#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 FORCED_WIDTH 640
#define FORCED_HEIGHT 480
#define FORCED_FORMAT V4L2_PIX_FMT_YUYV
#define FORCED_FIELD V4L2_FIELD_ANY
static int verbose = ;
#define pr_debug(fmt, arg...) \
if (verbose) fprintf(stderr, fmt, ##arg)
#define CLEAR(x) memset(&(x), 0, sizeof(x)) //相当于CLEAR(x) =memset(&(x), 0, sizeof(x))
enum io_method { //枚举，即只能取其中的一个值。也是一种数据结构
IO_METHOD_READ,
IO_METHOD_MMAP,
IO_METHOD_USERPTR,
};
struct buffer {
void *start;
size_t length; //size_t =unsigned int 用来表示sizeof的
};
static char *dev_name; //用来保存设备名
static enum io_method io = IO_METHOD_MMAP;
static int fd = -;
struct buffer *buffers;
static unsigned int n_buffers;
static int out_buf;
static int force_format;
static int frame_count = ;
static char *video_name="video.yuv";
FILE *fp; //保存视频
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 (- == r && EINTR == errno);
return r;
}
static void process_image(const void *p, int size)
{
pr_debug("%s: called!\n", __func__);
//采集视频
fwrite(p,size,,fp);//如果要查看采集视频的格式，在linux下可以通过安装v4l-utils,然后执行v4l2-ctl --all来查看视频采集的相关信息
// 保存为一张张图片
/* FILE *fp;
static int num = 1;
char picture_name[20];
sprintf(picture_name,"picture%d.jpg",num ++);
if((fp = fopen(picture_name,"w")) == NULL)
{
perror("Fail to fopen");
exit(EXIT_FAILURE);
}
fwrite(p,size,1,fp);
usleep(500);
fclose(fp);
*/
// 打印到标准输出
/*if (out_buf)
fwrite(p, size, 1, stdout);
fflush(stderr);
fprintf(stderr, ".");
fflush(stdout);
*/
}
static int read_frame(void)
{
struct v4l2_buffer buf;
unsigned int i;
pr_debug("%s: called!\n", __func__);
switch (io) {
case IO_METHOD_READ:
break;
case IO_METHOD_MMAP:
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (- == xioctl(fd, VIDIOC_DQBUF, &buf)) {
switch (errno) {
case EAGAIN:
return ;
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.bytesused);
if (- == xioctl(fd, VIDIOC_QBUF, &buf))
errno_exit("VIDIOC_QBUF");
break;
case IO_METHOD_USERPTR:
break;
}
return ;
}
static void mainloop(void)
{
unsigned int count;
pr_debug("%s: called!\n", __func__);
count = frame_count;
while (count-- > ) {
for (;;) {
fd_set fds;
struct timeval tv;
int r;
FD_ZERO(&fds);
FD_SET(fd, &fds);
/* Timeout. */
tv.tv_sec = ;
tv.tv_usec = ;
r = select(fd + , &fds, NULL, NULL, &tv);
if (- == r) {
if (EINTR == errno)
continue;
errno_exit("select");
}
if ( == 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;
pr_debug("%s: called!\n", __func__);
switch (io) {
case IO_METHOD_READ:
/* Nothing to do. */
break;
case IO_METHOD_MMAP: //会执行下面的
case IO_METHOD_USERPTR:
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (- == xioctl(fd, VIDIOC_STREAMOFF, &type))
errno_exit("VIDIOC_STREAMOFF");
break;
}
}
static void start_capturing(void)
{
unsigned int i;
enum v4l2_buf_type type;
int err;
pr_debug("%s: called!\n", __func__);
pr_debug("\tn_buffers: %d\n", n_buffers);
switch (io) {
case IO_METHOD_READ:
/* Nothing to do. */
break;
case IO_METHOD_MMAP:
for (i = ; i < n_buffers; ++i) {
struct v4l2_buffer buf;
pr_debug("\ti: %d\n", i);
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
pr_debug("\tbuf.index: %d\n", buf.index);
err == xioctl(fd, VIDIOC_QBUF, &buf);
pr_debug("\terr: %d\n", err);
if (- == err)
errno_exit("VIDIOC_QBUF");
pr_debug("\tbuffer queued!\n");
}
pr_debug("Before STREAMON\n");
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (- == xioctl(fd, VIDIOC_STREAMON, &type))
errno_exit("VIDIOC_STREAMON");
pr_debug("After STREAMON\n");
break;
case IO_METHOD_USERPTR:
break;
}
}
static void uninit_device(void)
{
unsigned int i;
pr_debug("%s: called!\n", __func__);
switch (io) {
case IO_METHOD_READ:
free(buffers[].start);
break;
case IO_METHOD_MMAP:
for (i = ; i < n_buffers; ++i)
