A MiniDisc (MD) is a magneto-optical disc-based data storage device initially intended for storage of up to 80 minutes of digitised audio. Today, in the form of Hi-MD, it has developed into a general-purpose storage medium in addition to greatly expanding its audio roots.
| File:MiniDiscLogo.png | |
 The Sony MZ1 MiniDisc player, the first to hit the market in 1992. | |
| Media type | magneto-optical disc |
|---|---|
| Encoding | ATRAC, linear PCM (with Hi-MD) |
| Capacity | 80 min (standard MiniDisc), up to 45 hours of audio (1GB capacity) (with Hi-MD) |
| Read mechanism | 780nm laser |
| Write mechanism | magnetic field modulation |
| Developed by | Sony |
| Usage | audio storage, data storage (with Hi-MD) |
- See also IBM's VM operating system family, where minidisk refers to a logical unit of storage.
MiniDisc was announced by Sony in 1991 and introduced January 12 1992. The music format was originally based exclusively on ATRAC audio compression. Recently, the option of linear PCM recording was introduced to attain truly CD-quality recordings. MiniDiscs are popular in Japan as a digital upgrade to cassette tapes, but have not been as popular world-wide.
Market history
Along with Philips and Matsushita' Digital Compact Cassette (DCC) system, the MiniDisc was targeted as a replacement for the Phillips analogue cassette audio tape system.
Despite enjoying a loyal niche (primarily musicians and audio enthusiasts), MiniDisc has met with only limited success. In Japan, it is still relatively popular, but doesn't enjoy that level of success in other major markets. Despite its popularity in Japan, flash memory and HDD-based audio players like Apple's iPod are becoming increasingly popular as playback devices.
The company avoided the mistake that it had made in the 1970s with the Betamax video recording system, and this time licensed the MD technology to other manufacturers, with JVC, Sharp, Pioneer, Panasonic and others all producing their own MD systems. In recent years MiniDisc has faced new competition from CD-Recordable, solid-state memory recording (flash memory), and hard disk recording, while the popularity of traditional cassette tape refuses to wane in certain quarters. MiniDisc is widely respected as being a very reliable format when it comes to portable audio storage, such as field recording.
The initial low uptake of MiniDisc was attributed to the small number of pre-recorded albums available on MD as a relatively small number of record labels embraced the format. The initial high cost of equipment was also a factor. Pre-recorded MDs disappeared from the market rather suddenly in the late 1990s.
MD Data
MD Data, a version for storing computer data was announced by Sony in 1993, but it never gained significant ground, so today MDs are used primarily for audio storage. The format was able to store 140 MB on a special disc, but was plagued by low write speeds and slow seek times. MD Data drives also could not write to audio-MDs, only the considerably more expensive data blanks. MD-Data2 blanks, which held 650 MB of data, were introduced around 1997, but were only used in Sony's short-lived MD-based camcorder.
The Hi-MD format, introduced in 2004, marked a return to the data storage arena with its ability to act as a USB drive.
Design
Physical characteristics
The disc is permanently housed in a cartridge (68 × 72 × 5 mm) with a sliding door, similar to the casing of 90 mm floppy diskettes. This shutter is opened automatically by a mechanism upon insertion (but cannot be opened manually by simply attempting to slide the shutter open as you can on a 3½-inch floppy disk). The audio discs can either be recordable (blank) or premastered. Recordable MiniDiscs use a magneto-optical system to record data. A laser heats one side of the disc to its Curie point, making the material in the disc susceptible to a magnetic field. A magnetic head on the other side of the disc 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 Faraday effect, the player senses the polarisation of the reflected light and thus interprets a 1 or a 0. Recordable MDs can be recorded on repeatedly; Sony claims up to one million times. As of May 2005, there are 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 long ago and are rarely seen. Premastered MiniDiscs use a mastering process and optical playback system that is very similar to CDs, making them physically dissimilar to recordable discs. The recorded signal of the premastered pits and of the recordable MD are very similar to that of the CD. Eight-to-Fourteen Modulation (EFM) and a modification of CD's CIRC code, called Advanced Cross Interleaved Reed-Solomon Code (ACIRC) are employed.
