| fdegrove |
Hi,
| quote: | | It's more fruitful and, frankly, more entertaining. |
Yeah...
Let's stop puncturing each others' equilibrium and have a coffee for a change...;)
| quote: | | So there is an abolute cause for acoustic feedback in a CD system. |
My concern was: does this sensitivity to microphony affect the digital datastream in any way?
If it doesn't then I assume it shouldn't be audible unless it upsets something else...But what?
Cheers,;) |
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| fdegrove |
Hi,
| quote: | | Did Mr. Randi really recall his challenge - I don't see anything on his pages ? |
No...
But then we don't have anything solidly paranormal...yet.
Although I do have my reservations about that at times....:angel:
Cheers,;) |
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| TNT |
Well id does not affect the digital bit stream but it would have an effect on the d/a conversion process because of an unstable clock. The bit content is perfect on the input pin of the d/a chip (not counting eventual eroor correction in the read process of the disc)
/ |
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| TNT |
| quote: | Originally posted by TNT
Well id does not affect the digital bit stream but it would have an effect on the d/a conversion process because of an unstable clock. The bit content is perfect on the input pin of the d/a chip (not counting eventual eroor correction in the read process of the disc)
/ |
This is why I think people do hear a diff. with shakti but it is not it's state funtion - beeing hevy.
In a shakti test I would like to do it should be attached to wires hanging from the roof 1 mm above the targeted equipment. That is <near>, no?
/ |
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| analog_sa |
| quote: | My concern was: does this sensitivity to microphony affect the digital datastream in any way?
If it doesn't then I assume it shouldn't be audible unless it upsets something else...But what? |
Frank,
You can't be serious asking this question. Maybe you should brush-up on jitter and DACs.
regards |
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| FrankWW |
| quote: | Originally posted by serengetiplains
Meitner says:
... Since it's around 800Hz, we have this problem with female voices, if you know somebody who can sing in that frequency range, very loud, they can shut CD players down, Cryogenic treatment doesn't change the frequency of that resonance, it just changes its Q [damping], Once you are talking high velocity vibrations, as they are at 800Hz, clamping doesn't change things much, We tried damping mats and all sorts of stuff: they improved things a little but never as much as the cryogenics did. |
| quote: | Originally posted by geewhizbang
A lot of things DO get very, very brittle at cold temperatures. With brittle items such as glass or plastic, it is possible that you get a network of fine cracks in such items but it is highly unlikely that you could hear any of these things or that these changes would be beneficial. |
"Cryogenic treatment doesn't change the frequency of that resonance, it just changes its Q [damping]," and "it is possible that you get a network of fine cracks in such items...."
I understand that one can damp an object's resonance by reducing it's rigidity. A network of fine cracks possibly would do that for a CD. HooHa!
I have no idea if that's how the cryogenic treatment damped the CDs' resonance. But I rather doubt it.
Cds are made of polycarbonate which appears in some rather low temperature applications, as, for instance, this cryogenic grinding mill:
http://www.reflexusa.com/cryogwigmil.html
Polycarbonate is one of the materials of choice for cryogenic equipment, as a cursory Google search would show.
The rabid PC overclockers get their machines to operate at extremely low temperatures using liquid nitrogen as the refrigerant and it would seem as long as the descent to low temperature is gradual the various parts survive without damage.
CDs are made from polycarbonate slugs which are heated to a high desicatng temperature before being pressed and the aluminum layer preciptated on and the back then laquered. There is no reason to think that a CD would take any particular damage from very low temperatures providing they are brought to them gradually.
Thus far I haven't found any report about cryogenic treatment changing the structure of polycarbonate except from people who treat CDs that way.
However, polycarbonate maybe annealed in the same manner as a metal.
http://www.rmplastics.net/polycarb.htm
I suspect that since CDs are not annealed after manufacture and that since Meitner reports their resonance is damped by cryogenic treatment that some process analogous to annealing takes place making the disc less rigid.
But it isn't necessary to know what the process is since Meitner's claim is very easy to check.. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by fdegrove
Now WTH is a CD-Data other than a CD-Rom with data on it?
