diff --git a/libavcodec/dsputil.c b/libavcodec/dsputil.c
index 9ee585c4d7..eb8592352e 100644
--- a/libavcodec/dsputil.c
+++ b/libavcodec/dsputil.c
@@ -44,6 +44,8 @@ op_pixels_abs_func pix_abs8x8_x2;
 op_pixels_abs_func pix_abs8x8_y2;
 op_pixels_abs_func pix_abs8x8_xy2;
 
+int ff_bit_exact=0;
+
 UINT8 cropTbl[256 + 2 * MAX_NEG_CROP];
 UINT32 squareTbl[512];
 
@@ -1697,6 +1699,7 @@ void dsputil_init(void)
 /* remove any non bit exact operation (testing purpose) */
 void avcodec_set_bit_exact(void)
 {
+    ff_bit_exact=1;
 #ifdef HAVE_MMX
     dsputil_set_bit_exact_mmx();
 #endif
diff --git a/libavcodec/h263.c b/libavcodec/h263.c
index 5ccb343181..c9a0a9d308 100644
--- a/libavcodec/h263.c
+++ b/libavcodec/h263.c
@@ -1420,14 +1420,17 @@ static void mpeg4_encode_vol_header(MpegEncContext * s)
         put_bits(&s->pb, 1, 0);		/* reduced res vop */
     }
     put_bits(&s->pb, 1, 0);		/* scalability */
-
+    
     ff_mpeg4_stuffing(&s->pb);
-    put_bits(&s->pb, 16, 0);
-    put_bits(&s->pb, 16, 0x1B2);	/* user_data */
-    sprintf(buf, "FFmpeg%sb%s", FFMPEG_VERSION, LIBAVCODEC_BUILD_STR);
-    put_string(&s->pb, buf);
 
-    ff_mpeg4_stuffing(&s->pb);
+    /* user data */
+    if(!ff_bit_exact){
+        put_bits(&s->pb, 16, 0);
+        put_bits(&s->pb, 16, 0x1B2);	/* user_data */
+        sprintf(buf, "FFmpeg%sb%s", FFMPEG_VERSION, LIBAVCODEC_BUILD_STR);
+        put_string(&s->pb, buf);
+        ff_mpeg4_stuffing(&s->pb);
+    }
 }
 
 /* write mpeg4 VOP header */
diff --git a/libavcodec/mjpeg.c b/libavcodec/mjpeg.c
index cfd5307fbb..6cfd83160e 100644
--- a/libavcodec/mjpeg.c
+++ b/libavcodec/mjpeg.c
@@ -390,16 +390,18 @@ static void jpeg_put_comments(MpegEncContext *s)
     }
 
     /* comment */
-    put_marker(p, COM);
-    flush_put_bits(p);
-    ptr = pbBufPtr(p);
-    put_bits(p, 16, 0); /* patched later */
+    if(!ff_bit_exact){
+        put_marker(p, COM);
+        flush_put_bits(p);
+        ptr = pbBufPtr(p);
+        put_bits(p, 16, 0); /* patched later */
 #define MJPEG_VERSION "FFmpeg" LIBAVCODEC_VERSION "b" LIBAVCODEC_BUILD_STR
-    put_string(p, MJPEG_VERSION);
-    size = strlen(MJPEG_VERSION)+3;
+        put_string(p, MJPEG_VERSION);
+        size = strlen(MJPEG_VERSION)+3;
 #undef MJPEG_VERSION
-    ptr[0] = size >> 8;
-    ptr[1] = size;
+        ptr[0] = size >> 8;
+        ptr[1] = size;
+    }
 }
 
 void mjpeg_picture_header(MpegEncContext *s)
diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
index ee184b1406..2caccce8a8 100644
--- a/libavcodec/mpegvideo.h
+++ b/libavcodec/mpegvideo.h
@@ -496,6 +496,8 @@ void ff_conceal_past_errors(MpegEncContext *s, int conceal_all);
 void ff_copy_bits(PutBitContext *pb, UINT8 *src, int length);
 void ff_clean_intra_table_entries(MpegEncContext *s);
 
+extern int ff_bit_exact;
+
 /* motion_est.c */
 void ff_estimate_p_frame_motion(MpegEncContext * s,
                              int mb_x, int mb_y);
diff --git a/tests/ffmpeg.regression.ref b/tests/ffmpeg.regression.ref
index e02c487cac..7dd3014fa2 100644
--- a/tests/ffmpeg.regression.ref
+++ b/tests/ffmpeg.regression.ref
@@ -9,9 +9,9 @@ ffmpeg regression test
 3ed8e11a8a8147c3e7d736593fccae79 *./data/out.yuv
 abe11239875a32f00fa2910828bba4fb *./data/a-h263.avi
 c1f6c8ee7a24d8345deddf1a24ca3756 *./data/out.yuv
-0c1d8af40b0b11b89fd7f9436faf62e2 *./data/a-odivx.avi
+440192aca11c310e01168ec24ea7807e *./data/a-odivx.avi
 145c98a175e760f8ba1997edf15b2964 *./data/out.yuv
-44d77cfad95830f10582275f69afe788 *./data/a-mjpeg.avi
+2846c8e3d97d7395eb746bfce44e0443 *./data/a-mjpeg.avi
 278033451d7a6bfeb8339abbe4228499 *./data/out.yuv
 202adaf59c09d703b55fc7dd95eace25 *./data/a-rv10.rm
 c1f6c8ee7a24d8345deddf1a24ca3756 *./data/out.yuv