Talk:Compact Disc Digital Audio

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Range of values[edit]

From the article, prior to my edit: "Sample values range from -32768 to +32767, which map from -1.0 to +1.0 when converting to float. (Is this correct? It may be that the lower bound is -32767)". The question at the end belongs in here, rather than out there. So now it is. --203.206.183.160 13:05, 20 July 2006 (UTC)

Don't know the answer myself, but this might help: It depends on the format in which the integer values are stored. A two's complement representation will range from -32768 to +32767, whereas a signed integer representation will have a lower bound of -32767 (the total number of integers is the same in any 16-bit representation, but signed integer has two zeros (+0 and -0), so two's complement allows one more number. --203.206.183.160 13:05, 20 July 2006 (UTC)

from dave:
Right that's my point exactly. What *is* the red book format stored on a standard CDDA disc? It makes life much easier if it really is -32767..+32767, that way you just divide by 32767 to get your float value. Else you have to do this:

valF = <integer val>;
if (valF == 0) {
  valF = 0;
} else if (valF > 0) {
  valF /= 32767.0f;
} else {
  valF /= 32768.0f;
}

Which is cumbersome. Also you can't perfectly cancel an integer signal (via subtracting it's negative) due to aliasing (since the ranges for positive and negative are actually different). There must be some red-book aware guru who can settle this matter? --davec 21:58, 31 July 2006 (UTC)

I don't understand what the relevance of interpreting the numbers as floating point actually is? The integer number representation represents a digital code value that is fed to a digital to analogue converter, which then converts the digital integer value into an output voltage or current. D-A converters do not - not that I have ever seen - take as input any kind of floating point numbers. They use either signed or unsigned integer numbers.

The only reason you might want to convert the integer form to floating point is if you wish to do some further processing such as the application of digital filtering algorithms.

And if you really do need to represent the sample value in floating point form, then you're only losing out one code value in the range of 65536 possible codes, and it's a maximum level value of 0dBFS, maximum volume level which hardly anybody mixes/masters the music at that level because it will end up being dangerously loud, so the small error in format conversion from integer to floating point is of little concern.

I'm not asking for your opinion or your interpretation of it's relevance. I'm asking *what is the spec*. If you know, just say what it is, if you don't know, well, then you don't know. So I ask again, What is the spec? davec 23:11, 20 June 2007 (UTC)
Look, just do the math. A sample has a depth of 16 bits. Therefore, there are 2^{16} = 65,536 possible levels of amplitude which can be represented. This makes it clear that the range cannot be only -32,727 to +32,767. Since the integer is two's complement signed, it represents values from -2^{(16-1)} to 2^{(16-1)}-1. Therefore, the range is -32,768 to +32,767. tgies 06:01, 22 June 2007 (UTC)

I don't know what this floating point stuff is about, but the data portion (the actual samples, 6 per frame) is PCM as in a WAV file and is (correctly stated here) as ranging from -32768 to 32767 (the sampleing order is interleaved but the samples are the same as WAV). jrg 17 July.

All of this talk about conversion to float is useful for certain kinds of processing of data after it is taken off the CDDA disc, however, there is no specification in the Red Book for such a conversion because the Red Book is not concerned with conversion to other formats, only with the native format of CDDA. It would be pointless for a specification such as the Red Book to spend time talking about conversions to other formats that are not used in CDDA. The proper conversion is to divide by 32768 for both positive and negative numbers. Don't worry that you cannot get precisely +1.0 with 32767/32768. The industry standard is to divide by 32768 because that does not create quantization noise, and because it is completely reversible without distortion. BrianWilloughby (talk) 07:50, 27 May 2009 (UTC)

Mastering formats[edit]

The Sony PAL format U-Matic 3/4" videotape was the original media for mastering Redbook Audio. The 44.1Khz sampling rate is directly related to this choice of media, not to any considerations about Nyquist Frequency or any of the other reasons given for why 48Khz was not chosen, which was the sample rate used for most other digital audio in the then new field.

http://www.edinformatics.com/inventions_inventors/compact_disc.htm

A Sony 1610 or 1630 PCM digital audio converter for U-Matic tape can store 6 samples (3 for each stereo channel) per video line.

