RK平台：V4l2 抓数据应用

这篇文章以c程序v4l2取流demo为例介绍一下应用取数据流的流程，demo参考官方例程修改，文章最后贴上完整的取流应用。

1.打开设备节点

取数据流的节点一般是video节点，如果是从rkcif节点取数据流的话，一般是video0节点，如果是多路虚拟通道的方式，一般是video0-video3分别对应vc0-vc3。如果按照如下命令来查看对应的video节点：

console:/ # grep -H '' /sys/class/video4linux/video*/name
/sys/class/video4linux/video0/name:stream_cif_mipi_id0
/sys/class/video4linux/video1/name:stream_cif_mipi_id1
/sys/class/video4linux/video10/name:rkcif_tools_id2
/sys/class/video4linux/video2/name:stream_cif_mipi_id2
/sys/class/video4linux/video3/name:stream_cif_mipi_id3
/sys/class/video4linux/video4/name:rkcif_scale_ch0
/sys/class/video4linux/video5/name:rkcif_scale_ch1
/sys/class/video4linux/video6/name:rkcif_scale_ch2
/sys/class/video4linux/video7/name:rkcif_scale_ch3
/sys/class/video4linux/video8/name:rkcif_tools_id0
/sys/class/video4linux/video9/name:rkcif_tools_id1

数据流节点为stream_cif_mipi_idx，这里以打开video0为例：

dev_name = "/dev/video0";
fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);

2.初始化设备

初始化设备包括查询设备功能、设置输出格式，申请buf等等。

2.1 查询设备功能

使用框架接口VIDIOC_QUERYCAP可以获取设备的功能，我们一般需要判断设备是否具有视频捕获的功能，需要判断V4L2_CAP_VIDEO_CAPTURE和V4L2_CAP_STREAMING，RK的平台实现都是按照V4L2_CAP_VIDEO_CAPTURE_MPLANE方式，因此这里需要注意，实现代码如下：

       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) &&!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE_MPLANE)) {fprintf(stderr, "%s is no video capture device\n",dev_name);exit(EXIT_FAILURE);}if (!(cap.capabilities & V4L2_CAP_STREAMING)) {fprintf(stderr, "%s does not support streaming i/o\n",dev_name);exit(EXIT_FAILURE);}

需要获取设备是否具备crop的能力，实现如下：

        cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;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;}}}

2.2 获取设置设备格式 VIDIOC_G_FMT, VIDIOC_S_FMT

VIDIOC_G_FMT可以获取设别格式，可以获取到当前的分辨率等信息，VIDIOC_S_FMT可以设置设备输出视频的分辨率格式等信息。使用如下：

        fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;// if (force_format) {fmt.fmt.pix.width       = width;fmt.fmt.pix.height      = height;fmt.fmt.pix.pixelformat = format;fmt.fmt.pix.field       = V4L2_FIELD_NONE;if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))errno_exit("VIDIOC_S_FMT");

3 申请buffer

在获取图像数据前需要内核帧缓存区，使用VIDIOC_REQBUFS，代码实现如下：

        req.count = 4;req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;req.memory = V4L2_MEMORY_MMAP;if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {if (EINVAL == errno) {fprintf(stderr, "%s does not support ""memory mappingn", dev_name);exit(EXIT_FAILURE);} else {errno_exit("VIDIOC_REQBUFS");}}

使用V4L2_MEMORY_MMAP的方式将缓存映射到用户空间：

        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;struct v4l2_plane planes[FMT_NUM_PLANES];CLEAR(buf);CLEAR(planes);buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;buf.memory      = V4L2_MEMORY_MMAP;buf.index       = n_buffers;if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type) {buf.m.planes = planes;buf.length = FMT_NUM_PLANES;}if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))errno_exit("VIDIOC_QUERYBUF");buffers[n_buffers].length = buf.m.planes[0].length;buffers[n_buffers].start =mmap(NULL /* start anywhere */,buf.m.planes[0].length,PROT_READ | PROT_WRITE /* required */,MAP_SHARED /* recommended */,fd, buf.m.planes[0].m.mem_offset);if (MAP_FAILED == buffers[n_buffers].start)errno_exit("mmap");}

4 开启采集

开启采集流程，需要先将buf放到缓存队列中，然后调用VIDIOC_STREAMON操作设备开启数据流的采集，实现如下：

                for (i = 0; i < n_buffers; ++i) {struct v4l2_buffer buf;CLEAR(buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;buf.memory = V4L2_MEMORY_MMAP;buf.index = i;if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type) {struct v4l2_plane planes[FMT_NUM_PLANES];buf.m.planes = planes;buf.length = FMT_NUM_PLANES;}if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))errno_exit("VIDIOC_QBUF");}type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))errno_exit("VIDIOC_STREAMON");

