MiniDisc


MiniDisc is a discontinued erasable magneto-optical disc-based data storage format offering a capacity of 60, 74, or 80 minutes of digitized audio.
Sony announced the MiniDisc in September 1992 and released it in November of that year for sale in Japan and in December in Europe, North America, and other countries. The music format was based on ATRAC audio data compression, Sony's own proprietary compression code. Its successor, Hi-MD, would later introduce the option of linear PCM digital recording to meet audio quality comparable to that of a compact disc. MiniDiscs were very popular in Japan and found moderate success in Europe. Although it was designed to succeed the cassette tape, it did not manage to supplant it globally.
By March 2011, Sony had sold 22 million MD players, but discontinued further development. Sony ceased manufacturing and sold the last of the players by March 2013. On January 23, 2025, Sony announced they would end the production of recordable MD media in February 2025.

Market history

In 1983, just a year after the introduction of the compact disc, Kees Schouhamer Immink and Joseph Braat presented the first experiments with erasable magneto-optical compact discs during the 73rd AES Convention in Eindhoven. It took almost 10 years, however, before their idea was commercialized.
Sony's MiniDisc was one of two rival digital systems introduced in 1992 that were intended to replace the Philips Compact Cassette analog audio tape system: the other was the Digital Compact Cassette, created by Philips and Matsushita. Sony had originally intended the Digital Audio Tape to be the dominant home digital audio recording format, replacing the analog cassette. Because of technical delays, the DAT was not launched until 1989, and by then the U.S. dollar had fallen so far against the yen that the introductory DAT machine Sony had intended to market for about $400 in the late 1980s then had to retail for $800 or even $1,000 to break even, putting it out of reach of most users.
Relegating DAT to professional use, Sony set to work to come up with a simpler, more economical digital home format. By the time Sony came up with the MiniDisc in late 1992, Philips had introduced a competing system, DCC, on a magnetic tape cassette. This created marketing confusion very similar to the videocassette format war of the late 1970s and early 1980s. Sony licensed MD technology to other manufacturers, with JVC, Sharp, Pioneer, Panasonic and others producing their own MD products. However, non-Sony machines were not widely available in North America, and companies such as Technics and Radio Shack tended to promote DCC instead.
Despite having a loyal customer base largely of musicians and audio enthusiasts, the MiniDisc met with only limited success in the United States. It was very popular in Japan and parts of Asia, and relatively so in Europe during the 1990s and into the 2000s, but did not enjoy comparable sales success in other markets. Meanwhile, recordable CDs, flash memory and HDD and solid-state-based digital audio players such as iPods became increasingly popular as playback devices.
The slow uptake of MiniDisc was attributed to the small number of pre-recorded albums available on MD, because relatively few record labels embraced the format. The initial high cost of equipment and blank media was also a factor. Additionally, home MiniDisc decks were less widely available, with most consumers instead connecting a portable MD device to their hi-fi system in order to record.
MiniDisc technology was faced with new competition from the recordable compact disc when it became more affordable to consumers beginning around 1996. Initially, Sony believed that it would take around a decade for CD-R prices to become affordable – the cost of a typical blank CD-R disc was around $12 in 1994 – but CD-R prices fell much more rapidly than envisioned, to the point where CD-R blanks sank below $1 per disc by the late 1990s, compared to at least $2 for the cheapest 80-minute MiniDisc blanks.
The biggest competition for MiniDisc came with the emergence of MP3 players. With the Diamond Rio player in 1998 and the Apple iPod in 2001, the mass market began to eschew physical media in favor of more convenient file-based systems.
By 2007, because of the waning popularity of the format and the increasing popularity of solid-state MP3 players, Sony was producing only one model, the Hi-MD MZ-RH1, available as the MZ-M200 in North America packaged with a Sony microphone and limited macOS software support.
The MZ-RH1 allowed users to freely move uncompressed digital recordings back and forth from the MiniDisc to a computer without the copyright protection limitations previously imposed upon the NetMD series. This allowed the MiniDisc to better compete with HD recorders and MP3 players. However, most pro users like broadcasters and news reporters had already abandoned MiniDisc in favor of solid-state recorders, because of their extended recording time, open digital content sharing, high-quality digital recording capabilities and reliable, lightweight design.
On 7 July 2011, Sony announced that it would no longer ship MiniDisc Walkman products as of September 2011, effectively killing the format.
On 1 February 2013, Sony issued a press release on the Nikkei stock exchange that it would cease shipment of all MD devices, with last of the players to be sold in March 2013. However, it would continue to sell blank discs and offer repair services. Other manufacturers continued to release MiniDisc players long after Sony stopped, with TEAC & TASCAM producing new decks up until 2020 when both its consumer and professional products, TEAC MD-70CD and TASCAM MD-CD1MKIII, were discontinued. In January 2025 Sony announced that production of blank MiniDiscs would be discontinued.

