V4L2 Camera 驅動 Capture測試程序

在網上找了一個測試程序， 看了看，是根據capture.c修改的。測試步驟如下

1. gcc -o capture_image capture_image.c

2. ctrl+alt+f1 切換到Ubuntu的控制台，切換到控制台模式是因為在圖形模式下看不到測試圖形，這可能和framebuffer的設置有關

3. sudo modprobe vivi

4. sudo ./capture_image -d /dev/video0

這時可以看到在屏幕左上角有一個640x480大小窗口，內容是彩色條格，彩色條格不停的移動，持續時間5秒

在ubuntu下還可以使用cheese測試

1. sudo apt-get install cheese

2. sudo modprobe vivi

2. 啟動 cheese後，就可以看到滾動的彩色條格

附上測試程序

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <getopt.h>
#include <fcntl.h>
#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 <asm/types.h>
#include <linux/videodev2.h>
#include <linux/fb.h>
#define CLEAR(x) memset (&(x), 0, sizeof (x))

struct buffer {
void * start;
size_t length;
};

static char * dev_name = NULL;
static int fd = -1;
struct buffer * buffers = NULL;
static unsigned int n_buffers = 0;
static int time_in_sec_capture=5;
static int fbfd = -1;
static struct fb_var_screeninfo vinfo;
static struct fb_fix_screeninfo finfo;
static char *fbp=NULL;
static long screensize=0;

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)
{
int r;
do r = ioctl (fd, request, arg);
while (-1 == r && EINTR == errno);
return r;
}

inline int clip(int value, int min, int max) {
return (value > max ? max : value < min ? min : value);
}

static void process_image (const void * p){


//ConvertYUVToRGB32
1;
unsigned char* in=(char*)p;
int width=640;
int height=480;
int istride=1280;
int x,y,j;
int y0,u,y1,v,r,g,b;
long location=0;

for ( y = 100; y < height + 100; ++y) {
for (j = 0, x=100; j < width * 2 ; j += 4,x +=2) {
location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
(y+vinfo.yoffset) * finfo.line_length;

y0 = in[j];
u = in[j + 1] - 128;
y1 = in[j + 2];
v = in[j + 3] - 128;

r = (298 * y0 + 409 * v + 128) >> 8;
g = (298 * y0 - 100 * u - 208 * v + 128) >> 8;
b = (298 * y0 + 516 * u + 128) >> 8;

fbp[ location + 0] = clip(b, 0, 255);
fbp[ location + 1] = clip(g, 0, 255);
fbp[ location + 2] = clip(r, 0, 255);
fbp[ location + 3] = 255;

r = (298 * y1 + 409 * v + 128) >> 8;
g = (298 * y1 - 100 * u - 208 * v + 128) >> 8;
b = (298 * y1 + 516 * u + 128) >> 8;

fbp[ location + 4] = clip(b, 0, 255);
fbp[ location + 5] = clip(g, 0, 255);
fbp[ location + 6] = clip(r, 0, 255);
fbp[ location + 7] = 255;
}
in +=istride;
}
}

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 == xioctl (fd, VIDIOC_DQBUF, &buf)) {
switch (errno) {
case EAGAIN:
return 0;
case EIO:



default:
errno_exit ("VIDIOC_DQBUF");
}
}

assert (buf.index < n_buffers);
printf("v4l2_pix_format->field(%d)/n", buf.field);
//assert (buf.field ==V4L2_FIELD_NONE);
process_image (buffers[buf.index].start);
if (-1 == xioctl (fd, VIDIOC_QBUF, &buf))
errno_exit ("VIDIOC_QBUF");

return 1;
}

static void run (void)
{
unsigned int count;
int frames;
frames = 30 * time_in_sec_capture;

while (frames-- > 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;
errno_exit ("select");
}

if (0 == r) {
fprintf (stderr, "select timeout/n");
exit (EXIT_FAILURE);
}

if (read_frame ())
break;

}
}
}

static void stop_capturing (void)
{
enum v4l2_buf_type type;

type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (-1 == xioctl (fd, VIDIOC_STREAMOFF, &type))
errno_exit ("VIDIOC_STREAMOFF");
}

static 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 == 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)
{
unsigned int i;

for (i = 0; i < n_buffers; ++i)
if (-1 == munmap (buffers[i].start, buffers[i].length))
errno_exit ("munmap");

if (-1 == munmap(fbp, screensize)) {
printf(" Error: framebuffer device munmap() failed./n");
exit (EXIT_FAILURE) ;
}
free (buffers);
}


static void init_mmap (void)
{
struct v4l2_requestbuffers req;

