In March 2013, Sony finally ceased production of digital mini-disc recording and playback equipment. Two facts are surprising about this event: how monstrously outdated this format is perceived today, although it is only twenty years old, and how long it has managed to exist in the world of the Internet and MP3. Let's remember how MiniDisc, which was very promising at one time, was born and why it did not become as popular as a CD.
The development of the MiniDisc standard began in 1986, when the world had already begun to embrace the first mass-produced digital audio medium - the CD. The CD format was introduced in March 1979, and the first mass-produced players went on sale in April 1982. Compact discs were well received by music lovers, who quickly appreciated the new medium's wide frequency and dynamic range. What was especially striking was the absolute silence during the pauses, against the backdrop of the characteristic crackling of the gramophone record, which the CD replaced.
The mini-disc was conceived as a successor to the compact cassette, only more convenient to use and storing recordings in digital form. Work on MiniDisc began in the mid-eighties - during the “golden age” of audio cassettes, when the “ceiling” of the capabilities of this medium was reached and its fundamental limitations became obvious to all leading manufacturers.
The new medium had to remain as compact and protected from external influences as a compact cassette, which would allow it to be used not only in home audio systems, but also in car and portable players. In terms of sound quality, it had to surpass an analog cassette and be as close as possible to a CD with a significantly lower capacity. Finally, an indispensable condition had to be the possibility of repeated independent recording on such a medium - with the functions of erasing and editing.
As a result, MiniDisc implemented several advanced technologies at that time, protected by many patents. The recording technology chosen was magneto-optical, in which a laser is used to store data, heating the ferromagnetic layer of the disk to the required temperature, and a magnetic head, changing the magnetization of the heated area. To play back the recording, a laser of lower power is used: when the beam is reflected from one or another area, depending on its magnetization, the plane of polarization changes, which is recorded by an optical sensor.
Magneto-optical technology gave the mini-disk important advantages: high reliability of recording storage and increased resistance to magnetic fields, fast random access to any fragment of the recording, as well as the ability to repeatedly erase and rewrite. The only significant drawback at that time was considered to be the high energy consumption of the laser during the recording process, which limited the use of burner drives in portable devices. However, it later became clear that MiniDisc is just as susceptible to demagnetization as regular film.
The disk, with a diameter of 2.5 inches (64 mm) and a capacity of 140 MB, was installed in a hard plastic case with a sliding shutter - almost like a computer floppy disk. To encode the music, Sony's proprietary Adaptive TRansform Acoustic Coding (ATRAC) algorithm was used, based on the psychoacoustic characteristics of human hearing. In its ideology, ATRAC is close to MP3 and other lossy audio encoding formats: information that is inaudible or barely audible for most people is removed from the file, and the remaining is compressed to the most compact volume possible. As a result, 74 minutes of recording on a 650 MB CD was compressed to 140 MB of mini-disk capacity. The base bitrate of the first version of ATRAC was 292 Kbps.
The MiniDisc format and equipment for recording and playing minidiscs were officially introduced on January 12, 1992, but the new product was received rather coolly. In terms of sound quality, the first players were inferior not only to DAT tape recorders with a lossless recording algorithm, but even to the now completely forgotten DCC digital cassettes, which also used a psychoacoustic compression scheme. At the same time, the equipment turned out to be comparable in cost to CD players, which provide much higher sound quality.
The fourth version of ATRAC, released in 1996, made it possible to further improve sound quality: all internal data processing was carried out with 24-bit precision while maintaining a 20-bit ADC. Version ATRAC 4.5 was used in the flagship models of the ES series and featured improved encoding quality at high bitrates. The ADC capacity has increased to 24 bits. The latest variant of the classic ATRAC DSP Type-R appeared in 1998 and, among other things, provided high-quality high-frequency encoding.
However, the MiniDisc already had a bad reputation among audiophiles, so Sony was forced to once again draw attention to the MiniDisc with high-quality decks of the top-end ES series - MSD-JA30ES and JA50ES, which received 20-bit analog-to-digital converters and excellent-sounding DACs. At the same time, it became possible to produce inexpensive devices with high sound quality. A good example is the MDS-JE500 deck, released in 1996 and built on a CXD2650R chip with the ATRAC 4 algorithm. These devices easily competed in sound quality with mass-produced CD players, and were ahead of them in terms of service functions.