PAL video (as recorded by a U-Matic VTR) has 294 lines and 50 fields per second, which gives 44,100 samples/second.

NTSC can store more samples per second due to its higher frame/field rate, but its higher capacity wasn't used. The most likely reasons being that more countries use the PAL TV standard than the NTSC standard, which would make PAL U-Matic VTR machines more common, and that the higher rate attainable would allow fewer minutes of music to be stored on an Audio CD.

NTSC recorders were not used - 60Hz monochrome units were. While 60Hz video has more frames/second, it has fewer lines/frame. According to John Watkinson in "an introduction to Digital Audio" (section 2.7) both 60Hz and 50Hz recorders give the same 44.1kHz figure. 60Hz video has 35 blanked lines while 50Hz video has 37. At 3 samples per video line, 3 x 60 x (525-35) / 2 = 3 x 50 x (625-37) / 2 = 44100 TheGiantHogweed 08:22, 18 July 2007 (UTC)

The 1610/1630 U-Matic (or Umatic) audio CD mastering format has held on until the past 2 to 4 years as the standard that CD mastering companies accepted above all others. As the U-Matic VTRs have gone out of service due to lack of replacement parts, other digital tape formats have become more popular for mastering. Yet even those are becoming less used due to the improvements in CD recorders "burn" quality at low speeds and the improvements in error checking at the mastering stage.

too technical[edit]

I'm adding the {{technical}} tag to this page. The meat of the article, describing the nature of the spec, needs some expansion I think. Perhaps a little about how the spec is used by manufacturers. I'm a relatively technical person and I was completely bewildered by the middle passage.Jasongetsdown 22:31, 15 November 2005 (UTC)

merge[edit]

This article should be merged to Rainbow Books. Please comment at Talk:Rainbow Books. Quarl (talk) 2006-01-15 11:42Z

I think this is a bad idea. The Rainbow Books page has its own content, and serves as a nice index to the various Book pages (Red Book, Yellow Book, etc.). There is no reason to merge it in here, and doing so would undoubtedly cause a loss of information (contextual or otherwise) in the process. I am strongly against. --Kadin2048 18:10, 23 May 2006 (UTC)
Copied comment (above) to Talk:Rainbow Books where discussion is held --H2g2bob 15:57, 22 June 2006 (UTC)
rm. tag --H2g2bob 21:45, 25 June 2006 (UTC)
I agree with Kadin2048 - I did not know of the term 'Rainbow books', only of the 'red book' spec (and of the various books describing the postscript spec, but that's not related to audio, although it may be included in the 'Rainbow books' series..). At best, a redirect (preferably directly to a section, if that is possible with WikiMeda) from 'Red Book' to a section of the 'Rainbow Books' article should be maintained.

De-facto vs. specified[edit]

"It also specifies the form of digital audio encoding (2-channel 16-bit PCM clocked at 44100 Hz). These parameters have become something of a de-facto standard."

How can a standard be both specified and de-facto? Tgies 06:07, 20 February 2006 (UTC)

I think what the author was trying to say may have been something like:
"It (the Red book standard) also specifies the form of digital audio encoding for audio CDs (2 channel stereo 16-bit PCM encoding at a 44.1 kHz sampling rate). These parameters have become something of a de-facto standard for all digital audio." T3h933k 01:30, 22 March 2006 (UTC)

16 bits per channel or 16 bits total?[edit]

This article implies that CD audio uses 16 bits per channel (in the maths calculating the bit-rate)... However, the bit rate that they come up with would mean that 74 minutes of audio (before error correction codes) would require 783MB to store ( 1411.2 * 60 * 74 / 8 = 783216KB ). If it were 16 bits for the two channels, this would mean it would require only 392MB before error correction codes, which seems more realistic given that a 74 minute CD holds 650MB of data. Can anyone more knowledgable comment on this? Thanks. -- David Scarlett(Talk) 07:01, 28 April 2006 (UTC)

