Frequently Asked Questions About Surround Sound
A collection of answers to frequently asked questions about surround sound (mostly the production of surround sound actually) originally posted November 1, 1998, but revised as per the Revisions list below.
Please send all comments, corrections and additional questions to Bobby Owsinski at firstname.lastname@example.org
December 22, 2004 - The previous version of
this FAQ was somewhat out-dated so it has been more or less rewritten
as of this date. Major new additions include entries in Virtual
Surround, Live Surround, and Television Surround.
1. GENERAL SURROUND QUESTIONS
1.11 BASS MANAGEMENT
1.12 SURROUND SYSTEM CALIBRATION
1.12.1 How do I calibrate the surround system?
2. SURROUND DELIVERY FORMATS FOR MUSIC
2.3.1 What does DVD stand for?
2.5.1 What's the difference between a DVD-Video and
2.6.1 What's a SACD?
2.7 DTS Music Disc
2.7.1 What's the difference between a DTS music disc
and a DVD?
2.8 DATA COMPRESSION
2.8.1 Why do I need data compression in the first
2.9 DVD PRODUCTION
2.9.1 How do I get my music onto a DVD (of any type)?
3. SURROUND FORMATS FOR MOTION PICTURE
4. SURROUND SOUND FOR TELEVISION
5. VIRTUAL SURROUND
6.9.1 What is ITU Recommendation 775?
6.9.2 What if I can’t place my speakers in the right
6.11.2 Can I use my existing mics to record in
7. ALTERNATIVE METHODS OF SURROUND ENCODING
8. LIVE SURROUND SOUND
1. GENERAL SURROUND QUESTIONS
1.1 Why is surround sound better than stereo?
(the father of THX and unofficial godfather of 5.1) has been
experimenting with a 10.2 system that employs stereo height channels as
well as side channels.
2.3.7 What is this WG-4 that I keep hearing about?
WG-4, or Working Group 4, is the committee assigned by the DVD Forum to work out the format standard for the DVD-Audio disc in conjunction with various record company organizations like the RIAA. WG-4 consists of 40 member companies with JVC as the chair.
2.3.8 Are there a lot of DVD players out there?
As of Sept. 2004, there are over 120 million DVD players in the United States and at least that many world-wide. The 120 million represents a penetration of about 65%, so there’s still lots of room for growth.
2.3.9 What is a hybrid disc?
All DVD's contain 3 zones: the video zone, audio zone and ROM zone. A DVD-V uses most of the disc for the video zone, a DVD-A uses most of it for audio, and the ROM zone is used for data just like a CD-ROM. A hybrid disc is one that contains the same program (although encoded differently) on both the video and audio zones. The ROM zone may be added to either type of disc (or used alone) for access to data when used on a computer.
2.4.1 What is a DVD-V?
DVD-Video burst upon the scene in 1996 primarily as a high quality movie delivery system, but the audio portion of the format is still quite an improvement over Red Book CD. And because there's automatic provisions for multichannel audio and a built-in (but limited) 96/24 option, DVD-V may yet become a major delivery format for audio before all is said and done.
The audio portion of a DVD-V can have up to eight bitstreams (audio tracks). These can be 1 to 8 channels of Linear PCM (LPCM), 1 to six channels (5.1) of Dolby Digital, or 1 to eight channels (5.1 or 7.1) of MPEG-2 audio (FIGURE 2). Also, there are provisions for optional DTS or SDDS encoding as well.
2.4.2 What are the advantages and disadvantages of the audio portion of a DVD-V for music?
Base Of Players - DVD-V audio can currently play on all DVD
players in the marketplace and, with a small bit of additional
authoring, all computer DVD-ROM drives as well (providing the PC has
the appropriate decoding hardware/software).
Compatibility With The Greatest Number Of Players - Unlike DVD-A which requires a player capable of playing it, DVD-V audio is universally compatible with existing and future DVD players.
No Confusion In The Marketplace - The average consumer doesn't know DVD-V from DVD-A, much less care. DVD-V audio eliminates any confusion in the marketplace as to which DVD will play on which player.
Potentially Better Sonic Quality – Stereo 48k/24bit and 96k/24 bit Linear PCM are possible, which beats CD right off. For 5.1 surround, Dolby Digital or DTS encoder is required but you’ll still have 48k/24 bit audio.
As Flexible As DVD-A - While there are choices for the audio
in DVD-V, the format lacks the scalability and super-high fidelity
options of DVD-A. But while professionals and audiophiles will
immediately hear the difference between 96/24 and 44.1/16 Red Book
audio, will the average consumer? It seems that the ordinary listener
can hear the difference between surround and stereo at any bit depth
and sample rate however.
96/24 LPCM Available On Only 2 Channels - The highest quality multichannel LPCM audio available is 48kHz at 20 bits for 6 channels. Using a data compression scheme such as Dolby Digital gives you 6 channels of 48/24.
Some Players Can't Handle 96/24 LPCM - Even if 96/24 LPCM is used, some players automatically decimate to 48kHz and truncate to 16 bits, thereby negating some of the benefits of the enhancement.
2.5.1 What's the difference between a
DVD-Video and DVD-Audio disc?
