运行Linux的一个摄像头采集的程序，为什么我摄像头采集的图像只有灰度信息，而且分辨率什么的还有问题，大神们帮忙看一下~我刚学V4l2…… - ITeye问答
谁来帮我看下 为什么我采集到的图像还是这样啊。。。只有灰度信息？是程序问题还是我的参数问题啊]
还有我发现 我在程序里面设定的分辨率是640*480的，当以640*480显示的时候是上面那张图
用的时候是下面这张图很明显横着的是连续的，竖着的图像没有了 求解啊~程序如下，就是书上的一个示例代码
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& /*getpid()*/
#include &error.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,
struct buffer {
static char *
static io_method
= IO_METHOD_MMAP;
static int
struct buffer *
static unsigned int
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)
do r = ioctl(fd, request, arg);
while (-1 == r && EINTR == errno);
static void process_image(const void *p)
fp = fopen("test","w+");
fputs(p, fp);
fclose(fp);
fflush(stdout);
static int read_frame(void)
struct v4l2_
switch (io)
case IO_METHOD_READ:
if (-1 == read(fd, buffers[0].start, buffers[0].length))
switch (errno)
case EAGAIN:
/* Could ignore EIO, see spec. */
/* fall through */
errno_exit("read");
process_image(buffers[0].start);
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:
/* Could ignore EIO, see spec. */
/* fall through */
errno_exit("VIDIOC_DQBUF");
assert(buf.index & n_buffers);
process_image(buffers[buf.index].start);
if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
errno_exit("VIDIOC_QBUF");
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:
/* Could ignore EIO, see spec. */
/* fall through */
errno_exit("VIDIOC_DQBUF");
for (i = 0; i & n_ ++i)
if (buf.m.userptr == (unsigned long) buffers[i].start
&& buf.length == buffers[i].length)
assert(i & n_buffers);
process_image((void *) buf.m.userptr);
if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
errno_exit("VIDIOC_QBUF");
static void mainloop(void)
count = 100;
while (count-- & 0)
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)
errno_exit("select");
if (0 == r) {
fprintf(stderr, "select timeout\n");
exit(EXIT_FAILURE);
if (read_frame())
/* EAGAIN - continue select loop. */
static void stop_capturing(void)
enum v4l2_buf_
switch (io)
case IO_METHOD_READ:
/* Nothing to do. */
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");
static void start_capturing(void)
enum v4l2_buf_
switch (io)
case IO_METHOD_READ:
/* Nothing to do. */
case IO_METHOD_MMAP:
for (i = 0; i & n_ ++i)
struct v4l2_
CLEAR(buf);
= V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory
= V4L2_MEMORY_MMAP;
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");
case IO_METHOD_USERPTR:
for (i = 0; i & n_ ++i)
struct v4l2_
CLEAR(buf);
= V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory
= V4L2_MEMORY_USERPTR;
buf.m.userptr
= (unsigned long) buffers[i].
buf.length
= buffers[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");
static void uninit_device(void)
switch (io) {
case IO_METHOD_READ:
free(buffers[0].start);
case IO_METHOD_MMAP:
for (i = 0; i & n_ ++i)
if (-1 == munmap(buffers[i].start, buffers[i].length))
errno_exit("munmap");
case IO_METHOD_USERPTR:
for (i = 0; i & n_ ++i)
free(buffers[i].start);
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_
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_
CLEAR(req);
= 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);
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. ++n_buffers)
struct v4l2_
CLEAR(buf);
= V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory
= V4L2_MEMORY_MMAP;
if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
errno_exit("VIDIOC_QUERYBUF");
buffers[n_buffers].length = buf.
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_
unsigned int page_
page_size = getpagesize();
buffer_size = (buffer_size + page_size - 1) & ~(page_size - 1);
CLEAR(req);
= 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);
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_
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_
struct v4l2_
struct v4l2_
struct v4l2_
if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap))
if (EINVAL == errno)
fprintf(stderr, "%s is no V4L2 device\n",
dev_name);
exit(EXIT_FAILURE);
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);
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);
/* 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. /* reset to default */
if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop))
switch (errno)
case EINVAL:
/* Cropping not supported. */
/* Errors ignored. */
/* Errors ignored. */
CLEAR(fmt);
= V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width
fmt.fmt.pix.height
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 = fmt.fmt.pix.bytesperline * fmt.fmt.pix.
if (fmt.fmt.pix.sizeimage & min)
fmt.fmt.pix.sizeimage =
switch (io)
case IO_METHOD_READ:
init_read(fmt.fmt.pix.sizeimage);
case IO_METHOD_MMAP:
init_mmap();
case IO_METHOD_USERPTR:
init_userp(fmt.fmt.pix.sizeimage);
static void close_device(void)
if (-1 == close(fd))
errno_exit("close");
static void open_device(void)
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 /* | 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"
static const char short_options [] = "d:hmru";
static const struct option
long_options [] = {
{ "device",
required_argument,
no_argument,
no_argument,
no_argument,
{ "userp",
no_argument,
{ 0, 0, 0, 0 }
int main(int argc,char **argv)
dev_name = "/dev/video0";
c = getopt_long(argc, argv,
short_options, long_options,
if (-1 == c)
switch (c) {
case 0: /* getopt_long() flag */
dev_name =
usage(stdout, argc, argv);
exit(EXIT_SUCCESS);
io = IO_METHOD_MMAP;
io = IO_METHOD_READ;
io = IO_METHOD_USERPTR;
usage(stderr, argc, argv);
exit(EXIT_FAILURE);
open_device();
init_device();
start_capturing();
mainloop();
stop_capturing();
uninit_device();
close_device();
exit(EXIT_SUCCESS);
目前还没有答案
已解决问题
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