diff --git a/v4l2/t.c b/v4l2/t.c
index 35612187..5bd0f904 100644
--- a/v4l2/t.c
+++ b/v4l2/t.c
@@ -7,8 +7,9 @@
 #include  <unistd.h>
 #include  <math.h>
 #include  <string.h>
+#include  <sys/ioctl.h>
 
-#include <linux/videodev2.h>
+#include  <linux/videodev2.h>
 
 #include  "funcs.h"
 #include  "../floatimg.h"
@@ -40,6 +41,13 @@ fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
 
 pr_v4l2_format("before ioctl", &fmt);
 
+foo = ioctl(vfd, VIDIOC_S_FMT, &fmt);
+fprintf(stderr, "ioctl -> %d\n", foo);
+if (foo < 0))	perror("ioctl S_FMT");
+
+pr_v4l2_format("after ioctl", &fmt);
+
+/*        todo V4L2_BUF_TYPE_VIDEO_CAPTURE */
 
 return k;
 }