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What is the storage capacity of MDs, CDs, DATs, DCCs?
MD: ~160MB for 74 min. in audio mode [140MB in Data Mode]What is the minimum allocation unit when recording on an MD?
About 2 seconds for "SP" mode audio, 4 seconds for "SP" monaural, 4 seconds for "LP2" and 8 seconds for "LP4" mode audio. Audio information on Minidisc is organized in cluster units, which constitute the minimum unit for write or over-write of data to the disc. Each cluster contains 32 sectors of audio data, 3 "link sectors", and 1 sector of "sub data". Each sector is 2332 bytes, and 2 sectors are grouped together into a 4664 byte block holding 11 sound groups. Each sound group is 424 bytes and contains 11.6 msec of SP stereo data or 23.2 ms of SP mono data (LP2 and LP4 are double and quadruple the SP audio duration). A cluster is then 74624 bytes (32*2332), containing 176 sound groups (74624/424), for 2.0416 seconds of stereo sound (176*11.6) or 4.0832 seconds of monaural. See also the section on Prerecorded vs. recordable disc layout.The sound group (1/86th second) constitutes the finest resolution at which the audio stream can be edited. Older consumer grade MD decks have an edit positioning accuracy of approx. 60 msec (5 sound groups) but many modern machines allow edit positioning in units of a single sound group (11.6ms).
In Sony's AES paper on ATRAC they talk about the bit allocation algorithm, and how it in general allocates more bits than are available, so they have a method for subtracting an offset from the allocations in order fit within their bit budget for a sound frame.
In the zero or simple input case, there can be unused bits in some frames, but since there is an unvarying (i.e. fixed) relationship between 11.6 ms of audio and a 424 byte "sound group" on the disc, the system is not flexible enough to actually take up less disc space when it doesn't need it.
What's the difference between the 60, 74 and 80 minute discs?
The pregroove wobble is at a higher linear frequency (cycles/cm.) on the 74 minute blanks, causing the recorder to spin the disc slower (74 min: 1.2 m/s vs. 60 min: 1.4 m/s) and thereby record more information in the same linear space. The 80 minute discs are made by decreasing the track pitch (i.e. space between tracks) from the MD standard's 1.6um to 1.5um (micrometers), the minimum allowed by the MD specification; like the 74' blanks, they also run at 1.2 m/s. There is also information encoded in the read-only TOC near the inner circumference of the disc telling the player how long the disc is. Originally it was difficult to make the 74' blanks, but nowadays the manufacturing costs of 60' and 74' discs are the same (as well as, presumably, the 80's).How does a pre-recorded MD differ from a recordable one?
Physically, a pre-recorded MD is just like CD, using the same optical parameters, material, and production methods. Only the data contents are different (compressed ATRAC audio vs. 16 bit linear PCM audio). Unlike recordable MD, pre-recorded MDs do not have the magneto-optical coating layers or the lubricating layers. They are made with the same plastic-aluminum structure as CDs, so there is no way to record or erase anything on them. Prerecorded MD's are also read exactly like CD's (the player focuses a laser on pits and valleys within a transparent polycarbonate substrate backed by a coating of aluminum thus reflecting or dispersing the beam).Recordable MD's are similar, but a pre-groove replaces the pits and valleys and an MO coating replaces the aluminum one. When recording, a laser is focused from one side of the disc onto the pre-groove and heats a spot on the MO recording layer to its Curie point while a magnetic field from a head in contact with the other side of the disc aligns magnetic domains within (read: magnetizes) the heated spot on the MO layer (the N/S orientation corresponding to 0s and 1s in the data). During playback the MD machine focuses the laser on the pre-groove again, but at lower power, and the data is read back by measuring changes in polarization of light reflected from the previously magnetized regions (the Faraday effect).
In order to playback both pre-recorded and recordable media, all MD units have a dual function optical assembly which can, depending upon the disc type, detect changes in either reflectivity or polarization.
In terms of audio quality, pre-recorded MDs are in theory no different than recordable MDs, although, as always, audio quality depends upon which version of ATRAC the discs are encoded with. Some users have noticed certain pre-recorded MDs that sound worse than a homemade copy of the same CD with a modern MD recorder. It's likely that the ATRAC encoders used for prerecorded MDs are improved over time just as they are in the consumer units.
Finally, recordable MDs have an extra hole in their case, which is sensed by a microswitch within the MD unit that connects to the REFLECT pin of the microprocessor. It tells the MD player's microprocessor whether signal reflectivity is high (for pre-recorded) or low (for recordable).
Is there a difference in the disc layout of a recordable MD and pre-recorded MD?
On recordable MDs, 32 out of 36 sectors in every cluster (the smallest recordable unit) are used for storing audio data. Of the remaining 4 sectors, 3 are needed to accommodate the start up and run out of the error correction code, as stated in the Minidisc IEEE paper: ``Because of the long interleaved ACIRC error correction code, three sectors must be used as "linking sectors." If the user changes or adds new data to the MD disc, two or three sectors for every start and end position of the new data need to be recorded.''. In other words, some space is wasted to accommodate re-recordability. On pre-recorded MDs, however, the data is fixed during mastering as one continuous stream, so these 3 extra sectors can be devoted to sub-data (but there is no documentation as to what this extra sub-data space could be used for). The Sony DADC MD handbook says that the maximum duration of a pre-recorded MD is 78:16.What is the status of Sony's push to have MDs replace CD-ROMs?
Sony wanted MD-Data to replace 3.5" floppy-disks (1.4 Mb, 2.8 Mb and 21 Mb floptical), not CD-ROM (a well implanted medium in the computer industry by now, and currently cheap). MD-Data's first incarnation was the MDH-10 SCSI drive, it provided 140 MB of data storage on an MD but was slow, expensive and incompatible with the Audio MD format (Data drives cannot read or write audio MD data except in "play" mode, which does not provide computer access to the data.). Sony subsequently released the MDM-111 for use in the IBM Thinkpad, but neither drive became popular and the MD-Data format has effectively been shelved, and appears only in certain niche products such as the MD still camera and MD document scanner.Can an MD Data drive be used to access the ATRAC data on an MD Audio disc?
No, there is a read-only label track on each MD that distinguishes an MD Audio and MD Data disc, MD equipment looks at this label to determine what kind of disc it is accessing. An MD audio disc inserted in an MD Data drive shows up as having 1k in disc, 0k available. The ATRAC encoded music information is not accessible. An MD Data drive user has written some information about the MD Data drive and cross compatibility.Presented here are the results of a small experiment I conducted to compare the raw block error rate of various brands.
The service manual for the Sony MDS-503 Minidisc Deck tells how to put the unit into test mode, and from there how to display the BLER (raw block error rate [per second]) as it reads the disk. Using this feature I compared the block error rates of TDK, Idemitsu, Maxell, Panasonic, Sony and Keep blanks.
In Andy Poggio's CD paper he says: "The CD specification allows for discs to have up to 220 raw errors per second. Every one of these errors is (almost always) perfectly corrected by the CIRC scheme for a net error rate of zero."
I have reason to believe that 220 is the threshold for MD as well, since MD uses [modified] CD logic for encoding data on the disc, and since 220 is actually one of the error thresholds used for setting the MDS-503 focus bias.
The un-surprising result: No discs had anywhere near an BLER of 220.
The procedure is to use "continuous recording" in diagnostic mode to make a test disk, then look at the error rate while reading back from the disk.
