diff --git a/src/keras_video/generator.py b/src/keras_video/generator.py
index 912dd98..0f6bcd1 100644
--- a/src/keras_video/generator.py
+++ b/src/keras_video/generator.py
@@ -391,16 +391,17 @@ def _get_classname(self, video: str) -> str:
         return classname
 
     def _get_frames(
-        self, video, nbframe, shape, force_no_headers=False
+        self, video, nbframe, shape, seq_time=0, force_no_headers=False
     ) -> Optional[Iterable]:
         cap = cv.VideoCapture(video)
         total_frames = self.count_frames(cap, video, force_no_headers)
+        fps = cap.get(cv.CAP_PROP_FPS)
         orig_total = total_frames
 
         if total_frames % 2 != 0:
             total_frames += 1
 
-        frame_step = floor(total_frames / (nbframe - 1))
+        frame_step = floor(total_frames / (nbframe - 1)) if seq_time ==0 else floor((seq_time * fps) / (nbframe - 1))
         # TODO: fix that, a tiny video can have a frame_step that is
         # under 1
         frame_step = max(1, frame_step)
diff --git a/src/keras_video/sliding.py b/src/keras_video/sliding.py
index e577dbe..58f6a7f 100644
--- a/src/keras_video/sliding.py
+++ b/src/keras_video/sliding.py
@@ -77,6 +77,9 @@ def __init_length(self):
             else:
                 seqtime = int(frame_count)
 
+            # add an asssert to check if nbframe is possible in sequence_time
+            assert self.nbframe < seqtime, "ERROR nbframe > sequence_time change parameter and restart !"
+            
             stop_at = int(seqtime - self.nbframe)
             step = np.ceil(seqtime / self.nbframe).astype(np.int) - 1
             i = 0
@@ -172,7 +175,7 @@ def __getitem__(self, idx):
 
             video_id = vid["id"]
             if video_id not in self.__frame_cache:
-                frames: Iterable = self._get_frames(video, nbframe, shape)
+                frames: Iterable = self._get_frames(video, nbframe, shape, self.sequence_time if self.sequence_time != None else 0)
             else:
                 frames: Iterable = self.__frame_cache[video_id]