if (- == munmap(buffers[i].start, buffers[i].length))
errno_exit("munmap");
break;
case IO_METHOD_USERPTR:
for (i = ; i < n_buffers; ++i)
free(buffers[i].start);
break;
}
free(buffers);
}
static void init_read(unsigned int buffer_size)
{
pr_debug("%s: called!\n", __func__);
buffers = calloc(, sizeof(*buffers));
if (!buffers) {
fprintf(stderr, "Out of memory\n");
exit(EXIT_FAILURE);
}
buffers[].length = buffer_size;
buffers[].start = malloc(buffer_size);
if (!buffers[].start) {
fprintf(stderr, "Out of memory\n");
exit(EXIT_FAILURE);
}
}
static void init_mmap(void) //（3）
{
struct v4l2_requestbuffers req;
pr_debug("%s: called!\n", __func__);
CLEAR(req);
req.count = ;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (- == 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");
}
}
pr_debug("\treq.count: %d\n", req.count);
pr_debug("\treq.type: %d\n", req.type);
pr_debug("\treq.memory: %d\n", req.memory);
pr_debug("\n");
if (req.count < ) {
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 = ; 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 (- == xioctl(fd, VIDIOC_QUERYBUF, &buf))
errno_exit("VIDIOC_QUERYBUF");
pr_debug("\tbuf.index: %d\n", buf.index);
pr_debug("\tbuf.type: %d\n", buf.type);
pr_debug("\tbuf.bytesused: %d\n", buf.bytesused);
pr_debug("\tbuf.flags: %d\n", buf.flags);
pr_debug("\tbuf.field: %d\n", buf.field);
pr_debug("\tbuf.timestamp.tv_sec: %ld\n", (long) buf.timestamp.tv_sec);
pr_debug("\tbuf.timestamp.tv_usec: %ld\n", (long) buf.timestamp.tv_usec);
pr_debug("\tbuf.timecode.type: %d\n", buf.timecode.type);
pr_debug("\tbuf.timecode.flags: %d\n", buf.timecode.flags);
pr_debug("\tbuf.timecode.frames: %d\n", buf.timecode.frames);
pr_debug("\tbuf.timecode.seconds: %d\n", buf.timecode.seconds);
pr_debug("\tbuf.timecode.minutes: %d\n", buf.timecode.minutes);
pr_debug("\tbuf.timecode.hours: %d\n", buf.timecode.hours);
pr_debug("\tbuf.timecode.userbits: %d,%d,%d,%d\n",
buf.timecode.userbits[],
buf.timecode.userbits[],
buf.timecode.userbits[],
buf.timecode.userbits[]);
pr_debug("\tbuf.sequence: %d\n", buf.sequence);
pr_debug("\tbuf.memory: %d\n", buf.memory);
pr_debug("\tbuf.m.offset: %d\n", buf.m.offset);
pr_debug("\tbuf.length: %d\n", buf.length);
pr_debug("\tbuf.input: %d\n", buf.input);
pr_debug("\n");
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_device(void) //static表示次函数只能在本文件中调用
{
struct v4l2_capability cap;
struct v4l2_cropcap cropcap;
struct v4l2_crop crop;
struct v4l2_format fmt;
unsigned int min;
pr_debug("%s: called!\n", __func__);
if (- == 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");
}
}
pr_debug("\tdriver: %s\n"
"\tcard: %s \n"
"\tbus_info: %s\n",
cap.driver, cap.card, cap.bus_info);
pr_debug("\tversion: %u.%u.%u\n",
(cap.version >> ) & 0xFF,
(cap.version >> ) & 0xFF,
cap.version & 0xFF);
pr_debug("\tcapabilities: 0x%08x\n", cap.capabilities);
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf(stderr, "%s is no video capture device\n",
dev_name);
exit(EXIT_FAILURE);
}
/* Select video input, video standard and tune here. */
CLEAR(cropcap);
cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if ( == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {
pr_debug("\tcropcap.type: %d\n", cropcap.type);
pr_debug("\tcropcap.bounds.left: %d\n", cropcap.bounds.left);
pr_debug("\tcropcap.bounds.top: %d\n", cropcap.bounds.top);
pr_debug("\tcropcap.bounds.width: %d\n", cropcap.bounds.width);
pr_debug("\tcropcap.bounds.height: %d\n", cropcap.bounds.height);
pr_debug("\tcropcap.defrect.left: %d\n", cropcap.defrect.left);
pr_debug("\tcropcap.defrect.top: %d\n", cropcap.defrect.top);
pr_debug("\tcropcap.defrect.width: %d\n", cropcap.defrect.width);