Nevermind, apparently it is 16 bits per channel and you can fit more audio data than general data due to different error correction schemes, which would explain why the audio data can take up more than the generic data capacity of the disc. This article explains it. -- David Scarlett(Talk) 12:31, 28 April 2006 (UTC)

[edit]

Can someone add to the article what the "Text" caption means in the Compact Disc Digital Audio logo? (see right.) Tempshill 01:50, 19 June 2006 (UTC)

Maybe it is "CD-Text" as describe at http://www.true-audio.com/Compact_disc --Joshtek 14:32, 20 July 2006 (UTC)

Standard?[edit]

Disregard: The article was renamed to "Compact Disc Digital Audio". Chealer (talk) 23:10, 6 March 2013 (UTC)

The Red Book is the informal name for the Compact Disc Digital Audio specification (more commonly known as CD-Audio). While the word "standard" is quite similar, it doesn't quite mean the same thing. Products such as CDs are produced to meet a specification. When they are tested, they either meet the specification or they don't. Specifications are specific. Standards can be something less specific (de-facto, etc.). I would suggest that this article be renamed Red Book (CD-Audio specification). Tvaughan1 13:36, 28 August 2006 (UTC)

Removed obsolescence section[edit]

I removed the section arguing that CDs are obsolete due to the popularity of iTunes/ iPod. This section cited no sources and seemed irrelevant to the topic of the blue book standard.

Licensing confusion[edit]

Is it really $5000 to license the standard itself? I am guessing it's $5000 for a manufacturer of audio CDs to implement the standard. Anyone can get the publication for $200. —mjb 23:01, 21 February 2007 (UTC)

Frequency response?[edit]

Does Red book indeed specify frequency response? It seems rather illogical.

The sampling frequency of 44 kHz implies a maximum sound frequency of 22 kHz. I have no idea where the lower limit comes from, but a lower could have been imposed to avoid damage to the user's equipment (Turritus 12:26, 24 April 2007 (UTC)).

22kHz is a theoretical upper bound for the frequency content, but practically, not acheived. The actual boundaries of the frequency response depend on the CD player and could be quite difficult to compute. Perfect reconstruction up to 22kHz would require the CD player to compute a large series of Sinc functions for every sample. See Nyquist–Shannon sampling theorem for a full explanation. Sirhans 22:19, 2 May 2007 (UTC)

The 20Hz lower limit is likely not a technical limitation of the red book standard, but was simply added because it's the generally-accepted (and often-cited) lower limit of human hearing -- the point below which supposedly 50% of people cannot hear the sound.

I certainly think frequency response is an incorrect choice of words for the concept... an electrical system has a frequency response, a set of data does not. A CD is a collection of data and therefore the latter.

By that analogy, so is a vinyl record or cassette. Irrespective if they contain data or not, they become part of an electrical system when played back. Therefore, frequency response of the CD format is absolutely a correct choice of words. Vinyl does not go down to 20hz, for example. —Preceding unsigned comment added by 71.62.11.217 (talk) 23:53, 29 September 2007 (UTC)

Kbps[edit]

Just a little note: According to our article on Kbps (data unit, following the disambiguation), a Kbps = 1000 Kbps. This is the standard typically used for digital audio and storage, so I think we should follow it. I recalculated and changed the nominal bitrate in the article from Kbps == 1024 bps to Kbps = 1000 bps. 4.242.108.211 (talk) 20:03, 25 March 2008 (UTC)

I notice the article likes to often use different units: kbits here, KiBs there. Please unify. Jidanni (talk) 00:52, 20 May 2008 (UTC)
The different units used are appropriate in context. tgies (talk) 09:33, 20 May 2008 (UTC)
Let's back to basics. Uppercase "B" stands for "Byte" and lowercase "b" stands for "bit". 1 single Byte = 8 bits. In computers, one "Kilo" (2^10) stands for 1024 and not 1000. Then, 1 KB (Kilobyte) = 1024 Bytes. That said, 1KB = 8Kb. Allan Davidson (talk) 14:37, 3 April 2013 (UTC)