Primarily the audio specs. The DVD-V has a maximum audio data rate of 6.144Mbs while DVD-A's bit rate is 9.6Mbps. DVD-A has provisions for MLP lossless encoding to enable multichannel 96/24 audio program. DVD-A can also contain two channels of 192/24 program.
2.5.2 Why is 96/24 better than 44.1/16?
First, understand that the first number (96) stands for the sample rate in 1000 per second increments. The second number (24) stand for the word length of the encoded digital data.
There are two parts to this answer. In order to understand which is better quality, a brief discussion of sampling rate and word length is in order.
The analog audio waveform is measured in amplitude at discrete points in time and this is called sampling. The more samples of the waveform that are taken, the better representation of the waveform that occurs, with a greater resultant bandwidth for the signal. Audio on a CD has a sampling rate of 44,100 times a second (44.1kHz) which yields a bandwidth of about 22kHz. A sampling rate of 96kHz gives a better digital representation of the waveform and yields a usable audio bandwidth of about 48kHz. Therefore, the higher the sampling rate, the better the representation of the signal and the greater the bandwidth
The more bits a word has, the better the dynamic range. Every bit means 6.02dB in dynamic range. Therefore, 16 bits yields a maximum dynamic range of 96dB, 20 bit equals 120dB DR, and 24 bit (there are no true 24 bit systems yet) a theoretical maximum of 144dB DR.
2.5.3 When was the DVD-A actually released?
The final audio specification for DVD-A was officially announced in early February 1999. However, because the encryption and watermarking part of the spec (so important to record labels) took so long to implement (and was never fully), DVD-A titles were never really released in any significant numbers until 2002.
2.5.4 Can I put my music videos on a DVD-A?
Sort of. A DVD-A has provision up to 99 still pictures per song. Any video material must be placed in the video zone (the DVD-V portion of the disc) and played back as a DVD-V with reduced resolution audio. The amount of this extra material is dependant upon how much space the audio program takes up, of course, and authoring for the video zone adds an additional cost.
2.5.5 How much playing time can I get on a DVD-A?
It depends on how much material, how many channels, the sample rate, the word length, and how it was encoded. Here's a chart with some examples:
2.5.6 Will a DVD-A play on all DVD players?
Initially no, because the DVD-A spec was written after the first and second generation of DVD players were already on the market so they are unprepared for the format. The video portion of a DVD-A will play on most players (if the disc is authored with a DVD-V zone) but the audio zone (the hi-res DVD-A portion) will not.
Many manufacturers now have universal players on the market that will play DVD-A, DVD-V, and any of the CD formats as well. In a few cases, these universal players will also play SACD too.
2.5.7 Will a DVD-A play on a CD player?
No. This is because the pits of a DVD are far smaller than those on a CD and require a laser of smaller wavelength than the CD uses.
2.5.8 What is SMART Content?
One of the more interesting aspects of DVD-A is a feature known as SMART (System Managed Audio Resource Technique) Content. SMART Content is an auto downmix provision that lets a consumer with only a stereo system have the multichannel mix automatically downmixed to that format. While on the surface it might seem like a scary thing having that great multichannel mix fold down to stereo, SMART Content actually gives the producer a choice in the way this downmix will take place by allowing the producer to select one of 16 downmix coefficients that get stored along with the audio data. SMART Content has the added byproduct of potentially eliminating the need to include a separate stereo mix on the disc, thereby freeing up space for either higher quality audio or additional data information. While this looks good on paper, not too many producers actually take advantage of it.
2.5.9 What is downmixing?
Downmixing occurs when the surround mix is automatically folded down into fewer channels. For example, a 6 channel 5.1 mix automatically becomes a stereo mix if only two channels exist in the playback system. Usually the results of downmixing are less than satisfactory as the balance of the instruments can change significantly.
2.5.10 What is Watermarking?
Watermarking is an embedded signal that applies a digital signature in the form of noise (supposedly inaudible) on a DVD-A. In a proposed, but never implemented, extension to this system, the digital watermark would actually put a faint image (either text or graphics) on the signal side of the disc that makes it extremely hard for pirates to duplicate. The watermark would also identify the artist, record company, catalog number and copyright holder. Sadly, watermarking hasn’t gotten to this point yet.
2.5.11 Does Watermarking affect the sound?
In some cases yes, in some cases no. Since it's a digital code that sounds like noise that's being added to the signal, it will be minutely audible under some circumstances. In order to minimize the affect on the audio, the WG-4 and the RIAA have taken great pains before selecting a watermarking method. This is one of the reasons why the DVD-A spec took so long to complete.
While many watermarks were evaluated, some of the more “golden eared” members of the industry were still able to hear the one chosen. Of course, this is because they know what to listen for.
What is Encryption?
Encryption is an advanced form of digital copy protection proposed for eventual inclusion on the DVD-Audio disc. It’s still not implemented.
2.5.13 What is Extensibility?
Extensibility is a feature of DVD-A that gives it the capability of using any new digital encoding technology that may become popular in the future. While this sounds all well and good, new hi-capacity formats like Blu-Ray should make any new type of encoding irrelevant.
