[HELP] How to add custom ffmpeg commands in audio encoding ?

[Selur]

You can't add a custom comman line for downmixing with ffmpeg in Hybrid, since Hybrid does not use ffmpeg for downmixing.
If you need to do this, Hybrid is the wrong tool for you.
Note that you can however use a enter a custom downmix instruction for sox, if when "Audio->Base->Audio Encoding Options->Filtering->Downmix" is set to custom. (see: http://sox.sourceforge.net/sox.html#EFFECTS under 'remix')

Cu Selur