竖屏视频加黑边

ffmpeg -y -i wh01.mp4 -vf "scale=trunc((326*a)/2)*2:326" result/temp.mp4
ffmpeg -y -i result/temp.mp4 -vf pad=580:326:0:(580-iw)/2:black result/wh01.mp4

参考文献：

https://www.cnblogs.com/yongfengnice/p/7095846.html