diff --git a/grc/satnogs_json_converter.xml b/grc/satnogs_json_converter.xml
index cbd03d9..b8a7f70 100644
--- a/grc/satnogs_json_converter.xml
+++ b/grc/satnogs_json_converter.xml
@@ -9,7 +9,7 @@
     <name>Extra JSON field</name>
     <key>extra</key>
     <value></value>
-    <type>string</type>
+    <type>raw</type>
   </param>
   
   <sink>
diff --git a/include/satnogs/ax25_decoder.h b/include/satnogs/ax25_decoder.h
index 0cb7649..6da42ea 100644
--- a/include/satnogs/ax25_decoder.h
+++ b/include/satnogs/ax25_decoder.h
@@ -136,7 +136,8 @@ private:
   uint8_t *d_frame_buffer;
   std::deque<uint8_t> d_bitstream;
   size_t d_start_idx;
-  size_t d_frame_start;
+  uint64_t d_frame_start;
+  uint64_t d_sample_cnt;
 
   void
   reset_state();
diff --git a/include/satnogs/decoder.h b/include/satnogs/decoder.h
index c0c01d6..0e1ee3d 100644
--- a/include/satnogs/decoder.h
+++ b/include/satnogs/decoder.h
@@ -110,10 +110,18 @@ public:
   int
   sizeof_input_item() const;
 
+protected:
+  void
+  incr_nitems_read(size_t nitems);
+
+  uint64_t
+  nitems_read() const;
+
 private:
   const int     d_sizeof_in;
   const size_t  d_max_frame_len;
   int           d_id;
+  uint64_t      d_nitems_read;
 };
 
 } // namespace satnogs
diff --git a/lib/ax25_decoder.cc b/lib/ax25_decoder.cc
index 765ba94..d1a7df1 100644
--- a/lib/ax25_decoder.cc
+++ b/lib/ax25_decoder.cc
@@ -57,7 +57,8 @@ ax25_decoder::ax25_decoder(const std::string &addr, uint8_t ssid, bool promisc,
     new uint8_t[max_frame_len + AX25_MAX_ADDR_LEN + AX25_MAX_CTRL_LEN
                               + sizeof(uint16_t)]),
   d_start_idx(0),
-  d_frame_start(0)
+  d_frame_start(0),
+  d_sample_cnt(0)
 {
 }
 
@@ -110,8 +111,11 @@ ax25_decoder::_decode(decoder_status_t &status)
         if (d_shift_reg == AX25_SYNC_FLAG) {
           d_bitstream.erase(d_bitstream.begin(),
                             d_bitstream.begin() + i + 1);
+          /* Increment the number of items read so far */
+          incr_nitems_read(i);
           enter_sync_state();
-          d_frame_start = i;
+          /* Mark possible start of the frame */
+          d_frame_start = nitems_read();
           d_start_idx = 0;
           cont = true;
           break;
@@ -120,6 +124,7 @@ ax25_decoder::_decode(decoder_status_t &status)
       if (cont) {
         continue;
       }
+      incr_nitems_read(d_bitstream.size());
       d_bitstream.clear();
       return false;
     case IN_SYNC:
@@ -151,10 +156,13 @@ ax25_decoder::_decode(decoder_status_t &status)
       for (size_t i = d_start_idx; i < d_bitstream.size(); i++) {
         decode_1b(d_bitstream[i]);
         if (d_shift_reg == AX25_SYNC_FLAG) {
+          d_sample_cnt = nitems_read() + i - d_frame_start;
           LOG_DEBUG("Found frame end");
           if (enter_frame_end(status)) {
             d_bitstream.erase(d_bitstream.begin(),
                               d_bitstream.begin() + i + 1);
+            /* Increment the number of items read so far */
+            incr_nitems_read(i);
             d_start_idx = d_bitstream.size();
             return true;
           }
@@ -271,6 +279,7 @@ ax25_decoder::enter_frame_end(decoder_status_t &status)
     metadata::add_time_iso8601(status.data);
     metadata::add_crc_valid(status.data, true);
     metadata::add_sample_start(status.data, d_frame_start);
+    metadata::add_sample_cnt(status.data, d_sample_cnt);
     status.decode_success = true;
     reset_state();
     return true;
diff --git a/lib/decoder.cc b/lib/decoder.cc
index fa690af..575710c 100644
--- a/lib/decoder.cc
+++ b/lib/decoder.cc
@@ -41,13 +41,16 @@ decoder::unique_id()
 }
 
