I just came across this intriguing snippet:

<action application="capture_video" data="#transcode{vcodec=h264,acodec=mpga}:std{access=file,mux=mp4,dst=/tmp/1.mp4}"/>

I can't find any documentation for capture_video; does it allow setting the sample rate? Can it be used more than once in a dialplan to create an mp4 at the conference rate and a wav at a higher rate?