upmix

From up- +‎ mix, formed from downmix.

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium. Particularly: “can the coinage be located?”)

upmix (third-person singular simple present upmixes, present participle upmixing, simple past and past participle upmixed)

1. (audio engineering) To demix a downmixed track and increase the number of channels: convert mono into stereo, or stereo into surround sound, etc.

• demix

• mix up, mix-up, mixup