TV  video Camcorder DigiCam Media Audio Theater Help companies  

   Home | Dolby | DVD Sound | DVD Intro | Surround sound

 Columbia ISA
[email protected]

SURROUND SOUND and DVD Players

Dolby Digital Decoding: 
One of the most exciting aspects of home theater and DVD is surround sound.  Many discs contain 5.1-channel Dolby Digital (DD) soundtracks which are six  discrete audio channels.

The Basics
Video features such as fast-scan, freeze-frame, and stop-frame motion (a kind of incremental slow-mo) can be found on most players. All have a built-in menu system that lets you set up and control the player, and let you navigate the menus on DVDs that provide access to the contents, including special features like storyboards and directors' comments.  

DVD players put out analog stereo signals as well as a digital audio bitstream from CDs and DVDs. The digital signal can carry Dolby Digital surround sound or standard PCM stereo, depending on how the disc is encoded or which audio track is selected. Most newer players can also pass a DTS-encoded digital signal from those discs with DTS soundtracks. 

Make sure your player is DTS-compatible (capable of passing the un-decoded signal from the disc to a decoder for processing) so that you'll have the option of passing the signal to an external processor or receiver with a DTS decoder. Look for the logo on the front of the DVD player which shows "DTS digital out" or "DTS compatible". A/V Receivers contain digital signal processing (DSP) chips that can handle both Dolby Digital and DTS decoding - the processor simply senses the signal format and switches in the appropriate decoding software. 
 

Where to have the decoder:
To hear surround sound, you'll need a decoder, which can reside either inside the DVD player or in your A/V receiver (or surround processor). In general, it's better if the decoder is in the receiver. There it is accessible to other components that output signals that need decoding, such as a satellite receiver, and it reduces the wiring between the player and the receiver: the un-decoded DD signal requires only one cable to carry it, whereas a decoded 5.1-channel analog signal requires six. Also, receivers are usually better equipped than a DVD player with onboard decoding to handle the bass-only low-frequency-effects (or ".1") channel.  A DD decoder in the player really makes sense only if your receiver lacks one.
 

And in the worst case, you can get along without Dolby Digital at all. The analog stereo signal in most DVDs is Dolby Surround-encoded, and any A/V receiver will be able to decode that into surround sound.

96/24 Compatibility.  When people think of DVD-Video, they think of its awesome picture quality. But DVD also offers awesome sound quality. In particular, it accommodates stereo sound sampled at 96 kHz and with a resolution of 24 bits - far above the CD standard in terms of frequency response and dynamic range. A few record labels are offering music-only DVD-Video discs with 96/24 specs. Some players won't play these discs. Some do play them, but at lower fidelity, downsampling the signal from 96 kHz to a lower sampling rate such as 48 kHz, or reducing the resolution to 20 bits or less, or both. Finally, some players play the full signal. 

Outputs.  Some people buy a component based on its flashing-light count. Smarter folks look at the back panel, because the number of inputs and outputs largely determines the utility of the component. Most DVD players don't have any inputs, but look carefully at the outputs. As mentioned previously, all models have both composite-video and S-video outputs. More and more DVD players also have a component-video output. Even if your current TV doesn't accept this, your next TV will.

When it comes to digital audio outputs, make sure the player at least has the same kind of output as your receiver's digital input. Some have only a coaxial or only an optical output, others have both, and still others have two of each. Of course, players with built-in Dolby Digital decoders also have a set of six analog outputs.

Special Features.  All DVD players let you play discs straight through, select among their contents, and amuse your friends with fast and slow playback. A few players add other useful features. For example, top-end players provide comprehensive video controls to tweak the picture and to reduce video noise. Some players automatically select the 5.1-channel soundtracks (if available), while other players require manual selection. If you have a big laserdisc collection, combi-players play both laserdiscs and DVDs as well as CDs.


Dolby and DTS:
Dolby is one of the best-known names on the planet. For starters, it appears on most cassettes. And Dolby has long been a benchmark for high-quality sound in movie theaters. Dolby Digital (DD), with its five discrete audio channels plus a dedicated low-frequency-effects (LFE) or ".1" channel for deep bass, hit the big screen in 1992 with the action/adventure flick Batman Returns. 

More than 9,000 movie theaters in North America are now equipped for Dolby Digital playback, which delivers more realistic and engaging sound than the Dolby Stereo system that was introduced to theaters in 1976 (it wasn't until the following year that Star Wars really turned moviegoers on to surround sound). On the domestic scene, most DVDs have Dolby Digital 5.1-channel soundtracks, and literally millions of decoders - mostly built into A/V receivers - are in consumers' hands.

A year after Dolby Digital made its debut, Digital Theater Systems (DTS) launched its rival format with the release of Jurassic Park.


Also a 5.1-channel system, DTS is conceptually the same as Dolby Digital yet incompatible with it. It has made impressive inroads against Dolby's lock on cinema sound. Thanks to backing by Hollywood moguls like Steven Spielberg, DTS playback equipment is installed in close to 9,000 movie theaters in North America. On the home side, DTS decoders are appearing in more and more components, including a number of A/V receivers, and the first batch of DTS-encoded DVDs became available sometime ago.  When the consumer-electronics industry's DVD Working Group sought the best audio coding technology for the new format back in 1995, Dolby Labs was fast out of the blocks. 


Dolby argued that its name recognition, its familiarity with the movie industry, and the choice of its system for audio coding in the new digital TV (DTV) standard made it a natural for DVD as well. The DVD group agreed, and Dolby Digital was selected as one of the two "mandatory" soundtrack formats for DVDs released in the U.S., meaning that at least one of them has to be on each disc. A two-channel PCM soundtrack like those found on CDs is the other mandatory format.

Late to the party, DTS argued that its coding method sounds better than Dolby Digital because it uses a higher bit rate and therefore the DVD standard should be changed. The DVD Working Group was not moved, and DTS was relegated to the dreaded "optional" status, meaning that any DVD carrying a DTS soundtrack must also have either a PCM or a DD soundtrack. Note, however, that a DD soundtrack is not necessarily 5.1-channel - it can range from mono to 5.1 channels, and can also be a two-channel stereo track carrying Dolby Surround information.

 

1