How to draw on frames during playback?

[ealbers]

All I need to do is to draw a few graphics onto each frame as the video plays back and redirect those frames to a output file.
I've tried the code below, hoping to get the callbacks in memory then use them for output in the std{access=file..} but it never seems to get to the 2nd duplicate

"#duplicate{dst=display,"
"dst={"
"transcode{vcodec=I444,acodec=s16l,vb=0,scale=0,ab=128,channels=2,samplerate=44100,soverlay,sfilter=marq{marquee=\"CrazySquirrl\",color=16777215,position=9}}"
":smem{"
"video-prerender-callback=%lld,"
"video-postrender-callback=%lld,"
"audio-prerender-callback=%lld,"
"audio-postrender-callback=%lld"
"}:duplicate{dst=display,dst=std{access=file,sub-filter=marq,mux=mp4,dst='%s'}}}}"
, (long long int)(intptr_t)(void*)&cbVideoPrerender
, (long long int)(intptr_t)(void*)&cbVideoPostrender
, (long long int)(intptr_t)(void*)&cbAudioPrerender
, (long long int)(intptr_t)(void*)&cbAudioPostrender
,filenamebuffer);