The table below shows the average and maximum BLERs for each brand. "In", "mid", and "out" refer to the three areas on the disc which are tested by default, they begin at cluster 40, 300, and 700 respectively.
| Brand | in | mid | out | |||
|---|---|---|---|---|---|---|
| avg | max | avg | max | avg | max | |
| TDK | 4.97 | 20 | 5.08 | 15 | 4.16 | 19 |
| TDK (1) | 4.05 | 22 | 5.00 | 15 | 3.66 | 18 |
| TDK (2) | 5.96 | 20 | 2.47 | 6 | 3.84 | 18 |
| IDEMITSU (3) | 2.11 | 15 | 1.15 | 5 | 1.22 | 5 |
| MAXELL | 1.18 | 4 | 3.05 | 15 | 2.24 | 8 |
| PANASONIC | 6.00 | 13 | 5.45 | 10 | 4.13 | 8 |
| SONY (4) | 43.03 | 88 | 3.93 | 14 | 2.00 | 7 |
| KEEP | 2.10 | 5 | 1.93 | 5 | 3.23 | 13 |
| Sony ES | 1.60 | 5 | 1.00 | 3 | 1.59 | 5 |
| Canfield Audio 60/GL-16658 | 7.05 | 13 | 8.50 | 19 | 5.82 | 12 |
| Canfield Audio 74/GL-16658 | 11.76 | 31 | 10.13 | 25 | 9.36 | 20 |
| Fuji 60/ 5Z20M536 | 0.87 | 5 | 0.76 | 3 | 0.83 | 3 |
Some discs had been recorded on previously in normal audio recording ("non-continuous") mode. The BLER of these areas was typically 20-50, and always higher than the areas made with "continuous-recording" in diagnostic mode.
The Sony disc was the only surprise, perhaps it had a weak/bad spot. In any case, it was still well within the presumed threshold for CIRC.
I am not sure if comparative quality judgements can be made from these results since the tests were done on three short (approx. 10 second) intervals of each disc. I think the main conclusion is that all the discs are well within the threshold of "identical" from a post error correction point of view.
The other consideration is longevity, and I quote two paragraphs from the excellent book by John Watkinson The Art of Digital Audio where he is discussing the magnetic layer of a Magneto-Optical disc:
Magnetic layers with practical Curie temperatures are made from proprietary alloys of iron, cobalt, platinum, terbium, gadolinium and various other rare earths. These are all highly susceptible to corrosion in air and are also incompatible with the plastics used for moulded substrates. The magnetic layer must be protected by sandwiching it between layers of material which require to be impervious to corrosive ions but which must be optically transmissive. Thus only dielectrics such as silicon dioxide or alumnium nitride can be used.So, perhaps, more expensive discs might last longer (rather than have a lower initial error rate). I don't know the real situation though, maybe all the manufacturers have excellent quality control....
The master is developed and electroplated as normal in order to make stampers. The stampers make pre-grooved disks which are then coated by vacuum deposition with the MO layer, sandwiched between dielectric layers. The MO layer can be made less susceptible to corrosion if it is smooth and homogeneous. Layers which contain voids, asperities or residual gases from the coating process present a larger surface area for attack. The life of an MO disk is affected more by the manufacturing process than by the precise composition of the alloy.
I've heard that after many recordings and edits an MD can become fragmented, is this a problem?
My comments are with reference to modern MD machines (ca. 1996), I am unfamiliar with the behavior of the older units. I am also speaking based upon my observation of simple experiments on an MDS-503, not on any intimate knowledge of MD technical specifications.There are two potential problems with fragmentation: interruption of music due to excessive seeking, and loss of free space.
Concerning interruption of music, fragmentation alone will not cause a problem. A typical MD player can buffer 10 seconds of music and read the disc at 150 Kbytes/sec. (roughly the 1x CD data rate) which is over 4 times the MD audio rate. You will only have problems if it takes the player more time over any 10 second period to access and read segments of music than it does to play them.
My simple tests with the '503 showed that it could not keep up with an arbitrarily long string of 2 second segments located at alternate ends of the disc (on a 74' MD), but that it could with 4 second segments. Assuming a full stroke seek takes about 2.3 seconds (measured by listening to the unit seek) and 3 seconds of music can be read in about 0.7 seconds, it would seem that the smallest segments a player could keep up with on a continual basis would be about 3 seconds long if they were located at worst case locations on the disc, and would cause the player to be constantly seeking and reading. You would need to have a string of segments this size or smaller, for at least 10 seconds duration, at opposite ends of the disc, to cause a problem.
This simply cannot happen through fragmentation alone since all free list segments are at least 12 seconds long (see below). A worst case seeking condition that caused intermittent muting could still be created if 3 second or shorter segments from opposite ends of the disk were catenated together, but free list segments are allocated in sorted order (see FAQ section on allocation), so that unless you are trying to create such a pattern, you are rather unlikely to make one in the normal course of editing.
The free space problem is caused by unused segments of disc space less than 12 seconds long that are not available for reuse. My simple tests showed that whenever the MDS-503 could coalesce space it did, so that lost space is only a problem when many small unused segments less than 12 seconds long are scattered throughout the disc, not adjacent to any existing free space. It is possible that in a normal editing operation of deleting dead space between tracks, up to 12 seconds per track could be lost, and on a disc with 25 tracks that would be 5 minutes lost to fragmentation. Though this does not seem troublesome, one real problem may occur in a sound effects application where all the tracks are tiny (< 12s), since if you were to delete every other track, nothing could be coalesced and there would be no change in the amount of free space.
Though the degree of fragmentation depends upon your recording and editing patterns, I cannot see it causing problems in any but extreme circumstances. It should also be noted that all fragmentation is eliminated when an "Erase All" operation is performed. This restores the disc to a single TOC entry containing all the free space.
MD Lens and Head cleaning discs are being sold, do these help?
Two users have reported that their car units began skipping badly, but that after cleaning the laser lens by hand the problem disappeared (though both noted that the lens did not appear to have any dust or dirt on it before cleaning). Subsequently one user now uses a TDK lens cleaning disc when problems develop, which appears to be as effective as hand cleaning. No reports yet on the need for or effectiveness of the head cleaning discs. (Thanks to Jon Long ([email protected]) and Shawn Lin ([email protected])However, Arnaud Devilder (MPO MD disc sales manager) says: "I have to say that these products are only MARKETING. Avoid using them, we saw in our test labs that these products are very bad for your hardware."
A very high durability of the [magnetic head] contact cycle can be achieved, e.g., more than a million passes.Taking the worse case scenario, an MD machine left in record-pause mode at the lead in (i.e. innermost) area of the disc [diameter: 32mm] and running at the highest linear velocity (1.4m/sec) would spin at [1.4/(.032*3.14159) * 60] = 836 rpm. At this speed, 1 million revolutions [passes] would take approx. 20 hours. So, record-pause for several hours is okay. A day or two is probably not.
Here's a tip when recording a CD unattended: put the CD player in repeat-all, this will cause the MD player to record to the end and stop (rather than go into record-pause). You can easily delete the extra tracks later.
Is there an audible difference between modern MD and CD/DAT?
Since MD stores audio using a data reduction technique (see ATRAC, below) there are considerable differences between the audio signal from a CD and that of an MD digitally recorded from it. Whether or not these differences are audible however depends to a large degree upon who is doing the listening, most MD users consider the sound quality of modern MD equipment to be essentially the same as CD. But even those who can hear differences usually find them to be undisturbing and inconsequential, frequently being unable to say which is which. (Note that a proper A/B comparison of the two formats necessitates using the same DAC. If an outboard DAC is unavailable, or the MD unit (such as a portable) does not provide digital out, the MD unit's monitor mode can be used to do D/A conversion of external digital signals, thereby allowing comparison with a common DAC.)A small double-blind test made by the ABX Company found that subjects did not find a difference between ATRAC processed music and its original, but could readily spot the difference when a special test signal was used for the comparison.
However, one significant difference with DAT is that differences with the original increase in each subsequent copy generation, even when recording digitally. Each time the MD is played, a full 16-bit data stream is regenerated from the compressed data. Each time it records, the input data stream is recompressed. The artifacts of the compression process build up from generation to generation. See ATRAC below.
What is ATRAC exactly? How does it compare to PASC?
