mini-disc as source?

[Craig Maier]

I am not sure about the numbers concerning the degree of lossy compression used in Minidiscs, however, I do know that DAT recorders use no compression whatsoever but Minidiscs do. Therefore, technically, DATs (and wavefiles) produce superior results (at least on paper, anyway). As for real world audio, it probably depends on the material and your ear. If you record Classical music, the difference in performance will probably be a lot more apparent than Rock and Roll, as an example. It all comes down to subjectivity and just how discerning your own personal sense of hearing is. We use Wavefiles and/or DAT for mastering for our own record label (Diamond Cut Productions).

[Dan McDonald]

mini-disc as source?

Just a question that has come up a few times in various discussions. I have a mini-disc recorder and it seems to do a very nice job recording live material. Other people have remarked that it uses a lossy compression scheme, so it's not a good recorder. Most of the material about it is not clear enough to understand what is lost in recording with a mini-disc. Does anyone know? It doesn't seem to be nearly as drastic as mp3 format, and I've read that it's hard to tell the difference between material recorded with a DAT and a mini-disc.

Dan

[Rick]

Re: mini-disc as source?

Dan
From what I have read, Sony and others have improved the compression schemes used in Minidiscs dramatically over the years, and the original ones were not that good. The popularity of MP3s have made people re-consider lossy compression schemes and some of the improvments have come as all of the research that has gone into MP3 and other lossy formats. Mini-discs do not use MP3 compression, but the concepts are very similar

Rick Carlson

[Dan McDonald]

Re: mini-disc as source?

Thanks, Craig. That is pretty close to what I suspected. It seems that mini-discs offer pretty good quality for recordings in the field, or for those with a tight budget who can't afford a portable DAT recorder, but for the best quality, always opt for the best.

Some of the materials testifying about how good mini-discs were that I read were written
by classical musicians. One said that if he switched between the mini-disc and a CD using the same material, but switching back and forth, he could tell a difference, but if he was just listening without an immediate comparison he couldn't discriminate between them. I just haven't seen the specs to see how they achieve the compression or what you lose.

Dan

[Dan McDonald]

Re: mini-disc as source?

Thanks, Rick. I recorded my stepdaughter's orchestra last night and converted it to wave file this morning. I don't know how it would compare to a dat recording, but it sounds quite a bit better than what I would have gotten with a good cassette recorder a decade ago. Especially since the mini-disc was $150 (with another $150 for the mic).

I have always figured the microphone makes a big difference, no matter what the recording device used.

Dan

[Beautman]

Re: mini-disc as source?

Although as a high end audio snob (and also a former classical musician) I was in no hurry to accept MD, I'm completely sold on it. Recent MD decks sound about as good as a lower end home CD player. (For portable playback use, MD sound better than the currently available portable CD players - sound quality has been sacraficed for ridiculously long battery life.)

I do agree that DAT sounds better than MD. But that's at several times the price. And DAT is also a dying format - major transport manufacturers have already stopped production and are using up old stock. Many studios have replaced DAT with hard drive recorders for higher resolution and easy editing. For portable use there's comptition from MD. I wouldn't be surprised if we're looking at the last generation of portable DAT decks.

But because of the price difference, the more useful comparison is MD vs. cassette. Dollar for dollar, there's no contest. MD blows analogue tape out of the water for portable recording. Plus, you can then make digital copies from MD, such as to your PC for editing and tweaking with Diamondcut.

Along those lines, I'm planning to try recording some accoustic 78s and cylinders from my Victrola and Amberola to MD via microphone, and then upload the recordings to my HD for noise reduction with Diamondcut. I'd imagine there'll be a loss of clarity frequency extension compared to using a modern cartridge, but maybe I can keep the dynamic immediacy that makes all-accoustic playback so much fun while cutting some of the noise.

When I'm seeking the best sound I can get on a live recording I record to a laptop. When that's unnecessary or impractical, MD has been very satisfactory.

[Beautman]

Re: mini-disc as source?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Beautman:


Along those lines, I'm planning to try recording some accoustic 78s and cylinders from my Victrola and Amberola to MD via microphone, and then upload the recordings to my HD for noise reduction with Diamondcut. <HR></BLOCKQUOTE>

I just tried one. (Nothing like replying to your one's own posts. . .)
Even with a quickie noise reduction job of a graying Batwing it came out swell. If anyone want an excerpt by email let me know.

