Last-modified: 21 January 1998
Copyright: © 1994, 1995, 1996, 1998 by Martin J Leese
Distribution is unlimited
A consortium has announced a Digital Versatile Disc format which can contain between 6 and 22 times as much data as the current audio CD format. (The higher figure is for a double-sided double-layered disc.) The proposal for an audio-only version of DVD, called High-Quality Audio Disc, has been released by the Acoustic Renaissance for Audio. The proposal, which is available on the ARA Web page, is for:
To carry Ambisonic Surround Sound the proposal suggests encoding the W, X, Y and Z signals onto the DVD as a set of five feeds for speakers arranged in a regular pentagon, plus an optional height channel. These either can be reproduced directly using the standard five speaker layout, or the W, X, Y and Z channels can very simply be reclaimed for processing by an Ambisonic decoder. I guess that the five speaker feeds will not include psychoacoustic shelf filtering.
HQAD is the first real opportunity for periphonic (full-sphere) Ambisonic source material to be released commercially. A periphonic decoder was demonstrated as long ago as 1980, but to date domestic full-sphere surround sound reproduction has been enjoyed only by a few enthusiasts with access to Ambisonic master tapes. The advent of HQAD and its accommodation of Ambisonics will, for the first time, bring full-sphere surround sound within the reach of everybody.
The advantages of periphony over horizontal surround sound are not only the possibility of using height for special effects but also that recordings sound more lifelike and less "hi-fi". For example, the timbre of orchestral instruments has the "feathery" quality heard at live events.
Practical periphony requires a minimum of six or eight speakers, some of which must be placed above and below the height of the listeners' ears. Readers interested in seeing the various speaker layouts which are possible should consult the Gerzon 1980 reference.
Of course, horizontal Ambisonic decoders will still be able to produce "no compromise" horizontal surround sound simply by ignoring the Z (height) signal.
Copies of A Proposal for the High-Quality Audio Application of High-Density CD Carriers (Version 1.3) can be obtained from:
J R Stuart, Chairman ARA
c/o the Secretariat
Acoustic Renaissance for Audio
Cambridgeshire PE18 6ED
E-mail: ara meridian-audio.com
Hirokazu Negishi, Founder ARA
Research & Development Headquarters
Cannon Inc Shinjuku Office
7-1 Nishi-Shinjuku 2-chome
E-mail: negishi gcds.cannon.co.jp