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Minidisc FAQ: MDLP (``Long-Play'') Mode Topics

  1. What is MDLP?

    Minidisc Long Play. It's a new encoding method for audio on Minidisc that offers two modes: one gives 160 minutes stereo ("LP2"), the second gives 320 minutes stereo ("LP4"). LP2 is stereo encoded (each channel is independent), LP4 is joint-stereo (both channels are coded simultaenously, see below).

  2. What encoder is used for MDLP?

    So called "ATRAC3", which is also used in the Sony MemoryStick Walkmans, Vaio Music Clip and Network Walkman.

  3. ATRAC3? Isn't that a step backwards? I thought modern Sony MD equipment was up to ATRAC 4 or something.

    Sony has chosen a confusing naming scheme for their variations of ATRAC. All Minidisc equipment before the advent of MDLP used ATRAC1 of some generation or another (note the lack of a space between ATRAC and the number 1). We should really be calling the ATRAC of the MZ-1 (Sony's very first MD machine) ATRAC1 version 1.0, for the MDS-501 (the first high-end MD deck) ATRAC1 version 2.0, etc. By this nomenclature, Sony's current MD decks (ca. 2001) are using ATRAC1 version 4.5 and ATRAC1 Type R. MDLP uses a new and incompatible encoding called ATRAC3 version 1.0, which we shorten to just ATRAC3 (note again the lack of a space between ATRAC and the 3).

  4. Oh that ATRAC3. Then what happened to ATRAC2?

    It was renamed to ATRAC3! Seriously though, audio coders are evolving computer programs with few natural dividing lines between them, though perhaps it's fair to rename them when their stored formats become incompatible. ATRAC2 (described briefly and in slightly more detail) differs substantially from the original, existing ATRAC system, having twice the transform window size (1024 samples [23.2ms], vs. 512 samples [11.6ms]), encoding tone components separately from other spectra, splitting the input signal into 4 bands instead of 3, and using Huffman coding on the final bit stream to squeeze out redundancy. ATRAC2 was apparently never incorporated into a product.

    ATRAC3 (as described briefly by Sony's ATRAC3 information page and in more detail by a TechnoWorld article (PDF)) appears quite similar to ATRAC2 in structure. The only difference is that ATRAC3 again uses the original ATRAC's QMF (Quadrature Mirror Filters) for band splitting, whereas ATRAC2 used PQF (Polyphase Quadrature Filters). Given the popularity of MP3, and the fact that there was no existing ATRAC2 format to be incompatible with, it seems plausible that marketing arguments, as much as anything else, convinced Sony to rename their high compression codec ATRAC3.

  5. Can the new LP mode tracks be played back on old, non-MDLP hardware?


  6. What happens when I try to play an LP track on old, non-MDLP hardware?

    The track is played as silence. A 20 min. LP2 track is played as 10 min. silence. A 20 min. LP4 track is played as 10 min. silence (because the MD unit thinks it's playing an SP mono track).

    The non-LP machine's display of the track name is also likely to show the characters "LP:" at the beginning of the title. These characters are put there by MDLP recorders in their factory default setting (this feature, called "LPstamp", can be disabled). MDLP machines will also strip off the initial "LP:" (if LPstamp is enabled) when displaying LP track names.

  7. Will the new MDLP units play back old ("SP" mode) discs?


  8. Will the new MDLP units record "old" (SP mode) tracks?


  9. Can old non-MDLP units title MDLP tracks?


  10. What bitrates are used?

    Standard ATRAC ("SP") is 292kbps, LP2 is ~132kbps, LP4 is ~66kbps. The LP mode bitrates are not simply 146kbps (292/2) and 73kbps (292/4) for this reason: In LP2 and LP4 modes 20 bytes of dummy data per 212 byte soundgroup are used to keep compatibility with SP mode, making them appear as normal ATRAC soundgroups containing silence. This allows LP2/4 tracks to play as silence on non-MDLP equipment. The intention is that older MD units should not produce random digital noise when playing LP tracks.

  11. You mean that 10% of an MD's capacity is wasted in LP mode due to lack of planning!?

    Yes. Sony defined a 2 bit field in the original MD specification to indicate non-standard track codings, allowing players to ignore unknown track types (see the MDLP-mode bit in the fragment headers). Unfortunately, non-MDLP units seem rather to ignore the mode bits and will try to play the MDLP audio anyway.

