CNET's quick guide to surround formatsDolby Formats
Upside:
Dolby Digital is the near-universal surround format.
Downside:
Sound quality, while acceptable for movies, is a far cry from
ultrahigh-resolution formats such as DVD-Audio and Super Audio CD (SACD).
Forecast: It is, and will likely
remain, the preeminent surround format. Dolby Digital is the most popular surround format and can be found
on virtually every DVD, including almost all DVD music discs, and many HDTV
programs. Pretty much every A/V receiver and HTIB on the market features Dolby
Digital processing.
Upside: Pro Logic
II can be found on most new receivers and HTIBs.
Downside:
None.
Forecast: This very popular format is in for
the long haul. First, Pro Logic II isn't one of those synthetic "jazz club" and
"stadium" modes and doesn't add synthesized reverberation or echoes. It's a
hardware-based format that's compatible with all stereo and matrix-encoded
surround software. Pro Logic II is an update of the original Pro Logic and can
be used to freshen up Dolby Surround-encoded videotapes and DVDs. It also works
wonders with stereo CDs and radio broadcasts.
Upside: Creates a
more spacious and focused surround effect than 5.1 surround.
Downside: Scarce
availability of EX-encoded DVDs; requires a Dolby EX receiver and additional
speaker(s); difficult to implement in a room where the prime listening position
is located near a wall.
Forecast: Because of EX's downsides, interest
in the format will likely remain low. Dolby EX is a 6.1-channel format, adding one (or two) rear
center-surround channel speakers to the standard 5.1 array. EX can deliver more
enveloping surround effects than standard Dolby Digital. EX processing can be
used to improve the sound of regular Dolby Digital-encoded DVDs. Unlike DTS ES,
Dolby EX features an extra rear channel that's matrix rather than discrete.
That's why ES can provide a more precise location for the rear-effects
soundstage.
Upside: Improved surround sound performance with high data rates and increased audio channels; Backward compatible with existing Dolby Digital decoders.
Downside: Requires new HDMI/FireWire interface and additional speakers.
Forecast: Elected by the DVD forum, this latest product from Dolby Laboratory will be the standard feature for future High-Definition materials. An extension of Dolby Digital (DD), the Dolby Digital Plus (DD+) has been chosen as the mandatory surround format for Blu-ray and HD-DVD. It supports up to 13.1 discreet channels with a maximum data rate of 6Mbps. To support the high data rate, HDMI and IEEE1394 (FireWire) have been selected as the new digital interface for DD+ connectivity. The latest Dolby format is backward compatible with existing DD decoders via down-mixing capability and SPDIF digital audio output. DD+ will be available from late 2005.
Upside: Simulated
surround over conventional headphones.
Downside:
Headphone surround isn't nearly as impressive as sound over speakers.
Forecast: The format is just now starting to
gain some momentum, and we expect more and more receivers and HDTVs to feature
Dolby Headphone processing. Dolby Headphone synthesizes five-channel surround effects over any
brand of headphone. It offers up to three processing "flavors" that simulate
rooms of varying sizes and acoustics. While Dolby Headphone technology offers a
substantially more spacious sound compared to the standard stereo headphone
experience, it does not synthesize quasisurround from conventional stereo
sources such as CDs, MP3s, or FM radio. Right now, you'll find Dolby Headphone
processing on the latest generation of higher-end receivers, but we expect the
feature will soon find its way onto more moderately priced
components.
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