High Definition Audio for Music Listening
One may think that audio CDs (CD-DA) provide the perfect sound.
Yet many audiophiles would soon tell you that in comparison to high quality analog audio recordings on LPs, CD sound is relatively cold and harsh especially when it comes to handling the upper most frequencies.
Partly, the popularity of the CD-DA format arises out of its ease of use - which also explains the incredible large market that this 20-year old medium holds today. Nevertheless, its substantial limitations such as occasional frequency clipping, limited dynamic range, spectrum limitations, and the development of new digital interconnects that are capable of supporting the transfer of high definition multi-channel audio and video in digital form among devices in the playback chain, is leading to a shift among music lovers towards DVD-Audio discs and SACDs.
At the same time, one has to acknowledge the fact that though the Super Audio CD and the DVD-Audio disc have been around since 1999 and 2000 respectively, yet the shift towards these two high definition audio formats has been slow - especially in the first few years of their existence.
Partly, the reason was that universal players capable of playing both formats were initially selling at around $1,000 - too expensive for these formats to gain popularity. In fact, it was not before 2003 that we started to see the first combined DVD-Audio disc/SACD players at under the $200 price tag. It was also at around this same time that DVD-Audio and SACDs were being priced at CD levels.
Today, you can get a good quality universal DVD player capable of handling DVD-Video, DVD-Audio, SACD, and CD, at around $150. A case in point is the OPPO DV-970HD Up-Converting Universal DVD Player which can produce excellent image quality when playing DVD-Video, supports SACD, DVD-Audio, and CD among others, and is also capable of upconverting 720p to 1080i via its HDMI. Ok, built quality may feel a bit too plastic and not up to the same standard as high-end players, but at this price bracket, the OPPO DV-970HD delivers some of the best value for your money.
DVD-Audio, SACD and other High Definition Formats
DVD-Audio discs and SACDs are capable of delivering up to six full-range channels of high resolution audio. These are not the only high definition audio formats; both Dolby and DTS, have got a full lineup of high definition formats that are capable of delivering high resolution multi-channel sound using either lossy or lossless encoding techniques.
But these Dolby and DTS formats are mainly audio-for-video formats, thus supporting full motion video in addition to the high quality audio on the same optical disc. In contrast, DVD-Audio and SACD are music-delivery formats, and though both support 'limited' visual content, yet neither is intended for movie viewing.
DVD-Audio vs SACD - a format war?
It is an undeniable fact that the main players behind DVD-Audio discs and SACD are in a format war with each other. Yet it is our opinion that the availability of inexpensive universal media players like the Oppo referred to above, and with optical media selling at rock bottom prices, will not only guarantee the co-existence of both formats, it will even render this format dispute between these two major players, rather transparent to the end user.
This is being stated as DVD-Audio discs and Super Audio CDs both capable of delivering the same level of high fidelity audio, where the end quality is mainly dependent on the playback setup rather than the audio format. And this, despite the fact that as we will soon see in this article, DVD-Audio and SACD use fundamentally different processes to achieve the same end result.
High Definition Audio formats for Music Listening
DVD-Audio: An Overview
As already expressed in our introduction on DVD-Audio and Super Audio CD, DVD-Audio - also referred to as DVD-A, is one of the two mainstream high resolution multi-channel audio formats available specifically for music listening.
This article will give you an overview of the DVD-Audio format. In particular, it explains the main features of this high definition audio, as well as compares DVD-A sound quality with that of the more popular CD-Audio format. Finally, we also explain what type of equipment setup is required to enjoy DVD-Audio.
DVD-Audio is a digital format designed for the delivery high-fidelity audio content on a DVD. It supports a number of different audio configurations, ranging from single-channel (mono) up to six full-range audio channels, at various sampling frequencies and bit depth.
DVD-Audio sound supports far greater detail and texture, and is more lifelike than CD audio. The main reason being that it can handle up to 256 times the sample resolution (quantization levels) with respect to CD-DA while delivering anything up to four times as much samples per second. For this reason, DVD-Audio is mainly of interest to audiophiles and home-theater enthusiasts who would like to enjoy the very best in music sound.
