Megapixels/main.c

#include <errno.h>
#include <fcntl.h>
#include <linux/videodev2.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <asm/errno.h>
#include <gtk/gtk.h>

#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;
};


struct buffer *buffers;
static unsigned int n_buffers;
static char *dev_name;
static enum io_method io = IO_METHOD_MMAP;
static int force_format_width = 640;
static int force_format_height = 480;
GObject *preview_image;


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

static void errno_exit(const char *s) {
	fprintf(stderr, "%s error %d, %s\\n", s, errno, strerror(errno));
	exit(EXIT_FAILURE);
}

static void start_capturing(int fd) {
	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;
	}
}

static void init_mmap(int fd) {
	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", 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 = 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");
	}
}

static void init_device(int fd) {
	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_width > 0) {
		fmt.fmt.pix.width = force_format_width;
		fmt.fmt.pix.height = force_format_height;
		fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
		fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
		printf("Requesting a cooler format!\n");

		if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
			errno_exit("VIDIOC_S_FMT");

		/* Note VIDIOC_S_FMT may change width and height. */
	} 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(fd);
			break;

		case IO_METHOD_USERPTR:
			//init_userp(fmt.fmt.pix.sizeimage);
			break;
	}
}

static void process_image(const void *p, int size) {
	GdkPixbuf *pixbuf;
	pixbuf = gdk_pixbuf_new_from_data(p, GDK_COLORSPACE_RGB, FALSE, 8, 640, 480, 2 * 640, NULL, NULL);
	gtk_image_set_from_pixbuf(preview_image, pixbuf);
}

static int read_frame(int fd) {
	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;
}

static void get_frame(int fd) {
	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(fd))
			break;
		/* EAGAIN - continue select loop. */
	}
}

int main(int argc,
		 char *argv[]) {
	GtkBuilder *builder;
	GObject *window;
	GObject *preview_box;
	GError *error = NULL;

	gtk_init(&argc, &argv);

	/* Construct a GtkBuilder instance and load our UI description */
	builder = gtk_builder_new();
	if (gtk_builder_add_from_file(builder, "camera.glade", &error) == 0) {
		g_printerr("Error loading file: %s\n", error->message);
		g_clear_error(&error);
		return 1;
	}

	/* Connect signal handlers to the constructed widgets. */
	window = gtk_builder_get_object(builder, "window");
	preview_box = gtk_builder_get_object(builder, "preview_box");
	preview_image = gtk_builder_get_object(builder, "preview");
	g_signal_connect (window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

	/* Load the css */
	GtkCssProvider *provider = gtk_css_provider_new();
	gtk_css_provider_load_from_path(provider, "camera.css", NULL);
	GtkStyleContext *context;
	context = gtk_widget_get_style_context(preview_box);
	gtk_style_context_add_provider(context, GTK_STYLE_PROVIDER(provider), GTK_STYLE_PROVIDER_PRIORITY_USER);

	/* Grab a frame from the camera */
	int fd;
	fd = open("/dev/video0", O_RDWR);
	if (fd == -1) {
		g_printerr("Error opening video device: /dev/video0\n");
		return 1;
	}
	init_device(fd);
	start_capturing(fd);
	get_frame(fd);

	/* Show application */
	gtk_widget_show(window);
	gtk_main();

	return 0;
}