LAV 5.1 audio doesn't work

LAV audio codec has a audio problem, there is only 2.0 audio even if i set mixer to 5.1 and expand mono audio
must use ffdshow for use all 5.1 audio system, there is a way to fix this? or maybe would be better set by default ffdshow for audio..

If the input is stereo, then it will just fill the other channels with silence. There is an option in LAV to skip mixing of stereo sources. Then Windows will do the mixing to 5.1.

ffdshow has the same behavior by default. Only when you enable "expand stereo" option, it will mix to the other channels. ffdshow will NOT be used by default. If you prefer it, you can choose it during installation.