//mmap framebuffer
fbp = (char *)mmap(NULL,screensize,PROT_READ | PROT_WRITE,MAP_SHARED ,fbfd, 0);
if ((int)fbp == -1) {
printf("Error: failed to map framebuffer device to memory./n");
exit (EXIT_FAILURE) ;
}
memset(fbp, 0, screensize);
CLEAR (req);

req.count = 4;
req.type = 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);
} else {
errno_exit ("VIDIOC_REQBUFS");
}
}

if (req.count < 4) { //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;

CLEAR (buf);

buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;

if (-1 == xioctl (fd, VIDIOC_QUERYBUF, &buf))
errno_exit ("VIDIOC_QUERYBUF");

buffers[n_buffers].length = buf.length;
buffers[n_buffers].start =mmap (NULL,buf.length,PROT_READ | PROT_WRITE ,MAP_SHARED,fd, buf.m.offset);

if (MAP_FAILED == buffers[n_buffers].start)
errno_exit ("mmap");
}

}



static void init_device (void)
{
struct v4l2_capability cap;
struct v4l2_cropcap cropcap;
struct v4l2_crop crop;
struct v4l2_format fmt;
unsigned int min;


// Get fixed screen information
if (-1==xioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
printf("Error reading fixed information./n");
exit (EXIT_FAILURE);
}

// Get variable screen information
if (-1==xioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
printf("Error reading variable information./n");
exit (EXIT_FAILURE);
}
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;


if (-1 == xioctl (fd, VIDIOC_QUERYCAP, ∩)) {
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)) {
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 (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.defrect;

if (-1 == xioctl (fd, VIDIOC_S_CROP, &crop)) {
switch (errno) {
case EINVAL:
break;
default:
break;
}
}
}else { }

CLEAR (fmt);

fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 640;
fmt.fmt.pix.height = 480;
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");

init_mmap ();

}

static void close_device (void)
{
if (-1 == close (fd))
errno_exit ("close");
fd = -1;
close(fbfd);
}

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 device/n", dev_name);
exit (EXIT_FAILURE);
}

//open framebuffer
fbfd = open("/dev/fb0", O_RDWR);
if (fbfd==-1) {
printf("Error: cannot open framebuffer device./n");
exit (EXIT_FAILURE);
}

//open camera
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"
"-t | --how long will display in seconds/n"
"",
argv[0]);
}

static const char short_options [] = "d:ht:";
static const struct option long_options [] = {
{ "device", required_argument, NULL, 'd' },
{ "help", no_argument, NULL, 'h' },
{ "time", no_argument, NULL, 't' },
{ 0, 0, 0, 0 }
};

int main (int argc,char ** argv)
{
dev_name = "/dev/video0";

for (;;)
{
int index;
int c;

c = getopt_long (argc, argv,short_options, long_options,&index);
if (-1 == c)
break;

switch (c) {
case 0:
break;

case 'd':
dev_name = optarg;
break;

case 'h':
usage (stdout, argc, argv);
exit (EXIT_SUCCESS);
case 't':
time_in_sec_capture = atoi(optarg);
break;

default:
usage (stderr, argc, argv);
exit (EXIT_FAILURE);
}
}

open_device ();

init_device ();

start_capturing ();

run ();

stop_capturing ();

uninit_device ();

close_device ();

exit (EXIT_SUCCESS);

return 0;
}

這個測試程序是根據vivi驅動hard code的， 並不一定適合其他的camera驅動
比如，我手頭上的logitech stv06xx usb camera, 因為不支持640x480模式，參見代碼59 60行，
代碼348行 if (-1 == xioctl (fd, VIDIOC_S_FMT, &fmt)) 應該是個協商的過程，
343 fmt.fmt.pix.width = 640;
344 fmt.fmt.pix.height = 480;
345 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
346 fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
這幾行只是應用的期望格式，驅動會根據這個格式選擇一個相近的格式返回，應用最後的顯示處理要根據返回的格式進行處理，即process_image要做相應修改