  12. Why aren't there LP monoaural modes that double the recording time?

    ATRAC3 in LP4 mode encodes audio in "joint-stereo" mode, encoding the left and right channels in one step (i.e. jointly) and exploiting the similarity between channels to increase compression. Because of this, the capacity increase when encoding a mono signal is not 2:1, but somewhat less. This, and the added complexity of a fractional increase in capacity, apparently disuaded Sony from providing a mono LP4 mode. ATRAC3 in LP2 mode on the other hand could be used to offer double playing time mono, but Sony's current machines do not offer it.

  13. If LP4 mode's left and right channels are coded jointly, then what kind of channel separation does it have?

    Unknown, but coding two completely unrelated signals on the left and right channels will not give spectacular results.

  14. How high quality is the LP mode audio?

    LP2 mode is reportedly quite close to standard ATRAC. LP4 mode has noticeable artifacts, but is still suitable for portable applications. Brian Youn has assembled some user comments on MDLP mode's quality. There are also comments in the Sony MZ-R900 equipment browser entry.

  15. Will an MDS-W1 move LP mode tracks?

    The Sony MDS-W1 double MD deck will not move LP mode tracks properly. When the MDS-W1 moves LP2 and LP4 tracks to another disc it sets their SP bits on in the UTOC track header, turning LP4 tracks into (silent) SP mono and LP2 tracks into (silent) SP stereo. The track's audio data is copied properly however, so with careful use of TOC cloning to restore the LP bit in the track header, copied LP tracks will play correctly.

  16. What MD equipment supports LP mode?

    See T's MDLP Equipment Table.

  17. How can I try out ATRAC3 and listen to some samples?

    Windows users can download this ATRAC3.zip file, unpack it into a new folder, then right click on the atrac3.inf file and choose "Install". This loads an ATRAC3 codec (.acm file) into the system so that .wav files containing ATRAC3 audio can be played (and recorded!) with your normal system tools (Sound Recorder, Windows Media Player 7, Winamp, Goldwave [encode ATRAC3 in Goldwave by selecting "File->Save As->Save as type: 'Wave', File Attributes: 'ATRAC3'"]). PlanetMG, a website that offers ATRAC3 and Windows Media audio files for download, also lets you download an ATRAC3 plugin for the Windows Media Player. RealPlayer's "RealAudio 8" supports Sony's ATRAC3 format as well.

    After loading you can listen to the following audio snippet of "Sichia". The example was intentionally chosen from difficult material, in order to highlight the audio quality differences at various bitrates.

    Sample: "Sichia" (de Lucia) track 4, 2:00-2:35
    CD: Passion Grace and Fire (McLaughlin, Di Meola, de Lucia)
    Original CD audio6MB
    ATRAC3 @ 132kbps580KB
    ATRAC3 @ 105kbps460KB
    ATRAC3 @ 66kbps290KB
    MP3 Stereo @ 56kbps/24khz245KB
    MP3 Stereo @ 56kbps/22khz246KB
    MP3 Stereo @ 56kbps/16khz244KB


    1. There are publicly available ATRAC3 files on the Web, however Sony is now using a custom format instead of WAV format; the header is incompatible with WAV so those files cannot be directly played with standard sound tools. However, the data is the same, all that's needed to make one work with the other is to replace one header with the other.
    2. This audio codec was assembled from publicly available bits on the Web and hence may not represent the ATRAC3 codec Sony currently supplies with their MDLP and MemoryStick audio devices. It is supplied for educational purposes only, please address all questions about commercial use and licensing of ATRAC3 to atrac3@Sony.co.jp.

  18. Where can I learn more about ATRAC3?

    Have a look at these links

  19. What happens if MD hardware is made to play MD audio data in the wrong mode?

    Using TOC cloning techniques, tracks recorded in one mode can have their UTOC bits changed to allow them to masquerade as audio data of a different mode (see the track mode bit assignments in the UTOC). David Tamkin has kindly conducted experiments that allowed him to produce this table:

    Mode of Recorded Audio Data Mode for Track Indicated in UTOC Result when played on MDLP unit Result when played on non-MDLP unit
    SP stereo SP stereo SP stereo SP stereo
    SP mono half-speed SP mono half-speed SP mono
    LP2 silent SP stereo
    LP4 silent half-speed SP mono
    SP mono SP stereo double-speed SP mono double-speed SP mono
    SP mono SP mono SP mono
    LP2 silent double-speed SP mono
    LP4 silent SP mono
    LP2 SP stereo silent silent
    SP mono silent silent
    LP2 LP2 silent
    LP4 nonstop squeal silent
    LP4 SP stereo silent silent
    SP mono silent silent
    LP2 double-speed LP4 silent
    LP4 LP4 silent

  20. Are there translations of the MDLP section of the FAQ?

    Yes, there is a full translation of the MDLP FAQ in Japanese.

