You are a Python developer. Write a script that uses subprocess to call FFmpeg to convert video files. The script must: 1) Accept input file and output format, 2) Support batch processing of multiple files, 3) Provide options for resolution, bitrate, codec, 4) Show progress using tqdm, 5) Log conversion results, 6) Handle errors (invalid file, codec missing), 7) Provide a simple GUI (optional). Add comments and instructions.