diff --git a/v4l2/Makefile b/v4l2/Makefile
index ffe72e8..57c8ea5 100644
--- a/v4l2/Makefile
+++ b/v4l2/Makefile
@@ -5,12 +5,15 @@ DEPS = ../floatimg.h  ../libfloatimg.a Makefile
 
 all:	grabvidseq t
 
-t:	t.c Makefile ${DEPS} funcs.o
-	gcc ${COPT} $< funcs.o ../libfloatimg.a -o $@
+t:	t.c Makefile ${DEPS} funcs.o v4l2_pr_structs.o
+	gcc ${COPT} $< funcs.o v4l2_pr_structs.o ../libfloatimg.a -o $@
 
 funcs.o:	funcs.c funcs.h Makefile
 	gcc ${COPT} -c $<
 
+v4l2_pr_structs.o:	v4l2_pr_structs.c v4l2_pr_structs.h Makefile
+	gcc ${COPT} -c $<
+
 #		---------------
 #		external things
 
diff --git a/v4l2/t.c b/v4l2/t.c
index 8e50e53..3561218 100644
--- a/v4l2/t.c
+++ b/v4l2/t.c
@@ -8,27 +8,49 @@
 #include  <math.h>
 #include  <string.h>
 
+#include <linux/videodev2.h>
+
 #include  "funcs.h"
 #include  "../floatimg.h"
 
+#include  "v4l2_pr_structs.h"
+
+
 int		verbosity;
 
 /* --------------------------------------------------------------------- */
 int essai(char *dev, int k)
 {
-int	vfd, foo;
+int			vfd, foo;
+struct v4l2_format	fmt;
 
 fprintf(stderr, ">>> %s ( '%s' %d )\n", __func__, dev, k);
 
 vfd = open_device(dev);
 fprintf(stderr, "\topen %s -> %d\n", dev, vfd);
 
-foo = init_device(0);
-fprintf(stderr, "\tinit -> %d\n", foo);
+memset(&fmt, 0, sizeof(fmt));
+pr_v4l2_format("after 0", &fmt);
+
+fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+fmt.fmt.pix.width       = 640;
+fmt.fmt.pix.height      = 480;
+fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
+fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
+
+pr_v4l2_format("before ioctl", &fmt);
+
 
 return k;
 }
 /* --------------------------------------------------------------------- */
+int liste_des_devices(int K)
+{
+fprintf(stderr, "%s not implemented\n", __func__);
+return -1;
+}
+/* --------------------------------------------------------------------- */
+
 void help(int k)
 {
 puts("Options :");
diff --git a/v4l2/v4l2_pr_structs.c b/v4l2/v4l2_pr_structs.c
new file mode 100644
index 0000000..4778628
--- /dev/null
+++ b/v4l2/v4l2_pr_structs.c
@@ -0,0 +1,64 @@
+/*
+ *	fonctions pour afficher les structures de V4L2
+ */
+
+#include  <stdio.h>
+
+#include  <linux/videodev2.h>
+
+#include  "v4l2_pr_structs.h"
+
+#define		FP	(stdout)
+
+extern int	verbosity;
+
+/* --------------------------------------------------------------------- */
+static char *fmttype2str(int type)
+{
+
+switch(type) {
+	case 0:		return "[zero]";
+	case 1:		return "video capture";
+	case 2:		return "video output";
+
+	case 13:	return "META capture";
+	}
+
+return "???";
+}
+/* --------------------------------------------------------------------- */
+int pr_v4l2_format(char *txt, struct v4l2_format *ptr)
+{
+fprintf(FP, "-- v4l2_format, %-15s  %p\n", txt, ptr);
+fprintf(FP, "   type %d   %s\n", ptr->type,/* enum v4l2_buf_type */
+			fmttype2str(ptr->type));		
+
+switch(ptr->type) {
+
+	case 1:		// fputs("   Capture\n", FP);
+			fprintf(FP, "   dims     %dx%d\n",
+					ptr->fmt.pix.width,
+					ptr->fmt.pix.height);
+
+			break;
+
+	default:	fputs("   ???\n", FP);		break;
+	
+	}
+
+fputs(".\n", FP);
+return 0;
+}
+/* --------------------------------------------------------------------- */
+int pr_v4l2_requestbuffers(char *txt, struct v4l2_requestbuffers *ptr)
+{
+fprintf(FP, "-- v4l2_requestbuffers, at %p\n", ptr);
+fprintf(FP, "   type %d\n", ptr->type);		/* enum v4l2_buf_type */
+
+
+return 0;
+}
+/* --------------------------------------------------------------------- */
+/* --------------------------------------------------------------------- */
+/* --------------------------------------------------------------------- */
+
diff --git a/v4l2/v4l2_pr_structs.h b/v4l2/v4l2_pr_structs.h
new file mode 100644
index 0000000..fd36a0d
--- /dev/null
+++ b/v4l2/v4l2_pr_structs.h
@@ -0,0 +1,9 @@
+/*
+ *	fonctions pour afficher les structures de V4L2
+ */
+
+/* --------------------------------------------------------------------- */
+int pr_v4l2_format(char *txt, struct v4l2_format *ptr);
+int pr_v4l2_requestbuffers(char *txt, struct v4l2_requestbuffers *ptr);
+/* --------------------------------------------------------------------- */
+