small fixes

app.py

@@ -42,7 +42,7 @@ def convert_to_wav(in_filename: str) -> str:
     _ = os.system(f"ffmpeg -hide_banner -i '{in_filename}' -ar 16000 '{out_filename}'")
     with open(out_filename, "rb") as f:
         s = "\n" + out_filename + "\n"
-        s += base64.b64encode(f.read())
+        s += base64.b64encode(f.read()).decode()
         logging.info(s)
     return out_filename