[FFmpeg-user] toggle between two streams

Paul B Mahol onemda at gmail.com
Fri Sep 3 16:30:52 EEST 2021


On Fri, Sep 3, 2021 at 3:19 PM Michael Koch <astroelectronic at t-online.de>
wrote:

> 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.
>

sendcmd supports expressions.

>
> Michael
>
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