摄像头怎么读取不了图片???
写了一个程序，在pc机的linux下可以读取图像。但是交叉编译后却不能读取了。
显示select timeout就是在select超时了。。。
怎么回事呢。。。。
当然我是改了设备文件的。
插入摄像头/dev目下了多了一个video2设备文件的。
附上源代码:
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<assert.h>
#include<fcntl.h>
#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>
#include<linux/videodev2.h>
#define CLEAR(x) memset(&(x), 0, sizeof(x))
struct buffer
{
void *start;
size_t length;
};
static char *dev_name = "/dev/video2";
static int fd = -1;
struct buffer *buffers = NULL;
static unsigned int n_buffers = 0;
FILE *fp;
char *filename = "test.yuv\0";
static void open_device(void)
{
fd = open(dev_name, O_RDWR|O_NONBLOCK, 0);
if(-1 == fd)
{
perror("open");
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 == ioctl(fd, VIDIOC_REQBUFS, &req))
{
if(EINVAL == errno)
{
fprintf(stderr, "%s does not support memory mapping\n", dev_name);
exit(EXIT_FAILURE);
}
else
{
perror("VIDIOC_REQBUFS");
exit(EXIT_FAILURE);
}
}
buffers = calloc(req.count, sizeof(*buffers));
if(!buffers)
{
fprintf(stderr, "Out of memory");
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 == ioctl(fd, VIDIOC_QUERYBUF, &buf))
{
perror("VIDIOC_QUERYBUF");
exit(EXIT_FAILURE);
}
buffers.length = buf.length;
buffers.start = mmap(NULL, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
if(MAP_FAILED == buffers.start)
{
perror("mmap");
exit(EXIT_FAILURE);
}
}
}
static void init_device(void)
{
struct v4l2_capability cap;
struct v4l2_format fmt;
if(-1 == ioctl(fd, VIDIOC_QUERYCAP, &cap))
{
if(EINVAL == errno)
{
fprintf(stderr, "%s is no v4l2 device\n", dev_name);
exit(EXIT_FAILURE);
}
else
{
perror("VIDIOC_QUERYCAP");
exit(EXIT_FAILURE);
}
}
if(!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))
{
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);
}
CLEAR(fmt);
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 320;
fmt.fmt.pix.height = 240;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if(-1 == ioctl(fd, VIDIOC_S_FMT, &fmt))
{
perror("VIDIOC_S_FMT");
exit(EXIT_FAILURE);
}
init_mmap();
}
void start_capturing(void)
{
unsigned int i;
enum v4l2_buf_type type;
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 == ioctl(fd, VIDIOC_QBUF, &buf))
{
perror("VIDIOC_QBUF");
exit(EXIT_FAILURE);
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if(-1 == ioctl(fd, VIDIOC_STREAMON, &type))
{
perror("VIDIOC_STREAMON");
exit(EXIT_FAILURE);
}
}
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;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if(-1 == ioctl(fd, VIDIOC_DQBUF, &buf))
{
switch(errno)
{
case EAGAIN:
return 0;
case EIO:
default:
perror("VIDIOC_DQBUF");
exit(EXIT_FAILURE);
}
}
process_image(buffers.start, buf.length);
return 1;
}
void mainloop()
{
unsigned int count;
count = 1;
while(count-- > 0)
{
for(;;)
{
fd_set fds;
struct timeval tv;
int r;
FD_ZERO(&fds);
FD_SET(fd, &fds);
tv.tv_sec = 2;
tv.tv_usec = 0;
r = select(fd + 1, &fds, NULL, NULL, &tv);
if(-1 == r)
{
if(EINTR == errno)
continue;
perror("select");
exit(EXIT_FAILURE);
}
if(0 == r)
{
fprintf(stderr, "select timeout\n");
exit(EXIT_FAILURE);
}
if(read_frame())
break;
}
}
}
static void stop_capturing()
{
enum v4l2_buf_type type;
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if(-1 == ioctl(fd, VIDIOC_STREAMOFF, &type))
{
perror("VIDIOC_STREAMOFF");
exit(EXIT_FAILURE);
}
}
static void uninit_device()
{
unsigned int i;
for(i = 0; i < n_buffers; i++)
{
if(-1 == munmap(buffers.start, buffers.length))
{
perror("munmap");
exit(EXIT_FAILURE);
}
}
free(buffers);
}
static void close_device()
{
if(-1 == close(fd))
{
perror("close");
exit(EXIT_FAILURE);
}
fd = -1;
}
int main()
{
// dev_name = "/dev/video0";
open_device();
init_device();
start_capturing();
fp = fopen(filename, "wa+");
mainloop();
fclose(fp);
stop_capturing();
uninit_device();
close_device();
exit(EXIT_SUCCESS);
return 0;
}
希望可以解答一下。各位飞凌的大神们。 板子为256RAM2GNandflash
内核为3.0.1 求解答啊！！！！！
用飞凌板子的自带程序也用不了，一样是显示select timeout...... 确实是。修改select它的等待时候可以解决select timeout的问题。。
不过。。不可能读取一张图片需要那么久啊！！！！
就算2440下select 2s都是绰绰有余的。
H264 编码后点播的视频那么卡，读取一张图片是得多久！！！
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