Upmixed

Upmixed refers to the process of converting a stereo recording into a multi-channel surround sound format or to a file created by such conversion. The term is used in music production, film post-production, and consumer playback to describe an upmixed track that has been expanded beyond the original two channels, typically to 5.1 or 7.1 channels. The objective is to provide a more immersive or widely compatible playback experience, while attempting to retain the integrity and balance of the original mix.

Techniques for upmixing include matrix decoding of stereo into surround (for example, channel distribution and center channel extraction), dedicated upmix algorithms, artificial reverb and ambient processing, and sometimes head-related transfer function (HRTF) processing for spatial cues. Many workflows combine automated tools with manual oversight by engineers and may include remastering steps.

Applications and formats include cinema soundtracks, Blu-ray releases, streaming services offering immersive audio, and video games. Some releases label the track as upmixed from stereo or provide a surround mix option, giving listeners a choice between original stereo and enhanced multi-channel playback.

Limitations and considerations involve potential phase anomalies, altered tonal balance, or localization errors. In some cases, the upmixed version may be perceived as inferior to a purpose-built multi-track surround mix, particularly if the original recording was not designed with multi-channel playback in mind. The suitability of upmixed material depends on the original recording, the target playback system, and listener preferences.