[Dan McDonald]

Re: mini-disc as source?

Hey Beautman,

I've done both - acoustic with a microphone and also through a cartrige, with 78s and with cylinders. You do get a different sound; I am not certain which I prefer, but there are a number of people I know who prefer the sound you get with the microphone. I think it may be a matter of whether you want to approximate the sound of the original performance versus the sound of the original reproduction. It seems to me that you get a better reproduction of the original performance using the cartridge, and a closer match to the way people originally heard it using the microphone. Of course, since I wasn't there for the original performances, I'm just guessing.

Dan

Dan

[Beautman]

Re: mini-disc as source?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Craig Maier:
Keep in mind that you can always run the Diamond Cut Bandpass filter with one of the various presets to obtain the sound of an olde Victrola. And if you want to add resonance, you can run the Notch filter in slot mode to further distort the signal in the manner of an acoustical phono. <HR></BLOCKQUOTE>

I'd rather [I] not [/i} run the band pass to eliminate frequencies where there's program material. But what I could conceiveably wish to do is approximate the jagged frequency response of a classic horn. I can see it on the equalizer, but it seems that it'd be too many hours of playing around to recreate. One of the reasons some people prefer Victors to some other brands is the way the horn response is tuned (this was actually something Victor had advertised).

I noticed a few other interesting differences. One is that there are no fast transients on the accoustic machines. I assume that's because the reproducer mass is so high.

Another is that sound rings in the horn, like a sort of built-in reverb chamber.

Finally, I did my recording samples with a binuaral mic configuation from about five feet in front of the horn. That captured the sense of space of a horn playing in an actual room (maybe too much so). Personally, I found it to be natural sounding cross between the dryness of tight mono and incorrect simulated stereo.

Of course, one can disagree on whether those qualities are positive or negative. I've been told that Nimbus is in bankruptcy, so perhaps that indicates that the marketplace has voted with its feet on the issue.

[Craig Maier]

Re: mini-disc as source?

I just subscribe to the theory that is much easier to mess up and distort a signal than to clean it up. So, I always try to start out with the best form of the signal that I can possibly obtain. That way, I can listen to it the way it was recorded. If I want to hear an olde phono sound, I can simulate that with any of a number of tools available in the software. But, whatever your own personal preference is that which you should be doing, at the end of the day.

[Craig Maier]

Re: mini-disc as source?

I always transfer electronically, because it represents the original performance more closely than an acoustical reproduction. Keep in mind that you can always run the Diamond Cut Bandpass filter with one of the various presets to obtain the sound of an olde Victrola. And if you want to add resonance, you can run the Notch filter in slot mode to further distort the signal in the manner of an acoustical phono.

[Peter Allen]

Re: mini-disc as source?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Dan McDonald:
Just a question that has come up a few times in various discussions. I have a mini-disc recorder and it seems to do a very nice job recording live material. Other people have remarked that it uses a lossy compression scheme, so it's not a good recorder. Most of the material about it is not clear enough to understand what is lost in recording with a mini-disc. Does anyone know? It doesn't seem to be nearly as drastic as mp3 format, and I've read that it's hard to tell the difference between material recorded with a DAT and a mini-disc.

Dan<HR></BLOCKQUOTE>


Sorry to butt in at the beginning of the thread again, but there are a few comments I'd like to make.

Firstly, the compression rate of MiniDisc is about 80% - at the time they were designed magneto-optical recording discs had a maximum capacity of about 120MB or thereabouts.

That sounds incompatible with hifi, but the principles of the compression algorithm are based on sophisticated psychoacoustics and the complex assignment of bits to where they are really needed (ie audible), and the rejection only of those parts of the input signal that make no difference to the sound.

The audiophile community I believe agrees that a modern MiniDisc copy is essentially indistinguishable from a source CD (both are based on 16 bit, 44.1kHz data streams), and this has applied for a fair number of years, although the earliest MD incarnations had audible artefacts. The proof is in the pudding, and it works.

Of course don't expect a "cheap" portable to behave as well as an expensive deck. The quality of the digital stream control, DACs and analogue stages are just as crucial for MiniDisc recorders as for CD players, and must equally affect the "sound" of the equipment.

Although I am a MiniDisc enthusiast for general home use, both because of the copy quality and the brilliant usability of the editing features that come with a hifi MiniDisc deck, I have my doubts about using recorded Minidiscs as a transfer medium to computer hard disc if audio restoration is intended.

