diff --git a/src/mkvextract_tracks.cpp b/src/mkvextract_tracks.cpp
index 031958176..8ec8f776d 100644
--- a/src/mkvextract_tracks.cpp
+++ b/src/mkvextract_tracks.cpp
@@ -582,6 +582,7 @@ unpack_real_video_frames(kax_track_t *track,
                          uint32_t timecode,
                          bool is_key) {
   unsigned char *src_ptr, *ptr, *dst;
+  uint32_t merged;
   int num_subpackets, i, offset, total_len;
   vector<uint32_t> packet_offsets, packet_lengths;
   rmff_frame_t *frame;
@@ -619,26 +620,30 @@ unpack_real_video_frames(kax_track_t *track,
     if (num_subpackets == 1) {
       *ptr = 0xc1;              // complete frame
       ptr++;
+//       merged = 0x8000;
+      merged = 0x0000;
 
     } else {
-      *ptr = num_subpackets + 1;
+//       *ptr = num_subpackets;
+      *ptr = 1;
       if (i == (num_subpackets - 1)) // last fragment?
         *ptr |= 0x80;
       ptr++;
 
       *ptr = i + 1;             // fragment number
-      if (is_key)               // key frame?
-        *ptr |= 0x80;
+//       if (is_key)               // key frame?
+//         *ptr |= 0x80;
       ptr++;
+      merged = 0;
     }
 
     // total packet length:
     if (total_len > 0x3fff) {
-      put_uint16_be(ptr, ((total_len & 0x3fff0000) >> 16));
+      put_uint16_be(ptr, merged | ((total_len & 0x3fff0000) >> 16));
       ptr += 2;
       put_uint16_be(ptr, total_len & 0x0000ffff);
     } else
-      put_uint16_be(ptr, 0x4000 | total_len);
+      put_uint16_be(ptr, merged | 0x4000 | total_len);
     ptr += 2;
 
     // fragment offset from beginning/end:
@@ -659,7 +664,7 @@ unpack_real_video_frames(kax_track_t *track,
     ptr += 2;
 
     // sequence number = frame number & 0xff
-    *ptr = track->packetno & 0xff;
+    *ptr = (track->packetno - 1) & 0xff;
     ptr++;
 
     memcpy(ptr, src_ptr, packet_lengths[i]);