[Savonet-users] add image to video stream

[k054]

I added this to the video stream script

source = video.add_image(
width=30,height=30,
x=10,y=10,
file="logo.jpg",
source)

as stated here http://savonet.sourceforge.net/doc-svn/video.html#logo

but this the image is not being shown and this shows up in the log instead.

2017/04/09 22:42:29 [decoder:3] Unable to decode "logo.png" as
{audio=0;video=1;midi=0}!

I'm guessing there's a package missing but... which one?

any hint?

thanks!