Feature request: Implement PSD upmixing for quad / 4.0 setups
Currently, PSD upmixing is only supported for 2.0->5.1 and 2.0->7.1 upmixing. Please consider to also implement it for 2.0->4.0 upmixing, since the simple method does not sound good.
@wtaymans: I also noticed that channelmix_f32_2_4_c
is missing the if (SPA_FLAG_IS_SET(mix->flags, CHANNELMIX_FLAG_ZERO))
check that all the other upmixing functions have. Without understanding what it actually does: Is this intended?