Technology

MiniDisc overview by Tadao Yoshida, October 1994: IEEE overview

ATRAC overview, October 1992: AES overview

A Magneto-Optical Disc is an Optical Disc technology that allows data to be written to a disc by a magnet head once the disc has been heated up to its curie point, typically done by a laser. After this process the disc can be read by a laser in a similar way to most modern optical discs. This technology was used for the MiniDisc format and allowed MiniDiscs to be rewritable well before CD-RWs entered the market. It's worth noting that the Orange Book Standard for Compact Discs does have a standard for CD-MO, which would have been a rewritable Magneto-Optical CD, however the standard was never used in a commercial product. 1)

MDLP is a way of extending the amount of music that is stored on a single MiniDisc - on an 80 min disc in SP (standard play), you can store 160 minutes in LP2 and 320 minutes in LP4 (note that this is Joint Stereo, where left and right channels are smushed together)

Due to the way MDLP stores the music, an LP2 or LP4 encoded track will play back as silence on a machine that doesn't support MDLP.

A mix of SP, LP2 and LP4 may be recorded on the same disc. Note that if you're recording a lot of tunes in LP4, you may run out of characters while naming tracks (1785 characters total, max)

Overview

Announced in mid-2001 and first introduced on the Sony MZ-N1 portable recorder in December of the same year, NetMD is an extension to the Minidisc format that allows direct transfers of compressed, ATRAC audio from a PC to Minidisc via USB interface. Audio transfers can be conducted at rates considerably faster than real time (up to 64x for LP4 audio on certain units).

When NetMD was first introduced, it included a frustrating “Check In/Out” system via the OpenMG and SonicStage software, which prevented you sending the same song to more than 3 MiniDiscs until a Check-In had wiped the track from one of those three discs. This has since been abandoned, likely due to the fact that you can't bring data from a standard NetMD back to a PC without re-recording it (Hi-MD can do this).


1)
Upgrading and repairing PCs By Scott Mueller, page 739: “The Orange Book comes in three parts: Part I describes a format called CD-MO (magneto-optical), which was to be a rewritable format but was withdrawn before any products really came to market”
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