checking if buffer filled and dequeuing, blocking forever with only 1 queued

git-svn-id: svn://anubis/misc/WebcamTracker@123 bd8a9e45-a331-0410-811e-c64571078777

WebcamTracker.cc

@@ -110,6 +110,42 @@ WebcamTracker::WebcamTracker(const char * device)
                 cerr << " (EINVAL)";
             cerr << endl;
         }
+
+        struct v4l2_buffer querybuf;
+        querybuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+        querybuf.index = 0;
+        ret = ioctl(m_fd, VIDIOC_QUERYBUF, &querybuf);
+        if (ret != 0)
+        {
+            cerr << "VIDIOC_QUERYBUF ioctl failed: returned " << ret
+                 << ", errno: " << errno;
+            if (errno == EINVAL)
+                cerr << " (EINVAL)";
+            cerr << endl;
+        }
+        if (querybuf.flags & V4L2_BUF_FLAG_DONE)
+        {
+            cout << "buf done" << endl;
+        }
+
+        v4l2_buffer dqbuf;
+        dqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+        dqbuf.memory = V4L2_MEMORY_MMAP;
+        ret = ioctl(m_fd, VIDIOC_DQBUF, &dqbuf);
+        if (ret != 0)
+        {
+            cerr << "VIDIOC_DQBUF failed! errno = " << errno;
+            if (errno == EAGAIN)
+                cerr << " (EAGAIN)";
+            if (errno == EINVAL)
+                cerr << " (EINVAL)";
+            if (errno == ENOMEM)
+                cerr << " (ENOMEM)";
+            if (errno == EIO)
+                cerr << " (EIO)";
+            cerr << endl;
+        }
+
     }
     else
     {