diff --git a/beat/backend/python/inputs.py b/beat/backend/python/inputs.py
index eb812e36cf8b5c4f54286ef8ee33da0ba88e0682..bf7118a92c593cfba5097d49aa4a68dea5f824da 100644
--- a/beat/backend/python/inputs.py
+++ b/beat/backend/python/inputs.py
@@ -68,8 +68,11 @@ class Input:
     self.data_format = data_format
     self.socket = socket
     self.data = None
+    self.data_index = -1
+    self.data_index_end = -1
     self.group = None
     self.comm_time = 0. #total time spent on communication
+    self.nb_data_blocks_read = 0
 
 
   def isDataUnitDone(self):
@@ -108,15 +111,19 @@ class Input:
     self.socket.send('nxt', zmq.SNDMORE)
     self.socket.send(self.group.channel, zmq.SNDMORE)
     self.socket.send(self.name)
+    self.data_index = int(self.socket.recv())
+    self.data_index_end = int(self.socket.recv())
     self.unpack(self.socket.recv())
     self.comm_time += time.time() - _start
+    self.nb_data_blocks_read += 1
 
 
   def unpack(self, packed):
     """Receives data through socket"""
 
     self.data = self.data_format.type()
-    logger.debug('recv: <bin> (size=%d)', len(packed))
+    logger.debug('recv: <bin> (size=%d), indexes=(%d, %d)', len(packed),
+                 self.data_index, self.data_index_end)
     self.data.unpack(packed)
 
 
@@ -239,7 +246,10 @@ class InputGroup:
             "channel `%s' while performing `next' operation on this group " \
             "(current reading position is %d/%d)" % \
             (name, self.channel, k, n))
+      inpt.data_index = int(parts.pop(0))
+      inpt.data_index_end = int(parts.pop(0))
       inpt.unpack(parts.pop(0))
+      inpt.nb_data_blocks_read += 1
     self.comm_time += time.time() - _start