 /**
- * Creates a generic decoder object
+ * @brief Construct a new decoder::decoder object
+ *
+ * @param input_item_size the sizeof() the input stream item
  * @param max_frame_len the maximum allowed frame size in bytes
  */
 decoder::decoder(int input_item_size, size_t max_frame_len)
   : d_sizeof_in(input_item_size),
     d_max_frame_len(max_frame_len),
-    d_id(base_unique_id++)
+    d_id(base_unique_id++),
+    d_nitems_read(0)
 {
 }
 
@@ -81,12 +84,41 @@ decoder::max_frame_len() const
   return d_max_frame_len;
 }
 
+/**
+ * @brief Return the size of the input stream
+ *
+ * @return int the sizeof() the input stream item
+*/
 int
 decoder::sizeof_input_item() const
 {
   return d_sizeof_in;
 }
 
+
+/**
+ * @brief Increaments the number of items read so far
+ *
+ * @param nitems the number of items read
+ */
+void
+decoder::incr_nitems_read(size_t nitems)
+{
+  d_nitems_read += nitems;
+}
+
+/**
+ * @brief Return the number of items read so far
+ *
+ * @return uint64_t number of items read so far
+ */
+uint64_t
+decoder::nitems_read() const
+{
+  return d_nitems_read;
+}
+
+
 } /* namespace satnogs */
 } /* namespace gr */
 
diff --git a/lib/json_converter_impl.cc b/lib/json_converter_impl.cc
index c77b299..5a01553 100644
--- a/lib/json_converter_impl.cc
+++ b/lib/json_converter_impl.cc
@@ -62,8 +62,16 @@ json_converter_impl::~json_converter_impl()
 void
 json_converter_impl::convert(pmt::pmt_t m)
 {
+  Json::CharReaderBuilder crb;
+  Json::CharReader *cr = crb.newCharReader();
+  Json::Value extra;
+  std::string err;
+
+
   Json::Value root = metadata::to_json(m);
-  root["extra"] = d_extra;
+  if (cr->parse(d_extra.c_str(), d_extra.c_str() + d_extra.size(), &extra, &err)) {
+    root["extra"] = extra;
+  }
   const std::string &s = root.toStyledString();
   const char *c = s.c_str();
   message_port_pub(pmt::mp("out"), pmt::make_blob(c, s.length()));
diff --git a/lib/metadata.cc b/lib/metadata.cc
index da8931c..5c435a9 100644
--- a/lib/metadata.cc
+++ b/lib/metadata.cc
@@ -162,6 +162,11 @@ metadata::to_json(const pmt::pmt_t &m)
     root[value(SAMPLE_START)] = Json::Value::UInt64(pmt::to_uint64(v));
   }
 
+  v = pmt::dict_ref(m, pmt::mp(value(SAMPLE_CNT)), pmt::PMT_NIL);
+  if (!pmt::equal(v, pmt::PMT_NIL)) {
+    root[value(SAMPLE_CNT)] = Json::Value::UInt64(pmt::to_uint64(v));
+  }
+
   v = pmt::dict_ref(m, pmt::mp(value(SYMBOL_ERASURES)), pmt::PMT_NIL);
   if (!pmt::equal(v, pmt::PMT_NIL)) {
     root[value(SYMBOL_ERASURES)] = Json::Value::UInt64(pmt::to_uint64(v));