LINGUIST List 4.796

Tue 05 Oct 1993

Disc: CD Technology

Editor for this issue: <>

Directory

1. Sherman Wilcox, Recording to CD
2. David Powers, Re: 4.783 Technology: CD vs MiniDisc

Eric Adolphson writes:

>CD's, as I'm sure everyone is aware, is a permanent media. It cannot be
>>recorded to.

This isn't quite accurate. CDs certainly can be recorded to, but only once
per "session". My company owns a CD mastering unit that we use for
recording digital (QuickTime) movies of American Sign Language. We can
record to the CD (easily done on the Mac, it's the same operation as
copying to any other type of volume: drag the items to the CD's desktop or
any folder on it). It takes approximately one hour to record an entire CD
(all 600+ Mbytes). Once recorded the data is permanent, but multiple
sessions can be recorded onto the same CD. Cost of this equipment was
$4000.

Message 2: Re: 4.783 Technology: CD vs MiniDisc

> It always seems strange to read discussions on recording equipment in
 Linguist.
> The main reason I say this is it is often strangely misinformed. Here's some
> history of the different digital recording formats, and the pluses and
 minuses.
>
>
> DAT, CD, MiniDisc and DCC.
>
> CD's, as I'm sure everyone is aware, is a permanent media. It cannot be
 recorded
> to. There is some confusion with CD's and Magneto-Optical drives. Magneto op
> Optical is a recordible CD. They are very expensive at present, but might well
> be the removable hard drive of the future.

There are several manufactures (e.g. Sony, Philips) offering writeable CDs -
that is ability to write a true CD that can be read on conventional players.
But it is a write-once capability. There is absolutely no relationship between
MO (Magneto-Optical) devices and CD's. The technology is completely different,
and the media mutually incompatible - in addition the capacity is at present
lower for MO, but they are faster than CD.

> True DAT is not available for the general public. It has been available over
> seas for years, but, because it allows for multiple generations of copies, it
> was blocked in this country by the recording industry who feared limitless
> CD quality tape piracy. Again, editing on these systems is primitive, but that
> is not what they are for. They are simply a recording system. There are some
> "editing" DAT systems out there. They operate similarly to older mult-deck
> tape recording systems, with all of the expertise of operation.

DAT was an ad hoc technique using video technology. Device are
expensive and cumbersome (although there is a portable DAT player
available). The big problem is the helical scan approach taken from
video technology. Editing is intrinsically a problem with such
technology.

> To get around the fears of the recording industry, Phillips produced the DCC f
> format, and Sony, the mini-disc. Both use a compression format, mainly to
> cause loss of signal over generation copying. Thus, they were allowed to offer
> them in the US. Of the two, DCC has better fidelity. Again, they are not for
> editing-- they are simply meant to record pre-edited audio.

That is the cynical view. In fact compression allows using simpler
hardware, and in particular mechanics. The Philips approach is
carefully tuned to the frequency characteristics of the ear in an
attempt to get the maximum compression without compromising quality
unduly. These digital devices use mechanisms to detect copying of a
copy of a CD, and ensure that further copies are made Analog, to
address the pirating concerns. The players are also compatible with
the standard (Philips) Compact Cassette. They are in my view the best
solution on the market. The Sony mini-disc took the industry by
surprise, as it was not clear what markets it would actually end up
competing with, and what it was actually intended to replace. It is
not likely to be supported by cross-licensing in the way Philips DCC
standard is.

> Now, DAT (Truest fidelity), DCC, Mini-disc, and good old analog tape are all
> fine media for copying. If you want full editing in the digital domain, you
> use a computer with the appropriate DSP board and a big hard disc.

Yes proper editing requires sophisticated capabilities, and computational
power. However, the DCC would be completely adequate for linguists' purposes.

(I have no connections with the industry other than as a user with contacts.
These are my personal evaluations and I represent nobody else's views.)

David Powers