2.5.14 What is Scalability?
A feature of DVD-A that allows the producer to select from various sample rates (44.1, 48, 88.2, 96, 176.4, and 192kHz) and word lengths (16, 20, 24). It is also possible for the producer to assign different sample rates and word lengths to different channel families, such as 96/24 to the front speakers and 48/16 to the surrounds.
Once again, this feature sounds better than it really is. It’s a production hassle to have different channels at different word lengths and sample rates and some of the DVD-A authoring software doesn’t implement the feature anyway.
What are the advantages and disadvantages of DVD-A for music?
Excellent Audio Quality – Depending upon the production techniques, DVD-A offers quality far better than that found on a CD.
- DVD-A is a somewhat open technology in that there are provisions for
new innovations beyond LPCM that can be implemented in the future.
Scalability – Theoretically, the program producer can choose the number of channels, bit depth, sample rate, and encoding method.
Value Added Material - Liner notes, album cover artwork, music videos, artist commentary and Internet links can all be included if there’s space.
Copy Protection – While watermarking provides some protection if used, the fact that the disc is so large and the bandwidth so great eliminates it (for now) from the illegal ripping that routinely happens with CDs.
the Consumer Accept Another Format? - While nobody argues that
this is a potentially powerful format, there are some that have strong
doubts as to whether the consumer will buy in wholeheartedly. So
far, only the audiophile market segment has bought in and that
demographic is shrinking.
Lack of Moving Pictures During the Song - Many in the production and distribution community believe this to be a liability, even though up to 99 still pictures per song may be used. However, if material such as liner notes, artist/producer and even engineer bios are included, this could actually be a nice adjunct. After all, one of the main complaints about CD's was the lack of information relative to what was previously found on LP's.
Watermarking Adds Artifacts To The Audio Signal In Some Cases - While everyone agrees on the need for some type of copy protection and program identification, it is all for naught if the process interferes with the audio quality. There is no clear consensus currently as to the effect of watermarking, with some claiming that the process is clearly audible and others stating that it's virtually transparent.
2.6.1 What's a SACD?
The Super Audio CD (SACD) is a disc format by Sony and Phillips containing both the DSD process for very high quality multichannel audio and an optional Red Book CD layer which is compatible with any current CD player. This means that any current CD will play on a SACD player and any SACD with a Red Book layer will play on any current CD player.
2.6.2 What is DSD?
Direct Stream Digital. At a very high sampling rate of 2.822 megahertz, DSD measures whether an analog waveform is rising or falling. This yields a single bit; either a 1 for a rising wave or a 0 for one that's falling. This single bit is then recorded directly, which avoids many of the unwanted side effects occurring when using the standard PCM process.
2.6.3 Does DSD sound better than everything else?
It depends on whom you talk to. Most people that have heard both DSD and 96/24 LPCM find them comparable if the audio source material was prepared under similar conditions. Many engineers have an issue with DSD regarding the theoretical limits of the system (said to be 120dB maximum dynamic range as compared to 144 for LPCM) and the fact that large amounts of noise are shifted to the frequency region above the audio bandwidth. Neither argument seems to have any bearing on the current listening tests however.
2.6.4 Does an SACD have pictures?
There are provisions for text and graphics, although few discs (if any) actually implement these features. However, SACD can theoretically use the current Blue Book standard for enhanced CD for picture, as opposed to the UDF file standard used by DVD.
2.6.5 When was the SACD be released?
Sony/Philips released SACD in Japan in May of 1999. Little by little, the format has gotten market penetration as the players have decreased in price (to less than $200, down from the initial $5000) and more titles (about 3000 as of December 2004) have come on the market.
2.6.6 What are the advantages and disadvantages of the SACD for music?
Performance - Wide bandwidth goes from DC to 100kHz with a
120dB dynamic range. No adverse filter artifacts thanks to elimination
of the brick wall filter, which is required in LPCM.
Plays on Current CD Players - With both backwards and forwards compatibility, consumers won't feel forced to buy expensive new hardware or give up their current libraries.
Another Format - As with DVD-A, will the average consumer be
willing to buy another piece of expensive hardware? Will consumers be
confused with yet another format choice?
Is The Sonic Performance Really Better - While DSD seems every bit the equal to the current state of LPCM, advances in converter technology could eventually move LPCM beyond the seemingly closed format of SACD.
New Production Equipment Needed - Because of the DSD technology, new analog to digital and digital to analog convertors, along with a dedicated recorder/editor is required. Although there are new models coming on the market, they are not nearly as available as LPCM technology.
2.7.1 What's the difference between a DTS
music disc and a DVD?
The DTS music disc differs from standard CDs in that it contains DTS encoded audio instead of PCM, but it is a CD in every other respect. The sampling rate is 44.1kHz, but the bit depth can be 16, 20, or 24 bits, just as with DVD. For several years most of the discs were 20 bit, but the system has always been 24-bit capable, and the discs coming out currently are mostly 24-bit. The DTS music disc has no provisions for other information such as videos or text. DVD-V or A is obviously a different animal with larger storage capacities and provisions for value added material as a result.
2.7.2 Does a DTS music disc have text, graphics and video too?
Not usually, although it can be authored like a typical enhanced CD.
2.7.3 Can DTS be encoded on a DVD?
Yes and in many different forms. DTS can be encoded on the audio portion of a DVD-V or the video zone of a DVD-A at either 16, 20 or 24 bits.
2.7.4 What are the advantages and disadvantages of the DTS music disc?
Superiority - Thanks to its low compression ratio and high bit
rate, the DTS encoding system is generally acknowledged to be the best
sounding of the current lossy compression systems.
Available Now - A wide library (over a hundred discs in all musical genres) of DTS music discs can be found right now at just about anywhere that DTS equipped receivers or decoders are sold.
a Decoder to Operate - Without a DTS decoder, the only output
you get from the player is white noise. However many receivers, even
the most inexpensive, now come with a DTS decoder built in.
Distribution Limited Due To Non-Compatible Discs - Because of possible consumer confusion with Red Book CD's (the customer puts it in his CD player only to get a white noise output), many of the biggest music retailers have refused to carry the DTS music disc to this point.
No Value Added Information - Because the DTS music disc uses the limited storage capacity of a CD, there's little room for additional text, graphic or video material.
2.8.1 Why do I need data compression in the
Two reasons. The first is to squeeze more data onto a finite storage space. The second reason is because the bit rate of DVD (the pipe that the data has to flow through) is capped at 6.144Mbps for DVD-V and 9.6Mbps for DVD-A and six channels of 96/24 LPCM is too much bandwidth to fit through the data pipe.
2.8.2 What's the difference between Dolby Digital (AC-3) and DTS encoding?
Both methods are what's known as lossy data compression schemes where some information that is masked by more prominent data is thrown away. This is done in order to fit a lot of data through a small data pipe. Dolby Digital (formerly called AC-3) takes 6 channels of 48kHz/24 bit information and compresses it at about an 11 to 1 ratio to an a maximum bit rate of 640kbps, although 384 is the average data rate used. The payload data rates for DTS are 1.2 Mbps for music discs and 1.5Mbps or 754kbps for DVD. The compression ratio varies according to the input word length; 3:1 is about right for 20 bits, 48 kHz, at 1.5Mbps.
2.8.3 What's the difference between lossy and lossless compression?
Lossy compression (such as Dolby Digital or DTS) is built around perceptional algorithms that remove signal data that is being masked or covered up by other signal data that is louder. Because this data is thrown away and never retrieved, it's what's known as "lossy". Depending upon the source material, lossy compression can either be completely inaudible, or somewhat noticeable. It should be noted that even when it is audible, lossy compression still does a remarkable job of recovering the audio signal and still sounds quite good.
Lossless compression (such as MLP) never discards any data and recovers it completely during decoding and playback.
2.8.4 What's MLP?
Meridian Lossless Packing is the compression standard used on the DVD-A in order to store six channels of 96/24 audio. MLP's main feature is that it never discards any signal information during data compression (which is why it's "lossless") and therefore doesn't affect the audio quality. MLP gives a compression ratio of about 1.85 to 1 (about 45%) and its licensing is administrated by Dolby Laboratories.
2.9.1 How do I get my surround music onto a
DVD (of any type)?
A DVD requires what’s known as authoring. After your music is mixed it must be first encoded (along with any video material as well) with the desired data compression, if any is required. This is actually a much longer and more labor intensive operation for video than for audio. The encoded audio material is then brought into a workstation where it is stitched together with any text, graphics and video, and the interactivity and navigation elements are created. The result is then either burned into a DVD-R or offloaded to a DLT (Digital Linear Tape) master and sent to the replicator.
2.9.2 How much does authoring cost?
Of course prices vary and packages abound, but a good reference price is $5 to 10 per program minute for audio and $25 or so per program minute for video. Authoring costs are generally determined per job since each is somewhat unique. As an example, it may cost only $1-2000 for something very simple requiring only importing of elements and simple navigation, but any degree of sophistication that really takes advantage of the format (like motion graphic menus, web links, multiple camera angles, etc.) can expand the cost to $15 to 25k or more. DVD-Audio authoring is usually more expensive since there are far fewer facilities that have the required equipment.
There are now many relatively inexpensive DVD authoring packages on the market, although many lack significant features like a Dolby Digital encoder or multichannel audio (you get stereo only).
2.9.3 Can I record music or video straight to a DVD?
A new generation of DVD recorder has recently come on the market making this possible. While most of the units are little more than toys, a few of the more expensive units can do a pretty nice, although relatively simple job. Anything requiring even a modicum of navigational sophistication still requires traditional authoring though.
2.9.4 How much digital storage space will I need if I record surround?
It varies from quite a bit more than a stereo program to a gigantic amount more, depending on the sample rate and word length used. For example (figures are for LPCM coding):
2.9.5 How much digital storage space will I need if I record 96/24?
A minute of true LPCM 96/24 stereo needs 35 Meg, and a minute of discrete 5.1 surround at 96/24 requires a whopping 104MB! This means that a 60 minute program will need 6.24 GB. This is another reason why data compression is necessary, since a DVD only has 4.32GB of effective storage capacity.
3.1 What are the current surround delivery
formats for motion picture?
Dolby Digital, DTS, Sony Dynamic Digital Sound (SDDS) make up the majority of major motion picture releases today, with Dolby Surround fading away quickly.
With Dolby Digital, the digitally encoded track is placed between the sprocket holes of the film in order to keep the analog optical tracks intact form playback in theaters without Dolby Digital decoding.
With DTS, the encoded audio is stored on a CD-ROM which is synced to the film via special time code track placed between the optical track and the film frame.
SDDS places the encoded digital signal outside the sprocket holes on both sides of the film. SDDS also utilizes a 7.1 format with center left and center right speakers added to the front array.
3.2 What is Dolby SR-D?
The term the film industry uses to identify 35 mm release prints containing both an analog Dolby Stereo SR encoded and Dolby Digital ("D") optical soundtracks. Dolby SR is Dolby's latest analog noise reduction system. SR-D is sometimes misused to mean the Dolby Digital format or presentations.
3.3 What's the difference between Dolby Surround, Dolby Pro Logic and Dolby Digital?
These are all encoding techniques to allow a multichannel signal to be delivered to the consumer. The main difference between them is the number of channels and how the signal is decoded. While Dolby Surround and Pro Logic are closely related (with the main difference being the fact that Surround uses a passive decoder while Pro Logic uses an active one), Dolby Digital is a completely different, more sophisticated technique and not compatible with the others.
Surround is a matrix encoding system that combines four
channels (Left, Center, Right and a limited bandwidth Surround channel)
into two channels. These two channels can be summed together for mono
playback, or played back as normal stereo. If the matrix is fed into a
passive decoder, then only the stereo signal plus a single limited
bandwidth surround channel is unfolded. Dolby Surround (4:2:4 matrix)
is the most widely used surround format today, with more than 10,000
programs having been produced in the format.
Dolby Pro Logic is the active decoder which takes the two channel Dolby Surround signal and unfolds it into Left, Center, Right and a limited bandwidth Surround channel which is reproduced through the Left Surround and Right Surround speakers. The main difference between Pro Logic and passively decoded Dolby Surround is that Pro Logic adds a fourth channel in the front center. It also has much better channel separation.
Dolby Pro Logic II, which has recently been
introduced, is an advanced matrix decoder that derives five-channel
surround (Left, Center, Right, Left Surround, and Right Surround) from
any stereo program material, whether or not it has been specifically
Dolby Surround encoded. On encoded material such as movie soundtracks,
the sound is more like Dolby Digital 5.1 (see below), while on
unencoded stereo material such as music CDs the effect is a wider, more
involving soundfield. Among other improvements over Pro Logic, Pro
Logic II provides two full-range surround channels, as opposed to Pro
Logic’s single, limited-bandwidth surround channel.
Dolby Digital is the official Dolby name for their AC-3 encoding, which takes 6 channels of audio (5.1), folds them into a single digital bitstream, then unfolds them again into separate streams for playback.
3.4 What is Dolby Stereo?
This is Dolby Laboratories' original analog surround system where 4 channels of sound where encoded with Dolby Type-A noise reduction and combined into 2 channels for placement on the film. During playback, a decoder was used to convert the 2 tracks on the film back into 4 channels of sound in the theater.
4.1 Can I get surround sound on my TV?
Yes, some television shows have been broadcast in surround for some time. During the 2002-2003 TV season, more than 300 current and syndicated TV series, specials and regular events were scheduled for broadcast in Dolby Surround over terrestrial analog TV stations, according to Dolby Labs, and events like the Tony Awards and Major League Baseball with SRS Circle Surround. On top of that, more than 130 digital standard definition TV (SDTV) and high-definition TV (HDTV) series, movies and special events were scheduled for broadcast in 5.1 during the 2003-2004 season in Dolby Digital via satellite, digital cable systems and terrestrial digital TV (DTV) stations.
In order to playback a surround encoded
broadcast, you must have the proper decoder (which is normally found in
the receiver of a home theater system).
4.2 Is surround mixed differently for
Yes, although we're early enough in the learning curve that everyone is still feeling it out. Because of the frequent cuts containing different visual perspectives, having the 5.1 soundstage change that frequently can be really disconcerting. For now, most 5.1 mixing maintains a cinema approach with the dialog in the center channel and very little on the sides to draw your attention away from the screen. Sports is a bit different though, with crowd sometimes maintaining a solid perspective in the rear channels.
4.3 Is television audio recorded in
A little, with mostly foley and crowds with a surround mic. As in film, most mixers would prefer just plain mono effects, preferring to do the placement and enhancement themselves to better fit the scene. The exception would be the Olympics or the X-Games, where the philosophy is more towards "hyper-realism" where a great number of mics (mono, stereo and surround) are employed to capture all the nuances in the audio of the performance.
4.4 What's that swishing sound I hear in my rear speakers when I play back a surround program?
That's the steering system of the Dolby Pro Logic decoder in your receiver extracting the rear channel information. Because the process is very phase dependant, the swishing sound (phase shift) can be evident during action scenes with a lot of panning. The latest Pro Logic II is less susceptible to this effect.
6.1 What do I need to get started?
The things that change the most between a stereo and a surround system is the monitor system (duh!). But it's not just the monitors that are important. The system feeding it is of equal or greater concern. So the minimum you'll need is the following:
like a bass manager and surround processors can be added later.
6.2 How do I change the control room level of all six channels at the same time?
That's the problem, isn't it? While many consoles and DAWs hype themselves as "surround ready", all they really refer to is the ability to pan around five speakers. Very few actually have the ability to control the monitor level of the surround system, which requires a precision six channel control room level control.
There are some fine add-on outboard solutions, however. Studio Technologies, Martinsound, SPL, Audient, Adgil, EMM Labs, Blue Sky, Tascam and SPL all have outboard add-on level control for the surround systems.
6.3 What multichannel mixdown decks are being used for surround?
For DVD-V work, the defacto standard is still the Tascam DA-88 family (DA-98, PCM800, etc), although many authoring houses are beginning to accept AIFF or WAV files. For DVD-Audio, most AIFF or WAV files are used for masters, although some machines being used include the DA-98HR and the Genex Magneto Optical recorder. Some people are even mixing to 1 or 2" eight track analog.
The broadcast industry has adopted this format for DTV since it easily transfers to four channel digital video media where linear PCM on channels 1 and 2 (as a reference, if required) and AC-3 on channels 3 and 4 are required. Also, these assignments not only represent logical pairings but the pairings used by AC-3 encoding.
The following two assignment methods are also used, but less and less these days.
and 8 usually contain the stereo version of the mix, if one is needed.
6.5 What kind of console do I need?
We now live in a world where fewer and fewer traditional consoles are being used and more and more mixing is being done inside a computer. Recently consoles (like Tascam and Yamaha on the low end and SSL and Euphonix on the high end) and DAWs (like Protools and Nuendo) have incorporated surround features like panners and multichannel master and group faders.
Regardless of which format you choose, you still need a way to control the level of the surround monitoring system, so that’s the primary feature to look for. Surround panners would be second with multichannel effects returns (or plug-ins if it’s a DAW) as third.
Surprisingly enough, a fair amount of surround mixing being done today is still being done on stereo or quad desks utilizing outboard surround panners and monitoring.
6.6 How can I get a surround mix from a stereo console?
Here's a little trick that will give any standard console the ability to do surround panning as long as you have at least 4 busses available. Although the following is a bit easier to visualize on a English-style split monitor desk, it can be performed on an in-line console just the same.
In the stereo world we're used to panning from left to right using a left and right stereo mix buss or odd/even recording busses. If we dedicate two mix buses, say busses 1 and 2 for example, to left and right front and busses and 3 and 4 to the rear, then we are restricted to only being able to pan back and forth between left and right either in the front or in the rear. The hard part, and what we want most, is the ability to pan front to back.
We can do this by just assigning the busses a little differently. Simply make busses 1 and 4 the front mix and 2 and 3 the rear. Now by assigning busses 1 and 2 you can pan left front to rear and busses 3 and 4 pans right front to rear (See Figure 1). Although it doesn't work perfectly, you do get the sense of panning diagonally as well by using 3 busses such as 1, 2 and 4 for left rear to right front for example. In fact, any combination of buss assignments (even all four at once) will get you most places that you want to go in the surround field.
This method doesn't give you the ability to pan to the center speaker though. You still need a hard buss assignment (buss 5 perhaps) or preferably an aux send for that. But it does stretch some added surround mileage out of that seemingly over-the-hill stereo desk.
6.7 Are there any surround signal processors available?
If you're referring to multichannel signal processors, more and more come on the market every day, especially in the digital domain. TC Electronic, Lexicon, Kurzweil, and Junger all have digital multichannel signal processors available. In the analog domain, the Drawmer 6 Pack is a very nice multichannel dynamics package.
6.8 What surround monitor systems are available?
Unlike a few years ago, just about every speaker manufacturer now sells at least one surround system. While there’s a lot of systems now on the market, there's only a few at the moment that sell an entire surround system complete with bass management though, so an outboard unit should probably be considered. (hint: because home surround system use one and you want to be able to hear the same things that the consumer is hearing).
6.9 Do I have to change the acoustics of my room to do surround?
If you're building a surround room from scratch, yes of course. This is a bit beyond the scope of this FAQ however. We suggest you contact an experienced design consultant.
If you're monitoring with a near field surround system, your room needn't change beyond what you might normally do for nearfield monitoring.
6.9.1 What is ITU Recommendation 775?
This is a recommendation for speaker placement in a surround setup that was based upon experimentation by the BBC. It’s a compromise, however, that provides less than optimum (yet adequate) imaging and envelopment.
ITU Recommendation 775
6.9.2 What if I can’t place my speakers in the right place?
Not to worry, most of us can’t. There always seem to be a rack or doorway in the way. The good thing is that poor placement can be somewhat overcome by proper system level calibration. Just remember that you will get two separate soundfields if the rear speakers are placed too far away from the engineer (not good).
6.10 Doesn't it take longer to do a surround mix?
No, it actually takes less time because surround sound automatically has a depth of field that you have to work hard to create when you're mixing in stereo. Most mixers find they need less EQ and fewer effects because there's more room in the soundscape to place things.
6.11 Do I have to change my recording style?
Unless you're doing Orchestral music, probably not. Pop, Rock, Jazz, Country and just about any other genre can be recorded the same as always. With most genres of audio, usually just a few things are recorded in surround. The surround magic generally comes in the mixing.
In Classical music, however, great pains are taken to actually record the sound of the recording environment along with the music, so the process does become more complicated in this situation.
6.11.1 Are there any surround microphones yet?
Yes, there are a few. A company called Rising Sun Productions out of Toronto has teamed with the National Science Foundation of Canada to produce a 6.1 mic called the “Holophone”. The Soundfield Mark V and model ST250 along with their model 451 processor works well. The SPL/Brauner Atmos mic and the Schoeps 360 are also available.
6.11.2 Can I use my existing mics to record in surround?
Yes you can. There are a number of techniques that work very well. Without getting too involved, the IRT Cross utilizes 4 mics in a square and is basically back-to-back ORTF stereo. Double MS utilizes the basic stereo MS configuration with a rear facing cardioid. The Hamasaki Square is similar to the IRT Cross except it utilizes mics with a figure 8 pattern instead of cardioids. Then there’s always the tried and true Decca Tree. Check the Books/DVD section for more detail.
I have been experimenting with a "hallo" consisting of 5 DPA (formerly B&K) 4061 miniature microphones that has worked surprisingly well (see my article on surround drum miking in issue #4 - NAB 99 of Surround Professional magazine).
6.12 Do I have to use the LFE channel being sent to the subwoofer?
No, in fact it might even be better if you don't use it at all unless that you're positive that the sub is calibrated correctly. An uncalibrated subwoofer can cause big surprises in the low end when the track is later played back on the typical home theater setup. It will sound awesome if you get it right, though. In general, the LFE channel should be used judiciously regardless of the type of material that you’re mixing.
6.13 What instruments do I put into the LFE channel?
Anything that requires some low frequency bass extension. Most people put a little kick and/or bass there if it's used at all. Just remember that the frequency response only goes up to 120Hz so you'll have to put the instrument into the main channels as well in order to gain some definition.
6.14 Do I have to use the center channel?
No, but it sure helps sometimes. In film mixing, the center channel is used primarily for dialog so the listener doesn't get distracted. In music it acts to anchor the sound and eliminate any drifting phantom images.
There are some mixers that continue to us the phantom center from the left and right front speakers and prefer to use the center speaker as a height channel or not use it at all.
6.15 Can I make a stereo track into surround?
There have been various strategies for doing this that range from flipping the channels out of phase and assigning them to the surrounds to putting L+R and L-R signals in the surrounds or center channel. Unwrap, an optional program in the TC6000, can do a nice job under the right circumstances. Boxes by SRS and Z-Sys also work well on certain material.
6.16 Should I do a separate stereo mix or can my 5.1 mix be played back in stereo?
Although it's possible to have the surround mix automatically downmixed to stereo either via SMART Content or by selection of the downmix parameters on the Dolby AC-3 encoder, the results are often unpredictable and many times unsatisfactory. It's probably best to prepare a separate dedicated stereo mix if there's remaining storage capacity on the delivery medium.
6.17 Do I need to own an encoder/decoder to mix surround?
If you're doing 5.1, no; but it helps to hear what the codec (coder/decoder) will do to the final product because codecs and their parameter settings can change the sound considerably. There's also quite a few parameters (like Dial Norm and downmixing) that the producer might like to tweak rather than leave for someone else down the production chain. While you can buy a dedicated Dolby Digital or DTS hardware processor, the codecs are now also available as plug-ins available for many DAWs, although the cost is usually around $1000 (as compared to $6 to 10k for hardware).
If you're mixing in a matrix-type surround format like Dolby Surround, you most definitely want to monitor through a encoder/decoder so that the action of the matrix process can be taken into account in the mix.
6.18 How do I master my surround project?
No problem. For a while there were few mastering facilities that could truly master in 5.1, but now just about every major mastering facility is equipped to do so. Some do it yourself methods are presented in "The Mastering Engineer's Handbook".
7.1 Are there other methods of encoding
surround besides the Dolby and DTS methods?
Yes, there are several others that have been tried over the years but haven't been widely accepted for one reason or another. These are:
7.1.1 Ambisonics - Ambisonics is the work of a group of British academics, most notably the late Michael Gerzon, who built on the previous work of famed audio pioneer Alan Blumlein.
Simplistically put, Ambisonics is a method of recording information about a soundfield and reproducing it over some form of loudspeaker array so as to produce the impression of hearing a true three dimensional sound image. This information can be played back in a stereo playback system if it is encoded utilizing a method called UHJ. For more information, go to:
7.1.2 SRS Circle Surround - Circle Surround is a 6:2:6 matrix system that allows broadcast and recording on any two-channel medium and employs a patented active steering process to direct information to its intended destination within the sound field.
