import sys
 
 #wav_file = sys.argv[-1]
-wav_file =  '/home/thomas/code/timeside/voix.wav'
+wav_file =  '/home/thomas/code/timeside/TimeSide/tests/samples/sweep.wav'
 
 # normal
 d = timeside.decoder.FileDecoder(wav_file)
 
 
             plugin = ':'.join(plugin_line)
             (time, duration, value) = self.vamp_plugin(plugin, wavfile)
+            if value is None:
+                return
 
             if duration is not None:
                 plugin_res = self.new_result(data_mode='value', time_mode='segment')
         stderr = stdout[0:8]  # stderr containing file and process information
         res = stdout[8:]  # stdout containg the feature data
 
+        if len(res) == 0:
+            return
+
         # Parse stderr to get blocksize and stepsize
         blocksize_info = stderr[4]