The sixth generation of ATRAC, which appeared in 1999, received its own name ATRAC3 (without a space). In this implementation, MDLP extended recording formats were added: 2LP with a bitrate of 132 Kbps and LP4 with a bitrate of up to 66 Kbps, allowing you to record up to 324 minutes of audio on an 80-minute disc. The ATRAC3 DSP Type-S modification combines the ATRAC3 codec with improved playback quality of low-bitrate MDLP recordings and the top-end first generation ATRAC1 Type-R codec.
At the end of 2001, the MiniDisc format finally made it possible to copy recordings to a minidisc not only in real time. The NetMD extension made it possible to send data in an accelerated mode via the USB interface from a computer running Windows through the proprietary SonicStage program. At the same time, recordings in SP mode could be copied at speeds up to 1.6x, in LP2 mode - at speeds up to 16x, and in LP4 mode - up to 32x or even 64x compared to the actual duration of the recorded program.
Finally, in January 2004, the latest incarnation of MiniDisc, Hi-MD, and the ATRAC3Plus codec came to market. At the same time, 1 GB Hi-MD mini-discs were released, on which you could record up to 45 hours of music with a minimum bitrate of 48 Kbps, up to 94 minutes of uncompressed music with a bitrate of 1411 Kbps and a sampling frequency of 44.1 kHz in the format Linear PCM or up to 980 MB of computer data. In 2005, the production of Hi-MD players with built-in MP3 support began, and in 2006, for the first time, it became possible to transfer digital files from MD players to a computer (with the exception of discs recorded via SonicStage or OpenMG).
The ATRAC Advanced Lossless codec made it possible to record music in ATRAC3 and ATRAC3plus formats, accompanied by a service stream to completely restore the original signal. At the same time, the player could decode both compressed and uncompressed formats, which ensured compatibility of such recordings with outdated equipment.
Hi-MD drives began to appear in computers manufactured by Sony. Such drives were displayed as removable drives with the FAT32 file system. File transfer was carried out using the operating system, and only to record an audio disc played on an MD player, it was necessary to use the SonicStage program.
The Hi-MD standard has finally eliminated many of the “copyright” restrictions of classic MiniDisks that are ridiculous by today’s standards - for example, intermediate transcoding into PCM of files transmitted via NetMD or the impossibility of digitally re-recording sound recorded “live” from a microphone or linear input neither via optical output nor via USB (Serial Copy Management System technology).
All these restrictions were originally designed to prevent “bit-by-bit” copying of DRM-protected files, allowing only analogue rewriting with loss of quality. In the latest versions of SonicStage, the only limitation remaining is the inability to edit tracks on a Hi-MD recorder recorded to disk using this program. There are no such restrictions when recording via optical or line input.
While Sony was perfecting algorithms for hardware encoding and decoding of compressed audio, the 21st century had arrived - the century of the Internet, MP3, Napster, file-sharing networks, iPods and flash players, CD, DVD and Blu-ray burners. It seems that all this time the creators of MiniDisc lived in some other reality and returned back only to 2004. The heroism with which Sony carried this long-outdated format until 2013 deserves a separate discussion.
Support for the MiniDisc format in Europe and North America was discontinued in 2008, as was access to the company's online music store Connect. However, mini-discs were not particularly popular either in the Old World or in the New. The fashion for pocket MD players went back to the late 90s, and after that mini-discs were used only at radio stations and in music studios, where quick access to different parts of the recording and ease of editing were required. In Russia, the last time I saw blank mini-discs in stores was at least ten years ago - right around the same time the boom of MP3 and CD burners began.
However, in Japan itself and in some other Asian countries, the minidisc has become much more widespread. It initially turned out to be a more affordable and convenient alternative to CD, which came in very handy for a country that spends a lot of time on trains. Japanese youth still happily buy singles from fashionable artists on mini-discs and record entire “live” concerts on them. The Japanese version of the Connect online store is not going to close either. It is not surprising that some other companies, including Onkyo, are not yet planning to abandon the production of MD-players, although Sony stopped producing portable MD-Walkman two years ago.
We can only say goodbye to another format, the fate of which turned out to be very difficult only because its creators tried to combine the incompatible: the digital technologies of the future with the habits of large corporations to ignore the surrounding reality and impose their archaic rules of the game.
The truth about minidiscs
One of the impressive inventions of the 20th century is the mini disc (MD). High-tech media that holds up to 5 hours of music, up to 140 MB of data; smaller in size than a 3.5-inch floppy disk, well protected from damage... A mini-disc is not only in many ways similar to a regular music compact disc (CD), but also surpasses it in a number of indicators.