This file can be found at http://www.minidisc.org/minidisc_faq.html

As always, I would be much obliged for any updates and corrections from Sony Engineering. -Eric Woudenberg

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What's New On RCI-Minidisc

Welcome to RCI minidisc information page.This section is still under construction.Stay tuned to this area for all hot technology from Asia


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MiniDisc can be regarded as the lastest technology shockwave introduced from Japan. Although this new technology has been around Asia for the past few years, it still remains relatively new to the West.

What makes MiniDisc so unique is its size, and its ability to be re-recorded up to 1 million times [as claimed by Sony]. Although very few would have the chance to prove Sony's claim, it is widely accepted that MiniDisc is highly reliable. Unlike tape, which has rather shabby quality, and CD, which is unbelievably scratchable, MiniDisc has almost no physical flaw! You could accidentally drop it on the floor and then step on it, yet still listen to the music without a problem. [Please also refer to Sony's MiniDisc TV commercial.]

The sound quality, of course, far exceeds that of tape. By enabling digital recording, most MiniDisc have CD quality sound output. Some even believe that because MiniDisc utilizes ATRAC Compression technology, it projects better and more distinctive sounds than normal CD. Also, you no longer need to press forward and rewind to find a song you want (as compared to tape recording) because MiniDisc allows title inputting to facilitate song searching. You can further edit the tracks through options like dividing, combining, or deleting. Your song can never be cut off short (unless you want it to).

Other major merits of MiniDisc include portability and design. Most MiniDisc recorders and players are equipped with 40 seconds anti-shock protection which allows MiniDisc users to listen to "unskip" music while performing in almost any other activities. Major electronic manufaturers such as Sony, Sharp, Kenwood/Pioneer [whose portable MiniDisc are clones of Sharp], Panasonic, and Aiwa are waging in MiniDisc warfares. They constantly re-innovate the designs and features of all MiniDisc related products. That is why all MiniDisc portables look futuristic. And this is also why MiniDisc goers often have to explain to the airport security guards that MiniDisc is "da bomb!" but not "a bomb" (Yes, it's something for us to brag about!)

In parts of Asia, MiniDisc has become so popular that almost all teenagers own one. Particularly in Japan, one may buy a MiniDisc disc for only 2 USD at nearby 7-11. Also, the technological progression in Japan has advanced tremendously that tape is already an extincted historical product. Aside from recording music from other CDs, major recording companies are now selling pre-mastered MiniDisc album for around 14 USD.

All these sound too good to be true?! However, one of the reasons why MiniDisc is still not so well known in the USA is because of its high price. Since MiniDisc technology is still considered high tech, many Americans would rather choose the cheap tape over the expensive MiniDisc. Average MiniDisc recorder's price ranges between 250 to 350 USD, whereas average MiniDisc player costs about 100 USD less. The average MiniDisc blank costs from 2.00 to 3.00 USD. As the average standard of living raises, it is expected that the MiniDisc market in the US will also enlarge and the price level will drop. More people will then benefit from this extremely user-friendly and cool technology and enjoy better music! Let's hope that someday we will all be able to purchase MiniDisc discs from the nearby supermarkets.

Want to be technologically advanced instead of being obsolete? Follow the trend! Get yourself a MiniDisc!

Minidisc FAQ: Hi-MD Topics

  1. What is "Hi-MD"?

    Introduced by Sony in January 2004, Hi-MD is a nearly complete revamping of the original Minidisc system. The most significant change is the introduction of Hi-MD media, which includes a new 1GB blank in the existing MD form-factor and a reformatting of existing MD media that doubles its capacity to 305MB. In addition, several important and long wished-for Minidisc capabilities have been incorporated into Hi-MD equipment.