Differences from cassette and CDs
MiniDiscs use rewritable magneto-optical storage to store the data. Unlike the Digital Compact Cassette, or the (analogue) compact audio cassette, the disc 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. At the beginning of the disc there is a table of contents (TOC), which stores the start positions of the various tracks, as well as meta information (Title, Artist) about them and free blocks. Unlike with the conventional cassette, a recorded song does not need to be stored as one piece on the disk, it can be stored in several fragments. Early MiniDisc equipment had a fragment granularity of 4 seconds audio. Fragments smaller than the granularity are not kept track of, which may lead to the usable capacity of a disc actually shrinking. Also, no means of defragmenting the disc are provided in consumer grade equipment. Defragmentation would require either two discs, or enough RAM to store the full contents of a MiniDisc, and computing power to rearrange the fragments so that each song is stored on the disc in one fragment only.
All consumer-grade MiniDisc devices feature a copy-protection scheme known as Serial Copy Management System. An unprotected disc or song can be copied without limit, but the copies can no longer be digitally copied.
Compression
The audio on a MiniDisc has been traditionally compressed using the ATRAC format (Adaptive TRansform Acoustic Coding). ATRAC was devised for MiniDisc so that the same amount of audio a CD can carry can fit on a disc far smaller than the CD. These days ATRAC is used on nearly all current Walkman devices, in addition to other formats. A CD, by contrast, contains uncompressed 16-bit stereo linear PCM audio. In MiniDisc's latest progression, Hi-MD, uncompressed CD-quality linear PCM audio recording and playback is offered in addition to ATRAC compression of varying bitrates - placing Hi-MD on par with uncompressed, CD-quality audio for the first time.
Sony's ATRAC codec differs from uncompressed PCM in that it is a psychoacoustic lossy audio compression scheme, so decompression of the compressed signal will not yield the original signal, although the compressed signal may sound identical to the original to the listener. The latest version of Sony's ATRAC is "ATRAC3plus" (Sharp, Panasonic, Sanyo and Pioneer have their own (but fully interoperable) ATRAC codecs). Original ATRAC3 at 132 kbit/s (also known as ATRAC-LP mode) is the format used by Sony's Connect audio download store. ATRAC3plus is not used in order to retain backwards compatibility with earlier NetMD players.
Anti-skip
MiniDisc has an advantageous feature that prevents disc skipping under all but the most extreme conditions. Older CD players had once been a source of annoyance to users as they were prone to mistracking due to vibration and shock. MiniDisc solved this problem by reading the data into a memory buffer at a higher speed than was required before being read out to the digital-to-analogue converter at the standard rate required by the format. The size of the buffer varies by model.
If the MiniDisc player were bumped, playback could continue unimpeded while the laser repositioned itself to continue reading data from the disc. This feature allows the player to stop the spindle motor for long periods, increasing battery life. The memory buffer concept introduced by MiniDisc was soon incorporated into portable CD players as well.
A buffer of at least ten seconds is required on all MiniDisc players, be they portable or stationary, full-sized units. This is needed to ensure uninterrupted playback in the presence of fragmentation.
Operation
The data structure and operation of a MiniDisc is similar to that of a computer's hard disk drive. The bulk of the disc contains data pertaining to the music itself, and a small section contains the Table of Contents (TOC), providing the playback device with vital information about the number and ___location of tracks on the disc. Tracks and discs can be named. Tracks may easily be added, erased, combined and divided, and their preferred order of playback modified. Erased tracks are not actually erased at the time, but are marked so. When a disc becomes full, the recorder can simply slot track data into sections where erased tracks reside. This can lead to some fragmentation but unless many erasures and replacements are performed, the only likely problem is excessive searching, reducing battery life.
