The Minidisc Faq del 2

What is the status of Sony's push to have MDs replace CD-roms?

Sony wants 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, has been released and provides 140 MB of data storage on an MD but is not compatible with the Audio MD format (Data drive cannot read or write Audio data except in "play" mode.)

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 compatability.

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.

I've heard some negative comments about optical digital interconnects. Does is matter whether I use optical or coaxial digital input when recording to MiniDisc? Is jitter a problem?

In a word: No. The perceived problems with optical interconnects relate to an optical cable's greater theoretical potential to distort the digital signal, particularly to create small inaccuracies in the arrival time of data bits ("jitter"). However, in MiniDisc recording jitter is not an issue since the digital input signal's sample values are recovered and passed directly into a memory buffer or into a sampling rate converter that is clocked with the clock embedded in the input signal. The sampling rate converter and/or memory buffer allow the audio samples to be subsequently read and passed to the ATRAC converter with an accuracy determined by the MD unit's internal quartz clock. Even if jitter was an issue however, it is doubtful that the short cable lengths involved in home HiFi systems could produce audible differences between optical and digital cables.

Regarding the occurance 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, Digtial Domain has written a very comprehensive paper on jitter in digital audio systems.

What's the scoop on digital connectors, and how can I make a digital connection between my source device with its digital coaxial output connector and my MD unit with its digital optical input connector?

The short answer: If you are trying to make a digital connection between devices with differing signal types, you will need a converter. Core Sound sells something called a "Digital Format Translator" for $95 which will convert between coaxial SPDIF and TOS-link optical. There is more information on Core Sound's DFT page.

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 prefered 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.

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.

Is there anyway I can "undo" an edit operation if I delete the wrong track while editing?

Sony MD decks have an UNDO button as well as a hidden super UNDO function. A user describes how to cancel a pending TOC update on modern Sony MD decks.

If your machine doesn't have 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 (steven.scholte@tip.nl) 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 (scottm@netbound.com)

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. The MDS-503 has an "undo" function for just this purpose.

Blank MDs are now available from several manufacturers. Do they all perform equally well? The only information available to me is the relative pricing so on what other basis can a reasoned choice of brand(s) be made? Since MDs store digital data, there will be no qualitative difference between the sound of various discs so long as the disc's raw bit errors fall within the bounds of what can be handled by the MD ACIRC error correction system.

Presented here are the results of a small experiment I conducted to compare the raw block error rate of various brands.

Blank MiniDisc Raw Block Error Rates Compared

Eric Woudenberg

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.

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 I assume free list segments are kept sorted, 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.

Dolby ProLogic Surround is encoded in the stereo signal through phase shifting. Does the MD's transform coding interfere with the "Surround" information after recording and playback? I have done extensive testing with this, and have yet to find a single instance where the MD encoding/decoding affected the Pro-Logic encoding in any way. In every test I did, the surround steering information remained intact, and the result sounded precisely like the original. Scott MacLean (scottm@netbound.com)

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 (jlong@soli.inav.net) and Shawn Lin (slin01@mail.orion.org)

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."

When a Sony MD deck (pre-MDS-JE520) is in record-pause mode, the disc is spinning and the magnetic head is in contact with it. How long can it safely be left in this state? In their IEEE paper on the MD system, Sony writes:

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.

On the Sony LIP-12 batteries, there is a little switch with a red dot in one position, what is this for? The switch has no electrical connection and is only provided to help you identify which batteries are charged. If you carry many batteries in the same bag, the ones showing a red dot can indicate empty, while those with the switch in the other position can indicate charged. You have to remember to move the switch after changing or charging batteries.