Merge pull request #67 from vmarandon/guess_stream_number

Add an automatic detection of the number of stream

Author: jlenain

src/ctapipe_io_nectarcam/__init__.py

@@ -1319,7 +1319,7 @@ class BlockNectarCAMEventSource:
 
     """
 
-    def __init__(self, block_size=4, allowed_blocks=None, **kwargs):
+    def __init__(self, block_size=None, allowed_blocks=None, **kwargs):
         self._arguments = kwargs  # blocks
         self._file_names = None
         self._block_file_names = list()
@@ -1366,6 +1366,8 @@ def __init__(self, block_size=4, allowed_blocks=None, **kwargs):
             self.show_empty_stats = bool(kwargs["show_empty_stats"])
             del self._arguments["show_empty_stats"]
 
+        if self.block_size is None:
+            self.block_size = self.guess_block_size_from_file(self._file_names[0])
         self._create_blocks()
         self._switch_block()
 
@@ -1392,6 +1394,26 @@ def call_wrapper(*args, **kwargs):
             else:
                 return attr_val
 
+    @staticmethod
+    def guess_block_size_from_file(filename):
+        # try to open the file
+        # read the first events
+        # look at the separation between ids
+        try:
+            with File(str(filename)) as f:
+                ids = list()
+                for e in f.Events:
+                    ids.append(e.event_id)
+                    if len(ids) > 100:
+                        break
+                ids = np.array(ids, dtype=int)
+                block_size = int(np.rint(np.median(np.array(ids[1:] - ids[:-1]))))
+                # print(f"{self.block_size = }")
+        except Exception:
+            print("Can't guess properly block size !")
+            block_size = 4
+        return block_size
+
     def _rewind(self):
         self._current_block = None
         self._switch_block()

src/ctapipe_io_nectarcam/tests/test_nectarcameventsource.py

@@ -253,3 +253,12 @@ def test_r1_waveforms():
             for event in inputfile_reader:
                 for telid in event.trigger.tels_with_trigger:
                     assert event.r1.tel[telid].waveform.shape == waveform_shape
+
+
+def test_blockdetection():
+    from ctapipe_io_nectarcam import BlockNectarCAMEventSource
+
+    assert (
+        BlockNectarCAMEventSource.guess_block_size_from_file(EXAMPLE_FILE_PATH_V6) == 4
+    )
+    assert BlockNectarCAMEventSource.guess_block_size_from_file(EXAMPLE_FILE_PATH) == 2