The data structure of the MiniDisc, where music is recorded in a single stream of bytes while the TOC contains pointers to track positions, allows for gapless playback of music, something which the majority of competing portable players, including most MP3 players, fail to implement properly. (Notable exceptions are CD players, nano and video capable iPods via the latest firmware updates).
At the end of recording, after the "Stop" button has been pressed, the MiniDisc may continue to write music data for a few seconds from its memory buffers. During this time, it may display a message ("Data Save", on at least some models) and the case will not open. After the audio data is written out, the final step is to write the TOC track denoting the start and endpoints of the recorded data. Sony notes in the manual that one should not interrupt the power or expose the unit to undue physical shock during this period. Sony actually advises using the AC power supply when recording, if possible, as the added power requirements during recording (noted above) drain batteries much quicker than playback. (But one strength of the MiniDisc lies in its portability for field recording, so sometimes batteries will be used.)
Format extensions
MDLP
In 2000, Sony announced MDLP (MiniDisc Long Play), which added new recording modes based on a new codec called ATRAC3. In addition to the standard, high-quality mode, now called SP, MDLP adds LP2 mode, which allows twice as much recording time (160 minutes on an 80 minute disc) of good-quality stereo sound, and LP4, which allows four times more recording time (320 minutes on an 80 minute disc) of medium-quality stereo sound.
The bitrate of the standard SP mode is 292 kbit/s, and it uses separate stereo coding with discrete left and right channels. For most people the sound quality is indistinguishable from a CD. LP2 mode uses a bitrate of 132 kbit/s and also uses separate stereo coding. For most people the sound quality is almost as good as SP. The last mode, LP4 has a bitrate of 66 kbit/s and uses joint stereo coding. The sound quality is noticeably poorer than the first two modes, but is sufficient for many uses.
Tracks recorded in LP2 or LP4 mode play back as silence on non-MDLP players.
NetMD
NetMD recorders allow music files to be transferred from a computer to a recorder (but not in the other direction) over a USB connection. In LP4 mode, speeds of up to 32× real-time are possible and three Sony NetMD recorders: MZ-N10, MZ-N910, and MZ-920 are capable of speeds up to 64× real-time. NetMD recorders all support MDLP.
NetMD is a proprietary protocol, and it is currently impossible to use it without proprietary software, such as SonicStage. Thus, it cannot be used under Linux, *BSD, and so on. A free implementation, libnetmd, is being developed, yet it cannot be used to upload music (as of December 2005).
Hi-MD
In January 2004, Sony announced Hi-MD [[1]]. It was released some months later.
With its introduction came the ability to use newly-developed, high-capacity 1-gigabyte Hi-MD discs, sporting the same dimensions as regular MiniDiscs.
The main features of Hi-MD include:
- the ability to save non-audio data such as documents, videos and pictures
- longer playback and recording times per disc
- the ability to digitally transfer recordings to and from Hi-MD to computer. (Previously only one-way (lossy ATRAC) digital transfers were possible)
- the ability to record in lossless linear PCM, offering CD-quality audio. This completely eliminates compression artifacts that occur when recording directly to lossy audio formats such as Sony's ATRAC, or other formats like MP3, AAC, Windows Media Audio (wma), Ogg Vorbis (ogg), etc. (Previously only recording to ATRAC lossy codecs was possible).
- the introduction of a new ATRAC3plus codec with new Hi-LP and Hi-SP bitrates.
Hi-MD offers several codecs to record audio: PCM, Hi-SP and Hi-LP, each being selectable on the Hi-MD Walkman itself. PCM is the highest quality mode, followed by Hi-SP (the default mode), then Hi-LP.
PCM mode allows 94 minutes (1h:34min) of lossless CD-quality audio to be recorded to a 1GB Hi-MD disc (or 28 minutes on a standard 80-minute MiniDisc recorded in Hi-MD mode).
Hi-SP allows seven hours and fifty-five minutes (7h:55m) of audio to be recorded on a 1GB Hi-MD (or 2h:20min on a standard 80-minute MiniDisc recorded in Hi-MD mode).
