Linux视频采集与编码 V4L2

这两天在Linux下用V4L2采集yuv视频然后用x264编码成h.264文件。

我将yuv视频保存到文件中，然后用pyuv播放器播放它，悲剧的是播放出来的视频花屏了。

如下所示：

我采集视频的参数为：

尺寸：640 * 480

YUV格式：YUYV即YUV422

我一直以为是我代码写错了，因为采集视频的程序我是参考V4L2官方示例代码的，并且我把官方示例代码来运行，发现采集的视频也是花屏的。然后我又猜想可能是我摄像头不能采集数据吗？可是我下载好几个camera都可以正常的拍照，录制视频。这样纠结了好久好久。直到我的手开始犯贱，我把pyuv播放器 Format中的 Interleaved 复选框勾起来了，奇迹出现了。pyuv上清清楚楚的显示出了我录制的视频 Orz

后来认真看代码发现我的设置中有这么一句：fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; 意思就是采集数据的时候使用的是隔行扫描的方式，也就是说我将采集到的yuv写到文件中的方式是用隔行扫描的方式保存。

于是如果不将 Interleaved复选框勾起来，播放器就不能正常的播放你的yuv文件。

下面是正常时候显示的图像：

嘿嘿，这是本人靓照 ^_^

yuv视频采集正常了，可是用x264编码出来的视频还是花屏到不堪入目！！！

这个是怎么办呢？请看我下一篇博文《YUYV编码成h.264：Linux视频采集与编码（二）》

附上V4L2视频采集代码：

 /*
  *  V4L2 video capture example
  *
  *  This program can be used and distributed without restrictions.
  */

 #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 = "test.yuv\0";

 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 = 100;

     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;
     fmt.fmt.pix.field = 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, "wa+");
     mainloop();
     fclose(fp);

     stop_capturing();

     uninit_device();

     close_device();

     exit(EXIT_SUCCESS);

     return 0;
 }