Preserving 7.1 audio in Blu-ray MKV

[hamburglar]

I've been using MakeMKV to create basically an MKV passthrough of a BD, and then using Handbrake to reduce the file size. The MKV files from MakeMKV have 7.1 audio, but whenever I use Handbrake, even if I do Passthrough for the audio, it always ends up only being 5.1 audio. How do I keep the 7.1 audio in there?

[aedipuss]

put both versions into mkvtoolnix and uncheck the large video and the 5.1 audio and the program will mux what you want into an mkv.