Hi-LP allows 34 hours on a 1GB Hi-MD (or 10h:10min on a standard 80-minute MiniDisc recorded in Hi-MD mode).
SonicStage software provides additional Hi-SP and Hi-LP bitrate choices, depending on the quality level desired. Up to 45 hours of audio can be recorded per disc at the lowest-quality setting.
Standard MiniDisc SP, LP2 and LP4 codecs are available on most units when using standard MiniDiscs in standard MD mode (as opposed Hi-MD mode), ideal for creating discs intended to be played back in older (pre-Hi-MD) MiniDisc units.
Data and audio on the same disc
Hi-MD discs offer the ability to store computer files in addition to audio data. For example, a Hi-MD disc could have both school or work documents, pictures, videos, etc. as well as music (playable in a Hi-MD Walkman) if desired.
When connected to a computer (via USB cable), a Hi-MD Walkman is seen as standard USB Mass Storage device, just like a USB stick or external hard drive. On a Windows computer, a Hi-MD device is listed as "Removable Disk" in "My Computer". The disc has a FAT filesystem. Hi-MD units are powered by the USB bus when connected - just like USB sticks, they don't require additional power (and don't use their own battery power) when plugged in to a computer.
Sony's SonicStage music management software is not needed to save and manipulate files on the discs; it is only required to get playable audio on and off the device; all files are manipulated using standard operating-system functions. However, when SonicStage software is active, the recorder is not treated as a data storage device - SonicStage "takes over" the management of the device.
When connected to a PC, "PC--MD" appears on the Hi-MD device's display to indicate the unit is connected in PC--MD mode. In PC--MD mode, pressing Play on the unit, for example, results in "PC--MD" flashing, indicating this function cannot be activated from the device when connected to the computer. It is essentially a slave to the computer in this mode. PC--MD status is constant as long as the unit is connected via USB cable (regardless of whether SonicStage is running or not).
To play back Hi-MD audio data on the PC, SonicStage is needed.
It can be done 2 ways:
- 1) Launch SonicStage. Play audio from Hi-MD inside SonicStage. The audio is played back on the computer's PC speakers. SonicStage reads and decrypts the audio data straight from the Hi-MD disc.
- 2) transfer the audio data to the PC in SonicStage. Play the audio back from the PC's hard drive (instead of playing it back from the Hi-MD unit directly)
Once the operation of transferring audio with SonicStage is completed, the audio itself can be saved in any number of ways (& audio formats). Saving audio in SonicStage in standard WAV format is a widely-accepted way to get the audio into many third-party applications like editors and sound analyzers. The user can then proceed to record CDs, edit the audio, archive to format of choice, etc.
Backward compatibility with standard MiniDiscs
Hi-MD units are backward-compatible with standard MiniDiscs. Discs can operate in MD mode (as normal) or the new Hi-MD mode.
A standard MiniDisc may be formatted to Hi-MD mode on a Hi-MD unit. This has the effect of increasing the capacity of a regular 80-minute MiniDisc from 177MB to 305MB. Standard MiniDiscs formatted in Hi-MD mode can store audio & data files just like the new 1GB Hi-MD discs. Formatting erases any previous files or audio that may have been on the disc, and the disc can only be recognised (and used) by Hi-MD devices.
Sony removes restrictions
Since the release of SonicStage 3.4 (Sony's music-management program), virtually all computer audio transfer restrictions were removed. These plagued earlier versions of SonicStage for some time. (Sony actually started a big push to dispense with the DRM restrictions with the release of SonicStage version 3.2. Version 3.4 dispensed with even more).
A side-effect of this is that the wording in many Sony Hi-MD user's manuals regarding "transfer authorizations" don't apply to users using SonicStage versions 3.2 and later. The ability to transfer Hi-MD audio to (and from) computer is now essentially unrestricted, unlike previous versions of the software.
Some of these restrictions included:
- limited transfers of microphone and "line-in" recordings
- barring of digitally-sourced uploads (ie. recordings that were made from USB or digital optical input).
