在之前一篇原本已經打算用 AWS Media Converter，畢竟價錢算是合理，但後來想到還有閒置的便宜 cloud instance (在 google cloud, 1vCPU, 1.7G ram, 50G HDD)，不如來試試看在上面跑 ffmpeg performance。

Introduction to MP4 GUI: One. Based on: Graphical interface program developed by FFmpeg (enterprise-level multimedia conversion processing project).