As already indicated in the previous section, DVD-Audio offers many possible configurations of audio channels, ranging from single-channel mono up to six full-range channels of surround sound, at various sampling frequencies and sample rates, ranging from stereo CD-DA quality sound i.e. 16-bit/44.1kHz x 2-channel sound, up to 5.1 surround at 24-bit/96kHz sound, or 24-bit/192kHz stereo sound.
This is all possible thanks to the much higher capacity of this DVD optical medium in comparison to compact discs. This leads to far higher audio quality as a result of the higher linear sampling frequency and higher sample resolution, better spatial sound reproduction due to the additional channels, and finally, the possibility of extended running time - however, this depends on the sound quality of the recorded audio signal.
Further more, the DVD-Audio format supports additional information like a table of contents, text subtitles, still images and video clips. Additionally, because the DVD-Audio format is a member of the DVD family, a single disc can have either two layers when delivered over a double layer DVD, (DVD-9), and even two sides that contain media when using two-sided discs (DVD-10, DVD-14, or DVD-18).
In the case of two-sided DVD titles, these would normally come with one side formatted as DVD-Audio and the other as DVD-Video. A common configuration includes a 'DVD-Video' zone on a DVD-Audio formatted single sided disc. In fact, many DVD-Audio titles come as a combination DVD-Audio/Video disc, with the DVD-Video portion of the DVD being used to include artist interviews and additional bonus material like music videos.
The presence of the DVD-Video zone on a DVD-Audio formatted DVD renders the DVD-Audio Disc compatible with DVD-Video players. Thus, while the high-resolution, multichannel lossless encoded audio is only playable on DVD-Audio hardware, the DVD-Video zone, which would normally contain also Dolby or DTS mixes, makes the disc compatible with all DVD players.
Other configurations include DVD-Audio, DVD-Video and DVD-ROM content on the same DVD disc. In reality, the possibilities are endless and may include a variety of combinations as supported by the DVD optical medium.
Just one final point about DVD-Video on
DVD-Audio formatted discs. While DVD-A does not include region coding and
therefore, is playable on all DVD-Audio players, yet the DVD-video component
could be restricted by region codes in a similar manner to a DVD-Video disc.
The table below summarizes the many different bit-rate/sampling rate/channel combinations supported by DVD-Audio:
It should be noted that:
For a detailed summary of the DVD-Audio specifications, please refer to the table below. This table includes also the corresponding specs for CD-DA (digital audio) disc; this should help make the comparison between the two optical media much easier.
DVD-Audio and Meridian Lossless Packing
Audio is stored on DVD-Audio discs either uncompressed - using Linear Pulse Code Modulation (PCM) format, or lossless compressed using Meridian Lossless Packing technology, also referred to as MLP Lossless™ (or simply MLP).
MLP Lossless™ is licensed by Dolby Laboratories; it is the core technology of DVD-Audio, providing up to 5.1 full-bandwidth channels of pure, lossless audio playback that is bit-for-bit identical to studio masters.
MLP Lossless enables producers to encode up to
six full-range channels of 96 kHz/24 bit audio, or two channels of 192
kHz/24 bit audio onto a DVD-Audio disc, using lossless encoding
technology - in other words, nothing is loss during the encoding and decoding process.
In other words, if the channel/resolution combination exceeds the maximum bitrate supported by DVD-Audio, lossless compression becomes mandatory. In uncompressed modes, it is possible to get up to 96kHz/16-bit or 48kHz/24-bit in 5.1 mode, and 192kHz/24-bit in stereo mode. MLP encoding is necessary to record 5.1 multi-track audio in 88.2kHz/24-bit, 96kHz/20-bit and 96kHz/24-bit.
DVD-Audio Sound Quality vs CD-DA
As indicated earlier on in our discussion, DVD-Audio does provide far better sound quality than CDs as a result of the higher resolution supported by the DVD-Audio format.
But to better appreciate this whole issue of better audio quality, it is important to first have an understanding of why a higher sampling frequency and a deeper sample bit-resolution lead to better sound.