Is the Red Book standard still being used?[edit]

The article doesn't say something as simple as that. "Maximum playing time is 74 minutes (including pauses)", however music CDs today can have 80 minutes, can't they? This leads to anyone who doesn't know too much about it to understand the Red Book is an old standard.--Jim88Argentina (talk) 03:32, 3 February 2009 (UTC)

There seems to be some confusion, possibly because the web is much younger than the CDDA standard itself. Many online sources of information quote the CD-R limit of 74 minutes as if it is the limit for CD as well. The story of the origin of the play length has also been retold so many times that it seems impossible to reference an original source. I have edited the article to cite a 1987 book which documents 79.8 minutes as the actual limit of CD. I remember being disappointed that the first CD-R blanks would only hold 74.0 minutes when I already had discs in my collection as long as 79.5 minutes. Today's CD-R blanks stretch the specifications a little tighter to reach almost 100 minutes, but the CD glass master typically has the 79.8 minute limit. The time code format can refer to 99 minutes, 59 seconds, and 74 frames, but that is different than the physical track length. Part of the difficulty is that the Red Book gives the size of the disk, the size of the spiral track, where it starts, and its pitch, but not the actual total length. No number is mentioned anywhere. The math to calculate the actual limit based on the specified nominal values is actually quite complicated, but I'm sure it involves pi and some sort of integral. BrianWilloughby (talk) 11:07, 26 September 2009 (UTC)

I am not qualified to do the edit myself, but this figure (79.8 minutes) needs to be removed or clearly specified as Red Book first edition (1980) unless a corroborated 1999 source can be found. The lone source identified (in BrianWilloughby's footnote) is a 1987 document, although the number evidently dates from the 1980 first edition of Red Book: see http://www.diyaudio.com/forums/digital-source/199800-burning-cds-older-players-3.html. The article states elsewhere that the 1980 standard is wholly superseded by the 1999 second edition, so it seems essential that the latter alone should be cited. 700MB/80-minute disks had been introduced prior to 1999, so unless the second edition standards do reflect higher limits, the article should also make it clear that Red Book "standards" were established for 650MB disks and have never been updated for the present 700MB format. That at least might encourage mastering services to be less fearful about near-threshold audio-lengths. Meanwhile several sites claim 79:57 as Red Book-compliant, e.g.: http://www.about-audio-mastering-software.com/red-book.html and http://recording.org/mastering-engineers-forum/21816-red-book-audio-cd-help-urgent.html. The latter's "mastering-engineers-forum" moderator asserts that Red Book does not specify a limit. BrianWilloughby's statement above, "the CD glass master typically has the 79.8 minute limit", is similarly problematic, as greater lengths are routinely accommodated without apparent mishap (are there documentable playability issues on 1980s CD readers?).ChuckH2D (talk) 05:42, 9 February 2012 (UTC)

Rename article to Compact Disc Digital Audio[edit]

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

No consensus to move. Vegaswikian (talk) 22:11, 20 April 2010 (UTC)

Red Book (audio Compact Disc standard)Compact Disc Digital Audio — Relisting  Ronhjones  (Talk) 00:29, 3 April 2010 (UTC)

For reasons as discussed below. Ham Pastrami (talk) 02:37, 19 March 2010 (UTC)

In my opinion this article should not be called as Red Book. Red Book should have only a brief description of what does contain that book. The other articles of the Rainbow Books, contain a small description, and then, an article of the physical disc itself such as CD-ROM (yellow book) , CD Enhanced (blue book), etc. The physical disc is named "Compact Disc Digital Audio" not Red Book. --Juan D. (talk) 03:34, 14 February 2009 (UTC)

