filter output

[jjgordon7109]

Not an issue, but a request. Your library is very nice, elegant, thanks for providing! Background: I compiled FFmpeg 4.2.2 using msys2 / gcc7.3.0. I compiled ffmpeg-cpp into a DLL using Qt and gcc7.3.0. Examples I have compiled are working well. I am interested in audio filters. I have started with the filtering_audio example. How do I get the output of each filter? For example, loudnorm uses a 2-pass approach (see http://k.ylo.ph/2016/04/04/loudnorm.html), where you parse the output of the first pass, and use those parameters in the second. Would appreciate if you can provide guidance.

[jjgordon7109]

Ok, I redirected stderr to a callback using solution at https://stackoverflow.com/questions/31181618/how-to-enable-the-ffmpeg-logging/31183796. This allows filter output to be collected. Next problem: loudnorm filter requires first pass to be run with no output file ("-f null -"). How to do this using ffmpeg-cpp?