atv4 incorrectly maps channels:
what it should do:
front-left > L
front-right > R
front-center > L+R
satellite-left > L
satellite-right > R
what it does:
front-left > L
front-right > R
front-center > L+R
satellite-left > L + RIGHT CHANNEL
satellite-right > R + LEFT CHANNEL(with phase inversion)
i put the problematic channels in capital letters
this was confirmed by creating a test ac3 track with different frequencies in each.
basically, each r/l satellite channel is sent to both stereo channels, and one of the satellite channels has 180 phase!!
simulated downmix in audacity, 1st play has the problem. Left side is being cancelled out by inverted right satellite channel