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Japan’s giant of consumer electronics, Matsushita, has set the stage for a
repeat of its ‘video war’ with Sony – this time over audio digital
recording.

At a private technical seminar last week engineers from Matsushita’s
headquarters in Osaka staged experiments designed to expose technical
defects in Mini Disc (MD), Sony’s digital audio system. They also played up
the benefits of the Digital Compact Cassette system, developed by Philips of
the Netherlands. Matsushita sells DCC systems through its Technics and
Panasonic subsidiaries, and has been closely involved with DCC’s development
since 1989.

Although Matsushita has long been a rival of Sony, it usually avoids public
wrangles. Almost two decades ago its technically inferior but more popular
VHS video system defeated Sony’s Betamax.

However, the issues involved in the ‘audio war’ are less clear. Sony has
emphasised that MD is more portable, resilient and easy to use than CD
players and especially DCC players. But now Matsushita is trying to force
the battle into one of sound quality.

Although DCC uses magnetic tape, and MD uses discs coated with a
magnetooptical medium that makes them erasable, both systems rely on data
compression to reduce the number of bits per second that they record.
Philips’s system reduces the number of bits by 75 per cent, while Sony’s
reduces it by 80 per cent.

Matsushita’s first tests analysed MD and DCC recordings of test tones and of
square wave pulses, which are theoretically the sum of every frequency.
These showed that DCC was faithful up to the extreme limit of human hearing,
around 20 kilohertz, while MD reproduced little sound over 15 kilohertz –
though this is the limit of most people’s hearing.

Tadashi Abe, general manager in charge of Matsushita’s DCC development, says
‘The sound disappears, making it more like FM radio than digital audio.’

Abe believes that DCC copes better with high frequencies, and sounds
‘brighter’, because its encoding splits the sound into more frequency bands
before analysing them, thereby making better use of the available bits.

Abe also recorded music from a CD onto both DCC and MD, and then copied the
copies. (Domestic users could not do this because of anti-piracy circuits
built into their systems.) Abe showed that in MD the process exaggerates any
distortion introduced by the recording circuitry. Even after one extra copy,
MD added a rough edge to the sound of a solo trumpet. After 10 copies, a
harpsichord sounded like an old bar-room piano. In each case DCC did
comparatively little damage to the sound.

Abe’s most telling test subtracts a recording made using data compression
from the original music. This leaves a difference signal which represents
the musical content omitted by the compression circuit. When DCC was used to
record castanets, which produce percussive high frequency sounds, the
difference signal was a light rhythmic tizz. With MD the difference signal
was louder and stronger, showing that the compression circuit had omitted
more musical content.

A spokesman for Sony, which had no advance warning of the tests, says: ‘You
can always lean any comparison of sound quality in whichever way you want.
We will be looking into what was said about MD.’