Redundancy on a CD-Rom with data on it? |
CD-Rom uses a different fundamental file structure. The CD Rom file structure writes appx. 20% of the Data with REDUNDANT information that aids arror recovery. There is no such mechanism for Red-Book Audio CD. The Error correction is extremely basic. This was seen at the time as sufficient, as interpolation and other concealment methodes INCORPORATED into the whole error correction would make any unreadable sections "inaudible".
| quote: | Originally posted by fdegrove
None, nothing whatsoever, if the file is damaged it's unreadable: end of story. |
CD Roms remain readable with much worse damage to the Disk than Audio CD's. Try it one day.
Sayonara |
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| ALW |
| quote: | | The vibration is not going to change how bits are read. So they cannot have ANYTHING to do with jitter. |
The signal from a CD mechanism is a high frequency analogue signal not a digital one. There's plenty of opportunity for it to be affected by a host of things, not least vibration, be that directly, or via secondary effects.
| quote: | | Does component microphony even exist in CD players or solid state amps? |
It certainly exists in electronics, so it's not impossible. Somewhere I have an LT data sheet (IIRC) on voltage references that actually has 'scope traces of the effect on output noise of tapping a capacitor with a pencil.
My guess is this is such a hard leap for you, because you obviously haven't looked at this in detail.
Here's my suggestion, design an RF phase locked loop oscillator with discrete circuitry, get it working, then tap it with something solid.
You'll see all sorts of odd behaviour on the RF output unless you're very lucky, spectral components that appear, increased phase noise and generally **** performance!
PLL's are notoriously vibration sensitive.
Explain why.
Andy. |
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| geewhizbang |
What comes out of the CD player is indeed just digital. The analog comes out of the DAC.
In the context in which I said this, anyway. I am quite aware that the signal going to the amplifier is analog.
The argument about the PLL jitter is possible. I will see what I can find out about it. Has anyone done any actual LISTENING tests? The kind that a scientist would accept, not something that is influenced by psychoacoustic bias?
The most ideal way to this would to have two identical players. One is isolated inside of an mdf box, and the other is exposed to the sound field of the speakers.
This is most definitely something that can be found with an ABX test if it is there or not.
So far this quartz crystal jitter is the only thing I've heard so far that makes any logical sense of why it would be so necessary to isolate a CD player from vibration.
*****
Back to Meisner, there is absolutely nothing there other than well-written blather about wonderful the cryo-stuff is, all couched in the finest scientific language, but without any actual understanding of the principles of science. He says his listening tests show an improved airiness in the sound. He quotes all sorts of examples of cryo cooling, but none of the examples has much to do with explaining why the cooled cables perform better.
It is highly unlikely that any chemical or physical changes result from the cooling, from what I know about physics.
We are just supposed to believe him. This golden ear camp fall for the most complete nonsense sometimes. And unfortunately, this very often makes it hard to get credibility when something that actually can be heard is discovered, but since it is coming from these loonies, nobody even tests it for a long time, and progress is delayed. |
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| TNT |
WOW - You just stated that "digital" signal does not exist!
/
| quote: | Originally posted by ALW
The signal from a CD mechanism is a high frequency analogue signal not a digital one. There's plenty of opportunity for it to be affected by a host of things, not least vibration, be that directly, or via secondary effects.
It certainly exists in electronics, so it's not impossible. Somewhere I have an LT data sheet (IIRC) on voltage references that actually has 'scope traces of the effect on output noise of tapping a capacitor with a pencil.
My guess is this is such a hard leap for you, because you obviously haven't looked at this in detail.
Here's my suggestion, design an RF phase locked loop oscillator with discrete circuitry, get it working, then tap it with something solid.
You'll see all sorts of odd behaviour on the RF output unless you're very lucky, spectral components that appear, increased phase noise and generally **** performance!
PLL's are notoriously vibration sensitive.
Explain why.
Andy. |
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| ALW |
| quote: | | What comes out of the CD player is indeed just digital. The analog comes out of the DAC. |
NO!
What comes out of the mechanism (i.e. what is read from the disc) is analogue not digital. It's an analogue signal representing the digital data.
It's not simply a digital system, there's plenty of opportunity for jitter on the disc, the reading process and the conversion of eye-pattern to digital data to affect sound. If this translates to input jitter at the DAC it will be audible.
The fundamental issue is this doesn't matter if you stay in the digital domain, since time is a non-issue, within reason. A cd copied digitally doesn't change the DATA on the disc if the copy is succesful, but it can change the replay process in a CD player as the disc can (will, in most cases with a CD-R drive) have jitter added in the recording phase. Jitter only matter at the D-A process, unless extreme.
