ffmpeg 是做什麼的？
Use for any FFmpeg/ffprobe work in the video pipeline — probing a media file, cutting/trimming/concatenating, retiming, scaling for YouTube 16:9 or Shorts/Reels 9:16, thumbnails, NVENC or CPU encoding choices, loudness normalization (-14/-16 LUFS), silence/dead-air removal, ducking music, burning or muxing subtitles, drawtext lower thirds, alpha overlays, GIF/WebP, image sequences, stream mapping/metadata/timecode, ffmpeg quoting in PowerShell/cmd/Git Bash, progress and exit-code handling, and v