That is because the job of the MiniDisc algorithm is to reproduce the input signal as faithfully as possible, with no distinction between noise and music. So those massive clicks and surface crackle will be using up valuable bits at the expense of the music. When you clean up the noise on the transferred recording, you will be left with a "clean" file that is effectively much more data compressed than the original 80% applied by the MiniDisc recorder.

Of course, assuming you have an analogue source, there is no problem using the MiniDisc recorder in record/pause mode, and feeding the 16 bit 44.1 kHz data stream produced by the MiniDisc recorder's ADCs to the computer. In this case no compression is being applied and the MD recorder is simply being used as an outboard standalone ADC. One more plus for MD recorders, especially for those wanting to work in the digital domain, but on a budget!

Finally, it is often stated that MiniDisc is better than MP3. Usually I find that closer questioning reveals that like is not being compared with like.

Until recently (with the introduction of *2 and *4 increased recording time/reduced recording quality options), MiniDisc has had a strictly enforced single fixed compression rate of 80%, and all attention was paid to making that degree of compression inaudible at the CD quality level, if not better.

By contrast, although clearly based on similar compression principles, MP3 arrived as a way of transferring large audio files over the slow Internet, and the amount of compression is selectable by the user. Thus most people would have first heard MP3 files coded at 32 or 64 kbps, which is roughly 5 to 10 times the compression of MD. Naturally enough such files sound absolutely rank in audiophile terms, and are plagued by electronicky artefacts and restricted frequency response.

By 96 kbps, an MP3 compressed file is clearly identifiable as such, but has no specific artefacts, just a generalized dulling of the sound. However, differences in the quality of the source audio can be clearly discerned. A 160 kbps MP3 can sound pretty stunning, and the best MP3s I have heard have been encoded at 256 kbps. While I have not done direct comparisons myself, the description of this degree of compression as CD quality does not seem unreasonable.

Most MP3 coders can compress to 320 kbps, with fixed or variable bitrate. A rough calculation suggests this degree of compression is similar to that of MiniDisc.
So a reasonable comparison of the inherent quality of MP3 and MiniDisc (ie of the compression algorithms used) requires that the MP3s be coded at 224 kbps VBR, 256 kbps or 320 kbps. I'd be interested to hear if anyone has done such a comparison.
Peter

[Peter Allen]

Re: mini-disc as source?

By happenstance, I've just come across the bitrates for MiniDisc in a computer magazine.

They are stated to be 66Kbps for LP4 mode, and 105 or 132 Kbps for LP2 mode, which suggests 264 Kbps for the original encoding quality envisaged by Sony.

That reinforces my point that anyone who generalizes that MP3 is inferior to MiniDisc or not CD quality, but has only heard MP3s encoded at 160kbps or less, has not made a meaningful statement.

Peter

[Dan McDonald]

Re: mini-disc as source?

Thanks for the information, Peter. I know to my ears I get very nice quality live recordings with the MD. However, I would still like to know exactly what is missing in the compression. I know Sony describes it as a "psychoacoustical" compression, but doesn't explain what they're doing very well. It may not change my opinion of MD or MP3, but it would be nice to know.

Dan

[Rick]

Re: mini-disc as source?

In an attempt to see what is missing from MP3's I have posted a picture of two spectrograms on our web site. I have not linked it to any page yet so use this URL:
http://www.diamondcut.com/WaveVsMp3.jpg

What this shows it two Spectrograms. The top one is of a section of music from a live recordings as a wave file (44kHz, 16bit,no compression). The bottom spectrogram is the same section only compressed at 128kByte MP3 format. It is blugrass music with lots of high frequency content (dobro's and Banjo's)

If you are not familiar with spectrograms, they are a graph of frequency vs time. The vertical axis is frequency from 10Hz to 22kHz, and the color represents the amplitude at each frequency. In this case white is low amplitude (-99dB) and Black is high amplitude (0dB). The sequence of color amplitudes is white-red-blue-black.

It should be obvious that something is missing. All of the low level high frequency information is gone. The red background in the top spectogram is full of high frequency information some of which is noise, but not all. Also some midband holes (white) shows up indicating that information was removed there also.
The Spectrograms are part of the new millennium that we are working on now. I wanted to show this because, to me at least, it shows graphically what the MP3 and to some extent minidisk compresssion does.