Try it, look at the eye pattern in a CDP with mastered and different copied discs - the difference is visible on a 'scope!
A CD player is a streaming system though, in which time is a critical factor.
Andy. |
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| fdegrove |
Hi,
| quote: | | CD-Rom uses a different fundamental file structure. |
No it does NOT.
A CD-ROM is just a blank writeable disc: Read Only Memory (or Media if you like)
| quote: | | The CD Rom file structure writes appx. 20% of the Data with REDUNDANT information that aids arror recovery. |
Absolutely NOT.
| quote: | | CD Roms remain readable with much worse damage to the Disk than Audio CD's. Try it one day. |
Which has nothing to do whatsoever with a damaged data file on a CD.
CD-ROM can be written to using a few standards, these can be mixed on the same CD-ROM but none of those include a single byte of redundant data.
The standards go according to the YellowBook specifications.
| quote: | | There is no such mechanism for Red-Book Audio CD. The Error correction is extremely basic. |
Digital encoding allows the use of error correction codes, which are necessary to correct errors resulting from the manufacturing process and minor damage or marks which may occur from handling and use.
The result is that the amount of data stored on a CD is nearly four times the data needed to represent the audio only. But this is a small price to pay for a robust format that allows recordings to be played back free of clicks, hiss and other defects associated with analogue media.
Pretty basic perhaps but it's there alright...
So, unless you invented your own standards, I get the impression you're as confused as a barking bird here...
| quote: | | You can't be serious asking this question. |
Tongue firmly in cheek, Peter....
Cheers,;) |
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| geewhizbang |
Now we have already had this argument.
There are most definitely read errors on CDs (or even hard drives for that matter) but there is redundant data written so that error correction can detect these mistakes and fix them.
If the error correction fails, you usually get a really colossal mistake. You don't get little errors, since the error correction fixes 100% of the errors.
Since the CD data reading process is designed to cope with dirty disks exposed to the fingerprints or worse, the error correction redundancy is rather high. So it takes a pretty big error to mess it up. If there are any little errors caused by vibration of the disk, they are not not going to affect the actual recomposed digital data NOT ONE SINGLE WHIT, IOTA or SMIGEN. |
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| TNT |
| quote: | Originally posted by geewhizbang
Now we have already had this argument.
There are most definitely read errors on CDs (or even hard drives for that matter) but there is redundant data written so that error correction can detect these mistakes and fix them.
If the error correction fails, you usually get a really colossal mistake. You don't get little errors, since the error correction fixes 100% of the errors.
Since the CD data reading process is designed to cope with dirty disks exposed to the fingerprints or worse, the error correction redundancy is rather high. So it takes a pretty big error to mess it up. If there are any little errors caused by vibration of the disk, they are not not going to affect the actual recomposed digital data NOT ONE SINGLE WHIT, IOTA or SMIGEN. |
Clear !
But these vibes migth cause other problem e.g. messing up the low jitter osc.
Well - then that was sorted out !
Shakti, anyone `????
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| ALW |
You're wrong.
If you examine the various CD books you'll see that CD-DA (Audio, Red Book) and CD-ROM (Data, Yellow book) do have a different data format, the latter having more powerful ECC and more precise data addressing.
The physical parameters of CD-ROMs are identical to those defined in the Red Book. However CD-ROM discs differ from CD audio discs in two important ways: -
The data on a CD-ROM disc are divided into sectors containing user data and additional error correction codes.
The data are contained in files and so a file system is needed so that the required files can be accessed easily and quickly.
This does make a difference and is the reason early drives had trouble performing digital audio extraction with any accuracy - the positional information is very low resolution.
CD audio is a streaming, not random-access format.
Andy. |
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| fdegrove |
Hi,
No I am not wrong.
| quote: | | If you examine the various CD books you'll see that CD-DA (Audio) and CD-ROM do have a different data format, the latter having more powerful ECC and more precise data addressing. |
Let's get this straight first of all: CD-ROM is not a data standard but the physical medium you can write to:
You could write CD-DA to CD-ROM for instance after which you'd have a CD with DA (digital audio) on it.
If you take that same CD-ROM you could also write DATA to it (files) in a number of formats including ISO 9660, JOLIET, MacIntosh HFS, etc.
