Update app.py

app.py

@@ -30,7 +30,7 @@ with st.sidebar:
     )
     progress_text = st.empty()
     progress_bar = st.progress(0)
-    # A container for our frame slider (viewer)
+    # Container for our dynamic slider (frame viewer)
     slider_container = st.empty()
 
 # Main page header and intro images
@@ -67,11 +67,11 @@ except Exception as ex:
     st.error(f"Unable to load model. Check the specified path: {model_path}")
     st.error(ex)
 
-# Initialize session state for frame viewer if not already set
-if 'viewer_frame' not in st.session_state:
-    st.session_state.viewer_frame = 0
+# We'll use a session_state variable to remember the current slider value.
+if "frame_slider" not in st.session_state:
+    st.session_state.frame_slider = 0
 
-# This container will display the currently viewed frame
+# A container to display the currently viewed frame.
 viewer_slot = st.empty()
 
 # When the user clicks the detect button...
@@ -99,7 +99,7 @@ if st.sidebar.button("Let's Detect Wildfire"):
         width  = int(vidcap.get(cv2.CAP_PROP_FRAME_WIDTH))
         height = int(vidcap.get(cv2.CAP_PROP_FRAME_HEIGHT))
 
-        # Determine sampling interval and output fps based on option selected.
+        # Determine sampling interval and output fps based on the option selected.
         if video_option == "Original FPS":
             sample_interval = 1
             output_fps = orig_fps
@@ -119,10 +119,6 @@ if st.sidebar.button("Let's Detect Wildfire"):
             sample_interval = 1
             output_fps = orig_fps
 
-        # Initial slider for frame viewing.
-        slider_val = st.session_state.viewer_frame
-        slider = slider_container.slider("Frame Viewer", min_value=0, max_value=0, value=slider_val, step=1, key="frame_slider")
-
         success, image = vidcap.read()
         while success:
             if frame_count % sample_interval == 0:
@@ -139,27 +135,37 @@ if st.sidebar.button("Let's Detect Wildfire"):
                 else:
                     progress_text.text(f"Processing frame {frame_count}")
 
-                # Update the slider's max value. Preserve current value.
-                current_index = st.session_state.get("frame_slider", len(processed_frames) - 1)
-                slider = slider_container.slider("Frame Viewer", 
-                                                   min_value=0, 
-                                                   max_value=len(processed_frames)-1, 
-                                                   value=current_index, 
-                                                   step=1, 
-                                                   key="frame_slider")
-
-                # If the user is at the latest frame, update the viewer.
-                if st.session_state.frame_slider == len(processed_frames)-1:
-                    viewer_slot.image(processed_frames[-1], caption=f"Frame {len(processed_frames)-1}", use_column_width=True)
-
+                # Only update slider if we have at least one processed frame.
+                if len(processed_frames) > 0:
+                    # Clear the previous slider widget.
+                    slider_container.empty()
+                    # Determine the current slider value.
+                    curr_slider_val = st.session_state.get("frame_slider", len(processed_frames)-1)
+                    # Ensure the slider value is within the new bounds.
+                    if curr_slider_val > len(processed_frames)-1:
+                        curr_slider_val = len(processed_frames)-1
+                    # Create a new slider. This slider's key is fixed because we cleared the container beforehand.
+                    slider_val = slider_container.slider(
+                        "Frame Viewer", 
+                        min_value=0, 
+                        max_value=len(processed_frames)-1, 
+                        value=curr_slider_val, 
+                        step=1, 
+                        key="frame_slider"
+                    )
+                    st.session_state.frame_slider = slider_val
+
+                    # If the user is at the most recent frame, update the viewer.
+                    if slider_val == len(processed_frames)-1:
+                        viewer_slot.image(processed_frames[-1], caption=f"Frame {len(processed_frames)-1}", use_column_width=True)
             frame_count += 1
             success, image = vidcap.read()
 
-        # Video processing complete.
+        # Finalize progress.
         progress_text.text("Video processing complete!")
         progress_bar.progress(100)
 
-        # After processing, allow downloading the shortened video.
+        # Create and provide the downloadable shortened video.
         if processed_frames:
             temp_video_file = tempfile.NamedTemporaryFile(delete=False, suffix='.mp4')
             fourcc = cv2.VideoWriter_fourcc(*'mp4v')
@@ -167,7 +173,7 @@ if st.sidebar.button("Let's Detect Wildfire"):
             for frame in processed_frames:
                 out.write(frame)
             out.release()
-            
+
             st.success("Shortened video created successfully!")
             with open(temp_video_file.name, 'rb') as video_file:
                 st.download_button(