There is an automatic channel rematrixing when either downmixing or upmixing is mandated by a difference in channel layouts between source and output. If you don't, channel mixing may (or may not) occur. ⚠ IMPORTANT WARNING: make sure to select the same channel layout as your input (if you have a 4.1 audio source do not select 7.1). For surround sound, will be of interest: libopus, aac (native), pcm formats (uncompressed).all (free) codecs supported by FFmpeg are available (check the box 'Show all codecs').
As a rule of thumb 64 kbs x number of channels should be CD quality. By default OBS-Studio selects 160 kbs for stereo. Click OK to the Warning pop-up and restart OBS. Settings > Audio: just select a channel different from Mono or Stereo in the Channels list. The audio channels can be surround sound channels or more general multichannel ones. OBS Studio can stream and record up to 8 audio channels.
Traditionally this is a feature reserved to professional broadcast appliances. OBS Studio is the first mainstream streaming software to support surround sound streaming and recording.