What we call a CD-ROM is 9/10 just the medium with data files on it, the same medium with audio on it written as CD-DA standard we'd call an audio CD.
In both cases the discs are nothing more than CD-ROMs just the way it's addressed is different.
In all cases none of the DATA formats contain a single bit of redundant information, CD-DA written formats do.
That ECC is handled differently in both cases is true but in the case of raw data there no extra information actually written to CD-ROM (the medium) that can be used for EC contrary to DA.
| quote: | | CD audio is a streaming, not random-access format. |
Yes. I never stated anything to the contrary.
To recap the CD-DA Red-Book standard descibes the physical properties of the Compact Disc (CD-ROM) and the digital audio encoding.
Beyond that standard you have the Blue Book which does the same for Enhanced CD, aka CD-Extra.
For info:
Philips Intellectual Property & Standards,
Email: info.licensing@philips.com
URL: www.licensing.philips.com
Fax: +31-40-2732113
Cheers, ;) |
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| runebivrin |
CD error correction details
I don't know if this is 100% correct, but it certainly reads like it. To summarize, all CD:s have error correction.
Data CD-s have more correction than audio CD:s, whereas audio CD:s have some degree of error concealment.
Given the playback process (if ECC is properly implemented), it's quite hard to understand how jitter in the bit retrieval can carry through all the way to the DAC. On the other hand, that jitter in the clock that feeds the DAC might cause audible artifacts is not unlikely.
I will refrain from guessing whether Shakti stones or spikes have any effect on the clock jitter level.
Rune |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by fdegrove
No it does NOT.
A CD-ROM is just a blank writeable disc: Read Only Memory (or Media if you like) |
A CD-Rom is NOT writable.
Further, the Data is encoded on CD's (all of them) in tracks of "Pit's and Land" just as on magnetic Disks it is as north/south magnetisation.
The "File System" is a structure imposed on top of the raw "Pit/Land" or "Nort/South" individual data bit's (the noughts and zeros in effect). This means that a certain specific block of ones and noughts forms a "bedinging of track/file" marker and that then the data is written into the file. Just how it is written and what methodes of revoering errors is implemented depends upon hardware and software implementations and these are are different for CD Rom and Redbook CD.
| quote: | Originally posted by fdegrove
Absolutely NOT.
|
Absolutely yes, ****.
| quote: | Originally posted by fdegrove
Which has nothing to do whatsoever with a damaged data file on a CD. |
The File a CD-ROM is damaged if a large enough number of data blocks are not recoverable and if the redundancy data fails to allow correction.
If a sufficient large number of data blocks are unreadable or read incorrectly with an Audio CD the error correction has already failed and must apply error concealement (I lump error corrction and error concealement into one mechanisms as this is how audio CD handels it).
| quote: | Originally posted by fdegrove
CD-ROM can be written to using a few standards,
|
CD-ROM = CD READ ONLY MEMORY
Meaning it cannot be written at all, you can only press it.
It seems you are erronously refer to the Writable CD-ROM, or more accuratly CD-WORM....
| quote: | Originally posted by fdegrove
these can be mixed on the same CD-ROM but none of those include a single byte of redundant data.
The standards go according to the YellowBook specifications. |
I may to re-read, however I remember the standard for DATA Files on CD-Rom to include reduant data.
| quote: | Originally posted by fdegrove
So, unless you invented your own standards, I get the impression you're as confused as a barking bird here...
|
One of us surely is.
http://www.cdrfaq.org/faq02.html#S2-17
"audio CDs use all 2352 bytes per block for sound samples, while CD-ROMs use only 2048 bytes per block, with most of the rest going to ECC (Error Correcting Code) data."
Hence CD-Rom uses 304 Bytes for every 2048 Bytes data as redudant data, or in other words around 15%. This data is REDUDANT as it is NOT the actual data but data other than that.
Again, ****.
Sayonara |
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| runebivrin |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
http://www.cdrfaq.org/faq02.html#S2-17
"audio CDs use all 2352 bytes per block for sound samples, while CD-ROMs use only 2048 bytes per block, with most of the rest going to ECC (Error Correcting Code) data."
Again, ****.
|
Did you actually bother to read the entire paragraph from which you quoted a part? I suggest you do...