The system encodes 6 channels (5.1 audio) into a matrixed stereo signal for recording or transmission. The decoder reallocates these six original signals to an array of loudspeakers. The system is claimed to be compatible with all current playback formats.
SRS Labs Circle Surround
7.1.3 Lexicon Logic 7 - Logic 7 is a surround encoding/decoding technique that will reproduce two-channel stereo, Logic 7 encoded 5.1 channel music and conventional 4-2-4 matrix Dolby Prologic encoding as well as standard two channel stereo.
A Logic 7 encoded mix can be stored and broadcast on any currently available two channel devices and played back as a fully compatible stereo mix with no decoder necessary. When played back through a Logic 7 decoder, the sounds will play back in their original positions, even if the rear signals are in stereo. Since the sounds are phase/amplitude encoded, they will also play back through a conventional Dolby Prologic decoder and even display some enhanced directionality. Standard stereo recordings played through a Logic 7 system are said to sound larger and more enveloping than conventional stereo.
7.1.4 MP3 Surround - Developed by Fraunhofer IIS, MP3 Surround is a format for storing compressed multi-channel audio material. It allows encoding multi-channel sound data in high quality at bit rates comparable to those currently used to encode stereo material. Most important, the new format is completely backward compatible to existing stereo MP3 software and devices but you need the decoder software to play the multichannel portion of the file. MP3 Surround also supports the same bit rates as MP3.
Although the current Fraunhofer IIS MP3 Surround Software 1.0 is limited to a 5.1 channel configuration, future versions of surround sound encoders and decoders could support other configurations as well (e.g., 7.1; 10.2). There is no limitation for the number of channels ultimately supported.
The next generation of DVD players may support MP3 Surround, enabling the user to enjoy the full multi-channel experience from an MP3 Surround file.
7.1.5 MPEG-4 aacPlus - is the combination of three MPEG technologies comprising Advanced Audio Coding (AAC), coupled with Coding Technologies' Spectral Band Replication (SBR), and Parametric Stereo (PS) technologies. SBR is a unique bandwidth extension technique which enables audio codecs to deliver the same quality at half the bit rate. PS significantly increases the codec efficiency a second time for low bit rate stereo signals.
SBR and PS are both forward and backward compatible methods to enhance the efficiency of any audio codec. As a result, aacPlus delivers streaming and downloadable 5.1 multichannel audio at 128 kbps, near CD-quality stereo at 32 kbps, excellent quality stereo at 24 kbps, and good quality for mixed content even below 16 kbps mono. This level of efficiency enables new applications in the markets of mobile and digital broadcast.
one of the main problems with touring live surround systems is the fact
that only a small minority of the audience may ever be in the “sweet
spot” to get the full effect, so material that is isolated in one
speaker may never be heard by the majority of the audience. This
is also a problem with stereo sound reinforcement systems, only less so.
8.2 What's the normal speaker arrangement for live surround sound?
While 5.1 is the overwhelming standard for both consumer and cinema surround, the number of channels for a live performance is usually based upon the requirements of the program. Many acts tour with a 4.0 quad sytem, a 6.0 system with speakers directly on the sides at 90 degrees from the center, or any other combination that best represents the program material.
8.3 Are more than 6
channels ever used?
Many large Las Vegas showroom acts such as Blue Man Group and Cirque du Soliel utilize systems featuring as many as 30 channels. This is made possible because the audience is usually seated and each speaker/channel's placement can be optimized
8.4 Is an LFE channel
used in live surround?
A separate LFE channel is sometimes not required since most touring and fixed sound reinforcement systems already supply sufficient low frequency response and headroom (thanks to some really massive subwoofers) to accommodate any low frequency effect that the artist requires.
9.1 Where can I get more information about surround sound production?
There are a lot of places. Try the following:
“How To Set Up Your Surround Studio DVD” contains everything you need to know before that first session.
“The Mixing Engineer’s Handbook” contains a section on mixing in surround.
“The Mastering Engineer’s Handbook” contains a section on mastering surround program and prepping for DVD delivery.
“The Recording Engineer’s Handbook” contains a section on recording in surround including microphones and microphone technique.
Tom Holman’s “5.1 Up And Running” is an essential reference book on the subject.
The Dolby website is a wealth of surround info.
Surround Professional Magazine is the bible of the surround industry.
This FAQ is written and maintained by Bobby Owsinski. Please send all comments, corrections and additional questions to email@example.com.
material was collected and adapted from a multitude of sources
Materials collected from the DVD Forum Conferences
The DVD FAQ by Jim Taylor
Premastering New Audio Formats by Sonic Solutions
Digital Entertainment Group
The Sony SACD Project
Consumer Electronics Association
Various manufacturers literature and white papers
And all-knowing wisdom of the following sages:
Tom Holman ("The Man") of TMH Corporation
John Kellogg of Dolby Labs
Gene Radzik of Dolby Labs
Bill Barns of Dolby Labs
David DelGrosso of DTS
Steve Cohen of Sony
Ken Kriesel of M&K
Rory Kaplan of DTS
Lore Kramer of DTS
Mark Waldrep of AIX Media Group
David Kawakami and Lon Neumann of the Sony SACD Group
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