ATRAC (Adaptive TRansform Acoustic Coding) divides the 16 bit 44.1 KHz digital signal into 52 sub-bands in the frequency domain (after a Fast Fourier Transform). The sub-bands in the low frequencies are finer than the ones in the high frequency range. A psycho-acoustic transfer function that takes advantage of the masking effect and the absolute hearing threshold then removes enough information to reduce the data stream to 1/5th of the original size. Each channel receives that treatment separately (the Sony MZ-1 portable MD recorder features one ATRAC encoder/decoder chip per channel). PASC (Precision Adaptive Sub-band Coding -- used in Philips now defunct DCC [Digital Compact Cassette]) divides the digital signal into equally spaced sub-bands and removes less information (to only 1/4th of the original size). PASC is essentially the MPEG Layer 1 audio standard (can be decompressed with MPEG Layer 1 players after a trivial preprocessing step).Both are data compression algorithms, used to store the information content from a stream of 16-bit samples in fewer bits. The purpose of compression is to reduce the rate at which the disk has to deliver or record bits, and to reduce the total number of bits stored. There are many compression algorithms. The ones used for computer data (for example in archiving programs) are lossless; the result of decompression is identical to the input.
PASC and ATRAC are both "lossy" algorithms. In order to get greater compression, they do not attempt to preserve every bit of the original data, but rather only the acoustically "important" bits. Considerable cleverness goes into finding the sounds masked by properties of the human auditory system, ones that you would not hear even if they were reproduced. By all accounts the two schemes do amazing well, considering they operate in real time.
See the AES paper on ATRAC for further technical details.
What is the bit rate of the Minidisc's ATRAC audio after compression?
For a stereo signal it's 292162.5 bits/sec. ATRAC compresses 512 incoming 16 bit samples (1024 bytes) into one ATRAC ``sound group'' (212 bytes) giving an audio compression ratio of 4.83:1. Here is the math:44100 samples/sec (incoming single channel rate)ATRAC3 (used in MDLP) runs at 132kbps (LP2) and 66kbps (LP4). See the MDLP FAQ for further details.
/ 512 samples/soundgroup (giving 86.133 soundgroups/sec/channel)
* 2 channels (giving 172.266 stereo soundgroups/sec)
* 212 bytes/soundgroup (giving 36.5K stereo bytes/sec)
* 8 bits/byte (giving stereo bits/sec)
= 292162.5 bits/sec.
VQF has a system offering 18:1 compression, pitched as something of an alternative to MP3.
The next question then becomes, why not copy the compressed data directly, thereby avoiding the asymmetry of compression and decompression? Unfortunately, consumer grade MD machines do not provide access to their compressed data, nor do they provide a way of directly recording compressed data, even if it were available. The S/PDIF digital interconnect only carries data in the linear (PCM) format. Professional machines however (such as the Sony MDS-B5 with direct ATRAC I/O) do allow exact bit for bit MD copies to be made.
What else (besides compression) affects the sound quality of MD?
The entire rest of the sound reproduction chain is important. The digital to analog converter (DAC) is key to reproducing the sound from the decompressed data. The audio amplifier circuitry is also critical. And there have been reports of MD playback machines (not Sony) that were made unlistenable by poor-quality attached headphones!Every component of the chain from the DAC to the eardrum is important to good sound reproduction. All elements other than the compression algorithm must be held constant before A: B comparisons are made, for example.
The decoder (playback) side of ATRAC has a fixed structure, and though ATRAC chips are all generally expected to decode with nearly the same quality, increases in digital signal processing accuracy may allow slight audio quality improvements (if those improvements have not already been made to modern ATRAC chips).
Since the ATRAC encoder plays the largest role in how an MD sounds, the implication for making digital copies between two MD units is to use the older unit for playback and the newer one for recording. When making analog copies, the relative quality of the A/D and D/A converters must be born in mind.
What's the difference between the various ATRAC generations, and how well do they interoperate?
The following sections refer to Sony's ATRAC. Sharp and Matsushita (among others?) have developed ATRAC chips of their own, though rather little has been made public about their evolution. While all manufacturer's ATRAC versions interoperate and are based upon Sony's original specification, it is not possible to compare their version numbers. Version numbers frequently serve to enumerate Minidisc/DSP chip generations as much as actual ATRAC algorithm changes, so there is no direct relation between version number and audio quality.
| ATRAC 1 | ATRAC 2 | ATRAC 3 | ATRAC 3.5 | |
|---|---|---|---|---|
| Introduction | 1993 (Too early due to DCC) | 1994 | 1995 | Current |
| Threshold | 15KHz | 18KHz | 18KHz | 18KHz |
| Noise | Big! | Much lower than ATRAC 1 | Dynamic filter: no noise in breaks | ==DAT |
| Sound | metallic | close to DAT | no difference to DAT in "blind listening test" | ~=DAT |
| Sparkling Noise | hearable | not much better | only hearable in very silent passages | gone |
| ATRAC 1 recorder MDS-101 | ATRAC 2 recorder MDS-501 | ATRAC 3 recorder MDS-303 | ATRAC 3.5 recorder MDS-JA3ES | |
|---|---|---|---|---|
| ATRAC 1 Player | (see table above) | 15KHz! Less noise | 15KHz! Less noise | 15KHz! Less noise, "sparkling noise" gone |
| ATRAC 2 Player | 15KHz threshold! Less noise, still metallic sound | (see table above) | No difference from ATRAC 2 recorder | No "sparkling noise", a bit less noise (as when recorded with 2.0) |
| ATRAC 3 Player | No big difference from above | No difference from ATRAC 2 player | (see table above) | No "sparkling noise", a bit less noise (as when recorded with 3.0) |
| ATRAC 3.5 Player | No big difference from above | "sparkling noise" still not better, but less noise than above | low level "sparkling noise" remains, a bit less noise than above | (see table above) |
In general, all ATRAC versions are fully compatible with each other. However, if you play or record something with 1.0 the result will be rather poor no matter from which version the source came from or goes to. If you take a higher version the result is generally be good enough, when you use ATRAC 3.5 for either playing or recording it gets even a bit better. For portables and car-players with 3.0, the weakest link is the A/D converter.
The practical result: buy a 3.5 or better for 'home use', record there, and you get better quality in your 3.0 portable or car-player.
| ATRAC 1 to ATRAC 1 | After 5 generations unacceptable, after 20 generations awful. |
| ATRAC 2 to ATRAC 2 | After 5 generations no hearable difference, after 20 generations tiny distortion. |
| ATRAC 3 to ATRAC 3 | Not much better than with ATRAC 2. |
| ATRAC 3.5 to ATRAC 3.5 | Slightly better than ATRAC 3, relating to noise. |
Translated by Felix Gers.
What actual changes have been made to ATRAC over the years?
There is not much information about this other than what Sony says in their brochures and what appears in occasional magazine articles (thanks primarily to Japanese MJ and German Stereo magazines for their detailed reporting). Since ATRAC's transform window size (11.6ms) and signal processing structure are fixed, the improvements come primarily through improvements to the signal processing step's mathematical accuracy and refinements to the bit allocation process. In brief:
| ATRAC 1 | 16x16 bit multiplication, no short mode blocks generated by encoder |
| ATRAC 2 and 3 | 16x24 bit multiplication |
| ATRAC 3.5 | Block Floating type calculation to improve performance on small signals (see: Japanese MJ Magazine MDS-JA3ES review) |
| ATRAC 4 | 24x24 bit multiplication, frequency response still 19kHz (see: German Stereo article on ATRAC 4) |
| ATRAC 4.5 | Adaptive High Band Control, frequency response pushed to 20kHz, noise lowered 3dB through higher computation accuracy (see: German Stereo MDS-JA50ES review) |
| ATRAC using Type-R DSP | Faster DSP allows two pass bit allocation algorithm that looks for redundancy and makes better use of available bits, providing further improvements to high frequency performance. (see: Sony blurb on ATRAC using Type-R DSP). Not known to have any improvements to decoding. |
| ATRAC using Type-S DSP | ATRAC chip that combines an upgraded ATRAC3 codec (with apparently improved decoding performance) and an ATRAC1 Type-R codec. (see: Sony MDS-JB980 equipment table) |
Is there any loss of information when I record from a CD?
There are two sources of distortion. One is the chain of components that brings the sound to the MD's input. If you go analog-to-analog, you introduce the CD's DAC and the MD's ADC chips, each with its own artifacts. However, you can bring the digital data stream directly to the MD; then the only source of differences is the ATRAC compression algorithm.The ATRAC encoder removes information from the audio material in order to store it on the MD (5: 1 compression with loss). To make better MD recordings from CD, connect the MD recorder to the CD player via a digital connection (if possible). Thus, the ADC (poor in the first generation machines) cannot affect the sound quality. Otherwise, when recording via the analog input, make sure to adjust the manual recording level on the MD machine so that the meter peaks just above -12 dB (on the Sony MZ-1, never enable the AGC for CD recording).
