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-rw-r--r--Documentation/DocBook/v4l/capture.c.xml659
1 files changed, 659 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/capture.c.xml b/Documentation/DocBook/v4l/capture.c.xml
new file mode 100644
index 00000000000..1c5c49a2de5
--- /dev/null
+++ b/Documentation/DocBook/v4l/capture.c.xml
@@ -0,0 +1,659 @@
+<programlisting>
+/*
+ * V4L2 video capture example
+ *
+ * This program can be used and distributed without restrictions.
+ *
+ * This program is provided with the V4L2 API
+ * see http://linuxtv.org/docs.php for more information
+ */
+
+#include &lt;stdio.h&gt;
+#include &lt;stdlib.h&gt;
+#include &lt;string.h&gt;
+#include &lt;assert.h&gt;
+
+#include &lt;getopt.h&gt; /* getopt_long() */
+
+#include &lt;fcntl.h&gt; /* low-level i/o */
+#include &lt;unistd.h&gt;
+#include &lt;errno.h&gt;
+#include &lt;sys/stat.h&gt;
+#include &lt;sys/types.h&gt;
+#include &lt;sys/time.h&gt;
+#include &lt;sys/mman.h&gt;
+#include &lt;sys/ioctl.h&gt;
+
+#include &lt;linux/videodev2.h&gt;
+
+#define CLEAR(x) memset(&amp;(x), 0, sizeof(x))
+
+enum io_method {
+ IO_METHOD_READ,
+ IO_METHOD_MMAP,
+ IO_METHOD_USERPTR,
+};
+
+struct buffer {
+ void *start;
+ size_t length;
+};
+
+static char *dev_name;
+static enum io_method io = IO_METHOD_MMAP;
+static int fd = -1;
+struct buffer *buffers;
+static unsigned int n_buffers;
+static int out_buf;
+static int force_format;
+static int frame_count = 70;
+
+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 fh, int request, void *arg)
+{
+ int r;
+
+ do {
+ r = ioctl(fh, request, arg);
+ } while (-1 == r &amp;&amp; EINTR == errno);
+
+ return r;
+}
+
+static void process_image(const void *p, int size)
+{
+ if (out_buf)
+ fwrite(p, size, 1, stdout);
+
+ fflush(stderr);
+ fprintf(stderr, ".");
+ fflush(stdout);
+}
+
+static int read_frame(void)
+{
+ struct <link linkend="v4l2-buffer">v4l2_buffer</link> 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, &amp;buf)) {
+ switch (errno) {
+ case EAGAIN:
+ return 0;
+
+ case EIO:
+ /* Could ignore EIO, see spec. */
+
+ /* fall through */
+
+ default:
+ errno_exit("VIDIOC_DQBUF");
+ }
+ }
+
+ assert(buf.index &lt; n_buffers);
+
+ process_image(buffers[buf.index].start, buf.bytesused);
+
+ if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;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, &amp;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 &lt; n_buffers; ++i)
+ if (buf.m.userptr == (unsigned long)buffers[i].start
+ &amp;&amp; buf.length == buffers[i].length)
+ break;
+
+ assert(i &lt; n_buffers);
+
+ process_image((void *)buf.m.userptr, buf.bytesused);
+
+ if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;buf))
+ errno_exit("VIDIOC_QBUF");
+ break;
+ }
+
+ return 1;
+}
+
+static void mainloop(void)
+{
+ unsigned int count;
+
+ count = frame_count;
+
+ while (count-- &gt; 0) {
+ for (;;) {
+ fd_set fds;
+ struct timeval tv;
+ int r;
+
+ FD_ZERO(&amp;fds);
+ FD_SET(fd, &amp;fds);
+
+ /* Timeout. */
+ tv.tv_sec = 2;
+ tv.tv_usec = 0;
+
+ r = select(fd + 1, &amp;fds, NULL, NULL, &amp;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. */
+ }
+ }
+}
+
+static void stop_capturing(void)
+{
+ enum <link linkend="v4l2-buf-type">v4l2_buf_type</link> 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, &amp;type))
+ errno_exit("VIDIOC_STREAMOFF");
+ break;
+ }
+}
+
+static void start_capturing(void)
+{
+ unsigned int i;
+ enum <link linkend="v4l2-buf-type">v4l2_buf_type</link> type;
+
+ switch (io) {
+ case IO_METHOD_READ:
+ /* Nothing to do. */
+ break;
+
+ case IO_METHOD_MMAP:
+ for (i = 0; i &lt; n_buffers; ++i) {
+ struct <link linkend="v4l2-buffer">v4l2_buffer</link> buf;
+
+ CLEAR(buf);
+ buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ buf.memory = V4L2_MEMORY_MMAP;
+ buf.index = i;
+
+ if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;buf))
+ errno_exit("VIDIOC_QBUF");
+ }
+ type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ if (-1 == xioctl(fd, VIDIOC_STREAMON, &amp;type))
+ errno_exit("VIDIOC_STREAMON");
+ break;
+
+ case IO_METHOD_USERPTR:
+ for (i = 0; i &lt; n_buffers; ++i) {
+ struct <link linkend="v4l2-buffer">v4l2_buffer</link> 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, &amp;buf))
+ errno_exit("VIDIOC_QBUF");
+ }
+ type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ if (-1 == xioctl(fd, VIDIOC_STREAMON, &amp;type))
+ errno_exit("VIDIOC_STREAMON");
+ break;
+ }
+}
+
+static 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 &lt; n_buffers; ++i)
+ if (-1 == munmap(buffers[i].start, buffers[i].length))
+ errno_exit("munmap");
+ break;
+
+ case IO_METHOD_USERPTR:
+ for (i = 0; i &lt; n_buffers; ++i)
+ free(buffers[i].start);
+ break;
+ }
+
+ free(buffers);
+}
+
+static void init_read(unsigned int buffer_size)
+{
+ buffers = 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);
