Today's question may not be directly about music production, but it is related, and concerns information any studio owner should be minimally on top of. "When I go see movies I see lots of terms like DTS, THX, Dolby Digital, AC-3, etc. I understand these relate to the soundtrack, but even after looking them up in your Word for the Day archives I'm still not sure I'm clear on how they relate to each other. Can you shed some light on this?" Dolby Digital and AC-3 are, for all practical purposes, the same thing, as they apply to your home theater setup. They specify a method of encoding multiple channels of audio on to some playback media. DTS is a competing and incompatible standard. THX has nothing to do with the encoding process. Instead it specifies playback hardware standards.A theater's (which could also be your home theater) digital sound system is made up of two areas. The first (Area 1) consists mainly of projection equipment and actually reads the soundtrack of the film, decodes it, and processes it. The signal that results is fed to the second area (Area 2), the theater's amplification and loudspeaker system.DTS or Dolby Digital technology is utilized in Area 1, where cinema sound processors convert the analog and digital sound information into audio. THX is involved in Area 2, specifically for loudspeaker placement, the types of speakers, the acoustics of the theater auditorium, as well as the amps and signal processors. To obtain THX certification, a theater must comply with their standards and also make use of equipment from THX-approved manufacturers. Home theater equipment with the THX logo also complies with THX standards for home theater systems. All DTS equipment is approved for THX usage.Studio owners who wish to build THX approved mixing rooms must base them on a select list of THX certified equipment. THX merely represents a standard of quality, not any specific type of data format. The data format is a function of the encoding/decoding process, which is where DTS or Dolby Digital come in to play.