Design

Physical characteristics

The disc is fixed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically when inserted into a drive. MiniDiscs can either be blank or prerecorded. Recordable MiniDiscs use a magneto-optical system to write data: a laser below the disc heats a spot to its Curie point, making the material in the disc susceptible to a magnetic field. A magnetic head above the disc then alters the polarity of the heated area, recording the digital data onto the disk. Playback is accomplished with the laser alone: taking advantage of the magneto-optic Kerr effect, the player senses the polarization of the reflected light as a 1 or a 0. Recordable MDs can be rerecorded repeatedly, with Sony claiming up to one million times. By May 2005, there were 60-minute, 74-minute and 80-minute discs available. 60-minute blanks, which were widely available in the early years of the format's introduction, were phased out.
MiniDiscs use a mastering process and optical playback system that is very similar to CDs. The recorded signal of the premastered pits and of the recordable MD are also very similar. Eight-to-Fourteen Modulation and a modification of CD's CIRC code, called Advanced Cross Interleaved Reed-Solomon Code are employed.

Differences from cassette and CDs

MiniDiscs use rewritable magneto-optical storage to store data. Unlike DCC or the analog Compact Cassette, MiniDisc is a random-access medium, making seek time very fast. MiniDiscs can be edited very quickly even on portable machines. Tracks can be split, combined, moved or deleted with ease either on the player or uploaded to a PC with Sony's SonicStage V4.3 software and edited there. Transferring data from an MD unit to a non-Windows PC can only be done in real time, preferably via optical I/O, by connecting the audio out port of the MD to an available audio in port of the computer. With the release of the Hi-MD format, Sony began to use Mac OS X-compatible software. However, the Mac OS X-compatible software was still not compatible with legacy MD formats. This means that an MD recorded on a legacy unit or in a legacy format still requires a Windows PC for faster than real-time transfers.
The beginning of the disc has a table of contents, which stores the start positions of the various tracks, as well as metadata and free blocks. Unlike a conventional cassette, a recorded song does not need to be stored as one piece on the disc and can be scattered in fragments, similar to a hard drive. Early MiniDisc equipment had a fragment granularity of four seconds of audio. Fragments smaller than the granularity are not monitored, which may lead to the usable capacity of a disc shrinking over time. No means of defragmenting the disc is provided in consumer-grade equipment.
All consumer-grade MiniDisc devices have a copy-protection scheme called the Serial Copy Management System. An unprotected disc or song can be copied without limit, but the copies can no longer be digitally copied. However, as a concession, the last Hi-MD players can upload to PC a digitally recorded file which can be resaved as a WAV file and thus replicated.

Audio data compression

The digitally encoded audio signal on a MiniDisc has traditionally been data-compressed using the ATRAC format.
ATRAC was devised to allow MiniDisc to have the same runtime as a CD. ATRAC reduces the 1.4 Mbit/s of a CD to a 292 kbit/s data stream, roughly a 5:1 reduction. ATRAC was also used on nearly all flash memory Walkman devices until the 8 series.
The ATRAC codec differs from uncompressed PCM in that it is a psychoacoustic lossy audio data reduction scheme. Like other lossy audio compression formats, it is intended to be acoustically transparent.
There have been four versions of ATRAC, each claimed by Sony to more accurately reflect the original audio. Early players are guaranteed to play later version ATRAC audio. Version 1 could only be copied on consumer equipment three or four times before artifacts became objectionable, as the ATRAC on the recorder attempted to compress the already compressed data. By version 4, the potential number of generations of copy had increased to around 15 to 20 depending on audio content.
The latest versions of Sony's ATRAC are ATRAC3 and ATRAC3plus. Original ATRAC3 at 132 kbit/s was the format that was used by Sony's defunct Connect audio download store. ATRAC3plus was not used in order to retain backwards compatibility with earlier NetMD players.
In the MiniDisc's final iteration, Hi-MD, uncompressed CD-quality linear PCM audio recording and playback is offered, placing Hi-MD on par with CD-quality audio. Hi-MD also supports both ATRAC3 and ATRAC3plus at various bitrates.