These restrictions had - in the past - severely impacted the utility and ease-of-use of Hi-MD.
One limit that still remains in current software is the inability to edit tracks transferred from SonicStage to the device. Attempting to add or erase track marks on-unit from tracks transferred through SonicStage will result in "NO EDIT" (or similar message) being flashed on the unit. No such editing restrictions exist when transferring via optical cable or via LINE-IN.
Sony mention this limitation in their manuals as necessary to prevent "loss of transfer authorization" on the edited tracks. Considering these transfer authorizations are gone now, it seems possible for Sony to get rid of this limitation as well - so that users may add & erase track marks on their Hi-MD units whenever they please, despite it being transferred from SonicStage.
The latest officially-downloadable release of SonicStage is SonicStage CP 4.2. It is available on the following Sony sites:
Native support for MP3
In 2005 Sony released its second-generation Hi-MD devices offering native support for the popular MP3 format (earlier, SonicStage would transcode MP3 files to ATRAC format before recording on the disc). Transcoding files to lossy formats always results in a lower quality file, but whether or not it's noticeable to the listener varies.
Sony's MP3 file support still means that the MP3s themselves had to go through SonicStage to be put on the device, and couldn't just be copied on the discs outside of SonicStage as you can with data files on Hi-MD (or Hi-MD-formatted MiniDisc media). SonicStage 'wraps' (encrypts) the MP3 files on the disc (as it does with all audio that's playable in a Hi-MD device). To many, the requirement of SonicStage for audio transfers has been a constant drawback.
At the release of the second-generation Hi-MD models in 2005, some controversy erupted. Some users argued that MP3 playback on the devices sounded dull; the treble seemed to be muffled in comparison to ATRAC-encoded files, which sounded 'brighter'. The results were consistent. Some users were outraged, others didn't seem to mind. The devices could be best described as having their MP3 playback crippled. Sony implemented a lowpass on MP3 playback, which could make MP3 sound dull in comparison to ATRAC. Some users say that this was done intentionally in hopes of fooling listeners into believing that Sony's ATRAC is audibly superior to MP3 (which many agree it is to begin with). Regardless of the intentions of Sony, the MP3 playback roll-off problem was notably absent with the release of a new model, the MZ-RH1 Walkman, in March 2006.
Hi-MD Photo
In 2005, Sony announced Hi-MD Photo [[2]].
The Sony MZ-DH10P Walkman was released to showcase the format. The unit offers a 1.3 megapixel digital camera and saves pictures to Hi-MD discs, but doesn't offer a microphone input to record live audio, as do most standard Hi-MD Walkmans. The unit was praised for its quality photos (despite the low megapixel count) as well as its full-colour display and unique photo & music features.
The MZ-DH10P Hi-MD Photo Walkman can perhaps be considered a rival the iPod Photo, which was available just before its release, despite the two products varying greatly in features and application (one is a camera, the other isn't, to name but one of many notable differences).
Upload of 'legacy' MiniDiscs
In March 2006, Sony released the the MZ-RH1 Hi-MD Walkman in Japan, which was later followed in other regions. With this unit, Sony enabled faster-than-realtime full digital transfers from standard MiniDiscs to the computer for the first time. Users with extensive MiniDisc collections, for example, could upload their recordings digitally faster than real-time via USB connection, just like Hi-MD recordings already offered.
One limitation is with transfers done from MiniDiscs recorded on NetMD devices. MiniDiscs that have had recordings transferred via USB from computer to the NetMD device cannot have those recordings uploaded to the computer digitally. However, NetMD live audio recordings (via MIC input) as well as LINE IN recordings can be transferred to the computer digitally with no restriction on the MZ-RH1.
These digital transfers of Standard (pre-Hi-MD) MiniDiscs are in addition to the essentially unrestricted Hi-MD-based transfers already available since the online availability of SonicStage 3.4.
With the MZ-RH1, Sony made tangible speed improvements to the device over previous generations of Hi-MD recorders. The result being that the transfer times to and from computer are, under certain circumstances, cut in half over previous models, but still noticeably slower than flash memory and hard drive-based portables, due to the nature of the Hi-MD magneto-optical system.