Agreed. Red Book is technical jargon. The proper name of the medium is Compact Disc Digital Audio (CDDA). Supposedly the article is interested in all aspects of the format, including, and not limited to, the Red Book specs. This would also be an unambiguous name for the subject.Ham Pastrami (talk) 02:22, 19 March 2010 (UTC)
  • Oppose this article is concerned with red book, CDDA is not necessarily red book compliant, and a larger article covering CDDA should be built, covering addition of data tracks, copy protection, etc. These discs still are allowed to the carry CDDA emblem, but are not red book. (there are also the discs that are not allowed to carry CDDA, like DualDisc, but are audio dics...) Further, the physical disc is the same for yellow book, blue book and red book, it is the CD, CD-R or CD-RW. The encoding standard is different. 76.66.192.73 (talk) 20:42, 27 March 2010 (UTC)
    Why should there be a "larger" article for CDDA when the red book spec is an obvious subtopic that can be included as part of the article? There is no cause for a split. DualDisc is neither red book (as stated in the article you linked to) nor CDDA so it's completely irrelevant to this discussion. Also, in spite of your claim to the contrary, the audio CDs that do not conform to red book are NOT allowed to use the CDDA logo, as with Copy Control. So do you have any evidence to support your rationale? Because so far a cursory examination disproves your claims. Ham Pastrami (talk) 07:03, 28 March 2010 (UTC)
The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Pre-emphasis[edit]

Some early CDs seem to have preemphasis applied to improve SNR, sometimes (but often not) signified by some flag in the TOC. Early CD players often had a light to show if preemphasis was present and would apply appropriate filtering, but I'm not sure if modern players do and most ripping solutions (except iTunes apparently) have no provisions for dealing with this. Is this part of the Red Book standard, and could someone provide more useful information regarding this? Found some discussions regarding this: [1], [2], [3], [4] --Zilog Jones (talk) 16:53, 7 April 2009 (UTC)

Unreliable sources[edit]

(discussion moved here from User talk:Mjb) Hello, you removed a reference to wiki.multimedia.cx on the Red Book (audio Compact Disc standard) article. You wrote: "the multimedia wiki is not a reliable source". Please, could you explain, why is it not a reliable source? MultimediaWiki is not open for any contributions. Any contributor must be approved. Mike Melason is the chief maintainer of MultimediaWiki. He monitors contributions/changes on that wiki. As far as I know, he is also the primary contributor to MultimediaWiki.--188.167.27.153 (talk) 06:47, 6 October 2010 (UTC)

I don't have to. It's a wiki, which is a self-published source. WP:SPS is clear enough. But in case it isn't, here:
The claim in question is that the Red Book "specifies the form of digital audio encoding: 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz". The truthfulness of this claim is not the least bit in doubt, so it doesn't even need citations. The ones that were provided use lousy sources.
MultimediaWiki is a semi-public wiki of multimedia software engineer Mike Melanson. He might vet his contributors and edit the content himself, but that's not particularly relevant because he's not an authority on the Red Book. He may know a lot about Flash Player and xine, but he's not an expert on the Red Book. He isn't an electrical engineer who builds CD players. He's just some guy who writes software. He might own a copy of the Red Book, but if he does, then he can simply give us a reference to the Red Book itself and then it won't be an issue. So it's up to you to show that it's not a violation of WP:SPS.
Now look at the other references. The homepage of Kade "Archer" Hansson? How was that even up for consideration? It's more self-published material from a non-authority on the content of the Red Book.
And lastly, the LPCM format info at digitalpreservation.gov, is promising as a source since it's essentially published by the Library of Congress. Well, it doesn't say what's in the Red Book other than "ISO/IEC 60908...covers the use of 16-bit LPCM in compact disks." All that tells us is that 16-bit LPCM can be used in compact discs and that the Red Book says how. That's close, but not really the same thing as the claim in question. There is a footnote there which goes on to say that according to Wikipedia, the Red Book defines the CDDA standard. Yes, it's true, but...they're getting their info from Wikipedia. This is far from an ideal source.
So really, all three references are inappropriate. If you really want to keep them, it's up to you to justify them. But like I said, I don't think we even need them. It's not very important that the claim that CD audio is defined by the Red Book as 44.1 kHz 16-bit LPCM be cited at all. Is it really up for debate? Besides, if references are provided, certainly someone has the actual book and can just point to the page or section number. It seems like a no-brainer that a claim along the lines of "the Red Book says X Y and Z" should just cite the Red Book itself, not wikis, personal homepages, or poorly-worded sources that don't support the claim and that ultimately refer back to Wikipedia. —mjb (talk) 09:48, 6 October 2010 (UTC)
Thank you for your answer and explanation. The references were added to the "LPCM" (linear PCM), because previously it was only "PCM" - see this change. I don't have Red Book specification and AFAIK it is not publicly available (for free). But I know CDDA uses Linear PCM. In my point of view it is questionable if we can trust someone who will add information such as "the information is on page 567 of Red Book" - directly on Wikipedia without any other reliable source. I think it is similar to adding "unreliable" sources, because most people cannot verify it.
I understand your opinion about the sources. But in the case of missing public specification there is no other choice in some technical articles on Wikipedia. --188.167.27.153 (talk) 16:22, 6 October 2010 (UTC)