When I record from tape, microphone, or other analog sources?
Yes, because the MD's analog to digital conversion circuits are involved, in addition to the ATRAC compression. High-end MD decks frequently have sophisticated analog circuitry, offering improved recording and playback performance over mid-range decks even when they share the same ATRAC chip.I don't have the equipment to make a digital recording, will my recordings sound okay?
Providing you've got a clean source signal, analog recordings generally sound fine, giving nearly inaudible differences from digital ones. Note however that many computer soundcards have noisy analog output stages, so when recording from a computer, digital transfers are recommended (one exception is the USB based Xitel MD-Port AN1 which runs outside of the PC chassis and produces good quiet analog output). When making analog recordings, do set the recording level manually to avoid the audible effects of the Automatic Gain Control (AGC) circuitry adjusting the level during very loud and very quiet passages.One advantage of analog recordings is that MD recorders flag them "SCMS-penultimate", meaning that a digital copy can be made of them. One disadvantage of analog recordings is that track marks will be laid down based upon the recorder's detection of silences in the analog source (depending upon recorder settings and capabilities); this is less reliable than using the digital indications of track changes available in an S/PDIF (digital) signal from CD players.
Regarding the 'R30: A user connected a 303 to the R30 using a POC (optical) cable and compared the two meters. The result: Just consider the top bar to be 'digital over' and try to adjust your level in such a way that the second bar doesn't light up too often when recording from an analogue source (even less when recording live). That should do it. Compared to the MZ-1 the R30 meter is not very useful.
Is it worth it to get the equipment necessary to make digital recordings?
Digital recording provides the most convenience when copying CDs: no recording levels need to be set, track marks are copied from the CD perfectly, and analog to digital conversion artifacts (real or imagined) are completely avoided. The one problem with digital recording is that SCMS will prevent further digital copies to be made from the copied MD.Crutchfield's Tip of the Week is devoted to analog vs. digital recording to Minidisc.
Which ATRAC chips are in which MD units?
This information came in part from a Japanese magazine "MJ" and the 9/96 issue of the German Stereo magazine:
| IC Generation | IC Part Number | MD Deck | Introduction Date |
|---|---|---|---|
| ATRAC 1 | CXD-2527 | MDS-101 | 2/93 |
| ATRAC 2 | CXD-2531 | MDS-102 MDS-501 | 11/93 2/94 |
| ATRAC 2 | CXD-2531R | MDM111 MDH-10 | |
| ATRAC ? | CXD-2535CR-1 | MZ-E40/E20 | |
| ATRAC 3 | CXD-2536R | MZ-R3 | 5/95 |
| ATRAC 3.5 | CXD-2536A | MDS-JA3ES | 6/95 |
| ATRAC 3.5 | CXD-2536B | MDS-503 | 10/95 |
| ATRAC 3.5 | CXD-2536AR | MZ-E40 | 1/97 |
| ATRAC 4.0 | CXD-2650R | MDS-JE500/S37 N. American MDS-JE510 MDS-JE700 | 8/96 |
| ATRAC 4.0 | CXD-2652R | MZ-R30 | 8/96 |
| ATRAC 4.0 | CXD-2652AR | MZ-R50/MZ-R55/MZ-R37 European MDS-JE510 | 8/97 |
| ATRAC 4.5 | CXD-2537R | MDS-JA50ES | 12/96 |
| ATRAC 4.5 | CXD-2654R | MDS-JE520 | 9/98 |
| ATRAC Type-R DSP | CXD-2654R | MDS-JA20ES/JA22ES | 5/98 |
| ATRAC Type-R DSP | CXD-2662R | MDS-JB940, MXD-D5C | 2000 |
| ATRAC ? (>= 4.0) | CXD-2660GA | MZ-R90/R91 | 10/99 |
| ATRAC ? (>= 4.0) | CXD-2671-201GA | MZ-R900 | 10/00 |
| ATRAC ? (>= 4.0) | CXD-2671-202GA | MZ-E900 | 10/00 |
| ATRAC Type-S DSP | CXD-2664 | MDS-JB980, MDS-JB780 | 8/02 |
| ATRAC ? | CXD-2655R | Grundig MD-P1 |
See also the ATRAC version table.
Regarding the occurrence of outright bit errors due to a marginal cable: S/PDIF contains only parity information, there is no error correction capability. If the errors are bad enough to cause bits to arrive with incorrect values, the likely result is that the digital audio receiver will not be able to lock on to the signal.
A short paper by DJ Greaves goes into further detail about S/PDIF, and has some comments about why jitter is not a problem even in equipment without buffers. Another paper by Tomi Engdahl goes into great detail about S/PDIF, even giving schematics for AES/EBU <-> S/PDIF conversion. Finally, Digital Domain has written a very comprehensive paper on jitter in digital audio systems.
A cheaper route, if you're willing to do a little electronics work, is to follow Shawn Lin's instructions for making a converter from parts.
What follows is a discussion of audio digital interfaces. These interfaces come in 2 classes, optical and electrical.
The optical format has two connector types: the small, squarish "TOS-link" connector and the optical miniplug, which has the same connector dimensions as a normal (electrical) mini-plug. You can buy optical cables with any combination of these two [male] connectors at the ends. TOS-link is usually limited to maximum cable lengths of 10 to 15 meters. The Sony part numbers for the optical cables are as follows: miniplug/miniplug: POC152HG, miniplug/TOS-link: POC151HG, TOS-link/TOS-link: POC-15HG. These cables can be ordered from Sony Parts (see below).
There are two electrical formats. [the following excerpted from the DAT-link manual]
SPDIF: (Sony/Philips Digital InterFace): This is the interconnect that is most often used on consumer DAT machines. The connectors are standard RCA phono connectors. This type of connector may also be lableled "IEC Type II" or simply "Digital I/O". Standard analog phono cables can usually be used for the digital data, however some cables that are designed for analog may not be able to carry the high rates needed for the digital data, especially over long distances. Many high-end audio stores carry special digital phono cables that solve this problem. [The pro-audio FAQ says not to use audio cables, but that video cables will work].
AES/EBU: This type of cabling is most often found on professional equipment. It uses three-pin XLR connectors. Cables designed for analog applications work fine for AES/EBU connections as well. However, note that shielded cables (most cables are shielded) must be used, otherwise unacceptable levels of radio or TV interference may be generated. This type of cabling is the preferred choice for long distance runs between digital audio equipment.
It is important to realize that there are subtle differences in the control information that is sent along with the audio data on these different connectors. The two main formats of this information can be broadly categorized into Consumer and Professional. For most applications, if you are using the SPDIF or fiber-optic connections, the consumer format applies. For AES/EBU connections, the professional format applies. Some DAT machines will not operate at all unless the correct format is used.
A conventional 16/20/... bit DAC uses resistive dividers to add a value proportional to the bit significance of each bit to its output voltage. As more bits are added to the DACs resolution, the more significant bits' accuracy must be improved to at least the value of the least significant bit, or there is no point in increasing the resolution. It is quite difficult to make a resistive divider network with the required accuracy.
With a 1 bit DAC, the output voltage is produced by pulse width modulating a single fixed voltage. The accuracy is determined by the stability of the clock that times the width of the pulses - it is not difficult to very accurately time duty cycles using a clocked counter. All that is needed to increase the resolution of a 1 bit DAC is a faster clock and a counter with more binary digits. -Colin Burchall
There are two classes of DACs. One-bit DACs and multi-bit DACs. A 20 bit DAC is (theoretically) better than a 16 or a 8 bit DAC. You can't compare them with one-bit DACs because they use another principle to convert from digital to analog. Multi-bit DACs always convert different values for the same time period. One-bit DACs convert the same value with different periods of time.
Multi-bit DAC: Fixed time period, varying voltage/current.
