Explain THIS one!

[UMWOOFWOOFF]

Hi everyone. I've been into MD's for nearly a decade now, but just finally made the jump to Hi-MD (mainly just to have a deck before the twilight) and got an Onkyo MD-133 from overseas.

I'm impressed so far with the quality of Hi-SP, as well as expectedly disappointed with Hi-LP. Also, the A/D converter in this deck is noisy as hell. I will definitely be using one of my MDS-JA555ES or 333ES decks for the A/D conversion. But, anyway, I noticed an interesting phenomenon that may or may not be common and well known, but I've never read about it.

I have a test CD of test tones, and I was copying some of them at Hi-SP to compare the artifacts of Hi-SP to Type R SP using two different standard MD discs (one formatted to Hi-MD). Well, just out of curiosity, I wanted to see what would happen if I tried to play the Hi-MD on a standard MD unit. What surprised me, was that even on my old MDS-JB920, the disc wouldn't play, but the display read "Hi MD disc". It read this on ANY deck I tried, even ones from the early 90's. How can this be? Did they plan Hi-MD even way back then, when they were developing LP? Seems strange...but I can't imagine how a 10 year old deck would "know" of a technology that hadn't been developed yet. But...that's not the strangest thing I found...

The Hi-MD test tone disc actually PLAYS for about 10 seconds on two decks...one of my MDS-W1 MD dubber decks, as well as one of my car decks, an mdx-c800rec. You can select different tracks, but they don't make a sound. Only the first 10 seconds of the first track plays. I didn't try it with music, just the test tones that I recorded to the one disc. After about 10 seconds, the sound just goes away.

I can't imagine how this could be; although, I've never really researched things like this with Hi-MD since this is my first deck. Is this common? None of my other decks play any sound, but they all ACT as if they are playing something, and every one of them lists "Hi MD disc".

What's the scoop on this behavior?

Thanks!

[Sparky191]

Now I'm guessing but....

http://www.minidisc.org/ieee_paper.html

...The MD-Data volume and file structure was developed to cope with the MD's physical limitations. The data track, similar to the music track on the MD Audio, is defined in the TOC and the U-TOC. The first cluster is used for a boot cluster, and a further 16 clusters are used for the Volume Management Area (VMA), where all files and directory management information are gathered. Because the VMA is physically centralized and is usually cached in semiconductor memory, the number of accesses and rewriting operations are minimized. Even more, considering the physical cluster actually means a minimum rewriting unit, the MD-Data file system can manage a logical block size ranging from 2 to 64 kbytes. These block sizes are uniquely selected depending on the application by the user. The file system can also support a hierarchical directory structure, short- and long-file names, additional information, etc. It allows easy connection of MD Data to various host systems and allows for media exchanges between different systems...

I assume the bootcluster is readable on all MD/HiMD units. It reads that and can go no further.

[Avrin]

As for the "Hi-MD disc" display, this is really simple. The legacy volume label of a Hi-MD formatted MD disc is actually set to "Hi-MD disc", so any old deck displays it. The actual Hi-MD volume label (the one you typed for the disc) is stored at a different place, so only a Hi-MD unit can display it. This is quite similar to pre-MDLP units displaying "LP:" before track names when an MDLP disc is inserted.

As for the actual playback for 10 seconds - this is really interesting. My assumption (I may be wrong) is that simple test tones (like sinewaves) are really easy to encode, so the encoding algorithm only uses its simplest part (the fixed first-order Fourier component in case of constant frequency tones, or its time-shifting version for sweeps), so there is no actual difference between ATRAC3plus and legacy ATRAC. That's why the decks play the sound. Try this with music or white noise to see what happens.

BTW, using sinewave test tones (even sweeps!) may lead to serious overestimation of Hi-MD and MDLP capabilities, since those are always encoded over the full frequency range (20 - 20,000 Hz in SonicStage, and 20 - 19,000 Hz in a Type R or Type S unit). On the other hand, encoding music or white noise clearly shows frequency limitations. For example, the frequency range of LP4 immediately becomes 20 - 13,300 Hz only.

Edited March 1, 2007 by Avrin