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'.
A 3D Blu-ray disc player capable of excellent AV performance. It comes with an impressive feature list - including SACD/DVD-A playback, 4K upscaling, 2D-3D conversion, DLNA networking, and wireless Internet streaming.
Connectivity and Playback Requirements between compatible Disc Players & AV Receivers
To play DVD-A music, you need a compatible DVD/Blu-ray disc player with DVD-A support and an AV receiver with either six analogue inputs or an encrypted digital I/P.
While DVD-Video audio formats such as Dolby Digital and DTS can be sent via a player's unprotected digital output to a receiver for conversion to analogue form, this is not the case with DVD-A.
Send DVD-A content over an unencrypted digital link and you will end up with CD-quality audio. Sending high resolution DVD-A content over an unencrypted digital interconnect will trigger the content protection mechanism to force the disc player to downgrade to ordinary DVD-Video audio quality (48kHz sampling rate), due to concerns with digital copying. Approved encrypted digital links 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.
Note: 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.
As already hinted in the previous section, you cannot 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-A 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-A 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 a 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 in the first part of this discussion, DVD-A 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 content, 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.
Furthermore, if you plan to be serious about listening to DVD-Audio content, 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 type of center speaker is matching the center channel speaker tonality with the rest of the speaker setup; this is referred to as speaker timbre matching as further explained in our guide to speaker selection in multi-channel audio.
The rest of the speakers, namely, the main left and right front speakers and the left and right surround speakers should ideally be identical.
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; and this applies to any high resolution audio listening. 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 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 either your DVD-A player or AV receiver employs 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.