D:\software\ffmpeg-2025-02-20-git-bc1a3bfd2c-full_build\bin\ffmpeg.exe -i download.mp4 -i download.m4a -sub_charenc UTF-8 -i download.srt ^
  -c:v libx265 -crf 28 -preset medium ^
  -vf subtitles=download.srt ^
  -c:a copy ^
  -y output_hard_sub.mp4

  # 关键调整：CRF提高到30，Preset改为slow，压缩文件会更小，但画质会略微降低，且编码时间更长

D:\software\ffmpeg-2025-02-20-git-bc1a3bfd2c-full_build\bin\ffmpeg.exe -i download.mp4 -i download.m4a -sub_charenc UTF-8 -i download.srt ^
  -c:v libx265 -crf 30 -preset slow ^
  -vf subtitles=download.srt ^
  -c:a copy ^
  -y output_hard_sub_h265.mp4