One-bit DAC: Fixed voltage/current, varying time period.
-Ralf Kuchenhart
Do MDs skip during playback? Why not?
Rarely. A read-ahead buffer stores a few seconds of the audio material in memory during playback. The ATRAC decoder takes the data from the buffer, rather than directly from the medium. Thus, if the mechanism mistracks because of shock or vibration, the data continues to flow from memory while the MD machine recovers. If no more data remains available (when the disturbance lasts a long time), the audio material gets interrupted. Also note that the read-ahead buffer exists on every MD machine as part of the MD format.Modern Sony portables (MZ-R900/700/500 and later) have an improvement to their skip resistance called "G-Protection", Sony describes it as follows:
For the first time in MiniDisc players/recorders, Sony offers Skip-Free* G-Protection technology. Now you can jog with it, blade with it, board with it and enjoy other favorite activities while listening to uninterrupted, skip-free music. The G-Protection technology recovers laser position 10 times faster than previous designs! So it can withstand the impact of actual jogging: 8G impacts at 3 times per second.
- Quicker Focus Recovery...after a shock
The laser pick-up adjusts its focal point quickly enough to react to bumps.- Faster Track Recovery...returns to the right spot
When bumped, fine access returns the laser pick-up quickly back to its original position so the data can continue to be read without interruption.- High Speed Rotation...refills the memory faster
Disc can rotate faster to read out the data much quicker.*Eliminates or reduces skipping during many active uses.
Does the size of the music buffer vary from player to player?
Yes. Modern MD machines (ca. 1997/98 and later) feature a 40-second read-ahead buffer (MDLP machines store 80 seconds in LP2 mode and 160 seconds in LP4 mode), but earlier machines only offered 10, and some of the first offered only 3 seconds of memory, such as the first production run of Sony MZ-1 portable MD recorders and the Aiwa AMD-100.The MJ Magazine MDS-JA3ES article provides a good basis for understanding how this feature works. ATRAC (and other transform audio coders) store audio in the frequency domain. The samples are stored as floating point numbers, with an exponent and a mantissa. The so-called Scale Factor is the exponent, which is stored in 6 bits, giving 64 (2^6) possible values and yielding final sample values in the range of -120dB to +6dB. Each Scale Factor step is 2dB. During an SF Edit operation, each soundgroup is read in from disc, the Scale Factors within it are incremented or decremented by a certain amount, and it is written out again. It's a much cheaper operation computationally than decoding to the full waveform, scaling it, and then recoding it.
Scale Factor Edit does have a limitation: If you use Scale Factor Edit to decrease volume to the point that some Scale Factors in the signal become zero, the information in those samples is lost and cannot be restored by a subsequent Scale Factor Edit operation to increase volume. Likewise, if Scale Factor Edit is used to increase volume beyond the point at which some Scale Factors in the signal attain the maximum possible Scale Factor value, previously distinct Scale Factor values will begin to "max out" at the highest value and the signal's fidelity and dynamic range will decrease unrecoverably. Due to this limitation, SF edit operations that taper track endpoints to or from zero volume cannot be reversed.
What happens if I bump my player when I'm recording?
Many users have reported problems if the MD recorder experiences shock and vibration while recording. Apparently the read-ahead buffer also works for recording, but strong disturbances could cause the laser to erase other spots on the MD, like the TOC or existing tracks, thus damaging previous recordings. To remain on the safe side, the MD recorder should not be subjected to shock or vibration while recording.MD drives certainly buffer during recording, otherwise MDs could not make recordings over discontiguous free blocks on the disc due to the dead time during interblock seeking. The bigger problem is, what happens when the recorder is jarred and the hot laser skids across already recorded material? One of the brochures for the professional MD units mentioned that they had a special circuit to cut the laser power when any shock occurred, thereby avoiding overwriting [much] already written material. On the normal consumer portables, you could probably lose some material when a shock occurs during recording. In any case, they're able to recover and get back on track.
How flexible is the process where I put the titles of the tracks on the MD?
The user-interface for title entry on many portable MD recorders is limited, requiring a button push to cycle past every letter. Most current home decks have a remote with a non-querty character input method. Notable exceptions are the Aiwa portable that uses the volume thumbwheel on the remote to select each character, and some modern MD decks (chiefly Sony) that allow titling with a separately available keyboard-like remote or even a standard PS/2 keyboard in some cases.Is there a limit to the length of the titles?
The titling capacity in the Minidisc UTOC is as follows:Is there anyway I can "undo" an edit operation if I delete the wrong track while editing?
All modern (ca 1996 and later) MD decks have an "undo" function for just this purpose.Modern Sony MD decks also have a hidden super UNDO function. A user describes how to cancel a pending TOC update on modern Sony MD decks.
If you have an older machine without an ``UNDO'' function, there are two approaches. If you've got an MDS-302, 303, S35, or S37, try this first:
This machine doesn't have a specific undo function, but it can be made to forget about the edits in a simple manner, without having to open the unit. When you have deleted a track by accident for example, you just unplug the unit. Make sure that the unit isn't playing or recording before you unplug it (press the Stop button first). Now wait for about 30 secs for the power supply capacitors to discharge. Press the AMS knob, and while holding it, plug the unit back in. If you're lucky the recorder will enter in Test Mode (it always did this correctly in my case). Now you can simply press the Eject button to remove the minidisc without the new TOC being written to disc! The reason that you must enter Test Mode is because when you just plug the unit back in, it still remembers that the TOC isn't written yet. The moment you plug it back in the new TOC is written to the disc and you have lost the deleted track forever! After you have removed the disc press the Repeat button to leave Test Mode. You have to unplug the unit and plug it back in to enter the normal user mode.
-Steven Scholte ([email protected])
The following is a method that will work for all machines, but it requires more work:
I'm sure everyone who has a Minidisc deck has done this. You're editing down a disc, splitting blank spots away from other tracks, then deleting the blank spots - and all of a sudden, your quick fingers just deleted the track, rather than the space. This is usually followed immediately with loud obscenities. :) I hear that some of the new units have an "undelete" feature, but my MDS-302 does not have one.I did this once (twice actually, within a half hour) while editing down a disc on which I had made a one-time live recording of a choral performance, that could not be re-recorded. Desparate, I remembered that the MD unit only wrote the TOC (Table of Contents) to the disc when the disc was ejected. When you do edits, it's actually only changing pointers in memory, which are then all written at once to the disc when it's ejected.
With this in mind, I unplugged the unit while it was still turned on. I removed the case, and examined the drive mechanism. There is a large gear at the back, and I found that by turning it by hand, it worked the eject mechanism, and the disc was slowly ejected as I turned it. Once I had the disc in my hand, I plugged the unit back in.
I figured it would be confused, so I took a blank MD, slid the write-protect tab open so that it wouldn't write to it, then plugged it into my recorder. Once it figured out that it had a new, fresh disc, I then ejected it and re-inserted the original disc with the live recording on it.
As I had hoped, the disc had been restored, and all the edits I had made (including the one wiping out an entire track) had been forgotten.
Now, whenever I do any editing, I periodically eject and re-insert the disc (just to write the edits to disc). This way, if I DO mess up and have to go through the manual eject sequence again, I won't lose ALL of my edits.
-Scott MacLean ([email protected])
The MDS-501 can me made to "forget" about editing simply by unplugging it. Even if you turn it back on and eject the same disc (without removing it the hard way) your edits will be lost.
For the MZ-R30 portable, this will work:
The MZ-R30 writes the TOC-Area after pressing the Stop-button or, if batteries are in use, after disconnecting the AC power adapter. After deleting anything, the R30 begins playing the succeeding piece automatically. As long as the R30 is playing, the TOC-Area is not written. To Undo a delete, take away all power sources while the R30 is playing; the TOC-Area will be the same as before the deletion took place. But note, if you use the AC power adapter and LIP-12 or LR6 AA in the supplied battery case, you must first remove all batteries before disconnecting the power adapter, otherwise the TOC-Area will be written right after disconnecting the power adaptor.
