[LAD] FFmpeg and JACK output

[Filipe Coelho]

Hello everyone.

I was in the need for ffmpeg to output directly to JACK, which is not 
supported upstream.
(It has JACK input support, as in recording something from JACK and feed 
it to something else, but not the other way around)

After trying a couple of methods that didn't work so great, like fifos 
or bridging through alsa loopback, I just went ahead and implemented 
this part in FFmpeg.

You can find the relevant code at 
https://github.com/falkTX/FFmpeg/tree/n4.4-jackoutdev


Not yet submitted upstream, still doing some testing.
If this is something useful for you, feedback / comments on the code is 
very welcome.
The relevant part sits at this file 
https://github.com/falkTX/FFmpeg/blob/n4.4-jackoutdev/libavdevice/jack_enc.c


Have a great weekend!