Dolby Digital, Dolby Surround, Dolby Pro Logic, DTS stuff in plain English?

Jan 01st, 2010 by dvdxplayer 4,636 views |1 Comments

Almost every DVD contains audio in the Dolby Digital (AC-3) format. DTS is an optional audio format that can be added to a disc in addition to Dolby Digital audio. Dolby Digital and DTS can store mono, stereo, and multichannel audio (usually 5.1 channels).

Every DVD player in the world has an internal Dolby Digital decoder. The built-in 2-channel decoder turns Dolby Digital into stereo audio, which can be fed to almost any type of audio equipment (receiver, TV, boombox, etc.) as a standard analog stereo signal using a pair of stereo audio cables or as a digital PCM audio signal using a coax or optical cable.

A standard audio mixing technique, called Dolby Surround, “piggybacks” a rear channel and a center channel onto a 2-channel signal. A Dolby Surround signal can be played on any stereo system (or even a mono system), in which case the rear- and center-channel sounds remain mixed in with the left and right channels. When a Dolby Surround signal is played on a multichannel audio system that knows how to handle it, the extra channels are extracted to feed center speakers and rear speakers. The original technique of decoding Dolby Surround, called simply Dolby Surround, extracts only the rear channel. The improved decoding technique, Dolby Pro Logic, also extracts the center channel. A brand new decoding technology, Dolby Pro Logic II, extracts both the center channel and the rear channel and also processes the signals to create more of a 3D audio environment. Dolby Surround is independent of the storage or transmission format. In other words, a 2-channel Dolby Surround signal can be analog audio, broadcast TV audio, digital PCM audio, Dolby Digital, DTS, MP3, audio on a VHS tape, etc.

Unlike Dolby Surround, Dolby Digital encodes each channel independently. Dolby Digital can carry up to 5 channels (left, center, right, left surround, right surround) plus an omnidirectional low-frequency channel. The built-in, 2-channel Dolby Digital decoder in every DVD player handles multichannel audio by downmixing it to two channels using Dolby Surround. This allows the analog stereo outputs to be connected to just about anything, including TVs and receivers with Dolby Pro Logic capability. Most DVD players also output the downmixed 2-channel Dolby Surround signal in digital PCM format, which can be connected to a digital audio receiver, most of which do Dolby Pro Logic decoding.

Most DVD players also output the “raw” Dolby Digital signal for connection to a receiver with a built-in Dolby Digital decoder. Some DVD players have built-in multichannel decoders to provide 6 (or 7) analog audio outputs to feed a receiver or amplifier with multichannel analog inputs.

DTS is handled differently. Many DVD players have a DTS Digital Out feature (also called DTS pass-through), which sends the raw DTS signal to an external receiver with a DTS decoder. A few players have a built-in 2-channel DTS decoder that downmixes to Dolby Surround, just like a 2-channel Dolby Digital decoder. Some players have a built-in multichannel DTS decoder with 6 (or 7) analog outputs. Some DVD players don’t recognize DTS tracks at all.

If you have a POS (plain old stereo), a Dolby Surround receiver, or a Dolby Pro Logic receiver, you don’t need anything special in the DVD player. Any model will connect to your system. If you have a Dolby Digital receiver, then you need a player with Dolby Digital out (all but the cheapest players have this). If your receiver can also do DTS, you should get a player with DTS Digital Out. The only reason to get a player with 6-channel Dolby Digital or DTS decoder output is if you want use multichannel analog connections to the receiver.

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