[FFmpeg-user] Can work out why this does what it does

[JULIAN GARDNER]

I am trying to do a little overlay test but cant work out why one works and one fails, the input file i use is one of my SD stream captures from BBC News, so a generic SD video will suffice

The 2 command lines

Working


ffmpeg -i <any input video file> -vcodec libx264 -preset ultrafast -b 3000k -acodec libfaac -async 1 -r 25 -filter_complex 'color=s=640x360:c=#80808080 [o1];[0:v] scale=640x360,drawbox=100:100:100:100:color=green [o0];[o0][o1] overlay' -y -f mpegts a.ts


This give the desired result or an opaque screen overlayed over video


Non working one

ffmpeg -i <any input video file> -vcodec libx264 -preset ultrafast -b 3000k -acodec 
libfaac -async 1 -r 25 -filter_complex 'color=s=640x360:c=#80808080,drawbox=100:100:100:100:color=red 
[o1];[0:v] scale=640x360,drawbox=100:100:100:100:color=green 
[o0];[o0][o1] overlay' -y -f mpegts a.ts


On this i get the color screen with no transparency and the red box

Any ideas why adding a drawbox will make the color layer lose its transparency

joolz