pr_debug("\tcropcap.defrect.height: %d\n", cropcap.defrect.height);
pr_debug("\tcropcap.pixelaspect.numerator: %d\n", cropcap.pixelaspect.numerator);
pr_debug("\tcropcap.pixelaspect.denominator: %d\n", cropcap.pixelaspect.denominator);
pr_debug("\n");
CLEAR(crop);
crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
crop.c = cropcap.defrect; /* reset to default */
if (- == xioctl(fd, VIDIOC_S_CROP, &crop)) {
switch (errno) {
case EINVAL:
/* Cropping not supported. */
break;
default:
/* Errors ignored. */
pr_debug("\tcropping not supported\n");
break;
}
}
} else {
/* Errors ignored. */
}
CLEAR(fmt);
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (force_format) {
fmt.fmt.pix.width = FORCED_WIDTH;
fmt.fmt.pix.height = FORCED_HEIGHT;
fmt.fmt.pix.pixelformat = FORCED_FORMAT;
fmt.fmt.pix.field = FORCED_FIELD;
pr_debug("\tfmt.fmt.pix.pixelformat: %c,%c,%c,%c\n",
fmt.fmt.pix.pixelformat & 0xFF,
(fmt.fmt.pix.pixelformat >> ) & 0xFF,
(fmt.fmt.pix.pixelformat >> ) & 0xFF,
(fmt.fmt.pix.pixelformat >> ) & 0xFF
);
pr_debug("\n");
if (- == 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 (- == xioctl(fd, VIDIOC_G_FMT, &fmt))
errno_exit("VIDIOC_G_FMT");
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
pr_debug("\tfmt.fmt.pix.pixelformat: %c,%c,%c,%c\n",
fmt.fmt.pix.pixelformat & 0xFF,
(fmt.fmt.pix.pixelformat >> ) & 0xFF,
(fmt.fmt.pix.pixelformat >> ) & 0xFF,
(fmt.fmt.pix.pixelformat >> ) & 0xFF
);
}
/* Buggy driver paranoia. */
min = fmt.fmt.pix.width * ;
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:
break;
}
}
static void close_device(void)
{
pr_debug("%s: called!\n", __func__);
if (- == close(fd))//==可以防止你写成=（相当与赋值）这样条件始终成立
errno_exit("close");
fd = -;
}
static void open_device(void)//
{
struct stat st;
pr_debug("%s: called!\n", __func__);//_func_表示此时在那个函数里面
if (- == stat(dev_name, &st)) {//获取文件信息
fprintf(stderr, "Cannot identify '%s': %d, %s\n",
dev_name, errno, strerror(errno));
exit(EXIT_FAILURE);//非正常退出 EXIT_FAILURE=1， EXIT_SUCCSES=0 正常退出
}
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, );//非阻塞模式打开文件
if (- == 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"
"Version 1.3\n"
"Options:\n"
"-d | --device name Video device name [%s]\n"
"-h | --help Print this message\n"
"-m | --mmap Use memory mapped buffers [default]\n"
"-r | --read Use read() calls\n"
"-u | --userp Use application allocated buffers\n"
"-o | --output Outputs stream to stdout\n"
"-f | --format Force format to 640x480 YUYV\n"
"-c | --count Number of frames to grab [%i]\n"
"-v | --verbose Verbose output\n"
"",
argv[], dev_name, frame_count);
}
//关于命令解析见百度getopt-long；
static const char short_options[] = "d:hmruofc:v";// 短选项 ：表示带参数
static const struct option //长选项
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' },
{ "output", no_argument, NULL, 'o' },
{ "format", no_argument, NULL, 'f' },
{ "count", required_argument, NULL, 'c' },
{ "verbose", no_argument, NULL, 'v' },
{ , , , }
};
int main(int argc, char **argv)
{
dev_name = "/dev/video0";
for (;;) {
int idx;
int c;
c = getopt_long(argc, argv,
short_options, long_options, &idx);
if (- == c)
break;
switch (c) {
case : /* 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;
case 'o':
out_buf++;
break;
case 'f':
force_format++;
break;
case 'c':
errno = ;
frame_count = strtol(optarg, NULL, );
if (errno)
errno_exit(optarg);
break;
case 'v':
verbose = ;
break;
default:
usage(stderr, argc, argv);
exit(EXIT_FAILURE);
}
}
if((fp = fopen(video_name,"wa+")) == NULL)
{
perror("Fail to fopen");
exit(EXIT_FAILURE);
}
open_device();
init_device();
start_capturing();
mainloop();
stop_capturing();
uninit_device();
close_device();
fprintf(stderr, "\n");
return ;
}
