High Definition Surround Sound Overview

Surround sound to match the high definition visual experience

article last updated on 10.14.2010 | printer-friendly format    

Introduction

High Definition Television (HDTV) introduced us to a whole new world of visual clarity.  The HDTV picture is so clear, so detailed, and so pristine that it begs for a matching surround sound experience... one that is equally immersive with its ability to capture the heart-pounding dynamics of an action movie to the more subtle nuances of a quiet moment in a romantic movie.  To answer the call, Dolby Laboratories and DTS, Inc. have offered their own solutions, known as Dolby TrueHD and DTS-HD Master Audio respectively.  Both of these new surround sound formats offer:

• 100% lossless encoding that matches the original high quality studio master bit-for-bit for an unmatched surround sound experience.

• Up to 7.1 channels of surround sound, with two additional back channels placed directly behind the audience for a thoroughly immersive surround sound experience.

• Complete artistic control over the down-mixing of multi-channel surround sound, enabling the movie director or soundtrack mixer to specify how a 7.1-channel surround sound mix is down-mixed to 5.1-channel or even 2-channel home theater configuration.  So no matter your loudspeaker configuration, you always get the mix that the creative team intended.

7.1-channel surround sound home theater system
(picture courtesy of DTS)

The end result is that either of these two surround sound formats can offer an acoustic experience that matches the jaw-dropping visual experience of high definition TV.  We will talk about Dolby TrueHD and DTS-HD Master Audio in turn, then discuss how you can enjoy these new high definition surround sound formats in the new Blu-ray Disc optical media format and the audio/video equipment that you would need.

Dolby TrueHD

Dolby TrueHD is Dolby Laboratory's state-of-the-art version of high definition surround sound that supersedes the Dolby Digital 5.1-channel and Dolby Digital Plus 7.1-channel surround sound formats.  Dolby Digital is the most popular surround sound format, prevalent on DVDs, HDTV over-the-air broadcasts, broadcast satellite, and of course cable network digital channel offerings.  While Dolby Digital is good, Dolby TrueHD is leaps and bounds better in every way imaginable, as summarized in the table that follows.

Key parameters of Dolby Digital vs. Dolby TrueHD

Lossy / Lossless: Dolby Digital uses a lossy compression algorithm to encode and pack the audio information into a DVD audio track or a broadcast bitstream.  Lossy means that mathematically, the playback does not replicate bit-for-bit (the 1's and 0's of digital data) the original bitstream that was encoded.  Through the science of psychoacoustics and noise shaping, Dolby Digital encodes the essence of the surround sound information.  Because of the data limitations, some audio fidelity is lost with lossy encoding.  In contrast, Dolby TrueHD uses a lossless encoding algorithm based on MLP Lossless technology, used in the DVD-Audio format for multi-channel music.  Lossless means that mathematically, the playback is able to re-create the original digital studio master recording bit-for-bit.  That means the audio information is pristine.  In playback, we get everything that the audio engineer produced, literally down to the last digital bit.  And that is as good as it gets!

Number of channels & typical channel configuration: Dolby Digital can support up to 6 channels in a 5.1-channel configuration.  That is "5" full-frequency channels and one low frequency effects ".1" channel.  Dolby TrueHD expands this to a maximum of 8 channels, adding two additional full-frequency channels for a total of "7" + ".1" low frequency effects.  Of course, the Dolby TrueHD decoding process can down mix the 7.1-channel soundtrack to playback for 5.1-channel home theater setup.

Maximum data rates: Because the Blu-ray Disc format affords greater data capacity, Dolby TrueHD soundtrack can use a data rate of up to 18 Mbps for just the surround sound information.  That is about 40 times the data rate for Dolby Digital on DVD.  As you can see, that is a phenomenal leap in the amount of information that can be captured using Dolby TrueHD.  What does this do for us?  Higher data rates mean higher frequency sampling rates and longer sampling word lengths, as described below.

Frequency sampling rate: A higher frequency sampling rate means that the sound in all frequency ranges will be encoded with more accuracy.  In everyday terms, the playback soundfield  will be more realistic and natural.  In particular high-pitched sounds within the audible spectrum with improve in tonal accuracy.

Sampling word length: Going from 16-bit word length to a longer 24-bit word length means that more dynamic range can be recorded.  Dynamic range refers the variations of loudness (without changing the playback volume) that spans from the loudest crescendos of music and an action movie explosions to the softness of a subtle nuance emanating from a supporting musical instrument and the whispers in a romantic movie.

While Dolby TrueHD is an optional surround sound format on the Blu-ray Disc format, it is very popular and is offered on many Blu-ray Disc titles.

DTS-HD Master Audio

DTS-HD Master Audio is a high definition surround sound format alternative to Dolby TrueHD.  It is DTS Inc.'s version of Dolby Laboratory's Dolby TrueHD.  Surely, there are technical differences, but from an everyday consumer standpoint, they are more alike than different.  DTS-HD Master Audio is state-of-the-art, offering 7.1-channel surround sound that is bit-for-bit identical to the original digital studio master recording.  It is available on select Blu-ray Disc titles.

Key parameters DTS Surround Sound vs. DTS-HD Master Audio

Which is Better: Dolby TrueHD or DTS-HD Master Audio?

