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

[JULIAN GARDNER]

> From: JULIAN GARDNER <joolzg at btinternet.com>

>To: ffmpeg-user at ffmpeg.org 
>Sent: Monday, 22 September 2014, 17:19
>Subject: [FFmpeg-user] Can work out why this does what it does
> 
>
>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


OK worked it out, drawbox does not work on any formats with ALPHA being present and coverts these down to non-alpha formats.

Looks like im going to have to add in code for working with alpha planes

joolz