Rune |
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| ALW |
| quote: | | Let's get this straight first of all: CD-ROM is not a data standard but the physical medium you can write to |
You're arguing silly semantics here but since we've started CD-ROM or CD-ROM XA is covered by the yellow book.
CD or CD-DA is the conventional description for red book discs it also covers CD-G, CD-TEXT, CD-G +MIDI, CD Single, CD Maxi Single, early Karaoke CD, CD Video Single (Extensions to CDDA).
CD-ROM is not the name used for the medium in the red book standard.
| quote: | | To recap the CD-DA Red-Book standard descibes the physical properties of the Compact Disc (CD-ROM) and the digital audio encoding. |
It covers the physical properties, but does not mention CD-ROM at all in this context.
Anyway, the point was you used your argument to try and repute Kuei's argument about the different formats having different error correction seemingly choosing to mis-interpret his obvious intentions by playing semantics.
Andy. |
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| ALW |
| quote: | | Did you actually bother to read the entire paragraph from which you quoted a part? I suggest you do... |
I've just read it - what difference does it make to the argument?
Andy. |
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| runebivrin |
I've read the past few posts as an argument as to whether audio CD:s have any error correction data at all, with Thorsten saying they don't. The document Thorsten quoted from says all CD:s have error correction data.
Now, if I have misinterpreted him, I apologise.
Could we just for the sake of discussion reach an agreement as to the issue of how error correction of audio CD:s work, without any excursions on the matter of the sound of those CD:s.
Rune |
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| fdegrove |
Hi,
I'll give you semanitcs:
Definitions of CD-ROM on the Web:
(Compact Disk - Read Only Memory) - A computer storage medium which can store large amounts of information; generally used to distribute software or multi-media for use on computers with CD-ROM drives. CD-ROM disks look just like music CDs, and cannot be altered by a user.
www.getnetwise.org/glossary.php
stands for Compact Disc Read-Only Memory. A small plastic disk, similar to audio compact disks, used for storing information in digital format. The information is read from the disk by a small laser beam and displayed on a computer screen.
www.library.arizona.edu/rio/glossary.htm
Compact Disc-Read Only Memory. A compact disc formatted for data storage. Most CD-ROMs can store 650 megabytes of data.
iet.ucdavis.edu/glossary/
Compact Disk, Read Only Memory; a high-capacity secondary storage medium. Information contained on a CD is read-only. Special CD-ROM mastering equipment available in the OIT Multimedia Lab can be reserved for creating new CDs.
www.oit.ohio-state.edu/glossary/
Pronounced see-dee-rom, abbreviation of Compact Disc-Read-Only Memory. A type of optical disk capable of storing large amounts of data -- up to 1GB, although the most common size is 650MB (megabytes). A single CD-ROM has the storage capacity of 700 floppy disks, enough memory to store about 300,000 text pages. CD-ROMs are stamped by the vendor, and once stamped, they cannot be erased and filled with new data. To read a CD, you need a CD-ROM player. All CD-ROMs conform to a standard size and format, so you can load any type of CD-ROM into any CD-ROM player. In addition, CD-ROM players are capable of playing audio CDs, which share the same technology. CD-ROMs are particularly well-suited to information that requires large storage capacity. This includes color large software applications, graphics, sound, and especially video.
www.cert.org/homeusers/HomeComputer...y/glossary.html
Compact Disc Read Only Memory. A 3.5in disc that can store upto 650MB of data. Once written by the manufacturer, the contents of a CD-ROM are permannent and cannot be altered. Read using a CD-ROM drive.
www.davcomuk.co.uk/files/tech/glossary.htm
Compact Disc - Read Only Memory. An optimal disc that is used to store text, graphics and audio data for computer applications. The contents may not be changed or rewritten.
www.axis.com/corporate/corp/glossary_general.htm
(Compact Disc - Read Only Memory) - plastic discs with a reflective metal coating which are read by a small laser beam. They are similar to audio compact discs. The differences lie in the way that the signals are processed after being read. CD-ROMs may contain audio, but they are primarily used for text. Many sources of information are now available on CD-ROM. Compare with online.
www.royalroads.ca/coppul/glossary.html
(Compact Disk Read-Only Memory) A computer technology which allows information to be stored on a compact disk and accessed through a microcomputer.
www.libraries.uc.edu/help/how/tutorial/glossary.html
Compact Disk, Read-Only Memory. A type of storage device that looks just like an audio CD and stores as much data as a large hard disk (600MB), making it a popular means of distributing fonts, photos, electronic encyclopedias, games, and multimedia offerings. As the name indicates, however, you can't save or change files on a CD-ROM, only read them. Pronounced see-dee rom.
www-rohan.sdsu.edu/glossary.html
Compact Disc - Read Only Memory.
www.siemensauto.com/glossaries/its_glossary.html
Computer-readable information on compact disks. Farrell Library has a number of reference services on CD-ROM. A CD-ROM drive (reader) is a component of most multimedia systems and most modern software is delivered on CD-ROM. 50X is the current standard for CD drives. The number refers to the speed at which data can be read from the drive.
www.oznet.ksu.edu/ed_asi490/Glossary/cgw.htm
Abbreviation for Compact Disk-Read Only Memory. Sometimes called a compact disk; storage devices for databases that are accessed by microcomputer.
www.lib.umd.edu/UES/er_glossary.html
Compact Disk - Read-Only Memory, uses essentially the same technology as an audio CD in order to store large amounts of information in a very compact format
www.ex.ac.uk/its/glossary.htm
Compact Disc-Read Only Memory. A compact disc having programs, data,and other information for computer applications.
www.mo-forum.gr.jp/english/glossary/
A computer disk that can store large amounts of information and is generally used on computers with CD-ROM drives.
www.ed.gov/pubs/parents/internet/glossary.html
Compact Disk-Read Only Memory. A computer-based device for storage of information. A personal computer and a CD player are needed to read the information.
library.usask.ca/tutorials/basics/tutorial/gloss.html
A read-only-memory compact disk, used to store printed information such as periodical indexes. This disk is used with computer.
www.lib.umich.edu/ugl/info/glossary.html
A memory disc for computers that holds 550 megabytes of data. CD-ROM can be used to store computer programs, databases, books, video, pictures and sound. These media are stored on the same disc to create "multimedia" information and playback.
www.pbs.org/als/satsupport/glossary.htm
Compact Disk Read Only Memory
exp.telecomitalialab.com/exp-portal/glossary/
Compact Disk-Read Only Memory. An information technology used for storing and reading large amounts of information which is accessed through a computer. CD-ROMs look like the compact discs from a music store; but instead of storing music, they store text and other data
www.nps.gov/ccso/library/glossary.htm
Compact Disk - Read Only Memory
www.nbc-med.org/SiteContent/glossary.asp
Compact Disk Read Only Memory. A storage medium. Data are "stamped" onto the disk during the manufacturing process. The disk is read-only.
odwin.ucsd.edu/glossary/glossary.html
Compact Disk-Read Only Memory, a storage medium popular in modern computers. One CD-ROM can hold 600 MB of data.
www.intermark.org/im-glossary.html
An abbreviation of the term Compact Disc, Read Only Memory (A Compact Disc used to store digital data, such as large programs, that can be read by a computer).
recordingeq.com/GlosPubAE.htm
a compact disk that is used with a computer (rather than with an audio system); a large amount of digital information can be stored and accessed but it cannot be altered by the user
www.cogsci.princeton.edu/cgi-bin/webwn
Oh, BTW....A CD-ROM is still a CD-ROM even before it contains any data. It's only after the data is written and the session is closed that it becomes Read Only Memory.
How that data is actually transferred to that media is totally irrelevant to the definition of the MEDIUM itself.
| quote: | | It covers the physical properties, but does not mention CD-ROM at all in this context. |
Of course it doesn't.
It just doesn't apply and that's exactly what the issue is about : whether that medium contains raw data, picures, graphics you name it, the medium is still the same.
There just isn't any particular format of data written to that medium that would go by the format: CD-ROM.
Cheers, ;) |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by runebivrin
Did you actually bother to read the entire paragraph from which you quoted a part? I suggest you do... |
I actually CAN READ and YES, I have read the paragraph.
Now let me state my contentions:
1) CD and Data Media on CD have differing error correction mechanisms.
2) The error correction mechanism for CD is very basic.
3) If the basic error correction fails to recover the error the CD-Players Digital Processor applies one of several strategies of error concealement, which include interpolating samples and repeating complete frames of data.
Now lets see the paragraph in total.
| quote: | from http://www.cdrfaq.org/faq02.html#S2-17
"Subject: [2-17] Why don't audio CDs use error correction?
