LINGUIST List 4.739

Tue 21 Sep 1993

Sum: The MiniDisc

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1. Celso Alvarez-Caccamo, Sum: The MiniDisc for linguists

[This message is being cross-posted to four lists]L

A while ago I asked about the possible use of the new digital
mini-disc (MD) (SONY, AIWA, SHARP) for recording and/or making
backup copies of speech data. I wanted to know about its sound
quality, reliability, and foreseeable future in the market. The
message was distributed to four lists: LINGUIST, ETHNO (Comserve),
MD-L (a list on the technical aspects of the mini-disc; thanks to
Ernie Limperis for the lead), and LLTI (Language and Learning
Technology; thanks to Bert Peeters for the lead). The volume of
responses offering information was unexpectedly low. I got no
feedback from linguists using the MD. Apparently very few
linguists working on spoken data have moved into digital
technology. Am I right? However, some linguists showed interest
in knowing what I got.

These are the contributors to my query, from the four lists.
Thanks to all of them:

(Ernie Limperis) <ernienli.com>
bert peeters <peeterspostoffice.utas.edu.au>
Janik Joire <janikgfx.engga.uwo.ca>
(David Bogartz) <bogartzzdi.ziff.com>
<Bruce_Chapmanvos.stratus.com>
Rick Pering <peringhplrick.hpl.hp.com>
(Daniel MacKay) <danielnstn.ns.ca>
Susann Luperfoy <susannstarbase.mitre.org>
(ca2) <Carolyn_T_ADGERumail.umd.edu>
Robert D Hoberman <RHOBERMANccmail.sunysb.edu>
Kimberly Jones <KJONESARIZVMS.bitnet>
<ASHELDONvx.cis.umn.edu>
David Stampe <stampeuhunix.uhcc.Hawaii.Edu>
Susan Hill <HILLUMBC2.UMBC.EDU>

And this is what I got:

The MiniDisc uses a laser beam to record and read digitally coded
data. It works by compressing the digital data with a 4-1 ratio
compressing algorithm, and it's able to fit 600 megabytes (!) of
memory on a 128 MB disc. As for frequency response, it handles up
to 15 khz, which should be good enough for human voice. Each disc fits
at least 60 minutes of sound (some fit 74). The MD will play back
the same disc 1,000,000 times without losing data. It has an LCD
(Liquid Crystal Display) screen for viewing the track's number and
label (programmable). As for battery autonomy, it can record up
to 60 m. and play back 75 m.

Models: There are now three types of MD in the market: portable
(recorder/player and only player), home unit, and car model. I
guess that the portable model is the most useful for linguists, as
it can also be easily plugged in an amplifier, for reproduction
and backup copies.

Reportedly, resistance to movement in the portable model is
"excellent", as the MD uses a 10-second buffer to prevent skips
from disturbing the flow of sound. The buffer remains filled with
data after a shock for the laser to resume proper decoding. This
feature is a must for linguists in the field.

Sound quality: In my respondents' and my own experience (I tried
the MD once to record voice), sound quality is excellent.
Background noise is practically zero (I couldn't perceive any).
One person compares its sound to that of a CD. In someone else's
opinion, the DAT (Digital Audio Tape) is still ahead.

Access time, editing and programming: Reportedly, the access time
is as fast as (or faster than) one in a CD. The MD is excellent
for editing, programming, and listening to the recording over and
over. One obvious application: if you program a minidisc track,
or a number of them, then you can very easily copy segments of it
to tape without having to go back and forth. This feature should
be great for transcription, analysis, class sessions, talks, etc.

Bruce Chapman explains how the track programming and deletion
work:

 "The ability to delete tracks from anywhere on the disk is
 great, too; however, the MZ-1 [the SONY portable model]
 doesn't allow you to "permanently" make track 1 into track 9
 without deleting 1 and re-recording it as 9. It also appears
 that you can only record FIFO (first-in,first-out) - If I have
 5 tracks recorded I cannot record a sixth over the first one
 without losing the other 5 (I could record it over the fifth,
 only losing that track). In summary, you have the ability to
 delete any track and the space for it will be reclaimed for
 later recordings, but you do not have complete flexibilty in
 swapping tracks (short of using the programmed play mode, but
 this has to be done every time you put the disk in)."

Here are some of the problems reported in these early models (most
comments refer to the portable SONY MZ-1):

o overheating when recording with the AC/DC converter, since it's
 so compact and it uses laser. The LCD indicator tells you to
 wait until the unit cools down. Perhaps this doesn't happen
 with the desk units. It doesn't happen when playing back. May
 be due to the fact that the electronics use up a lot of power.

o "multiple generation copies": A couple of people said that
 after the 10th generation of digital copies (MD-MD) frequencies
 start to be lost. This refers to digital copies, not to the
 original MD, of course. So, it seems good enough.

o if a digital disc gets damaged, it may happen that no
 information can be retrieved, whereas, with a tape recorder,
 you could always get something out of it. This could represent
 a *serious* problem for linguists, as conversational data are
 irrepetible. The best strategy would be to record and make a
 backup copy immediately after in MD or DAT.

o Frequency response: The MD "clips off" extremely high or low
 frequencies/volumes, when the chip doesn't recognize a high/low
 coded number. The MD "runs out of dynamic range", which means
 that when the signal level is codified in too high a number, it
 can't be stored in the digital medium, and the number (and
 signal) is "clipped". This produces some distorsion, but for
 all practical purposes the effects on human voice may be
 negligible.

o As for the future of the MD, Daniel Mckay thinks that "The
 discs could well outlive the availability of the players -- in
 25 years' time, will you be able to find a MD player to play
 all of your mint-condition MDs?" This may sound as a little
 exaggerated, though. Apparently SONY is making all sorts of
 efforts to ensure that its first MD customers are fully
 satisfied, so as to guarantee the MD's continuity. My main
 concern is that, at least, the MD wouldn't have the same future
 as the Beta video system.

o Some mechanical problems reported with early units: head
 movement, buttons sticking, etc.

In short, the MD seems as a promising technology -- when recorder
and disc prices go down! (the MZ-1 sells for about US$700, and
each 60-minute tape is about US$15 or equivalent). One obvious
advantage is the future computer treatment, analysis, and
manipulation of digitalized voice, when interfaces and software
are developed and accessible. One obvious drawback that I see is
the impossibility (in current MD models) to slow down the
recording for easier transcription -- particularly when dealing
with conversational data.

When I move into MD for recording speech, I'll keep you posted.
If SONY knew that there were, say, a couple of thousand (?!)
linguists interested in the MD technology, they might try to help
us get what we want: self-transcribers! One person from the MD-L
list (I think) suggests that minidiscs could reserve more space
for text data, so that entire songs (or conversations) could be
entered and displayed either on the LCD or on an external monitor.
Clearly, the future is the interface between digital recorders and
computers, and the integration of text and sound.

Celso Alvarez-Caccamo
Depto. de Linguistica Geral e Teoria da Literatura
Universidade da Corunha, Galiza, Spain
lxalvarzudc.es