SCMS stands for "Serial Copy Management System" and is the way copies of digital music are regulated in the consumer market. In essence, it prevents more than one generation of digital copying. It is implemented through information that is added to the stream of data that contains the music when one makes a digital copy (a "clone"). When making an analog copy only the music is transferred so there is no SCMS, and copying is totally unrestricted. Decks considered "professional" -- usually more expensive and with pro features, such as balanced XLR input/output -- are exempt from needing SCMS. Different manufacturers' pro decks behave differently: some allow one to set the SCMS code how one wishes, some only if the pro i/o is used, and some ignore it completely.
SCMS Bit Definitions:
Bits Meaning Explanation
---- ------------ ----------------------------
00 Permitted No restrictions at all
11 Restricted Allow 1 generation
10 Prohibited Do not allow copies
SCMS Operation on consumer decks:
Source Recorded on copy
-------------- --------------------------------
Analog input 11
CD 10
Digital, 00 11 or 00 (depending on model)
Digital, 11 10
Digital, 10 Will not record
Dubbing MD to MD with SCMS:
Play Deck Connection Record Deck SCMS Problem?
-------------- ------------- -------------- --------------
Consumer MD Digital Pro MD No
Pro MD Digital Consumer MD No
Pro MD Digital Pro MD No
Consumer MD Digital Consumer MD Yes
any MD Analog any MD No
SCMS does not limit the number of times you can copy a certain CD or MD. For instance, you can make 20 copies of a CD - you just can't copy any of the 20 copies.
It is ironic that if SCMS is to prevent unauthorized duplication of copyrighted information it has the above loopholes that a professional ripoff artist can easily use. And it is unfortunate that supposedly legitimate users, such as musicians recording their own music on cheaper, consumer decks, are restricted in the number of generations they can copy their music. [jfw/rg]
Is there an adapter for the strange little headphone connector on the MZ-E3's remote?
Sony makes an adaptor for that bizarre headphone connection. It's $13.34 (US). Call Sony at 1-800-488-SONY to order one. The part number is: in the US: PC-MP1HG, in Asia: PC-MP1S.Is there a Sony distributor I can order things from?
You can call Sony Direct Response at 800/222-7669, there are about 10 Sony Factory Outlet stores around the country and they can give you the location of the one nearest you.You can also try here:
SONYIn California, Sony has a "factory outlet" store:
Gallery of Consumer Electronics
663 N Michigan Ave
Chicago IL 60611
(312) 943-3334
(312) 943-0817 (fax)
Tracy Outlet CenterThere is another Sony outlet store in the Grove City Outlet Mall, Grove City PA, three miles south of I-80 on I-79.
1005 Pescadero Ave., Ste. 183
Tracy, CA 95376
Tel: 209-832-3440
Fax: 209-832-4435
You can also get Sony service manual and parts/accessories at:
Sony Electronics Inc.
National Parts Center
8281 N.W. 107th Terrace
Kansas City, Missouri 64153
phone: 800-488-7669 (parts)
816-891-7550 ext 33 (publications/manuals)
In Europe, you can order Original Sony Parts here:
Gehado Electronic Service GMBHand Sony service manuals can be ordered here:
Freigrafenweg 29
44357 Dortmund
germany, Tel: +49-231-937-000-21,22,23...28
Schaltungsdienst Heinz Lange
Zehrensdorfer strasse 11
12277 Berlin
Germany, Tel: +49-30-72-38-13
In the US, Tritronics carries Service Manuals and parts for Aiwa, Sony, Sharp, JVC, Panasonic, Denon and others:
www.tritronicsinc.comAlso at Pacific Coast Distributors (search for "Sony" and indicate model "md"). Chiefly (only?) for Sony's car MD units.
Tritronics
1306 Continental Drive
Abingdon, MD 21009
Telephone: 800 638 3328
Where is a good US Service Center for MD repair?
Try here for Sony equipment:Sony Electronics Inc.
Factory Service Center
Sony Service Center
390 University Avenue
Westwood, MA 02090
Phone: +1 800 282 2848
Fax: +1 617 329 1345
Sony also has a National Direct Response Center at 800-222-7669, representatives there can help you troubleshoot problems with Sony equipment.
Try one of these for Sharp equipment (or call 1-800-BE-SHARP and use your touch tone phone to find an authorized service representative near you):
Video Electronics & Parts
5260 Northwest 167 St.
Miami Lakes, FL 33014
305-623-8875
A $35 diagnostic fee is charged, but will be subtracted from the repair charges.
Advisory TV & Radio
175 7th Avenue
New York, NY 10011 USA
212 243 0786
In the UK, Sharp (and other maker's?) parts can be ordered from:
Partmaster Direct (A Dixons subsidiary): 0870 9090444.
Or here for direct factory service:
Sharp Engineering SEK
2-chome, 13-17
Kitaku, Higashi Tabata
Tokyo, JAPAN
Enclose a note describing the problem in simple and clear English.
Where can I get a case for my Minidiscs?
Any storage case for audio cassette tapes will work just fine for MDs, as long as it does NOT have individual compartments into which the cassettes are to inserted. Any open shelf for cassettes will be just the right depth for MDs, with about an inch of extra headroom which is actually fairly convenient (leaves room for your hand to grab a disc).
I did find the
Napa Valley "Cassette Crate 12", a single-shelf crate that (obviously)
holds 12 cassettes, and it clearly would hold about twice that number
of MDs in their little sleeves. So presumably the 2-shelf model that
I got might be called "Cassette Crate 24". And any other brand would
be just as good.
If it helps, the Napa Valley outfit is:
Napa Valley Box Co. Inc.but their stuff is in practically all good music stores. (Oddly, in spite of their name, they are nowhere near the Napa Valley, and their products are made in Mexico.) -Gary Milliken ([email protected])
11995 El Camino Real
San Diego, CA 92130
(619) 259-3000
I am using a plastic rack that is actually meant for DAT-tapes. You know the type that c-cassettes used in the history. You can hang the rack on the wall and attach several of them together... Two MDs fit into a space for one DAT. It might not be very nice looking furniture in the living room, but for example in a studio it is actually quite handy as when You hang the racks so that You can store the disks horizontally you can also easily read the labels... -Janne Auvinen Turku, Finland([email protected])
DAT cases work the best for storage. I bought mine in San Fran for under $35. It will hold a total of 80 MD's. It is heavily padded and comes with a durable shoulder strap and casing. -[email protected]
Thomas Halasz ([email protected]) reports that the hard plastic box that comes with Ferrero Roche Chocolates (Italy) is the perfect size for holding 25 MDs, sans jackets. The box is transparent with an articulated lid. The chocolate is good too.
Other users report: ``I just stick my MD's Sans case in a plastic 3X5 index card box. It holds 25, fits like a glove, and cost $2.'' and ``Here's a really cool MD storage idea (at least I think so); the wood crates that hold three bottles of wine with sliding wooden covers and wooden dividers. Fits perfectly, one box holds lots of MD's. Just watch out for slivers.''
Yet another simple suggestion: Just glue a stack of MD cases together. ([email protected])
You can also check the MD page accessories table for suppliers of cases.
How can I make labels on a computer for my MD sleeves?
A standard Avery label fits almost perfectly onto a minidisc sleeve with no cutting. It is Avery Label J8666 (perhaps also known as J7666). It is their 3.5" disk face only label. Word can automatically format for this label in it envelopes and labels section.Here are some pointers for printing labels for the Minidiscs themselves using the blank stickers that come with each MD blank disc:
These are the dimensions needed to print on the labels that come with Memorex Minidiscs using Microsoft Word. The dimensions are:Top Margin: 0.57"
Side Margin: 0.91"
Label height: 1.91"
Label width: 1.4"
Number across: 1
Number down: 1From the Labels dialog, click the "Options" button and then the "New Label" button and you will see a window with entry boxes for the above data along with a text box where you can enter a name for this type of label. (I used "Memorex Minidisc".) Click the "OK" button and the label data will be saved for future use.
Note that the actual dimensions of the label are slightly different than these (probably because Word and my printer don't exactly agree on how long 1" really is...) but these are what I found to work after some trial and error. Note also that this is for the main label only - also on the same sheet are 3 skinny labels that aren't printed to (but are accounted for in the side margin). If your printer will feed such a small sheet (which mine, surprisingly, did) then you're all set. If it won't, then you can tape the sheet to the top, right corner of a regular piece of paper and feed that through.
