In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

What do you need in addition to the LaserDisc in order to experience surround sound?, Context: Only one 5.1 surround sound option exists on a given LaserDisc (either Dolby Digital or DTS), so if surround sound is desired, the disc must be matched to the capabilities of the playback equipment (LD Player and Receiver/Decoder) by the purchaser. A fully capable LaserDisc playback system includes a newer LaserDisc player that is capable of playing digital tracks, has a digital optical output for digital PCM and DTS audio, is aware of AC-3 audio tracks, and has an AC-3 coaxial output; an external or internal AC-3 RF demodulator and AC-3 decoder; and a DTS decoder. Many 1990s A/V receivers combine the AC-3 decoder and DTS decoder logic, but an integrated AC-3 demodulator is rare both in LaserDisc players and in later A/V receivers.
playback equipment