[FFmpeg-user] change inputs or mapping while recording

Edward Park kumowoon1025 at gmail.com
Fri Apr 24 22:56:12 EEST 2020


> How can this be done with FFmpeg? Do you have an example? I know how commands / sendcmd works. The opacity could be toggled, or the streamselect filter could be used. But where does the switching signal come from, while FFmpeg is running?

The specific messaging protocol/method would depend on a variety of factors including personal preference, but to parrot an example given in the manual using zmq, 

% ffmpeg -i INPUT -filter_complex 'null[main];movie=INPUT2,zmq,lumakey at toggle=tolerance=1,[main]overlay,realtime' OUTPUT

and sending commands to the named lumakey filter would mimic toggling between the two streams if they were the same size and position. 
i.e. using the zmqsend example program,

% zmqsend <<<"lumakey at toggle tolerance 0"

Ted Park

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