Formats greater than 16-bits[edit]

On some CDs, the packaging will mention 20-bit remastering, 24-bit, Super Bit Mapping or some such. (The mid- to late-1990s Impulse! Records catalog comes to mind.) If the Red Book standard is 16-bits at 44.1 kHz, do these other "formats"(?) have any real meaning or usefulness (i.e. what good is 24-bit, 96 kHz remastering, if the ultimate product is restricted to 16-bit 44.1 kHz)? Or are they in fact not compliant with Red Book standards? -- Gyrofrog (talk) 19:13, 18 February 2011 (UTC)

That higher bit-depth, higher sample-rate marketing hype refers to the equipment and processing that was used before or during the final conversion to Red Book format. If you take an analog source, try to filter out frequencies above the Nyquist limit (22.05 kHz), and digitize the result directly to 16-bit, 44.1 kHz, then maybe do other signal processing, there can be some measurable (but not necessarily audible) noise introduced, for various reasons. You're more likely to get better results if you digitize to a higher bit depth and sample rate, do all your other processing in that domain, and convert to Red Book format at the very end. This usually involves some kind of dither and noise shaping (Super Bit Mapping is one such method).
The Compact Disc article would be the place to mention this stuff, but the problem will be finding reliable sources. It's no problem finding "audiophile" publications that parrot press releases or make subjective claims of sound quality improvements offered by such technologies, but it's much harder to find any literature which says exactly how the technology works, what problems they're trying to solve, what their measurable effects on the audio are, and most importantly, whether any double-blind testing has proven people can actually hear the difference between identical, level-matched recordings that differ only by the use of these mastering techniques (if such things could ever be found, which I doubt). It's probably best to avoid the subject. —mjb (talk) 21:57, 18 February 2011 (UTC)
OK, thanks for the info. One wonders if the improvement in sound (for example, with a re-release) has more to do with better sound levels than with sampling rates. -- Gyrofrog (talk) 23:51, 18 February 2011 (UTC)

Files section[edit]

There were a couple items of reader feedback (see the link near the top of this page) which I attempted to address in a series of edits today.

I want to know which of the files on a commercial CD a normal CD player reads.
[I was looking for the] difference between mp3 and cd format.

I believe I got both of these taken care of by adding a "files" section which explains that there are no files on a CD, that operating systems like Windows may offer virtual files as a sort of abstraction of the CD TOC, and that the common audio file formats are actually the product of ripping.

This basically amounts to a difficult-to-source "what Red Book is not" section, which I don't particularly like having... but it doesn't really seem to be the kind of thing that the average reader can easily figure out otherwise. —mjb (talk) 07:34, 26 September 2012 (UTC)

Data encoding section[edit]

The technical details really weren't all that detailed, nor did they really explain the relationship between the physical pits-and-lands and the LPCM audio data, which is a crucial element of the Red Book standard. I attempted to address this by adding a data encoding section, summarizing info from Ken Pohlmann's The Compact Disc Handbook, since I don't have access to the actual standard.

