Upmixing

Upmixing converts audio from a lower channel count, such as mono or stereo, into a format with more channels, like 5.1 surround or immersive Atmos. Naive upmixing simply copies channels (channel replication), which passes technical checks but sounds spatially flat. True upmixing relies on separating the source into individual elements so they can be placed coherently across the new channel layout.