-Ross Miller ([email protected])
Though ATRAC2 was never incorporated into an exported Sony product, the Sony PlanetMG FAQ states "a second format, called ATRAC Data, is used by Sony in a digital music distribution system offered via the SkyPerfecTV satellite service in Japan". This "ATRAC Data" is most likely ATRAC2, however Sony's MDS-DL1 and SkyPerfectTV press release makes no mention of "ATRAC Data", and certainly any audio stored on a Minidisc would have to conform to existing ATRAC standards for Minidisc.
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.
Sony has measured ATRAC3plus fidelity at 64kbps and found its audio quality equivalent to 128kbps MP3 (mech. trans.) Sony's current PC software produces ATRAC3plus output at user selectable bitrates of 132, 105, 66, 64 and 48 kbps. AV Watch Japan has done a bit of ATRAC3plus signal analysis and comparison with ATRAC3 (mech. trans.) ATRAC3plus is described briefly on Sony's ATRAC3 site (local copy).
Can the new LP mode tracks be played back on old, non-MDLP hardware?
No.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.
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.Why aren't there LP monaural 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.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 audio | 6MB |
| ATRAC3 @ 132kbps | 580KB |
| ATRAC3 @ 105kbps | 460KB |
| ATRAC3 @ 66kbps | 290KB |
| MP3 Stereo @ 56kbps/24khz | 245KB |
| MP3 Stereo @ 56kbps/22khz | 246KB |
| MP3 Stereo @ 56kbps/16khz | 244KB |
Notes:
Getting the PC version of RealProducer to encode at these rates is a bit tricky, since the PC GUI is neither convenient nor obvious. Here are the steps:
It initially displays a "New Session" dialog box, asking for the name of the .wav file you wish to convert, and the name of the target ".rm" file you wish to create; browse to these or fill them in.
Here, the bitrate is selected in an indirect fashion through the "Target Audience" checkbox. This checkbox is intended for you to specify the sort of network bandwidth your audience will have. What it does is select ATRAC3 bitrate of the file you will encode.
This leads you to the Target Audience Settings dialog:
in which you can set your preferred ATRAC3 bitrate for each of the possible network speeds. However, with the "basic" version of the program, you are not allowed to change anything in this dialog box. It is only useful for selecting different target audiences and then seeing what ATRAC3 bitrate each corresponds to. When encoding Stereo Music, the correspondences are as follows (we include here the "Sichia" clip mentioned above, encoded at each bitrate for comparison):
| 512K DSL/Cable Modem | 352Kbps Stereo Music | Sichia@352kbps |
| 384K DSL/Cable Modem | 264Kbps Stereo Music | Sichia@264kbps |
| 256K DSL/Cable Modem | 132Kbps Stereo Music | Sichia@132kbps |
| Corporate LAN | 105Kbps Stereo Music | Sichia@105kbps |
| Dual ISDN | 44Kbps Stereo Music | Sichia@44kbps |
| Single ISDN | 20Kbps Stereo Music | Sichia@20kbps |
| 56K Modem | 20Kbps Stereo Music | Sichia@20kbps |
Where can I learn more about ATRAC3?
Have a look at these links
(ATRAC3 Block Diagram)
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 |
What NetMD software packages are there?
Commercial
(Version 2)
(Older Version)
Sony also has instructions for downloading and using RealOne Player.
Non-commercial
(Note that none of the non-commercial packages provide
high-speed downloading from a PC or Mac since the secure DRM aspects
of the NetMD USB protocol have not been cracked)
What restrictions does NetMD impose on transfers?
What is known about the information transferred over the USB link?
NetMD hacking is still in its infancy. So far, however:
The PCM is encrypted in transit because Sony is trying to prevent unauthorized access to "locked" ATRAC3 audio that may have been purchased from online music distributors; failing to encrypt the PCM data would allow hackers an easy way of making off with an "open" copy of the song.
Is there any way of transferring MP3s to MD without using OpenMG Jukebox?
Dino Inglese, a Minidisc T-Station message board member offers this tip for using Simple Burner to circumvent OpenMG Jukebox (see his humorous original posting). CAVEAT: You will need Nero, and Nero's Imagedrive feature, or something similar that can create a virtual CD disc image and allow you to mount it to your desktop.
I am not an expert, but I found these first 3 steps took around 2 minutes or less for a regular size audio CD (i.e. burning and converting about 10 MP3 tracks to an audio CD 'image' on my hard drive). I have a 1GHz/PIII, so that helps with the MP3->PCM conversion times. A faster machine would mean proportionately faster MP3 conversion and image creation.
If your machine is fairly fast then Simple Burner's CD->ATRAC conversion is done in on-the-fly in RAM with the disk hardly ticking over at all.
Wouldn't the transfers go even faster with USB 2.0?
Current NetMD download speeds require less than 20% of USB 1.1's 12Mbps peak bandwidth:
What other NetMD FAQs are there?
What new capabilities does Hi-MD equipment provide vs. the existing Minidisc?
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].
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:
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) | Created by ... | ||
|---|---|---|---|---|
| 305MB Hi-MD formatted Minidisc | 1GB Hi-MD Media | recording with Hi-MD equipment | downloading from PC to Hi-MD equipment | |
| Linear PCM 1.4mbps | 28m | 1h 34m | O yes | X no |
| ATRAC3plus 256kbps "Hi-SP" | 2h 20m | 7h 55m | O yes | O yes |
| ATRAC3plus 64kbps "Hi-LP" | 10h 10m | 34h | O yes | O yes |
| ATRAC3plus 48kbps | 13h 30m | 45h | X no | O yes |
| ATRAC3 132kbps "LP2" | 4h 50m | 16h 30m | X no | O yes |
| ATRAC3 105kbps | 6h 10m | 20h 50m | X no | O yes |
| ATRAC3 66kbps "LP4" | 9h 50m | 32h 50m | X no | O yes |
| ATRAC 292kbps "SP" | Not supported on Hi-MD media | |||
Note: (1)As stated in Sony literature
For calculating available Hi-MD capacity when using a mix of recording modes, Peter Ravn has made a Javascript-based Hi-MD space planning calculator.
What happens if I try to play a Hi-MD formatted disk in a non-Hi-MD machine?
A non-Hi-MD machine can read neither the 1GB Hi-MD media nor an original Minidisc reformatted in Hi-MD format. The result depends upon which of these two are used:What happens if I try to record on a 1GB Hi-MD blank with a non-Hi-MD machine?
The unit will report a read error and will not read/write on the Hi-MD disc.What is the audio quality of ATRAC3plus?
Updated: At Sony's Hi-MD annoucement they showed a chart depicting the relative standing of their ATRAC codecs. The diagonal lines indicate the audio quality equivalence of today's ATRAC3plus at 64kbps with the first version of ATRAC (ca. 1992) at 292kbps:
|
| Sony diagram from Hi-MD announcement Photo courtesy AV Watch |
The first generation ATRAC was a far cry from the quality of Type-R DSP for ATRAC introduced in 1998, and in fact it was probably similar in quality to MP3 at 128kbps. This view is 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 |
If indeed ATRAC3plus at 64kbps is equivalent to MP3 at 128kbps this is good news for two reasons: 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 quite likely better than original ATRAC at 292kbps.
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.Hi-MD Flash website (Japanese) has this diagram (click to enlarge):
How fast will I be able to transfer music from my PC to an MD with SonicStage?
Sony says that downloading can run at up to 100X realtime (assuming 48kbps audio content).What are the technical specifications of the Hi-MD disks?
