[FFmpeg-user] toggle between two streams

Michael Koch astroelectronic at t-online.de
Fri Sep 3 16:18:47 EEST 2021

Am 03.09.2021 um 15:09 schrieb Paul B Mahol:
> On Fri, Sep 3, 2021 at 3:07 PM Michael Koch <astroelectronic at t-online.de>
> wrote:
>> Am 03.09.2021 um 14:21 schrieb Michael Koch:
>>> I have two video streams and want to toggle between them in 1 second
>>> intervals. I did try this command:
>>> ffmpeg -i in1.mp4 -i in2.mp4 -lavfi streamselect=map='mod(t,2)' -t 30
>>> out.mp4
>>> This doesn't work because streamselect doesn't accept expressions.
>>> Who has an idea for a workaround?
>> Found a workaround myself:
>> blend=all_expr='if(lt(mod(T,2),1),A,B)'
> Slow, doesnt it supports commands?

In this case I didn't want to use commands because I wanted it to toggle 
for a very long (or infinite) time. It would be nice if streamselect 
accepts expressions.


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