Hi-MD selling points
Unlike many audio devices in Hi-MD's price range, Sony's Hi-MD models are widely-regarded for their high-quality recording, and are generally considered the highest quality recording devices in their price range. Many competing devices that do record often only record in lossy codecs such as MP3 and WMA, sacrificing quality over Hi-MD's lossless linear PCM recording abilities. Quality is further affected with the poor-quality audio circuitry often found in many consumer-level recording devices, such as cheap internal microphones and poor audio circuitry - even when they do offer recording to high-quality formats.
Hi-MD's strengths over other popular digital audio players on the marketplace include:
- They excel at recording live audio; the entire 20Hz-20KHz audible frequency range can be captured, making them eminently suitable for live music recording, not merely passable tools for voice dictation like so many other products
- They don't employ low-quality internal microphones at all.
- Connection flexibility (nearly all recorders offer microphone, digital optical and analogue line inputs)
- Hi-MD units employ high-quality low-noise components and circuit design (low noise MIC pre-amp, LINE IN, etc)
- The ability to record without employing lossy codecs such as WMA, MP3, AAC, ATRAC, etc.
Many portables out there in MD's price range can record, but very few come close to matching Hi-MD's sonic qualities. Choice and design of audio circuitry is instrumental to Hi-MD's high-quality, low noise results.
Other unique features like on-the-fly trackmarking, synchro record, and on-disc-editing of tracks and titles allow Hi-MD to be used completely independently of a computer if desired. A playback-speed manipulation feature called SpeedControl - available on selected Hi-MD models - makes Hi-MD particularly useful to musicians and language students. A-B Repeat is another feature. This allows a user to make a certain section of a track within a track repeat itself; (the user selects points A and B).
Some common features of Hi-MD models on the market include:
- linear PCM recording at 16bits, 44.1KHz sampling rate (identical to CD with no lossy compression)
- gapless playback
- OPTICAL input (on most models) for recording from digital sources such as CD players and receivers and sound cards with digital optical output
- LINE-IN for recording from analogue sources at high quality (all units offer low-noise inputs)
- MIC input (with plug-in power) and low-noise pre-amps for low-noise live recording (on all recorders)
- automatic gain control (AGC) as well as manual level adjustment (on all recorders)
- level meters to monitor recording levels (on all recorders)
- high and low sensitivity microphone settings (on all recorders)
- remote controls (nearly all models with included remotes as standard, and all Hi-MD Walkmans with the capability to accept a remote control)
- USB connection for two-way digital transfers (computer-to-Walkman and Walkman-to-computer)
Many non-computer recording tasks can be performed in addition to regular computer-based transfer, which is a particular strength of Hi-MD units. For example, audio can be transferred to the units without a computer via OPTICAL input, LINE IN via analogue cable and live audio via the MIC input. They can also be powered for a long time without ever needing to be hooked up to a computer at all; all units employ user-removable batteries for recording and playback away from power sources. This differs from most devices that employ an internal embedded battery that must be recharged to be used when its power runs out, which isn't an ideal proposition when travelling or when away from power sources.
Optical inputs found on nearly all Hi-MD devices allow digital transfers from many CE-devices.
Synchro Recording is a feature that makes the most of the digital optical input capability of most Hi-MD devices. It's a feature that starts and stops recording automatically in synchronization with the sound source. For example, pressing play on a CD player with the Hi-MD recorder connected to it via the digital optical cable in Syncho Recording mode will automatically start the recording on the Hi-MD unit, and stop when the digital signal ends (the end of the CD).
Transfers over digital optical cable typically maintain the high sound quality of the original - and without a computer. It's similar to transferring over USB connection on the PC in that the cable itself transmits digital information native to the device (and doesn't convert the information to analogue, resulting in a slight quality loss). The main difference between optical and USB transfers is that the optical transfer is real-time (ie. 1 hour of material takes one hour to transfer). Many non-computer (and computer) devices offer optical outputs that Hi-MD can record from with high quality.