Sampling frequency: A digital representation of an analog signal is as faithful to the source, as much as the digital to analog conversion is able to follow the original raw analog waveform. In an ideal world, a recording would yield an exact replica of the original signal. However, when it comes to a digital representation, the original source is represented by a series of samples taken at regular intervals - depending on the sampling frequency, and therefore, any data in between the samples is lost. Thus, opting for a higher sampling rate would enable the digital representation to follow more closely the signal source.
The diagram below compares the higher quality DVD-Audio digital representation of a 10kHz signal using a sampling rate of 192kHz, as against the 44.1kHz sampling resolution of a CD-DA output.
CD DA vs DVD-Audio: A digital representation of a 10kHz analog signal
At this point, many would argue that if the human hearing is limited to around 20kHz, then the 44100 samples per second supported by the CD-DA format should pose no problems to handle the full range of audible frequencies, as these would yield a maximum frequency response of over 22kHz.
This reasoning is based on Nyquist sampling theorem which states that for a band-limited signal, the highest frequency response is equal to half the sampling frequency. By band-limited, we understand a signal whose Fourier transform or power spectral density, is zero above a certain finite frequency.
The truth is that studies show that though the human hearing is generally very poor above 20,000kHz, yet it is very sensitive to phase distortions. Now, roll-offs in the ultrasonic frequency range component part of the signal, would produce phase and amplitude effects into in the audible part of the audio spectrum.
Thus, while sampling frequencies twice that what we can hear is a minimum requirement, it can be shown both mathematically and through various studies, that twice is not fast enough to accurately capture correctly the characteristic of the high frequency components of an audio signal.
The audible effects may be subtle, but undesirable. Thus, being aware of the human hearing sensitivity to phase distortions, it is only logical to presume that considerable decrease in the level of such distortions would result in the systems with a wider signal spectrum.
This means that higher sampling frequencies offer better accuracy in reproducing high frequency audio information of an audio signal.
Sample Depth (word length): The sampling rate is just one aspect out of the two that defines the resolution of a digital signal. Directly related to the sampling rate is the sample depth or sample bit-resolution - often referred to in PCM terminology as 'word length'.
Each sample of the analog signal is characterized by the magnitude of its voltage value, which in itself can take an infinite number of values. This is not the case with its digital representation, which can have only a finite number of values, depending on the number of bits used in the data word (a series of bits) that will eventually represent that sample value.
The more bits in the the data word, the wider the range of analog voltages that the digitized sample can represent; more bits also means finer gradations of values in that range - thus enabling the digitized sample to follow more closely the actual value of the analog signal.
This also means that the more bits representing a sample, the wider will be the difference between the softest and the loudest sounds that the system can handle. This is referred to as 'dynamic range' and represent the difference between floor noise and the loudest sounds.
The CD format supports a sample length of 16bits, leading to a dynamic range of about 96 dB (decibels). DVD-Audio supports various sample word lengths and including 20-bit and 24-bit audio. 20-bit yields around 120 dB while at its 24-bit maximum audio quality, DVD-Audio supports a dynamic range of approximately 144 dB.
With today's state-of-the-art audio system components supporting a signal-to-noise ratio of around -120dB, the 144dB is only theoretical in that the limiting factor at this point would turn out to be the noise level inherent in the electronics - mainly due to thermal noise. This means that at present, the 24-bit sample depth supported DVD-Audio is more than adequate.
Whether you will be able to hear the difference in sound quality between high resolution audio from a DVD-Audio and standard audio from a CD-DA is all a matter of the type of audio playback setup that you have. The difference is there and is significant - just try to play the same piece of music on CD and then switch on to DVD-Audio. If you have the appropriate audio playback setup, once you hear the sound from a DVD-Audio, you will surely be amazed at what you have been missing.
Backward Compatibility, DVD-Audio Players, and Content Protection
To ensure backward compatibility with DVD-Video players, most DVD-Audio discs contain, as a minimum, a Dolby Digital 5.1-channel audio track on the disc which can be downmixed to two channels by the DVD player for listeners with no surround sound setup. Some discs may also include a DTS 96/24 5.1-channel, soundtrack.