  2. What new capabilities does Hi-MD equipment provide vs. the existing Minidisc?

    • Hi-MD equipment can record audio to Hi-MD media in uncompressed PCM (16bits/44.1khz, i.e. CD format) as well as in Sony's ATRAC3plus encoding at 256kbps ("Hi-SP") and 64kbps ("Hi-LP").
    • Hi-MD recorders can be used as USB connected data drives on any PC supporting USB storage devices.
    • Microphone and line input (i.e. analog source) recordings made on Hi-MD equipment can be uploaded at high-speed to Windows PCs via SonicStage (Sony's copyright-protecting audio transfer software).

  3. What is Hi-MD media?

    There are two Hi-MD media formats: a new 1GB magneto-optical medium based upon DWDD ("Domain Wall Displacement Detection") technology, and the original Minidisc magneto-optical medium (60', 74' and 80') reformatted to double its capacity.

  4. What is "Domain Wall Displacement Detection" (DWDD)?

    Domain Wall Displacement Detection is one of a class of optical readout methods called Magnetic Super Resolution ("MSR"). MSR techniques address the fact that Magneto-optical systems can write much finer than they can read; magnetic domains ("bits") can be recorded on the disk that are smaller than the laser spot*, such domains cannot be read back directly since the laser spot will illuminate several domains at once.

    DWDD Conceptual Diagram
    (Courtesy Canon)

    In DWDD, the recording medium is actually a 3 layer sandwich consisting of (from top to bottom) the displacement (aka readout) layer, the switching layer, and the memory layer. When the switching layer is heated to its Curie temperature (which is below the Curie temperatures of the memory and readout layers), it allows a small magnetic domain in the memory layer to appear larger than it really is in the readout layer.

    The Magnetic Super Resolution technique was first discovered by Sony, and Sony has a DWDD patent that references 4 Canon patents. See Canon's DWDD explanation for further information.

    [*Magneto-optical systems like Minidisc that use Magnetic Field Modulation are able to record domains smaller than the laser spot because they actually create crescent shaped regions that are magnetized as the recording layer cools below its Curie temperature. The size of these regions is determined by the switching rate of the signal sent to the magnetic head. See Sony's pictoral description of MO systems].

  5. Is this like DVD technology then?

    No, it's completely different. DVD is an optical format, with closer tracks (0.74μm vs. 1.6μm), smaller pits (0.40μm vs 0.83μm), higher numerical aperature (0.6 vs 0.45), and shorter wavelength laser (640nm vs. 780nm) than CD. Hi-MD on the other hand is Magneto-Optical, using a laser to read and a magnet and a laser to write. In fact, Sony managed to create Hi-MD while holding to the original Minidisc's laser parameters, presumably so that backward compatibility would not bring undue complexity. This means however, that pre-recorded 1GB Hi-MDs [that used CD Pit/Land recording] are not possible.

  6. How did Sony increase capacity on the existing Minidisc to 305MB?

    Sony diagram from Hi-MD announcement
    Photo courtesy AV Watch

    Several changes were responsible for the increase in capacity:

    1. The way data bits are encoded into bits on the disk (the modulation system) was changed from EFM ("Eight to Fourteen Modulation", the Compact Disc's method) to the more efficient RLL1,7 (typical of hard drives).
    2. The readout electronics were changed from a simple peak detector to a more sophisticated Partial Response Maximum Likelihood ("PRML") system that essentially uses digital signal processing techniques to extract the disk data signal from inter-symbol noise, allowing bits to be packed closer together.
    3. The error correction system and "sector structure" were changed to increase data packing efficiency to 80% (Sony doesn't mention what these changes were however).
    Changes #1 and #2 brought a factor of 1.38x, #3 brought 1.48x, for a total of 2.04x.

  7. What audio encodings and capacities exist on Hi-MD media?

    On Hi-MD media, these audio encodings can be created:

    Encoding Mode Recording capacity(1)Origin
    305MB Hi-MD
    formatted Minidisc
    1GB Hi-MD MediaRecorded with
    Hi-MD equipment
    USB download
    to Hi-MD equipment
    Linear PCM 1.4mbps 28m 1h 34m yes?
    ATRAC3plus 256kbps "Hi-SP" 2h 20m 7h 55m yesyes
    ATRAC3plus 64kbps "Hi-LP" 10h 10m 34h yesyes
    ATRAC3plus 48kbps 13h 30m 45h yes
    ATRAC3 132kbps "LP2" 4h 50m 16h 30m yes
    ATRAC3 105kbps 6h 10m 20h 50m yes
    ATRAC3 66kbps "LP4" 9h 50m 32h 50m yes
    ATRAC 292kbps "SP" Not supported on Hi-MD media

    Note: (1)Recording durations as stated in Sony literature

  8. Is Hi-MD equipment compatible with original MD recordings?

    Hi-MD equipment can play original Minidisc recordings.

