V4L2获取usb视频流测试代码

V4l2

#include "funset.hpp"
#include <string.h>
#include <assert.h>
#include <iostream>
 
#ifndef _MSC_VER
 
#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 <linux/videodev2.h>
 
namespace {
 
#define CLEAR(x) memset(&(x), 0, sizeof(x))
 
enum io_method {
	IO_METHOD_READ,
	IO_METHOD_MMAP,
	IO_METHOD_USERPTR,
};
 
struct buffer {
	void *start;
	size_t length;
};
 
char* dev_name;
enum io_method io = IO_METHOD_MMAP;
int fd = -1;
struct buffer* buffers;
unsigned int n_buffers;
int out_buf;
int force_format = 1;
int frame_count = 10;
int width = 640;
int height = 480;
FILE* f;
 
void errno_exit(const char *s)
{
	fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
	exit(EXIT_FAILURE);
}
 
int xioctl(int fh, int request, void *arg)
{
	int r;
 
	do {
		r = ioctl(fh, request, arg);
	} while (-1 == r && EINTR == errno);
 
	return r;
}
 
void process_image(const void *p, int size)
{
	/*if (out_buf)
		fwrite(p, size, 1, stdout);
	fflush(stderr);
	fprintf(stderr, ".");
	fflush(stdout);*/
	fwrite(p, size, 1, f);
}
 
int read_frame(void)
{
	struct v4l2_buffer buf;
	unsigned int i;
 
	switch (io) {
	case IO_METHOD_READ:
		if (-1 == read(fd, buffers[0].start, buffers[0].length)) {
			switch (errno) {
			case EAGAIN:
				return 0;
 
			case EIO:
				// Could ignore EIO, see spec. fall through
 
			default:
				errno_exit("read");
			}
		}
 
		process_image(buffers[0].start, buffers[0].length);
		break;
 
	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:
				return 0;
 
			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 (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
			errno_exit("VIDIOC_QBUF");
		break;
 
	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:
				return 0;
 
			case EIO:
				// Could ignore EIO, see spec. fall through
 
			default:
				errno_exit("VIDIOC_DQBUF");
			}
		}
 
		for (i = 0; i < n_buffers; ++i)
		if (buf.m.userptr == (unsigned long)buffers[i].start && buf.length == buffers[i].length)
			break;
 
		assert(i < n_buffers);
		process_image((void *)buf.m.userptr, buf.bytesused);
		if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
			errno_exit("VIDIOC_QBUF");
		break;
	}
 
	return 1;
}
 
void mainloop(void)
{
	unsigned int count = frame_count;
	while (count-- > 0) {
		for (;;) {
			fd_set fds;
			struct timeval tv;
			int r;
 
			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)
					continue;
				errno_exit("select");
			}
 
			if (0 == r) {
				fprintf(stderr, "select timeout\n");
				exit(EXIT_FAILURE);
			}
 
			if (read_frame())
				break;
			// EAGAIN - continue select loop
		}
	}
}
 
void stop_capturing(void)
{
	enum v4l2_buf_type type;
 
	switch (io) {
	case IO_METHOD_READ:
		// Nothing to do
		break;
 
	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");
		break;
	}
}
 
void start_capturing(void)
{
	unsigned int i;
	enum v4l2_buf_type type;
 
	switch (io) {
	case IO_METHOD_READ:
		// Nothing to do
		break;
 
	case IO_METHOD_MMAP:
		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");
		break;
 
	case IO_METHOD_USERPTR:
		for (i = 0; i < n_buffers; ++i) {
			struct v4l2_buffer buf;
			CLEAR(buf);
			buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
			buf.memory = V4L2_MEMORY_USERPTR;
			buf.index = i;
			buf.m.userptr = (unsigned long)buffers[i].start;
			buf.length = buffers[i].length;
 
