Hi everyone,
I am trying to write some C code to acquire a single image using the v4ctl library. I am using a raspberry pi v2 camera (IMX219) with a jetson nano.
I have the following code:
#include <errno.h>
#include <fcntl.h>
#include <linux/videodev2.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <unistd.h>
uint8_t *buffer;
static int xioctl(int fd, int request, void *arg)
{
int r;
do r = ioctl (fd, request, arg);
while (-1 == r && EINTR == errno);
return r;
}
int print_caps(int fd)
{
struct v4l2_capability caps = {0};
if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &caps))
{
perror("Querying Capabilities");
return 1;
}
printf( "Driver Caps:\n"
" Driver: \"%s\"\n"
" Card: \"%s\"\n"
" Bus: \"%s\"\n"
" Version: %d.%d\n"
" Capabilities: %08x\n",
caps.driver,
caps.card,
caps.bus_info,
(caps.version>>16)&&0xff,
(caps.version>>24)&&0xff,
caps.capabilities);
// struct v4l2_cropcap cropcap = {0};
// cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
// if (-1 == xioctl (fd, VIDIOC_CROPCAP, &cropcap))
// {
// perror("Querying Cropping Capabilities");
// return 1;
// }
// printf( "Camera Cropping:\n"
// " Bounds: %dx%d+%d+%d\n"
// " Default: %dx%d+%d+%d\n"
// " Aspect: %d/%d\n",
// cropcap.bounds.width, cropcap.bounds.height, cropcap.bounds.left, cropcap.bounds.top,
// cropcap.defrect.width, cropcap.defrect.height, cropcap.defrect.left, cropcap.defrect.top,
// cropcap.pixelaspect.numerator, cropcap.pixelaspect.denominator);
int support_grbg10 = 0;
struct v4l2_fmtdesc fmtdesc = {0};
fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
char fourcc[5] = {0};
char c, e;
printf(" FMT : CE Desc\n--------------------\n");
while (0 == xioctl(fd, VIDIOC_ENUM_FMT, &fmtdesc))
{
strncpy(fourcc, (char *)&fmtdesc.pixelformat, 4);
if (fmtdesc.pixelformat == V4L2_PIX_FMT_SGRBG10)
support_grbg10 = 1;
c = fmtdesc.flags & 1? 'C' : ' ';
e = fmtdesc.flags & 2? 'E' : ' ';
printf(" %s: %c%c %s\n", fourcc, c, e, fmtdesc.description);
fmtdesc.index++;
}
/*
if (!support_grbg10)
{
printf("Doesn't support GRBG10.\n");
return 1;
}*/
struct v4l2_format fmt = {0};
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 1280;
fmt.fmt.pix.height = 720;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_SGBRG10P;
fmt.fmt.pix.field = V4L2_FIELD_NONE;
if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
{
perror("Setting Pixel Format");
return 1;
}
strncpy(fourcc, (char *)&fmt.fmt.pix.pixelformat, 4);
printf( "Selected Camera Mode:\n"
" Width: %d\n"
" Height: %d\n"
" PixFmt: %s\n"
" Field: %d\n",
fmt.fmt.pix.width,
fmt.fmt.pix.height,
fourcc,
fmt.fmt.pix.field);
return 0;
}
int init_mmap(int fd)
{
struct v4l2_requestbuffers req = {0};
req.count = 1;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req))
{
perror("Requesting Buffer");
return 1;
}
struct v4l2_buffer buf = {0};
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
if(-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
{
perror("Querying Buffer");
return 1;
}
buffer = (uint8_t*)mmap (NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
printf("Length: %d\nAddress: %p\n", buf.length, buffer);
printf("Image Length: %d\n", buf.bytesused);
return 0;
}
int capture_image(int fd)
{
printf("\n Entered Capture Image Function \n\n");
struct v4l2_buffer buf = {0};
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
if(-1 == xioctl(fd, VIDIOC_QBUF, &buf))
{
perror("Query Buffer");
return 1;
}
if(-1 == xioctl(fd, VIDIOC_STREAMON, &buf.type))
{
perror("Start Capture");
return 1;
}
int size = buf.bytesused;
fd_set fds;
FD_ZERO(&fds);
FD_SET(fd, &fds);
struct timeval tv = {0};
tv.tv_sec = 2;
int r = select(fd+1, &fds, NULL, NULL, &tv);
printf("\n Returned from select() call \n\n");
if(-1 == r)
{
perror("Waiting for Frame");
return 1;
}
printf("\n Returned from frame call \n\n");
// if(-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
// {
// perror("Retrieving Frame");
// return 1;
// }
if (-1 == ioctl(fd, VIDIOC_DQBUF, &buf))
{
printf("\n Entered ioctl call \n\n");
perror("Queue Buffer");
return 1;
}
printf("\n Returned from retrieving frame call \n\n");
printf ("saving image\n");
int file = open("output.raw", O_WRONLY);
write(file, buffer, size);
// IplImage* frame;
// CvMat cvmat = cvMat(480, 640, CV_8UC3, (void*)buffer);
// frame = cvDecodeImage(&cvmat, 1);
// cvNamedWindow("window",CV_WINDOW_AUTOSIZE);
// cvShowImage("window", frame);
// cvWaitKey(0);
// cvSaveImage("image.jpg", frame, 0);
return 0;
}
int main()
{
printf("\n Running single image acquisition\n\n");
int fd;
fd = open("/dev/video0", O_RDWR);
if (fd == -1)
{
perror("Error: Opening video device");
return 1;
}
if(print_caps(fd))
return 1;
if(init_mmap(fd))
return 1;
int i;
for(i=0; i<5; i++)
{
if(capture_image(fd))
return 1;
}
close(fd);
return 0;
}
The code never returns and gets hung. I noticed 2 issues:
[1]
printf(“Image Length: %d\n”, buf.bytesused);
returns 0 which seems odd to me.
[2]
if (-1 == ioctl(fd, VIDIOC_DQBUF, &buf)) { printf("\n Entered ioctl call \n\n"); perror("Queue Buffer"); return 1; }
The ioctl function never returns and hence the program gets stuck. This explains the behavior I am seeing.
I adapted this code from the v4l2 capture.c example so i am not too sure why I am getting this behavior. I would greatly appreciate it if someone could help me figure out what is going wrong here. Thank you :)