[FFmpeg-user] change inputs or mapping while recording

Michael Koch astroelectronic at t-online.de
Fri Apr 24 23:31:15 EEST 2020

Am 24.04.2020 um 21:56 schrieb Edward Park:
> Hi,
>> 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"

That works only under Linux, right? It seems libzmq is not enabled in 
the FFmpeg build for Windows from Zeranoe.


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