5 获取数据

开启数据流之后，就可以调用VIDIOC_DQBUF将已经捕获好视频的内存拉出已捕获视频的队列，DQBUF之后必须重新将BUF放到缓存队列中。

                CLEAR(buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;buf.memory = V4L2_MEMORY_MMAP;// struct v4l2_plane planes[FMT_NUM_PLANES];memset(planes, 0, sizeof(struct v4l2_plane)*FMT_NUM_PLANES);if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type) {buf.m.planes = planes;buf.length = FMT_NUM_PLANES;}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");}}if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type)bytesused = buf.m.planes[0].bytesused;elsebytesused = buf.bytesused;assert(buf.index < n_buffers);process_image(buffers[buf.index].start, bytesused);if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))errno_exit("VIDIOC_QBUF");

6 结束流程

获取完数据之后如果需要结束流程需要按照这个流程结束，要调用VIDIOC_STREAMOFF去关闭数据流，munmap缓存，最后close文件节点。

7 完整代码

完整的demo代码如下：

/**  V4L2 video capture example** Copyright (C) 2022 Rockchip Electronics Co., Ltd.* Authors: */#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 <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>#define CLEAR(x) memset(&(x), 0, sizeof(x))#define FMT_NUM_PLANES 1enum io_method {IO_METHOD_READ,IO_METHOD_MMAP,IO_METHOD_USERPTR,
};struct buffer {void   *start;size_t  length;
};static char            *dev_name;
static char            *streamfile_name;
static enum io_method   io = IO_METHOD_MMAP;
static int              fd = -1;
struct buffer          *buffers;
static unsigned int     n_buffers;
static int              out_buf;
// static int              force_format;
static int              frame_count = 10;
static int width = 1920;
static int height = 1080;
static int format = V4L2_PIX_FMT_NV12;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 fh, int request, void *arg)
{int r;do {r = ioctl(fh, request, arg);} while (-1 == r && EINTR == errno);return r;
}static void process_image(const void *p, int size)
{// if (out_buf)//         fwrite(p, size, 1, stdout);fflush(stderr);fprintf(stderr, ">");// fflush(stdout);char file_name[64] = {0};FILE *fp = NULL;// snprintf(file_name, sizeof(file_name),//      "/data/dump_%dx%d.yuv", width, height);snprintf(file_name, sizeof(file_name),"%s", streamfile_name);fp = fopen(file_name, "ab+");if (fp == NULL) {printf("fopen yuv file %s failed!\n", file_name);return;}// printf("size %d \n", size);fwrite(p, size, 1, fp);// printf("Write success YUV data to %s",file_name);fflush(fp);
}static int read_frame(void)
{struct v4l2_buffer buf;struct v4l2_plane planes[FMT_NUM_PLANES];unsigned int i;int bytesused;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_MPLANE;buf.memory = V4L2_MEMORY_MMAP;// struct v4l2_plane planes[FMT_NUM_PLANES];memset(planes, 0, sizeof(struct v4l2_plane)*FMT_NUM_PLANES);if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type) {buf.m.planes = planes;buf.length = FMT_NUM_PLANES;}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");}}if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type)bytesused = buf.m.planes[0].bytesused;elsebytesused = buf.bytesused;assert(buf.index < n_buffers);process_image(buffers[buf.index].start, bytesused);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_MPLANE;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");}}if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type)bytesused = buf.m.planes[0].bytesused;elsebytesused = buf.bytesused;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, bytesused);if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))errno_exit("VIDIOC_QBUF");break;}return 1;
}static void mainloop(void)
{unsigned int count;count = frame_count;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_MPLANE;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_MPLANE;buf.memory = V4L2_MEMORY_MMAP;buf.index = i;if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type) {struct v4l2_plane planes[FMT_NUM_PLANES];buf.m.planes = planes;buf.length = FMT_NUM_PLANES;}if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))errno_exit("VIDIOC_QBUF");}type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;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_MPLANE;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_MPLANE;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_MPLANE;req.memory = V4L2_MEMORY_MMAP;if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {if (EINVAL == errno) {fprintf(stderr, "%s does not support ""memory mappingn", 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;struct v4l2_plane planes[FMT_NUM_PLANES];CLEAR(buf);CLEAR(planes);buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;buf.memory      = V4L2_MEMORY_MMAP;buf.index       = n_buffers;if (V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE == buf.type) {buf.m.planes = planes;buf.length = FMT_NUM_PLANES;}if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))errno_exit("VIDIOC_QUERYBUF");buffers[n_buffers].length = buf.m.planes[0].length;buffers[n_buffers].start =mmap(NULL /* start anywhere */,buf.m.planes[0].length,PROT_READ | PROT_WRITE /* required */,MAP_SHARED /* recommended */,fd, buf.m.planes[0].m.mem_offset);if (MAP_FAILED == buffers[n_buffers].start)errno_exit("mmap");}
