[gst-devel] dynamic overlaying of images on video

gael neuez gneuez at hotmail.com
Wed Aug 29 14:24:25 CEST 2007

I'm currently trying to design a Win app that takes a video and overlays 
1..N images on top of it. Basically, I want to display the thumbnails of 
soccer players in a football game video, given the position of each player 
in each frame.
The videomixer plugin does allow to overlay images on a video stream (e.g. 
gst-launch videotestsrc ! videomixer name=mix ! ffmpegcolorspace ! 
directdrawsink filesrc file=my_image1.jpg ! jpegdec ! mix.  filesrc 
file=my_image2.jpg ! jpegdec ! mix.  ...)
My problem is that the position of each overlay sink pad is fixed to (0,0), 
so all layers overlap each-others. I have modified the component such that 
each pad has a fixed (hardcoded) position in the output frame. But this is 
static, not dynamic...
I was thinking of deriving the videomixer element, adding an additional text 
sink pad. This pad would be fed with a txt file giving the (x,y) pos for 
each image to be overlaid.
In fact, I'd also like to extend this to the pango textoverlay (for 
displaying the name of the player below its thumbnail in the video, I again 
need to specify the position where the text must be set).

Would that make sense to you, or is there any better/nicer solution? Has 
anyone experienced that kind of problem?

Thanks & Regards,

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