To the consumer, it no longer matters as it once did when the DVD-Video format was first introduced and the surround sound format "war" was between Dolby Digital and DTS Surround Sound.  Because both Dolby TrueHD and DTS-HD Master Audio are lossless formats that replicate the original studio master bit-for-bit and offer up to 7.1 channels of surround sound, both formats offer unprecedented, jaw dropping surround sound experiences.

Blu-ray Movies Featuring Dolby TrueHD or DTS HD Master Audio

Many first-rate action movies released on Blu-ray Disc come with either the Dolby TrueHD or DTS-HD Master Audio, depending on the studios' preference.  Some of the movies with the finest Dolby TrueHD or DTS-HD Master Audio surround sound mixes include:

   
Some great Blu-ray Disc movies featuring Dolby TrueHD

Some great Blu-ray Disc movies featuring DTS-HD Master Audio

What Equipment Do I Need to Enjoy These New High Definition Surround Sound Formats?

As with most things in electronics, to fully enjoy the new Dolby TrueHD or DTS-HD Master Audio high definition surround sound formats, you will have to invest in some new equipment.  To enjoy the high definition picture, you must have a high definition TV (of course).  But from an audio equipment standpoint, here are some options in how you can take advantage of the 7.1-channel Dolby TrueHD or DTS-HD Master Audio soundtracks from Blu-ray Disc media:

Option 1 (Preferred). Blu-ray Disc player and an AV receiver both with Dolby TrueHD and DTS-HD Master Audio decoding built-in: If your equipment is new, you only need to hook them up with an HDMI v1.2 cable (HDMI v1.3 recommended, minimum):
(a) a Blu-ray Disc player that decodes Dolby TrueHD and DTS-HD Master Audio;
(b) a 7.1-channel AV receiver with Dolby TrueHD and DTS-HD Master Audiodecoding;
(c) a single HDMI v1.2 cable (HDMI v1.3 recommended, minimum) to hook up the Blu-ray Disc player to the AV receiver to pass both the video and multi-channel audio information;
(d) a second HDMI v1.2 cable (HDMI v1.3 recommended, minimum) to hook up your AV receiver to your HDTV to pass the video signal.
(e) seven full frequency loudspeakers (or five for 5.1-channel configuration) and an optional subwoofer for the "0.1" LFE channel;

Option 2. AV receiver does not have Dolby TrueHD or DTS-HD Master Audio decoding: If your equipment is a little older but still offers 7.1-channel analog inputs, you can make use of this AV receiver by:
(a) a Blu-ray Disc player that decodes Dolby TrueHD and DTS-HD Master Audio, and outputs the 7.1-channel surround sound signal as analog audio outputs.
(b) a 7.1-channel AV receiver with 7.1-channel analog audio input;
(c) eight analog audio interconnects to hook up the Blu-ray Disc player's 7.1-channel analog outputs to the AV receiver's 7.1-channel analog inputs;
(d) an HDMI v1.2 cable (HDMI v1.3 recommended, minimum) to hook up your Blu-ray Disc player to your HDTV to pass the video signal.
(e) seven  full frequency loudspeakers (or five for 5.1-channel configuration) and an optional subwoofer for the "0.1" LFE channel.

Option 1 is the preferred option for better audio quality, as it keeps the audio signal in the digital domain (which is not plaque by analog signal degradation) until it reaches the AV receiver where the digital audio signal is converted to analog audio signals for amplification and driving the loudspeakers.  If you have a 5.1-channel system, you can still get great results with your existing 5.1-channel configuration, as the AV receiver will down mix the 7.1-channel program to 5.1-channel.

What if you cannot upgrade your equipment right away? With a Blu-ray Disc movie and a Blu-ray Disc player using just the stereo analog audio output, you will notice the higher quality sound using just a stereo if it is amplified by a stereo receiver and played through loudspeakers.  If you do not have at least a stereo receiver and dedicated loudspeakers, you are not likely to hear any difference in sound quality compared to DVD, let alone a missing out on the surround sound experience.

Configuring your 7.1-channel surround sound system

The last step is to set up your loudspeakers in the new 7.1-channel configuration.  For this, we encourage you to read the Dolby Laboratories and DTS Inc. information on loudspeaker layout and configuration.  For an acoustically balanced soundfield, do consider buying the identical loudspeakers when adding the two new surround back channels.  If it has been years since you bought your loudspeaker system and your loudspeaker line has been discontinued, at least consider a similar line within the same manufacturer or one that is at least similar is design and construction.  The newer AV receivers offer automatic calibration with a microphone and will digitally compensate through equalization for differences between loudspeaker characteristics.  If you are not ready to invest in two additional surround back channels, staying with your 5.1-channel will still yield awesome results.  Enjoy!

Additional Info: Proper setup/connection of equipment and placement of surround sound loudspeakers are key to getting the most out of any surround sound systems.  For a more detailed discussion of these topics, try the following links:

• home theater cable/connection hook-up guide:

  • Dolby connections guide

• speaker configurations:

  • Dolby speaker layout and configuration  for 2.0-ch, 5.1-ch and 7.1-ch surround sound systems

  • DTS spreaker layout and configuration for 5.1-ch and 7.1-ch surround sound systems

Did you find this high definition surround sound overview helpful?  Let us know your thoughts, send an e-mail to us at Staff@TimeForDVD.com.

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