FFmpeg: How to convert vertical video with black sides, to video 16:9, with blurred background sides

Question

How to make this by using FFmpeg?

Example without FFmpeg:
Adobe After Effects
Sony Vegas Pro

Answer 1

I solved!

ffmpeg -i input.mp4 -lavfi '[0:v]scale=ih*16/9:-1,boxblur=luma_radius=min(h\,w)/20:luma_power=1:chroma_radius=min(cw\,ch)/20:chroma_power=1[bg];[bg][0:v]overlay=(W-w)/2:(H-h)/2,crop=h=iw*9/16' -vb 800K output.webm 

Input: https://www.youtube.com/watch?v=17uHCHfgs60
Output: http://www.youtube.com/watch?v=CgZsDLfzrTs