Here are the specifications for the original Minidisc, its Hi-MD formatted version, the Hi-MD 1GB disk, and (for comparison) Sony's 650MB "MD-View" disk that was used in their Minidisc camcorder.
| Current MD format | Existing MD formatted into �Hi-MD� | Hi-MD 1GB Disc | MD-View (from MD Discam) | |
|---|---|---|---|---|
| Data Capacity | 177MB | 305MB | 1.0GB | 650MB |
| Magneto-Optical Recording Method | Magnetic Field Modulation | Magnetic Field Modulation | Domain Wall Displacement Detection | Magnetic Field Modulation on two layer medium (record layer and record assist layer) |
| Laser Wavelength (λ) | 780nm | 780nm | 780nm | 655nm |
| NA of Objective Lens | 0.45 | 0.45 | 0.45 | 0.52 |
| Diameter | 64.8mm | 64.8mm | 64.8mm | 64.8mm |
| Thickness of Substrate | 1.2mm | 1.2mm | 1.2mm | 1.2mm (but with new substrate resin) |
| Tracking Format | Groove Recording | Groove Recording | Groove Recording | Groove Recording |
| Addressing | Wobbling Groove (ADIP) | Wobbling Groove (ADIP) | Wobbling Groove (ADIP) | Interlaced Wobbling Groove (ADIP with 1 address per track) |
| Data Modulation | EFM | 1-7RLL | 1-7RLL | 1-7RLL |
| Data Detection | Bit by Bit | PRML | PRML | Bit by Bit |
| Bit Length | 0.59μm | 0.44μm | 0.16μm | 0.34μm |
| Shortest Mark Length | 0.83μm | 0.58μm | 0.21μm | |
| Track Pitch | 1.5μm | 1.5μm | 1.25μm | 0.95μm |
| Data Transfer Rate | 1.25Mbps @1.2m/s | 4.37Mbps @2.4m/s | 9.83Mbps @1.98m/s | 9.4Mbps |
What websites have Hi-MD information?
English: Japanese:Unless you have NetMD equipped Minidisc gear however, the only route onto or off of a Minidisc is through realtime recording and playback (except for the high-speed CD/MD decks). And NetMD or not, you can't get at the compressed audio directly from a computer. This is the biggest functional difference between MD and computer connected MP3 players and CD-R burners.
Seriously: one must weigh this question for themselves. There are tons of happy MD and CD campers out there, just consider the usage patterns that are likely to be convenient for you and whether MD or CD fits them better.
How do you transfer a CD track to a Minidisc?
From Audio Equipment: Connect a cable from the CD player's headphone or line-out jack to the MD recorder's line-in jack. This cable is called a "1/8th inch to 1/8th inch stereo mini-plug cable" and is available in Radio Shack and other such electronics stores. (A recording between a CD player and an MD recorder can also be achieved with a digital optical cable.)See also the MP3 handling tutorials.
As for direct transfers from Minidisc to PC, such a capability would be great! (And a petition was sent to Sony asking them to add it.) Unfortunately Minidisc was designed with a so-called "audio/data firewall" that prevents the ATRAC audio data on MDs from being accessed directly by computer. This was done to comply with Recording Industry concerns over music piracy. (The fact that Sony has introduced the Digital Relay CRX10U-A2 [a portable MP3/audio CD player that is fully USB connectable for seamless audio/data transport to/from PC] is an irony due to the CD's grandfathered status as a computer peripheral that appeared before the Home Recording Rights Act [a law that impedes consumer bit for bit copying of audio content, see SCMS]).
One year after Minidisc appeared, Sony announced MD Data -- it consisted of a slightly modified Minidisc blank and the MDH-10, an MD data drive with SCSI interface. This permitted users to use MDs as a computer data storage format. Unfortunately, due to the requirement for a firewall, MD Data drives cannot read or write ATRAC data on Audio MDs.
Despite the built-in firewall, one company does sell a system for direct computer access to ATRAC audio data. By modifying the firmware in Sony's original MDH-10 data drive, EDL in Britain has been able to create the Minidisc Transfer Editor, a PC package allowing direct computer based transfer of ATRAC from MD to PC, with ATRAC to .wav file conversion done on the PC. The system is intended for audio professionals (radio stations, etc), and carries a price tag (~US$5000) to match.
But can I use Minidiscs to hold actual MP3 or other computer files?
Yes, the Hi-MD format allows you to use your Hi-MD recorder as 1GB external USB drive. Prior to Hi-MD, [std-MD] audio MDs were not capable of holding computer data. A now-obsolete branch of std-Minidisc, called MD Data, was capable of holding 140MB of data per disc (functioning much like a Zip or floppy disk, but using Minidisc technology). MD Data discs were not compatible with std-MD audio discs. You can read about the old MD Data units in the Equipment Browser.
I'm still confused, can you just tell me what cables I need?
From Shawn Lin's MD Recording FAQ, here is a brief guide to the type of cables usually required:
| SOURCE | RECORDER | CABLE REQUIRED |
|---|---|---|
| Home Equipment | Minidisc Home Deck | Stereo RCA cable (two RCA plugs on each end) |
| Portable Equipment | Minidisc Home Deck | Stereo RCA cable to 1/8" stereo miniplug |
| Cheap PC Soundcard | Minidisc Home Deck | Stereo RCA cable to 1/8" stereo miniplug |
| High-End PC Soundcard | Minidisc Home Deck | Stereo RCA cable (two RCA plugs on each end) |
| Home Equipment | Minidisc Portable | Stereo RCA cable to 1/8" stereo miniplug |
| Portable Equipment | Minidisc Portable | 1/8" stereo miniplug to 1/8" stereo miniplug |
| Cheap PC Soundcard | Minidisc Portable | 1/8" stereo miniplug to 1/8" stereo miniplug |
| High-End PC Soundcard | Minidisc Portable | Stereo RCA cable to 1/8" stereo miniplug |
Enough about recording to MD... can I record from MD unit to my computer (or another audio device)?
With the proper cables, yes. You would use the same analog cables listed above for recording to another audio device from MD, simply switch the inputs/outputs. For a computer, this would mean connecting an analog cable (usually a 1/8" male to 1/8" male miniplug cable) between your MD unit's line out to your sound card's line in. If you're looking to transfer audio from MD to your computer digitally, you need an MD unit that is capable of digital output (all current portable MD recorders lack this feature, but most home MD decks have it) plus the correct digital audio cable.Can all things be done on a portable Minidisc recorder that can be done on a larger Minidisc deck?
Yes, almost all. The Minidisc decks usually have finer editing precision when dividing tracks (so called "rehearsal mode" with 11ms or 60ms accuracy), and some have PS/2 keyboard connectors to make titling easier. Decks may have somewhat better analog input/output quality (but unlike portables, usually do not have microphone inputs). When recording digitally from a CD, MD decks and portable recorders are essentially equivalent. The one major difference is that home MD decks usually have digital output, the portables do not.Has a portable MD unit ever been released that has a built-in AM/FM tuner?
The only two units that feature an AM/FM tuner are the Sony MZ-F40 MD player (released in May 1997) and the new Sony MZ-G750 MD recorder (released beginning of 2001).I've heard rumors that Minidiscs are on their way out... is MD a sinking ship?
Technology is always advancing and rendering older mediums obsolete. It is true that Minidiscs have been around since 1992, and have had a slow time picking up momentum. However, Minidiscs have proven their advantages over lots of other competing products (one of the best things going for Minidiscs is that the discs are cheap!), and will certainly continue to appear on store shelves for years to come.What's the difference between an MD and the 3-inch CD-Rs used in the Sony CD1000 digital camera? Sony sold a digital camera in Japan in 1998 called the Cybershot DSC-MD1 that recorded images to an MD. What is the difference between that technology and the technology used to record images to a CD-R?
The MD and the 3-inch CD-Rs used in the Sony CD1000 are completely different. MD: magneto-optical recording on cartridge enclosed 64mm disc. CD-R: dye based (i.e. optical) recording on an unenclosed 300mm or 80mm (3-inch) disc. The two formats are completely incompatible.If I took an MD out of its cartridge, could I play it in one of those new mini-CD players such as Compaq's PM-1?
Hardly. There would be multiple problems trying to play a bare MD in a CD player:
The MD and mini-CD track pitch and optical parameters (spot size) are the same however.
* If it's a USB to digital (e.g. TOSlink) PC-Link it will not work on those rare MD recorders (e.g. MZ-R5ST) that have only microphone or analog audio inputs.
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