Digital Information Exchange 1987 (part 1)
The Digital Information Exchange is now in its fourth year and shows no sign of outliving its purpose. It seems that the more information you have about digital technology and applications, the more you need. And perhaps one of the most important attributes of the aware sound engineer is the ability to differentiate between knowledge useful in the workplace, and the sort of knowledge that is more the province of design and production engineers. At the Digital Information Exchange, both kinds of knowledge are on offer. Take what you need, and file the rest for possible future reference.
Day 1 of the DIE was devoted to Broadcast applications. Like it or not, the previously insular sound and video, studio and broadcast fields are rapidly coming together onto a multi-media common ground. Actually, people seem to like it, and for studio personnel Day 1 offered a fascinating insight into these related fields.
Following a welcome from Ian Jones from HHB and a brief introduction from the excellent chairman Nick Hopewell-Smith, the first presentation was from Neil Gilchrist of BBC Research on Digital Stereo for Television.
Transmitting digital stereo into the home is not a straightforward matter. 16-bit stereo, as we know and love it in the CD format, is ruled out because it cannot be fitted into the existing bandwidth available for each TV channel. Neil first outlined the possible alternatives, such as the pilot tone system as used in stereo FM radio which would be susceptible to noise and distortion. Also the Sound in Syncs system which is already used for programme distribution, but which cannot be made compatible with all existing TV receivers.
NICAM 728 is a development of the BBCs NICAM 3 system which uses near instantaneous digital companding to provide a rugged signal, decodable in a NICAM receiver, yet able to co-exist with the FM mono signal as transmitted currently, and can fit into the television bandwidth. Neil explained how a carrier may have its phase shifted to any of four states to convey blocks of bits, representing the sound signal.
TV viewers in the London area, if they have a NICAM-ready TV or video, can already benefit from unannounced test transmissions in digital stereo. A VHS cassette with NICAM sound played as part of the presentation demonstrated that the system is an order of magnitude better than a conventional VHS audio track and likely also to be superior to so-called hifi VCRs.
Mike Bennett of Sony Broadcast took the stage to explain how well digital technology is penetrating Eastern Europe. Many countries are recording digitally, in stereo and on multitrack, and are manufacturing CDs. Two problems - it can take up to four years to order a piece of equipment from the West, getting the necessary licences and foreign currency. Also, there are very few CD players as yet, and therefore practically no home market.
Al Hart from Modern Videofilm in Hollywood is engaged in bringing that bastion of archaic technology, the film industry, into the late 1980s. Al explained a few home truths about the six track magnetic film recorders currently in use. Like how it can take up to eight hundred reels of mag film to make up the sound for a feature film, and also how lucky you will be if you are not plagued by problems such as noise and azimuth misalignment. Als concern was to get digital technology in the system at a point where it would stop the quality rot - at the dubbing stage.