[FFmpeg-user] change inputs or mapping while recording

[Stephan Monecke]

I just spent two hours unsuccessfully trying to get the given example to work.

zmqsend <<<"lumakey at toggle tolerance 0" never terminates.

I guess, nothing is more permanent than a temporary solution ...

Cheers,
Stephan

P.s. The zmq example given in the docs directly segfaults for me with
a freshly compiled ffmpeg.

Am Mo., 27. Apr. 2020 um 20:50 Uhr schrieb Stephan Monecke
<stephanmonecke at gmail.com>:
>
> That looks really interesting! Thanks a lot, I'll have a look at it!
>
> Besides daily checking, I managed to overlook ALL the replies ... sorry for my late answer and thanks a lot for yours!
>
> OBS is not an option since everything is done automatically / from command-line (and afaik OBS transcodes what would additionally overburden the small machine).
>
> It needs to be light and reliable.
>
> For now, I came up with the nginx rtmp plugin that, used as a local loopback device, now acts as a multiplexer.
>
> Two mutually exclusive systemd services forward the respective rtsp stream to the nginx server and ffmpeg records from it.
>
> That way, by starting one or the other service, I switch the stream.
>
> The starting of the two services is bound to the two corresponding arrow keys of a simple Logitech R400 presenter via xbindkeys (the remaining two keys toggle a recording and a YouTube live-stream).
> They are present in abundance at the institute and the setup is practically free of cpu usage even on this weak machine.
>
> That way, the lecturer can switch between blackboards / cameras and fully control the procedure just via the presenter.
> Best regards,
> Stephan Monecke
> --
> Sent from my mobile device. Please excuse my brevity.
>
> Am 24. April 2020 21:56:12 MESZ schrieb Edward Park <kumowoon1025 at gmail.com>:
>>
>> 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"
>>
>> Regards,
>> Ted Park
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