+ }
+}
+
+static void init_mmap(void)
+{
+ struct <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> req;
+
+ CLEAR(req);
+
+ req.count = 4;
+ req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ req.memory = V4L2_MEMORY_MMAP;
+
+ if (-1 == xioctl(fd, VIDIOC_REQBUFS, &amp;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 &lt; 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 &lt; req.count; ++n_buffers) {
+ struct <link linkend="v4l2-buffer">v4l2_buffer</link> 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, &amp;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_userp(unsigned int buffer_size)
+{
+ struct <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> req;
+
+ CLEAR(req);
+
+ req.count = 4;
+ req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ req.memory = V4L2_MEMORY_USERPTR;
+
+ if (-1 == xioctl(fd, VIDIOC_REQBUFS, &amp;req)) {
+ if (EINVAL == errno) {
+ fprintf(stderr, "%s does not support "
+ "user pointer i/o\n", dev_name);
+ exit(EXIT_FAILURE);
+ } else {
+ errno_exit("VIDIOC_REQBUFS");
+ }
+ }
+
+ buffers = calloc(4, sizeof(*buffers));
+
+ if (!buffers) {
+ fprintf(stderr, "Out of memory\n");
+ exit(EXIT_FAILURE);
+ }
+
+ for (n_buffers = 0; n_buffers &lt; 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);
+ }
+ }
+}
+
+static void init_device(void)
+{
+ struct <link linkend="v4l2-capability">v4l2_capability</link> cap;
+ struct <link linkend="v4l2-cropcap">v4l2_cropcap</link> cropcap;
+ struct <link linkend="v4l2-crop">v4l2_crop</link> crop;
+ struct <link linkend="v4l2-format">v4l2_format</link> fmt;
+ unsigned int min;
+
+ if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &amp;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 &amp; 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 &amp; 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 &amp; 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, &amp;cropcap)) {
+ crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ crop.c = cropcap.defrect; /* reset to default */
+
+ if (-1 == xioctl(fd, VIDIOC_S_CROP, &amp;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 = 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, &amp;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, &amp;fmt))
+ errno_exit("VIDIOC_G_FMT");
+ }
+
+ /* Buggy driver paranoia. */
+ min = fmt.fmt.pix.width * 2;
+ if (fmt.fmt.pix.bytesperline &lt; min)
+ fmt.fmt.pix.bytesperline = min;
+ min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
+ if (fmt.fmt.pix.sizeimage &lt; 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;
+ }
+}
+
+static void close_device(void)
+{
+ if (-1 == close(fd))
+ errno_exit("close");
+
+ fd = -1;
+}
+
+static void open_device(void)
+{
+ struct stat st;
+
+ if (-1 == stat(dev_name, &amp;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);
+ }
+
+ fd = open(dev_name, O_RDWR /* required */ | 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"
+ "Version 1.3\n"
+ "Options:\n"
+ "-d | --device name Video device name [%s]\n"
+ "-h | --help Print this message\n"
+ "-m | --mmap Use memory mapped buffers [default]\n"
+ "-r | --read Use read() calls\n"
+ "-u | --userp Use application allocated buffers\n"
+ "-o | --output Outputs stream to stdout\n"
+ "-f | --format Force format to 640x480 YUYV\n"
+ "-c | --count Number of frames to grab [%i]\n"
+ "",
+ argv[0], dev_name, frame_count);
+}
+
+static const char short_options[] = "d:hmruofc:";
+
+static const struct option
+long_options[] = {
+ { "device", required_argument, NULL, 'd' },
+ { "help", no_argument, NULL, 'h' },
+ { "mmap", no_argument, NULL, 'm' },
+ { "read", no_argument, NULL, 'r' },
+ { "userp", no_argument, NULL, 'u' },
+ { "output", no_argument, NULL, 'o' },
+ { "format", no_argument, NULL, 'f' },
+ { "count", required_argument, NULL, 'c' },
+ { 0, 0, 0, 0 }
+};
+
+int main(int argc, char **argv)
+{
+ dev_name = "/dev/video0";
+
+ for (;;) {
+ int idx;
+ int c;
+
+ c = getopt_long(argc, argv,
+ short_options, long_options, &amp;idx);
+
+ if (-1 == c)
+ break;
+
+ switch (c) {
+ case 0: /* getopt_long() flag */
+ break;
+
+ case 'd':
+ dev_name = optarg;
+ break;
+
+ case 'h':
+ usage(stdout, argc, argv);
+ exit(EXIT_SUCCESS);
+
+ case 'm':
+ io = IO_METHOD_MMAP;
+ break;
+
+ case 'r':
+ io = IO_METHOD_READ;
+ break;
+
+ case 'u':
+ io = IO_METHOD_USERPTR;
+ break;
+
+ case 'o':
+ out_buf++;
+ break;
+
+ case 'f':
+ force_format++;
+ break;
+
+ case 'c':
+ errno = 0;
+ frame_count = strtol(optarg, NULL, 0);
+ if (errno)
+ errno_exit(optarg);
+ break;
+
+ default:
+ usage(stderr, argc, argv);
+ exit(EXIT_FAILURE);
+ }
+ }
+
+ open_device();
+ init_device();
+ start_capturing();
+ mainloop();
+ stop_capturing();
+ uninit_device();
+ close_device();
+ fprintf(stderr, "\n");
+ return 0;
+}
+</programlisting>
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-11-14 17:52:46 +0000