diff --git a/src/mpeg2.c b/src/mpeg2.c
index 3f22337..7f04e04 100644
--- a/src/mpeg2.c
+++ b/src/mpeg2.c
@@ -57,6 +57,9 @@
 #include "surface.h"
 
 #include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include <sys/ioctl.h>
@@ -221,6 +224,27 @@ int mpeg2_set_controls(struct request_data *driver_data,
 	 * surface's permanent request_fd (iter6 per-OUTPUT-slot binding;
 	 * picture.c:284 sets surface_object->request_fd at BeginPicture).
 	 */
+	/* iter35 DIAG: dump v4l2_ctrl_mpeg2_* contents. LIBVA_MPEG2_DUMP_FRAME=1 */
+	if (getenv("LIBVA_MPEG2_DUMP_FRAME")) {
+		uint8_t *sb = (uint8_t *)&sequence;
+		uint8_t *pb = (uint8_t *)&pic;
+		uint8_t *qb = (uint8_t *)&quant;
+		unsigned int k;
+		fprintf(stderr, "mpeg2: SEQ size=%zu  ", sizeof(sequence));
+		for (k = 0; k < sizeof(sequence); k++)
+			fprintf(stderr, "%02x ", sb[k]);
+		fprintf(stderr, "\nmpeg2: PIC size=%zu [0..32]=", sizeof(pic));
+		for (k = 0; k < 32 && k < sizeof(pic); k++)
+			fprintf(stderr, "%02x ", pb[k]);
+		fprintf(stderr, "\nmpeg2: PIC [32..end]=");
+		for (k = 32; k < sizeof(pic); k++)
+			fprintf(stderr, "%02x ", pb[k]);
+		fprintf(stderr, "\nmpeg2: QUANT size=%zu [0..16]=", sizeof(quant));
+		for (k = 0; k < 16; k++)
+			fprintf(stderr, "%02x ", qb[k]);
+		fprintf(stderr, "\n");
+	}
+
 	struct v4l2_ext_control ctrls[3] = {
 		{
 			.id = V4L2_CID_STATELESS_MPEG2_SEQUENCE,