However, as already pointed out in our introduction on DVD-Audio and SACD, today, universal DVD players capable of handling DVD-Video, DVD-Audio, CD-DA, and even SACD are relatively inexpensive and are selling at under $150.
DVD-Audio Players and AV Receivers
In order to play DVD-Audio, you need a preamplifier or AV receiver with either six analogue inputs, or an encrypted digital interconnect. The reason being that while DVD-Video audio formats such as Dolby Digital and DTS can be sent via the player's digital output to a receiver for conversion to analogue form and distribution to speakers, DVD-Audio cannot be delivered via an unencrypted digital audio link at anything above ordinary DVD-Video quality (i.e. 48kHz sampling rate), due to concerns about digital copying.
Approved encrypted digital formats by the DVD Forum include Meridian Audio's MHR (Meridian High Resolution) and HDMI (High Definition Multimedia Interface 1.1 or higher. In view that HDMI encryption is different from the DVD-A encryption, the DVD player will have to decrypt the six audio channels, then re-encrypted into an HDMI signal and sent to the amplifier or AV receiver which will then decrypt the digital signal and to extract the 6 high definition audio channels.
It should be noted that when working with an encrypted digital interconnect like HDMI with HDCP, all devices in the playback chain will have to be equipped with a valid decryption key, otherwise, it would not be possible to play the DVD-Audio disc. More on HDMI and HDCP can be found under the respective sections of the side.
As already hinted in the previous section, you would not be able to get an unencrypted digital out from a DVD-Audio player. The reason is copyright protection. DVD-Audio discs employ a copy protection mechanism called Content Protection for Prerecorded Media - more commonly referred to as CPPM.
CPPM is managed by the 4C Entity - 'the four company entity', a consortium formed by IBM, Intel, Matsushita and Toshiba to establish a common platform for digital rights management schemes.
CPPM is used to prevent users from extracting the raw digital audio stream to computers and portable media players. In other words, it is used to prevent a bit-for-bit of the DVD-Audio digital content. It is a far superior encryption mechanism than the content scrambling system originally devised for use on DVD-Video discs as it makes use of a media key block (MKB) to authenticate the DVD-Audio player.
The player must use its own unique key to decrypt the MKB. If a DVD-Audio player's decryption key is compromised, that key can be rendered useless for decrypting future DVD-Audio discs. This is somewhat similar to the HDCP content protection scheme designed to eliminate the possibility of intercepting digital video and audio data as it travels between source and display across Digital Visual Interface (DVI) and High Definition Multimedia Interface (HDMI) connections.
DVD-Audio discs also supports the use of digital watermarking technology. This is optional and is used to deal with analog piracy by detecting illegal copying through the analog path. This means that when used, digital watermarking is audible - though not necessarily to the human ear - in that it can be picked up along the analog copy and detected through the use of appropriate gear.
However, there is a lot of controversy surrounding the use of digital watermarking in high resolution audio content in that while those in favor says it is inaudible to human listening due to its inherent subtlety, yet others say that it is detectable under certain instances.
Audio Playback Setup for DVD-Audio
As indicated earlier on in our discussion, DVD-Audio supports a much wider dynamic range than CD sound. In other words, if you want to get the very best in music quality when listening to DVD-Audio, you need to have the appropriate setup, not just a DVD-Audio player or a universal DVD player supporting DVD-A. In particular, a good quality preamplifier/surround sound processor with a signal-to-noise ratio of at least -110dB is desirable.
Further more, if you plan to listen a lot to DVD-Audio seriously, you will also need to consider investing in five identical, full-range speakers. The problem is that from a practical perspective, it is difficult to make use of a floor-standing speaker for the center channel if your audio system also serves as part of your home theater setup. This in view that in a home theater implementation, the center speaker is usually placed horizontally orientated just under or above the TV - unless you make use of a front projection setup and an acoustically transparent projection screen, in which case a floor standing center speaker placed centrally just behind the screen would do a nice job for both music listening and movie viewing.
However, more important than the center speaker is having four identical speakers for the left/right front speakers and the left/right surround speakers. We are not saying that making use of the same audio setup used for a home theater implementation would not suffice; it is just that it is not the very best setup for DVD-Audio playback. At the same time, one has to keep in mind that there is also a financial implication to invest in four or five identical full range speakers.
Another issue is speaker placement. As pointed out in our article on speaker placement in the home theater, speaker placement for music listening differs from that for movie viewing. We suggest to go through our speaker placement article for the relevant details. If your audio playback setup will serve you for both music listening and movie viewing - as is the case with most home entertainment setups, the best approach would be to opt for a flexible speaker mounting solution that would enable you to easily adjust your speaker placement for both purposes.
What if for practical reasons, you will instead be making use of the same 5.1-channel speaker set-up that you have for home theater rather than a set of dedicated four or five identical full range speakers?
Sure, you can still enjoy DVD-Audio - just make sure that the DVD-Audio player has adequate bass management support that allows you to route the bass frequencies to those speakers that can handle it best. At the same time, keep in mind that these compromises are less than ideal for the very best in DVD-Audio experience.
This article would not be complete without mentioning something on the availability of DVD-Audio content.
The first DVD-Audio content first appeared in around 2000. The first label to release DVD-Audio titles was Silverline / 5.1 Entertainment; it was soon followed by other major music labels including Warner Bros. Records, Universal Music and EMI.
Initially, take-up was slow. Today, the availability of relatively inexpensive universal DVD players and with DVD-Audio discs priced at CD level, is helping this high resolution audio format to catch up with more music lovers.
Selection is still very much limited though we are starting to see more than 10 to 15 new title releases every month. At present, the DVD-Audio catalog includes several hundred titles ranging from Bach to Beethoven, Eric Clapton to Seal, Beatles to Mark Knopfler, Queen... covering all sort of music genres, from classical concerts to rock, pop, jazz, etc.
An interesting development in the area of DVD-Audio discs is the move towards the release of CD/DVD packages and DualDisc rather than standalone DVD-Audio releases. In fact, a number of titles originally released as DVD-Audio discs, are being re-packaged accordingly.
CD/DVD-Audio packages would include two separate discs, a CD and a DVD, with the same music content being available on both - thus enabling those with no access to a compatible DVD player, to use the CD for music listening. Further more, the DVD would normally include some bonus material as well as the 5.1 surround sound and stereo content presented in both DVD-Audio MLP, DTS, and Dolby. This also means that the DVD can also be played using a conventional DVD-Video player to enjoy standard DVD-Video quality 5.1 surround.
The DualDisc is an interesting development over the separate CD/DVD pack in that the two are now literally fused to form a single disc - in other words, no more two discs, but one disc that has it all!
This two-sided disc is made up of a CD on one side and a DVD with DVD-Audio content on the other.
In reality, the DVD side may contain all sorts of other bonus material found on DVD, not just the DVD-Audio, but video footages, lyrics, as well Dolby Digital and DTS sound tracks for compatibility reasons.
It is a new medium that has something for everyone - a CD side that is playable in any CD player, and a DVD side that may deliver enhanced sound for audiophiles and other bonus material for music lovers like music videos, artists interviews, photo galleries, song lyrics, etc.
An extensive range of CD/DVD-Audio DualDisc titles covering all sorts of genres, is available online at our home theater store under the Music - DualDisc category of the store.
DVD-Audio - Still unsure if it is the way to go?
If you are unsure but interested, our advise is to go to your local home theater retail store and arrange for a demo. Possibly, get hold of a CD/DVD pack having the same pieces of music and listen to a couple of tracks on both the CD and the DVD-Audio; switch back and forth between the two to better appreciate the difference. The probability is that you would not leave the store without a brand new compatible DVD Audio player!
More Information at
Practical Home Theater Guide
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Speaker Placement in Multi-Channel Audio Proper speaker placement is necessary to achieve a seamless...
Settings in Surround Sound Systems
TV Viewing Distance
Home Theater Design:
Room acoustics and lighting
Guide to Home Theater Seats
Theater Equipment Placement
Selecting and Installing Speaker Wire
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