From the very beginning, Sony developers (namely, they have the honor of inventing the MD format) set themselves the task of creating a “small-caliber” media for music files, capable of displacing the recognized favorite of the audio market - the compact cassette, and bypassing it in the most important parameters - sound quality and size. Managed! The result was a plastic disk enclosed in a flat miniature case, coated with a special layer, on which music is recorded (and then read) using a laser.
The advantages of the new product over the “honored veteran” are obvious and undeniable. Imagine: a lightweight, durable and compact mini-disk can withstand a million (!) rewrites. A cassette is not capable of even a thousandth of this. Each time it is played, it degrades the properties of the audio recording on magnetic tape... 
Bypass CD
It should be remembered that Sony itself was instrumental in the development of the CD format, so it was especially difficult for its engineers to develop a medium that could compete with the established compact disc in the market.
How is a minidisc different from a CD? Firstly, the convenience of recording. By the time the first MDs were released, the ability to independently record a music CD was practically inaccessible to the average music lover - for this there were only computer peripherals, and such devices cost a lot of money (in addition, access to them, like to any professional equipment, was strictly limited) . And a mini-disc can be recorded directly in a player, both portable and stationary. A computer is not needed for this simple procedure.
Secondly, MD is a “reusable” media. You can selectively erase information recorded on it (say, a song you don’t like, one from an entire album). For a “disposable” CD (CD-R), this is impossible in principle, and a “rewritable” (CD-RW) must either be cleaned completely or use special preparation for recording - formatting, which eats up a sixth of the useful volume and is quite labor-intensive for an inexperienced person. user. And again - all this only with the help of a computer.
Thirdly, you can record both music and data on a mini-disc (albeit with the help of special equipment). Different CDs are produced for audio files and computer data (universal CD-Rs can be used to record music, but only in computer drives; household audio CO recorders refuse to read such discs).
Fourthly, in terms of sound duration, MD is not only not inferior to CD, but, thanks to recent improvements, even surpasses it. Fifthly, a mini-disc is 2.5 times smaller than a CD. And finally, the durable housing and sliding MD curtain reliably protect its working layer from accidental damage. Very often they write about comparing the sound of a CD (a kind of standard of sound quality) and its copies on various media. This is true. Recordings on compact cassettes are most often a copy of a CD. It is logical that owners of MD players save their favorite tunes from CDs to a mini-disc.
In order to record the same amount of musical information on a smaller medium as on a CD, a special sound compression algorithm was developed taking into account the characteristics of human hearing. It was called ATRAC. The sound recorded on MD is slightly different from the original, but not enough to be felt by the naked ear. Each re-recording from one mini-disc to another leads to the accumulation of errors and distortions, which at some point become noticeable to the ear. But the sound quality of the first MD copies from a CD is practically indistinguishable from the original.
It is argued that even a non-professional music lover will always distinguish an MD recording from a CD recording. What about the fact that well-known companies - Yamaha, Kenwood, Denon - have long been producing stationary Hi-Fi-class mini-disc equipment intended for use as part of a home audio system?
MD has been adopted not only by hi-fi companies, but also by professional musicians working in the entertainment business. Today, not a single serious band going on tour can do without MD equipment. Musical accompaniment, effects and even “plywood” are recorded on the mini-disc. MDs are also widely used on radio stations, the extensive music library of which is collected mainly on mini-discs. They are much more convenient than any other media: they allow you to quickly find the desired piece of music or composition, do not get dirty, do not scratch, do not break, do not deteriorate over time, and take up very little space. 
Mini Discs for Hobos
But still, Hi-Fi class MD equipment is not a “consumer product”. Demand for it is restrained both by its low price and the need to have a home audio system.
Portable mini-disc players have proven to be much more popular. They are much smaller than cassette players and have many advantages in terms of control - more and more models are equipped with a remote control that is simply clipped to the lapel or collar. A miniature indicator displays information about the track being played, the artist, and the duration of the musical fragment. (By the way, the mini-disc contains detailed information of this nature. This is another blow to the reputation of the old cassette tape. And if you also take into account the almost instantaneous access to any fragment, accelerated playback, the ability to loop playback of a piece of music and even the entire disc... )
All portable mini-disc players are divided into two categories: simply players - playback devices - and recorders that can independently record mini-discs from an external source. Among them there are recorders with both an analog input, to which you can send an audio signal even from a microphone, and with a digital one (also called an S/PDIF input). With the latter, it is possible to transfer music from a CD player equipped with an S/PDIF output almost losslessly. You can even use a computer with a sound card equipped with such a “digital” connector for this.
