change causal mode for direction forward-backward

src/spikeinterface/preprocessing/filter.py

@@ -27,8 +27,8 @@ class FilterRecording(BasePreprocessor):
     Generic filter class based on:
 
       * scipy.signal.iirfilter
-      * scipy.signal.filtfilt or scipy.signal.sosfiltfilt
-      * scipy.signal.lfilt or scipy.signal.sosfilt when causal_mode = True
+      * scipy.signal.filtfilt or scipy.signal.sosfiltfilt when direction = "forward-backward"
+      * scipy.signal.lfilt or scipy.signal.sosfilt 
 
     BandpassFilterRecording is built on top of it.
 
@@ -57,10 +57,10 @@ class FilterRecording(BasePreprocessor):
         - numerator/denominator : ("ba")
     ftype : str, default: "butter"
         Filter type for `scipy.signal.iirfilter` e.g. "butter", "cheby1".
-    causal_mode : bool, default: False
-        If true, filtering is applied in just one direction.
-    direction : "forward" | "backward", default: "forward"
-        when causal_mode = True, defines the direction of the filtering
+    direction : "forward" | "backward" | "forward-backward", default: "forward-backward"
+        Direction of filtering:
+        - forward and backward filter in just one direction, creating phase shifts in the signal.
+        - forward-backward filters in both directions, a zero-phase filtering. 
 
     Returns
     -------
@@ -82,8 +82,7 @@ def __init__(
         add_reflect_padding=False,
         coeff=None,
         dtype=None,
-        causal_mode=False,
-        direction="forward",
+        direction="forward-backward",
     ):
         import scipy.signal
 
@@ -121,7 +120,6 @@ def __init__(
                     margin,
                     dtype,
                     add_reflect_padding=add_reflect_padding,
-                    causal_mode=causal_mode,
                     direction=direction,
                 )
             )
@@ -137,7 +135,6 @@ def __init__(
             margin_ms=margin_ms,
             add_reflect_padding=add_reflect_padding,
             dtype=dtype.str,
-            causal_mode=causal_mode,
             direction=direction,
         )
 
@@ -151,13 +148,11 @@ def __init__(
         margin,
         dtype,
         add_reflect_padding=False,
-        causal_mode=False,
-        direction="forward",
+        direction="forward-backward",
     ):
         BasePreprocessorSegment.__init__(self, parent_recording_segment)
         self.coeff = coeff
         self.filter_mode = filter_mode
-        self.causal_mode = causal_mode
         self.direction = direction
         self.margin = margin
         self.add_reflect_padding = add_reflect_padding
@@ -180,7 +175,13 @@ def get_traces(self, start_frame, end_frame, channel_indices):
 
         import scipy.signal
 
-        if self.causal_mode:
+        if self.direction == "forward-backward":
+            if self.filter_mode == "sos":
+                filtered_traces = scipy.signal.sosfiltfilt(self.coeff, traces_chunk, axis=0)
+            elif self.filter_mode == "ba":
+                b, a = self.coeff
+                filtered_traces = scipy.signal.filtfilt(b, a, traces_chunk, axis=0)
+        else:
             if self.direction == "backward":
                 traces_chunk = np.flip(traces_chunk, axis=0)
 
@@ -191,14 +192,7 @@ def get_traces(self, start_frame, end_frame, channel_indices):
                 filtered_traces = scipy.signal.lfilt(b, a, traces_chunk, axis=0)
 
             if self.direction == "backward":
-                filtered_traces = np.flip(filtered_traces, axis=0)
-
-        else:
-            if self.filter_mode == "sos":
-                filtered_traces = scipy.signal.sosfiltfilt(self.coeff, traces_chunk, axis=0)
-            elif self.filter_mode == "ba":
-                b, a = self.coeff
-                filtered_traces = scipy.signal.filtfilt(b, a, traces_chunk, axis=0)
+                filtered_traces = np.flip(filtered_traces, axis=0)            
 
         if right_margin > 0:
             filtered_traces = filtered_traces[left_margin:-right_margin, :]
@@ -378,7 +372,6 @@ def __init__(
             band=band,
             margin_ms=margin_ms,
             dtype=dtype,
-            causal_mode=True,
             direction=direction,
             **filter_kwargs,
         )
@@ -388,7 +381,6 @@ def __init__(
             band=band,
             margin_ms=margin_ms,
             dtype=dtype.str,
-            causal_mode=True,
             direction=direction,
         )
         self._kwargs.update(filter_kwargs)