In addition to digital optical input, recording via analogue sources is possible via the line input. On Hi-MD Walkmans, the same physical connector accepts both optical and analogue "minijacks", the only difference being the cable used for the connection. Track marks allow you to know the start of new tracks. When recording from analogue sources, they are normally automatically placed after the recorder detects silence of a specified period followed by a sound. When recording from analogue sources, true silence is more difficult to detect, hampering the automatic accurate track-marking offered on Hi-MD units (unlike digital recordings via the optical cable in which track marks are placed accurately). To help with this, Hi-MD units offer Combine & Divide track feature for manual intervention of track marks. All these are on-unit features, not requiring use of a computer (but they are offered in SonicStage, Sony's music management program for the computer, too).
Track, artist and album titles can be input manually without the need for a computer, too. All tracks can be erased, moved, created, edited - directly on the unit. Labelling tracks, groups or discs can be performed even while the recorder is recording, playing, or stopped. Many Hi-MD units also have a built-in clock which will record the date and time of recordings automatically.
The flexibility extends to the batteries. Most digital audio players require recharging via USB and only include a single non user-replaceable battery. User-replaceable batteries are standard on MiniDisc and Hi-MD units. This allows for easy battery switching when travelling and/or after extended recording or playback sessions. Several models accept a ubiquitous AA battery. The small size of the discs, their general robustness and removable nature are looked upon favourably by some loyal users, even in the face of constantly larger hard drive and flash memory-based devices.
Criticism
Criticisms of the Hi-MD format cited by users include:
- the requirement of SonicStage to transfer music to and from the device when using a computer (and SonicStage's own peculiarities and limitations). Many argue music should be able to be natively placed on the device without a proprietary application needing to be installed, much the same way as regular files are placed on Hi-MD discs.
- Hi-MD units store non-audio information (such as start and end time of tracks) in the "system file" area of the disc. The system file is updated after any recording or edits on disc (like new recordings, moving track positions, adding tracks, removing tracks, track titling, etc). For example, recording and then pressing "stop" on the unit will result in the unit saving any in-memory audio data to disc - then updating the "system file" area of the disc. SYSTEM FILE WRITING is commonly seen on the display of a Hi-MD unit at this time (DATA SAVE may appear instead, when edited track names, disc name, artist names, etc. are being saved). In both cases, it is at this point the recorder spends several seconds updating the system file area of the disc. Sony warns not to shock the unit at this time or remove the power to the unit because the entire recording can be 'lost' if the system file area is not written to or updated properly. This is seen as a weakness of a disc-based format. To avert power-related problems when writing, the Hi-MD estimates whether the battery power is adequate in advance of any recording or editing taking place on the unit. "NotENOUGH POWER TO REC" and "NotENOUGH POWER TO EDIT" are two messages that may appear in the display when the recorder estimates the power to not be enough. Power-related problems are largely averted this way, but shocking the unit still may be an issue at this critical stage of writing.
- Hi-MD units are mechanical devices, and as such, emit a noise intermittently. A disc is read (or written to) in bursts. This means that when recording (for example), the audio data is fed to a memory buffer first, then written to disc as that memory buffer is filled. The audible maifestation of this is that a spinning motor noise is heard for a short period, followed by a far longer period of silence. Then some spinning whir again, then silence. The cycle is repeated. The same applies to playback, only differently: a disc is spun faster than required for normal playback (to fill the memory buffer), then stops spinning and the audio information is emptied (played back) from memory normally. As the memory buffer depletes, the disc spins up again, maintaining the fill of the memory buffer, only to spin down the disc again (into silence). The buffer memory allows the disc to spin down completely most of the time, conserving battery life. However, during live recording operations with a microphone, this can be a problem. If the microphone is directly connected to the unit (ie. directly connected to the MIC jack without a wire), or simply in close enough proximity with a fairly quiet background, this intermittent motor noise can be audibly present in the recording - if some basic precautions aren't taken. This contrasts with flash-based recorders with no moving parts for recording, who are able to record in silence with no self-noise. (In practice, unfortunately, too many flash recorders in Hi-MD's price range are simply poor recorders, chiefly due to poor component choice, lossy encoding methods, inadequate recording features and/or poor circuit design).