It is quite natural that there are also mini-disc players on the market with a built-in radio receiver. As a rule, they even provide recording from the receiver to a mini-disk.
Double... quadruple!
Not so long ago, the younger brother of MD was born - the MDLP format. Two additional letters in the name hint at the possibility of slow playback - Long Play. MDLP has two modes - LP2 and LP4 (the playing time of the mini-disc increases by two and four times, respectively). A “double” modification of a standard mini-disc for 74 minutes will “hold” more than two hours of sound, and a “quadruple” modification will last about 5 hours; but there are also 80-minute discs... This, of course, affects the sound quality, but not enough to talk about noticeable losses. It’s just that some specificity appears in the sound, but that’s all.
The advent of MDLP made it possible to halve the time for rewriting from one MD to another (until now it was necessary to wait for those same 74 minutes). But this only applies to the standard recording mode; for slow-motion LP2 and LP4 you will have to wait two hours (or, accordingly, five) until the process is completed.
Alexey Adamenko
Topic status: Closed.
There are several methods of recording on rewritable (“reversible”) media, but for mini-discs the magnetic field modulation (MFM) method was chosen as the most reliable and makes it possible to rewrite an almost infinite number (up to 1 million) times. Moreover, with each new entry, the old data is automatically erased.
The essence of this method is that when ferromagnetic materials are heated above a certain temperature, called the Curie point, their magnetic susceptibility curve sharply rises and increases many thousands of times. If such a material is heated at a certain point to a temperature slightly above the Curie point, and the material is exposed to a magnetic field too weak to leave a mark on the cold areas, then the heated point, after cooling to a temperature below the Curie point, will retain magnetization, i.e., its the magnetic state will be fixed.
A recordable magneto-optical mini-disk is formed on a polycarbonate substrate, on which a magneto-optical (working) layer is located between two dielectric layers. A reflective aluminum layer, a protective layer and a silicone lubricant are applied on top of this structure, along which the magnetic head will slide. In Fig. Figure 3 shows a cross section of the disk.
The magneto-optical layer of the mini-disk is a special alloy of iron, terbium and cobalt (FeTbCo) with very low coercivity. This is important so that, despite the fact that the magnetic head does not directly touch the working environment, the magnitude of the magnetizing field would be sufficient and would not require its increase, which would inevitably entail greater heat generation and increased power consumption.
To record information on a magneto-optical layer, it is necessary to influence it not only by the magnetic field of the recording head, but also to simultaneously heat the corresponding point of the carrier to the Curie temperature. This is done using a laser beam.
For the FeTbCo alloy used in mini-discs as a recording medium, the temperature corresponding to the Curie point is approximately 185 C.
Thus, different polarities of magnetization of preheated spots in the magneto-optical layer correspond to digital logical levels “1” and “0”. The size of such a recording spot, and, consequently, the recording density on magnetoelectric disks is determined by the size of the focused laser light spot and the duration of the reversal cycle of the modulating magnetic field of the recording head. For this purpose, a special head was developed that allows rapid magnetization reversal (approximately 100 ns). It is obvious that the surface layers of the disk do not prevent the instantaneous heating of the working layer. Recording is performed by superimposing new records on the previous ones with automatic destruction of the latter.
Reading information from disks
As already mentioned, there are two types of disks and each of them uses its own reading system. A non-recordable disc is similar to a CD. To read it, the same laser is used as for writing, but at a lower energy level. The reflected laser beam varies in intensity depending on the information recorded in the form of pits (indentations) on the surface of the disk.
A recordable disc uses a different reading system, since the data is not recorded by a pit system, but is stored in the form of a magnetic layer magnetization polarity that changes from point to point. In this case, information is also read using a laser.
The laser beam hits the disk surface, passes through the magnetic layer and is then reflected from the reflective layer. However, passing through the magnetic layer, the plane of polarization of the laser beam changes depending on the polarity with which this layer is magnetized at a given point. The rotation of the polarization vector of a light beam under the influence of the magnetic medium through which it passes is called the Kerr effect.
So, there are two types of reading mini-discs:
reading a non-writable CD type disc in which the RF output signal is the same as that of a CD;
reading a recordable disc type MO: here the RF flow is continuous, but with changing polarization.
The same dual-function laser is used to read information from both types of disks. However, another element is added to the optical head of the system (when compared with a CD) - a polarization analyzer, the so-called Wollaston prism.
The rotation of the polarization vector, even under the most favorable conditions, does not exceed one degree, and light receivers do not respond to polarization. The job of a Wollaston prism is to convert the angle of polarization into light intensity.
