) {  
            fprintf(stderr, "%s is no V4L2 device/n", dev_name);  
            exit(EXIT_FAILURE);  
        } else {  
            errno_exit("VIDIOC_QUERYCAP");  
        }  
    }  
  
    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {  
        fprintf(stderr, "%s is no video capture device/n", dev_name);  
        exit(EXIT_FAILURE);  
    }  
  
    switch (io) {  
    case IO_METHOD_READ:  
        if (!(cap.capabilities & V4L2_CAP_READWRITE)) {  
            fprintf(stderr, "%s does not support read i/o/n", dev_name);  
            exit(EXIT_FAILURE);  
        }  
  
        break;  
  
    case IO_METHOD_MMAP:  
    case IO_METHOD_USERPTR:  
        if (!(cap.capabilities & V4L2_CAP_STREAMING)) {  
            fprintf(stderr, "%s does not support streaming i/o/n", dev_name);  
            exit(EXIT_FAILURE);  
        }  
  
        break;  
    }  
  
    /* Select video input, video standard and tune here. */  
  
    CLEAR(cropcap);  
  
    cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
  
    if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {  
        crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
        crop.c = cropcap.defrect; /* reset to default */  
  
        if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) {  
            switch (errno) {  
            case EINVAL:  
                /* Cropping not supported. */  
                break;  
            default:  
                /* Errors ignored. */  
                break;  
            }  
        }  
    } else {  
        /* Errors ignored. */  
    }  
  
    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_YUYV ;//; V4L2_PIX_FMT_YUV422P
    fmt.fmt.pix.field = V4L2_FIELD_NONE;//V4L2_FIELD_INTERLACED;  
  
    if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))  
        errno_exit("VIDIOC_S_FMT");  
  
    /* Note VIDIOC_S_FMT may change width and height. */  
  
    /* Buggy driver paranoia. */  
    min = fmt.fmt.pix.width * 2;  
    if (fmt.fmt.pix.bytesperline < min)  
        fmt.fmt.pix.bytesperline = min;  
    min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;  
    if (fmt.fmt.pix.sizeimage < min)  
        fmt.fmt.pix.sizeimage = min;  
  
    switch (io) {  
    case IO_METHOD_READ:  
        init_read(fmt.fmt.pix.sizeimage);  
        break;  
  
    case IO_METHOD_MMAP:  
        init_mmap();  
        break;  
  
    case IO_METHOD_USERPTR:  
        init_userp(fmt.fmt.pix.sizeimage);  
        break;  
    }  
}  
  
static void close_device(void) {  
    if (-1 == close(fd))  
        errno_exit("close");  
  
    fd = -1;  
}  
  
static void open_device(void) {  
    struct stat st;  
  
    if (-1 == stat(dev_name, &st)) {  
        fprintf(stderr, "Cannot identify '%s': %d, %s/n", dev_name, errno,  
                strerror(errno));  
        exit(EXIT_FAILURE);  
    }  
  
    if (!S_ISCHR(st.st_mode)) {  
        fprintf(stderr, "%s is no device/n", dev_name);  
        exit(EXIT_FAILURE);  
    }  
  
    fd = open(dev_name, O_RDWR /* required */| O_NONBLOCK, 0);  
  
    if (-1 == fd) {  
        fprintf(stderr, "Cannot open '%s': %d, %s/n", dev_name, errno,  
                strerror(errno));  
        exit(EXIT_FAILURE);  
    }  
}  
  
static void usage(FILE * fp, int argc, char ** argv) {  
    fprintf(fp, "Usage: %s [options]/n/n"  
            "Options:/n"  
            "-d | --device name   Video device name [/dev/video]/n"  
            "-h | --help          Print this message/n"  
            "-m | --mmap          Use memory mapped buffers/n"  
            "-r | --read          Use read() calls/n"  
            "-u | --userp         Use application allocated buffers/n"  
            "", argv[0]);  
}  
  
static const char short_options[] = "d:hmru";  
  
static const struct option long_options[] = { { "device", required_argument,  
        NULL, 'd' }, { "help", no_argument, NULL, 'h' }, { "mmap", no_argument,  
        NULL, 'm' }, { "read", no_argument, NULL, 'r' }, { "userp", no_argument,  
        NULL, 'u' }, { 0, 0, 0, 0 } };  
  
int main(int argc, char ** argv) {  
    dev_name = "/dev/video0";  
  
    for (;;) {  
        int index;  
        int c;  
  
        c = getopt_long(argc, argv, short_options, long_options, &index);  
  
        if (-1 == c)  
            break;  
  
        switch (c) {  
        case 0: /* getopt_long() flag */  
            break;  
  
        case 'd':  
            dev_name = optarg;  
            break;  
  
        case 'h':  
            usage(stdout, argc, argv);  
            exit(EXIT_SUCCESS);  
  
        case 'm':  
            io = IO_METHOD_MMAP;  
            break;  
  
        case 'r':  
            io = IO_METHOD_READ;  
            break;  
  
        case 'u':  
            io = IO_METHOD_USERPTR;  
            break;  
  
        default:  
            usage(stderr, argc, argv);  
            exit(EXIT_FAILURE);  
        }  
    }  
  
    open_device();  
  
    init_device();  
  
    start_capturing();  
  
    fp = fopen(filename, "w");  
    mainloop();  
    fclose(fp);  
  
    stop_capturing();  
  
    uninit_device();  
  
    close_device();  
  
    exit(EXIT_SUCCESS);  
  
    return 0;  
}