For posterity, given the examples that are out there I found the problem: setup bg output #transcode{vcodec=MJPG,vb=2500,scale=Auto,width=1280,height=720,acodec=none,scodec=nonechannels=2,sfilter=mosaic{alpha=255,width=1280,height=720,cols=2,rows=2,position=1,order="ch1,ch2,ch3,ch4",keep-a...