How to set background to subtitle in ffmpeg?

Question

It is described here how ot burn a srt file into a video. However, I want to put a semi-transparent background to the subtitles so that the texts can be read more easily. H

Answer 1

ffmpeg -i input.mp4 -filter_complex "subtitles=input.srt:force_style='BackColour=&H80000000,BorderStyle=4,Fontsize=11'" output.mp4

BackColour=&H80000000 means having a %50 opaque black background.

Its a hex representation of color, AABBGGRR.