[FFmpeg-user] Piping realtime data to drawtext filter?

[Sebastian Arcus]

I would like to overlay on footage recorded from a usb webcam data 
acquired in realtime from a GPS receiver. I'm mainly interested in 
current vehicle speed. Drawtext takes static text on the command line - 
the only bit of realtime data it can display is the date.

Is there any way to feed it constantly updating data, such as data 
coming from my gps receiver through gpsd?

Sebastian