diff --git a/src/tscut/tools/ffprobe.py b/src/tscut/tools/ffprobe.py
index c5912a3..b608b9b 100644
--- a/src/tscut/tools/ffprobe.py
+++ b/src/tscut/tools/ffprobe.py
@@ -346,7 +346,7 @@ def get_nearest_idr_frame(ffprobe_path: str, input_file: IO[bytes], timestamp:ti
 @typechecked
 def get_nearest_iframe(ffprobe_path:str, input_file: IO[bytes],
                        timestamp:timedelta, before:bool=True,
-                       delta_max:timedelta=timedelta(seconds=15))-> tuple[int,dict]:
+                       delta_max:timedelta=timedelta(seconds=15))-> tuple[int,dict | None]:
     infd = input_file.fileno()
     set_inheritable(infd, True)
 
@@ -399,8 +399,11 @@ def get_nearest_iframe(ffprobe_path:str, input_file: IO[bytes],
 
         delta+=timedelta(seconds=1)
 
-    if iframe is not None:
+    if iframe is not None and frames is not None:
         its = get_ts_frame(iframe)
+        if its is None:
+            logger.error("Impossible to retrieve timestamp of i-frame !")
+            return 0, None
         nb_frames = 0
         for frame in frames:
             ts = get_ts_frame(frame)
diff --git a/src/tscut/tools/timeframe.py b/src/tscut/tools/timeframe.py
index 08bf7c9..5899de4 100644
--- a/src/tscut/tools/timeframe.py
+++ b/src/tscut/tools/timeframe.py
@@ -70,7 +70,7 @@ def parse_timestamp(ts:str) -> timedelta|None:
     return res
 
 @typechecked
-def parse_time_interval(interval: str) -> tuple[timedelta, timedelta] | None:
+def parse_time_interval(interval: str) -> tuple[timedelta, timedelta] | tuple[None, None]:
     """
     Parse a time interval string into a tuple of two timedelta objects.
 
@@ -99,7 +99,7 @@ def parse_time_interval(interval: str) -> tuple[timedelta, timedelta] | None:
     m = p.match(interval)
     if m is None:
         logger.error("Impossible to parse time interval")
-        return None
+        return None, None
 
     values = m.groupdict()
     hour1 = 0
@@ -208,7 +208,7 @@ def get_ts_frame(frame: dict) -> timedelta|None:
     return ts
 
 @typechecked
-def get_packet_duration(packet: dict) -> int:
+def get_packet_duration(packet: dict) -> int | None:
     logger = logging.getLogger(__name__)
 
     if 'duration' in packet: