A Guide to DVD-Audio Discs (2)
Connectivity Requirements, Playback Setup and Content Protection

Our discussion on DVD-Audio continues by looking at the connectivity requirements between DVD players and AV receivers; we also discuss the correct playback setup for DVD-A listening.

In the process, we will touch upon a rather hotly debated issue among Audiophiles - content protection and the use of 'digital watermarking'.

Connectivity Requirements
between Compatible DVD Players and AV Receivers

In order to play DVD-A music, you need a compatible DVD player that can handle DVD-A discs, and a preamplifier or AV receiver with either six analogue inputs or an encrypted digital interconnect.

While DVD-Video audio formats such as Dolby Digital and DTS, can be sent via a player's unprotected digital o/p to a receiver for conversion to analogue form, this is not the case with DVD-A.

If you try to send DVD-A digital content over an unencrypted digital audio link, the content protection mechanism will force the DVD-Audio player or compatible DVD-player to downgrade to  ordinary DVD-Video audio 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. This 'new' digital signal is then sent over HDMI to the amplifier or AV receiver which will then decrypt the digital signal to re-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 site.

Copy Protection

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 copy 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 in concept to the way the HDCP content protection scheme works, except that HDCP is 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 support 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

Having a DVD-audio player or compatible universal DVD player and an AV receiver is only part of the game. If you want to get the very best out of your DVD-Audio listening, then there is the need for more.

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/-120dB 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. This problem would not arise when making 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 going 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 your home 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 such a compromise is less than ideal for the very best in DVD-Audio listening experience.

More on the DVD-Audio Disc will follow soon.	Last updated on: 10th February 2007
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  ...Part 3: DVD-Audio Titles, CD/DVD packages and DualDisc releases

...back to DVD-Audio/SACD Section Index

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