Burning CDs

Reed Lover wrote: Certif1ed wrote: Oh - and goose is right - simply transferring a file to CD is lossless - it has to be because the CRC check would tell your computer that the two files are not the same. Try this; Create an Excel spreadsheet and stuff it with data until the file size is about 40Mb. Now copy it. Copy it again. Does any data get lost? I rest my case!  So a directly copied CD doesn't lose anything - it's impossible, AFAIK - although I'm open to decent scientific persuasion. How can a data file lose data without corrupting the file? The only way the sound can be changed is to apply an algorithm to the data file, such as a codec - ie if you convert it from CDA to Wav and back again. A straight copy of the CDA can change nothing. I guess it depends on how the burning software operates - whether it unpacks and repacks the data before burning or not. I use Nero 6 and haven't noticed any difference between copies and originals. A perfect CD (ie no scratches, other damage etc) will be read perfectly by a perfect optical drive.The problem is that CD's and CD Drives are not perfect mediums (media?) for storing/tranferring data and different drives have different ways of dealing with large errors.Some drives take a guess (interpolate) on what the values should be based on the previous and following values.  Other drives just set the bytes to 0.  Some drives do a good job of reporting these conditions, while some others don't report any errors.  It is all up to the person who programmed the firmware in the drive.  You can see how many drives can give lots of errors in the final wav file but not report any errors to the extraction application.So it is down to the quality of the drive. Suppose you extract the audio track from the copy, and it's an exact binary match of the track you wrote from your hard drive, but the CDs don't sound quite the same. What then? Most people don't notice any difference between originals and duplicates. Some people notice subtle differences, some people notice huge differences; on better CD players, the differences are harder to hear. Some say CD-R is better, some say worse. While it's true that "bits are bits", there "are" reasons why CD-Rs may sound different even when the data matches exactly. An excellent paper on the subject is "The Numerically-Identical CD Mystery: A Study in Perception versus Measurement" by Ian Dennis, Julian Dunn, and Doug Carson, submitted to the Audio Engineering Society (Preprint 4339, 101st AES convention). It's available for download in PDF form at http://www.prismsound.com/downloads/cdinvest.pdf. The paper is primarily concerned with why pressed CDs created at different plants or with different methods sound different, but the observations are relevant to CD-R as well. The conclusions in the paper suggest that low-frequency modulations in the disc affect the servo and motor electronics, causing distortion noticeable to a critical listener.

Fascinating paper - I don't have time to read it all ATM, but I will.

I note in the first page it states; "The final digital data feeding the LBR is not precisely the PCM audio data from the pre-mastering studio; the PCM data is pre-encoded as 'EFM'information to allow the pits of the final disc to be successfully tracked and read by the player. The EFM coding process is not strictly deterministic, i.e. the same PCM data can be represented by different EFM patterns; the selection of the most appropriate pattern is determined by an algorithm in the encoder."

- this was the point I was making earlier about applying codec algorithms.

I'm not sure about the "Low frequency modulations...causing distortion" theory, as that would seem to necessarily involve altering the audio data somehow. I can see how it would affect analogue signals - but digital signals corrupt when they deteriorate (as in the artefacts you get on Digital TV or poorly compressed MPEG encoded files), and it's hard for me to see how a properly CRC'd file would not be affected such that a CD reader would be completely unable to read it, if the file was an exact binary copy.

Garion81 wrote: Reed Lover wrote: ""interpolation" issue.     Is this some kind of scheme to have the world intregrated with the Poles?  or vise versa?  Are all the CD manufactures in on this? An Example: I just received my mail order bride from Poland to do my part in Interpolating the world.

Interpolate or interpollinate ?

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Report on Nerdy Computer Joke - for Dummies.

By Cert.

It has been suggested that the above joke is worthy of a report - so I have investigated the humourous aspects thoroughly, and would like to humbly submit the following report to my peers, especially those with limited knowledge of computers or computing terms - or anyone else with kidney problems.

It transpires that a "Byte" cannot possibly walk into a bar, since a byte is a representation of intangible data, which itself is not readable by the average computer user. Not to stray too far off-topic, and to accept that in a joke, a byte may indeed walk into a bar - as may other improbable entities, it is useful to the uninitiated to understand what a byte is in order to fully comprehend the humourous aspects of the joke posted above.

First, though, it's necessary to understand the reply of the byte to the bartender's assessment of its well-being. We can look no further than the giant of the computing world, the company Microsoft - source of the well-known joke that runs as follows;

Bill Gates heard about Hugh Grant's encounters with the famed lady of purchasable virtues, Divine. He therefore made an appointment with her that he might sample her services. Once business had concluded, he stated his appreciation thus;

"That was wonderful - I can see why you're called Divine".

To which the renowned good time girl replied;

"And I can see why you called your company Micro Soft..."

Mr Gates' wonderful company provides this clear and precise explanation of the term "parity";

The quality of sameness or equivalence, in the case of computers usually referring to an error-checking procedure in which the number of ones must always be the same — either even or odd — for each group of bits transmitted without error. If parity is checked on a per-character basis, the method is called vertical redundancy checking, or VRC; if its checked on a block-by-block basis, the method is called longitudinal redundancy checking, or LRC. In typical modem-to-modem communications, parity is one of the parameters that must be agreed upon by sending and receiving parties before transmission can take place. See also fault tolerance; stripe set; stripe sets with parity.

This also helpfully explains where the pun on the word "bit" was extruded - but does not fully explain the relevance to the byte. Fortunately, that is simple to explain; a byte comprises 8 bits.

Interestingly, but not at all relevant to this discussion, 4 bits are known as a nibble. It can be surmised that further humour can derived from these terms - but that discussion is outside the scope of this report, and, one might suggest, abuses the terms of reference.