}static void init_userp(unsigned int buffer_size)
{struct v4l2_requestbuffers req;CLEAR(req);req.count  = 4;req.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;req.memory = V4L2_MEMORY_USERPTR;if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {if (EINVAL == errno) {fprintf(stderr, "%s does not support ""user pointer i/on", 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 = malloc(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) &&!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE_MPLANE)) {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_MPLANE;if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;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_MPLANE;// if (force_format) {fmt.fmt.pix.width       = width;fmt.fmt.pix.height      = height;fmt.fmt.pix.pixelformat = format;fmt.fmt.pix.field       = V4L2_FIELD_NONE;if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))errno_exit("VIDIOC_S_FMT");/* Note VIDIOC_S_FMT may change width and height. */// } else {//         /* Preserve original settings as set by v4l2-ctl for example *///         if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt))//                 errno_exit("VIDIOC_G_FMT");// }//fjw// width = fmt.fmt.pix.width;// height = fmt.fmt.pix.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 devicen", 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""argc: %d""Version 1.3\n""Options:\n""-d | --device name   Video device name [%s]\n""-p | --help          Print this message\n""-w | --width         width of image\n""-h | --height        height of image\n""-m | --mmap          Use memory mapped buffers [default]\n""-r | --read          Use read() calls\n""-u | --userp         Use application allocated buffers\n""-a | --dma           Use application allocated dma buffers\n""-o | --output        Outputs stream to stdout\n""-f | --format        Force format to YUYV\n""-t | --stream-to     stream-to file default /data/dump_out.yuv\n""-c | --count         Number of frames to grab [%i]\n""-b | --test         test\n""",argv[0], argc, dev_name, frame_count);
}static const char short_options[] = "d:pw:h:mruaof:t:c:b";static const struct option
long_options[] = {{ "device", required_argument, NULL, 'd' },{ "help",   no_argument,       NULL, 'p' },{ "width",   required_argument,       NULL, 'w' },{ "height",   required_argument,       NULL, 'h' },{ "mmap",   no_argument,       NULL, 'm' },{ "read",   no_argument,       NULL, 'r' },{ "userp",  no_argument,       NULL, 'u' },{ "dma",  no_argument,       NULL, 'a' },{ "output", no_argument,       NULL, 'o' },{ "format", required_argument,       NULL, 'f' },{ "stream-to", required_argument,       NULL, 't' },{ "count",  required_argument, NULL, 'c' },{ "test",  no_argument, NULL, 'b' },{ 0, 0, 0, 0 }
};int main(int argc, char **argv)
{dev_name = "/dev/video0";streamfile_name = "/data/dump_out.yuv";// stdout = fopen("out.yuv", "wb");for (;;) {int idx;int c;c = getopt_long(argc, argv,short_options, long_options, &idx);if (-1 == c)break;switch (c) {case 0: /* getopt_long() flag */break;case 'd':dev_name = optarg;break;case 'p':usage(stdout, argc, argv);exit(EXIT_SUCCESS);case 'w':width = strtol(optarg, NULL, 0);break;case 'h':height = strtol(optarg, NULL, 0);break;case 'm':io = IO_METHOD_MMAP;break;case 'r':io = IO_METHOD_READ;break;case 'u':io = IO_METHOD_USERPTR;break;case 'o':out_buf++;break;case 'f':// force_format++;format = v4l2_fourcc(optarg[0], optarg[1], optarg[2], optarg[3]);break;case 't':streamfile_name = optarg;break;case 'c':errno = 0;frame_count = strtol(optarg, NULL, 0);if (errno)errno_exit(optarg);break;default:usage(stderr, argc, argv);exit(EXIT_FAILURE);}}open_device();init_device();start_capturing();mainloop();stop_capturing();uninit_device();close_device();fprintf(stderr, "\n");return 0;
}