work even with one video

app.py

@@ -136,7 +136,13 @@ def retrieve_results(selected_dataset, selected_sequence, selected_models, selec
     # opt_fill = ":fill=black"
     opt_fill = ":fill=white"
     # opt_fill = ""
-    ffmpeg_command_str = "ffmpeg -y " + inputs_str + " -filter_complex \"" + input_scaling_str + ";" + xstack_input_str + "xstack=inputs=" + str(num_inputs) + ":layout=" + layout_str + opt_fill + "\"" + opt + " output.mp4"
+    if num_inputs > 1:
+        ffmpeg_command_str = "ffmpeg -y " + inputs_str + " -filter_complex \"" + input_scaling_str + ";" + xstack_input_str + "xstack=inputs=" + str(num_inputs) + ":layout=" + layout_str + opt_fill + "\"" + opt + " output.mp4"
+    else:
+        # remove last paranthesis
+        idx = input_scaling_str.rfind("[")
+        input_scaling_str = input_scaling_str[:idx]
+        ffmpeg_command_str = "ffmpeg -y " + inputs_str + " -filter_complex \"" + input_scaling_str + "\"" + opt + " output.mp4"
     print(ffmpeg_command_str)
     ret = subprocess.call(ffmpeg_command_str, shell=True)
 
@@ -147,6 +153,7 @@ def retrieve_results(selected_dataset, selected_sequence, selected_models, selec
     video_bytes = video_file.read()
     return video_bytes
 
+
 st.title("Result Analysis Tool")
 
 base_data_dir = "data"