I also sought to clarify that the term sector comes from the CD-ROM/DAE/SCSI world and is not part of the Red Book standard, as far as I know.

This led me to the article's info about CD data rates, which I attempted to consolidate into its own section. I thought it would be interesting to add the raw data rates of CDDA, which get into the Mbps range. Again, this info comes from Pohlmann's book.

I would appreciate review of these additions, and please discuss or make corrections as needed. Thanks! —mjb (talk) 07:34, 26 September 2012 (UTC)

Thanks for your additions. I'm not aware of factual issues with your additions, but I think some of the section's content would better be in Compact discs. As I understand it, the CD started with CDDA, so the physical details of CDs were once specific to CDDA. However, since this is no longer the case, I believe we should factorize the common parts of all CD variants (CDDA, CD-ROM, etc.) to Compact discs. For example, the 3 pictures on the left would be pertinent there. Even if they apply here, I believe we should avoid duplication and just move there. --Chealer (talk) 00:56, 7 March 2013 (UTC)
Ok, I just moved two of those pictures to the CD article. I also tried expanding the data encoding sectiona bit, since it contained several abbreviations with no links and it was difficult to follow at first. I will also probably try to restructure sections a bit, since there seems to be duplication between the Data encoding and the Data structure sections, and the order of the sections currently does not follow any clear logic. Sega381 (talk) 14:03, 14 May 2013 (UTC)
I tried to address some of the shortcomings by merging duplicated information, and by restructuring some sections. However, there is still some duplicated information and I am still not convinced of the logic for the ordering of the sections. We may still want to move some common information to the CD article. Sega381 (talk) 14:47, 14 May 2013 (UTC)

Format deviations[edit]

DVD Audio is not a format deviation but a rival successor format. If this is included so should SACD, which in its hybrid form is at least compatible with CDs. Also, if such details are included in this article I suggest a new heading of Successor Formats... but where do you end? MP3/Ogg/Blu Ray Audio/etc? I suggest removing DVD audio completely. But should we include hybrid SACD since it is compatible? Derekjc (talk) 17:21, 3 April 2013 (UTC)

Storage Capacity[edit]

Under the heading 'Storage Capacity and Playing Times' there is much discussion on the time restrictions of Audio CD's, but no data that I can find on the actual storage capacity in MB. I came here, specifically to find this information, and thought it would be a "given" in an article such as this. I can only assume that it was intended, due to the title of the section in question, but somehow was overlooked.

A remedy would be greatly appreciated. — Preceding unsigned comment added by 1.178.223.3 (talk) 07:39, 23 November 2013 (UTC)

Heh, you're right. Unfortunately it's hard to talk about capacity when the technicalities of the data format haven't yet been explained. We also must avoid doing original research.
A number is probably mentioned in some literature somewhere, and if we say anything in the article, that's what we should use. But since it goes hand-in-hand with maximum playing time, you can expect that different sources will have different numbers, and that's if they mention a data quantity (instead of just duration) at all.
If we could do original research, we'd just multiply the 4.3218 Mbps rate (for the CIRC-encoded audio data + subcode) by the 82:34 (4954 seconds) playing time of the longest known CD (at least, the one mentioned in the article) and get a result of a little over 2.61 GB. That's how much data is represented by the pits and lands, as seen by the laser. But when you ask about storage capacity, you probably just want to know about how much audio data it holds. That's 4954 seconds of 16-bit (2-byte) 2-channel LPCM at 44.1 KHz, or 4954×(2×2×44100) = 873,885,600 bytes = 833.402 MB. —mjb (talk) 09:14, 23 November 2013 (UTC)

SHM-CD[edit]

It would be nice if somebody could add a section on this, or remove the redirect link. It's not cool to have a redirect for SHM-CD to this page, and then have this page utterly silent about it.

-TMusgrove. — Preceding unsigned comment added by Tmusgrove (talkcontribs) 20:57, 25 February 2014 (UTC)