			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");
		break;
	}
 
	f = fopen("usb.yuv", "w");
	if (!f) {
		errno_exit("fail to open file");
	}
}
 
void uninit_device(void)
{
	unsigned int i;
 
	switch (io) {
	case IO_METHOD_READ:
		free(buffers[0].start);
		break;
 
	case IO_METHOD_MMAP:
		for (i = 0; i < n_buffers; ++i)
		if (-1 == munmap(buffers[i].start, buffers[i].length))
			errno_exit("munmap");
		break;
 
	case IO_METHOD_USERPTR:
		for (i = 0; i < n_buffers; ++i)
			free(buffers[i].start);
		break;
	}
 
	free(buffers);
	fclose(f);
}
 
void init_read(unsigned int buffer_size)
{
	buffers = (struct buffer*)calloc(1, sizeof(*buffers));
	if (!buffers) {
		fprintf(stderr, "Out of memory\n");
		exit(EXIT_FAILURE);
	}
 
	buffers[0].length = buffer_size;
	buffers[0].start = malloc(buffer_size);
 
	if (!buffers[0].start) {
		fprintf(stderr, "Out of memory\n");
		exit(EXIT_FAILURE);
	}
}
 
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 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
		if (EINVAL == errno) {
			fprintf(stderr, "%s does not support memory mappingn\n", dev_name);
			exit(EXIT_FAILURE);
		} else {
			errno_exit("VIDIOC_REQBUFS");
		}
	}
 
	if (req.count < 2) {
		fprintf(stderr, "Insufficient buffer memory on %s\n", dev_name);
		exit(EXIT_FAILURE);
	}
 
	buffers = (struct buffer*)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, // 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");
	}
}
 
void init_userp(unsigned int buffer_size)
{
	struct v4l2_requestbuffers req;
	CLEAR(req);
 
	req.count = 4;
	req.type = 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/on", dev_name);
			exit(EXIT_FAILURE);
		} else {
			errno_exit("VIDIOC_REQBUFS");
		}
	}
 
	buffers = (struct buffer*)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_size;
		buffers[n_buffers].start = malloc(buffer_size);
 
		if (!buffers[n_buffers].start) {
			fprintf(stderr, "Out of memory\n");
			exit(EXIT_FAILURE);
		}
	}
}
 
void init_device(void)
{
	struct v4l2_capability cap;
	struct v4l2_cropcap cropcap;
	struct v4l2_crop crop;
	struct v4l2_format fmt;
	unsigned int min;
 
	if (-1 == 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");
		}
	}
 
	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);
		}
		break;
 
	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);
		}
		break;
	}
 
	// 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.defrect; // reset to default
		if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) {
			switch (errno) {
			case EINVAL:
				// Cropping not supported
				break;
			default:
				// Errors ignored
				break;
			}
		}
	} else {
		// Errors ignored
	}
 
	CLEAR(fmt);
	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	if (force_format) {
		fmt.fmt.pix.width = width;
		fmt.fmt.pix.height = height;
		fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
		fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
 
		// Note VIDIOC_S_FMT may change width and height
		if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
			errno_exit("VIDIOC_S_FMT");
	} else {
		// Preserve original settings as set by v4l2-ctl for example
		if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt))
			errno_exit("VIDIOC_G_FMT");
	}
 
	// Buggy driver paranoia
	min = fmt.fmt.pix.width * 2;
	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:
		init_userp(fmt.fmt.pix.sizeimage);
		break;
	}
}
 
void close_device(void)
{
	if (-1 == close(fd))
		errno_exit("close");
 
	fd = -1;
}
 
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 devicen\n", dev_name);
		exit(EXIT_FAILURE);
	}
 
	fd = open(dev_name, O_RDWR | O_NONBLOCK, 0); // O_RDWR: required
	if (-1 == fd) {
		fprintf(stderr, "Cannot open '%s': %d, %s\n", dev_name, errno, strerror(errno));
		exit(EXIT_FAILURE);
	}
}
 
} // namespace
 
int test_v4l2_usb_stream()
{
	// reference: https://linuxtv.org/downloads/v4l-dvb-apis-new/uapi/v4l/capture.c.html
	dev_name = "/dev/video0";
 
	open_device();
	init_device();
	start_capturing();
	mainloop();
	stop_capturing();
	uninit_device();
	close_device();
 
	fprintf(stdout, "test finish\n");
	return 0;
}
 
#else
 
int test_v4l2_usb_stream()
{
	fprintf(stderr, "Error: this test code only support linux platform\n");
	return -1;
}
 
#endif

reference

fengbingchun V4L2获取usb视频流测试代码