  9. Can Hi-MD equipment record in the original Minidisc format?

    It depends upon the equipment. Sony's Hi-MD LAM-X1 will record audio in all Hi-MD (PCM, Hi-SP, Hi-LP) and original-MD (SP, LP2, LP4) modes.

  10. If I reformat an original Minidisc blank to Hi-MD format, can I later reformat it back to the original Minidisc format?

    Yes. Hi-MD formatting does not cause an irreversable change to the disk. Since a non-Hi-MD machine cannot read a Hi-MD reformatted disk it will report "BLANK DISK", at which point you can record on it.

  11. What happens if I try to play a Hi-MD formatted disk in a non-Hi-MD machine?

    A non-Hi-MD machine will not be able to read either the 1GB Hi-MD media or an original Minidisc reformatted in Hi-MD, so it will report "BLANK DISC" when you insert it.

  12. What happens if I try to record on a 1GB Hi-MD blank with a non-Hi-MD machine?

    This is yet unknown, but it will almost certainly not work since the 1GB blank's recording layer is of a vastly different construction than the original Minidisc. In any case, non-Hi-MD equipment can only treat the blank as a non-Hi-MD medium.

  13. What is the audio quality of ATRAC3plus?

    At Sony's Hi-MD annoucement they showed a chart depicting the relative standing of their audio codecs. The diagonal lines presume to indicate the audio quality equivalence of ATRAC3plus at 64kbps with ATRAC at 292kbps:

    Sony diagram from Hi-MD announcement
    Photo courtesy AV Watch

    However, this assertion is not well supported by scientific listening experiments conducted on Sony's behalf by Intertek Testing Services (UK) and TESTFactory (Germany). Both reports showed a near equivalency of ATRAC3plus at 64kbps with MP3 at 128kbps:

    From ITS Test Report, showing near equivalency of
    ATRAC3plus@64kbps and MP3@128kbps

    Still, this is heartening, since 1) 1GB blanks will be able to hold 34 hours of audio equivalent to MP3@128k and 2) ATRAC3plus at 256kbps should be quite good, and likely better than original ATRAC at 292kbps.

  14. Can I drag and drop ATRAC files between a Hi-MD system and a PC?

    No, SonicStage and SimpleBurner must be used to transfer audio between a PC and Minidisc.

  15. What are the technical specifications of the Hi-MD system?

      Current MD format Formatting existing MDs into “Hi-MD” format Hi-MD 1GB Disc
    Data Capacity 177MB 305MB 1.0GB
    Magneto-Optical Recording MethodMagnetic Field ModulationMagnetic Field Modulation Domain Wall Displacement Detection
    Laser Wavelength (λ) 780nm 780nm 780nm
    NA of Objective Lens 0.45 0.45 0.45
    Diameter 64.8mm 64.8mm 64.8mm
    Thickness of Substrate 1.2mm 1.2mm 1.2mm
    Tracking Format Groove Recording Groove Recording Groove Recording
    Addressing Wobbling Groove (ADIP) Wobbling Groove (ADIP) Wobbling Groove (ADIP)
    Data Modulation EFM 1-7RLL 1-7RLL
    Data Detection Bit by Bit PRML PRML
    Bit Length 0.59μm 0.44μm 0.16μm
    Shortest Mark Length 0.83μm 0.58μm 0.21μm
    Track Pitch 1.5μm 1.5μm 1.25μm
    Data Transfer Rate 1.25Mbps @1.2m/s 4.37Mbps @2.4m/s 9.83Mbps @1.98m/s

  16. What websites have Hi-MD information?

    English: Japanese: Dutch:

Copying Status: Public Domain. However, no liability is accepted for the correctness and safety any procedures or advice given here.This FAQ is distributed in the hope that it will be useful.Also,this file can be found at http://www.minidisc.org/minidisc_faq.html.