- relatively poor storage capacity (1GB per disc) compared to hard-drive and some recent flash-based digital audio players
- slow transfer rates when transferring audio (and data) to and from the computer. Flash memory-based and hard drive-based devices offer far faster speeds. This is largely believed to be a limitation of the magneto-optical system employed in MiniDisc/Hi-MD: if the disc spins too fast, the less time any single ___location on the disc has to heat up to the required temperature for the magnetic head to elicit change on that spot. Power-consumption constraints and backward compatibility may also be a limitation here.
- the larger size of Hi-MD units in comparison to many far smaller units available on the market today. Most of these smaller portable audio devices are flash memory-based units not limited in their miniaturization by the physical dimensions of a Hi-MD.
Marketing moves
In 2006, Sony tried to position Hi-MD as a Digital Audio Tape (DAT) replacement, placing the MZ-M200 Hi-MD Walkman under the Pro Audio section of its "Broadcast & Business Solutions Company" website, alongside its professional flash memory-based recorder, the PCM-D1 [3]. Digital Audio Tape (DAT) is a high-quality digital tape format that found a niche with musicians and studios, and is valued for its high-quality sound reproduction. DAT portables have commonly been used for field recording, but have gradually been replaced by solid-state and hard drive-based units linke the Aaton Cantar, the Zaxcom Deva, and similar units from Fostex and Sound Devices. (Sony and Fostex ceased manufacturing DAT devices at the end of 2005, though parts and blank tapes should be available through 2010).
The MZ-M200 Walkman is Sony's (re-labelled) MZ-RH1 Walkman with an added microphone included. The consumer model of the same Hi-MD recorder, the MZ-RH1, is targeted to a more general customer on Sony's consumer electronics sites and comes with no microphone bundle. The microphone bundle is perhaps included to communicate its intended role as a recording device more effectively, and the higher price reflects the added value of the microphone.
Traditionally, Sony had not marketed Hi-MD or MiniDisc with its professional products (where DAT has been previously marketed). Given the improvements in Hi-MD, such as linear PCM recording (offering truly CD-quality sound without lossy compression), as well as improvements in SonicStage, MD users hoped that marketing efforts like this might see Hi-MD's use as a serious recording tool grow.
While MD was a reasonable success in Asia (particularly in Japan and Hong Kong), its relative failure in North America and Europe have led many to conclude the format has failed (as of early 2007). For audio playback purposes, the market has leaned more towards either solid-state or hard drive-based systems, often with the capacity to store just as much audio (or significantly more) per device. For professional recording, many use flash-based or hard drive-based units, too - offering features such as professional XLR microphone inputs, among other pro-centric features. These units are typically significantly larger and heavier than a Hi-MD Walkman, often with reduced battery life and higher prices. It's for these reasons Hi-MD fills a niche for high-quality recording and editing purposes in a compact size - and still remains a good general-purpose playback device. Stealth recordists, in particular, continue to favour Hi-MD.
Sony ceased marketing table-model MD recorders in North America in 2004, and has slowed the introduction of new models. In 2006, the only Hi-MD Walkman released was the MZ-NH1. This was the first time since the format's introduction (in 2004) that Sony had released just one new Hi-MD unit per year. The unit was designed with a particular focus on ease-of-recording, and has received a positive reception from many recording enthusiasts.
Recording modes
Modes marked in green are available for recordings made on the player, while those marked in red are only available for music downloaded from a PC. Capacities are official Sony figures; real world figures are usually slightly higher. Second generation Hi-MD players also support MP3 compression natively, in a multitude of bitrates. Recently, 352 kbit/s and 192 kbit/s ATRAC3plus have also been made available for 1st and 2nd generation H-MDs.