Tuesday 18 March 2014

MUSINGS: "The CD can be said to be an analog disc, just like the LP" (UHF Magazine, 2014)

(On occasion, I will refer to copyright works under the principle of "fair use" for the purpose of commentary. This is one of those posts.)

I don't get a chance to hang out at the local large bookstore chain (Chapters) very often. When I do, I will wander over to the magazine rack and see what's on offer for the month. Here in Canada, there is one (and I think the only) magazine catered to audiophiles published in the country - UHF Magazine (Ultra High Fidelity) from Montreal. Here is Issue #94 (March? 2014):

So it was with interest to see an article on "A critical look at the Compact Disc for music delivery" referred to on the front cover written by Mr. Paul Bergman titled "Inside The Compact Disc". I figure it might be interesting to scan the article quickly to see if there's anything new to be gleaned... Alas, within a couple of minutes of scanning page 25, this paragraph just jumped out at me from the article:
To save space, individual binary digits are not stored. The length of a pit corresponds to the number of "one" samples before a "zero" is encountered. The length of a pit or land is of course an analog value, and for that reason the CD can be said to be an analog disc, just like an LP.
Wow... Ponderous man... So a CD is a material thing. All material properties have variability - the length of a "land", the depth of a "pit", the transition between "lands" and "pits". So what? As long as it's within the margin of error within specification, a one is a one and a zero is a zero. No problem. It's not like the length of a pit is going to end up with any other interpretation than either 1 or 0 by the decoding circuitry. It's binary; there is no 0.5. It's digital. The author even talks about the use of Reed-Solomon coding for error correction and mentions interpolation when errors are detected.

Here's another nugget from the same article (p. 26):
Though the CD is not, as I have explained, a purely digital medium, some true digital media do exist. Reference Recordings, for instance, uses a data DVD to distribute its 24-bit 176.4kHz music files...
So data DVDs are "pure digital" and (audio) CDs are not? Does the author not know that "lands" and "pits" also underlie the physical structure of a DVD as well (higher track density of course)?

I assume that the author would consider CD-ROM "pure digital" since it too contains data (as if digital audio is not data) and DVD evolved from it?

Presumably the author doesn't understand that the only difference between the "Red Book" (1980) CD format and CD-ROM "Yellow Book" (1988) is in the data structure. The older Red Book format is much simpler - an inner lead-in segment which contains the TOC (Table of Contents) that gets read when you first insert the disk. When you select the track, the player will look for the time code corresponding to the start of the track and start playing music through to the end of the track sequentially. (The data stored in the TOC is contained in the ".cue" sheets in CD rips.)

Yellow Book and all that followed, leading to the DVD-Books and modern Blu-Ray Disc formats have a much more complicated structure which contains an actual file system; typically ISO9660 or UDF. This adds the extra layer of complexity and features like file names, permissions, directories, opportunity to append/delete/move for rewritable media, etc... Error correction is also much better at the expense of some storage space. I can only assume the author of that article somehow associates these characteristics with "pure digital".

How strange... In 2014, a "technology" magazine would even declare that the Audio CD is somehow not a "pure" or "true" digital medium. I guess the editors must have missed this! Hopefully the readership can send a few "Letters to the Editor" to set this straight.

Well, it's only been about 32 years since the reflective polycarbonate disks came out...

Perhaps the author is taking to heart the title "The Analogue Compact Disc" from Robert Harley writing for Stereophile a little too strongly! That article was from 1994 and speculated about jitter rather than questioning the digital-ness of an audio CD. Even in that article, I'm concerned about this declaration: "It's becoming incontrovertible that CDs containing the same 1s and 0s produce varying levels of sound quality." Incontrovertible. Really?


  1. Good catch...
    UHF Magazine has some trouble understanding the technology in general...

    1. Funny little magazine. This is not the 1st time I've heard of this belief that "CDs are analogue" from them... I think they had some comment like this years ago but figured I'd let it go then. But in 2014... Something has got to be said!

  2. With a vinyl LP, you can choose to read the left channel or the right channel. There are no other channels, nothing in between left and right, or left of left, or right of right. Since there are only two possible channels, vinyl is therefore a binary medium. It is as digital as a computer. QED.

    1. OMG. You're right, sir! Your reasoning is beyond reproach, foolproof and water tight. I better start on the next blog post extolling the virtues of the truly pure digital sound of vinyl!


  3. These days, being printed is no guaranty that you know s*it about anything. ;)