We've ascertained that ffmpeg's conversion from VP6A to RGBA sets all the alpha values to 0. The #ffmpeg IRC channel didn't have much of a clue about using swscale to convert from VP6A (YUVA) format, and it may be that it doesn't work at properly, or that the EncodedVideoFrame from the parser never contains alpha data (though in this case I'd think alpha would be set to 255 rather than 0).

I'll have a look at the original YUVA data itself (though probably not until Monday) and write a converter if it's valid.

I wonder if gst can convert it successfully (for when the gst handler gets some attention).

easyvideo2.swf will play one video half superimposed on another.

The parameters url1 and url2 specify the video to load.