(2001/08/01)
Actually, they do. It is true that audio CDs use all 2352 bytes per block for sound samples, while CD-ROMs use only 2048 bytes per block, with most of the rest going to ECC (Error Correcting Code) data. The error correction that keeps your CDs sounding the way they're supposed to, even when scratched or dirty, is applied at a lower level. So while there isn't as much protection on an audio CD as there is on a CD-ROM, there's still enough to provide perfect or near-perfect sound quality under adverse conditions.
All of the data written to a CD uses CIRC (Cross-Interleaved Reed-Solomon Code) encoding. Every CD has two layers of error correction, called C1 and C2. C1 corrects bit errors at the lowest level, C2 applies to bytes in a frame (24 bytes per frame, 98 frames per sector). In addition, the data is interleaved and spread over a large arc. (This is why you should always clean CDs from the center out, not in a circular motion. A circular scratch causes multiple errors within a frame, while a radial scratch distributes the errors across multiple frames.)
If there are too many errors, the CD player will interpolate samples to get a reasonable value. This way you don't get nasty clicks and pops in your music, even if the CD is dirty and the errors are uncorrectable. Interpolating adjacent data bytes on a CD-ROM wouldn't work very well, so the data is returned without the interpolation. The second level of ECC and EDC (Error Detection Codes) works to make sure your CD-ROM stays readable with even more errors.
It should be noted that not all CD players are created equal. There are different strategies for decoding CIRC, some better than others.
Some CD-ROM drives can report the number of uncorrected C2 errors back to the application. This allows an audio extraction application to guarantee that the extracted audio matches the original. The Plextor UltraPlex 40 is one such drive.
See http://www.cdpage.com/dstuff/BobDana296.html for an overview of error correction from the perspective of media testing. If you really want to get into the gory technical details, try http://www.ee.washington.edu/consel...5x7/iec908.htm.
|
Okay, contention 1:
"It is true that audio CDs use all 2352 bytes per block for sound samples, while CD-ROMs use only 2048 bytes per block, with most of the rest going to ECC (Error Correcting Code) data."
Contention supported by the source.
Contention 2:
"All of the data written to a CD uses CIRC (Cross-Interleaved Reed-Solomon Code) encoding. Every CD has two layers of error correction, called C1 and C2. C1 corrects bit errors at the lowest level, C2 applies to bytes in a frame (24 bytes per frame, 98 frames per sector). In addition, the data is interleaved and spread over a large arc."
This is a lot of verbiage, but it says in short that data is distributed such that adjecent samples end up in different areas of the CD and that there are basic checksums for pairs of bytes and for frames of 24Bytes. That's it.
For Data CD however "CD-ROMs use only 2048 bytes per block, with most of the rest going to ECC (Error Correcting Code) data."
So, contention supported by the source
Contention 3:
"If there are too many errors, the CD player will interpolate samples to get a reasonable value. This way you don't get nasty clicks and pops in your music, even if the CD is dirty and the errors are uncorrectable."
Contention supported by the source.
Now, exactly what where you referring to, if anything at all?
Sayonara |
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| ALW |
Frank,
None of that is relevant to your argument, which was that CD-ROM is the medium for all CD formats.
It isn't.
An audio CD is pressed, and becomes simply a CD (or CDDA disc to be pedantic).
It wasn't a CD-ROM before that point and it doesn't become one afterwards, even if it's blue book.
A pressed DATA disc becomes a CD-ROM. Only yellow and orange book discs are CD-ROM's.
The blank discs you buy are CD-R, or CD-RW, what they then become, depends upon what you write to them.
As I said it's largely semantic.
Andy. |
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| fdegrove |
Hi,
| quote: | | As I said it's largely semantic. |
No, it's not.
Need I give the definition of "Compact Disk" as well?
Definitions of Compact Disk (CD) on the Web:
A data storage medium in which information is stored on a small, disk that is read by laser technology rather than by a magnetic transducer. CD-ROM is much like the audio CDs which hold sound data, a CD-ROM holds applications or data to be used by a computer. The computer can read the information contained on the CD-ROM; but because it is "read only," the user cannot record new information on it. CD-Recordable is a CD on which additional information may be recorded for future use. A special device is required to record data; however once recorded, it can be read by PC computers with appropriate software.
www.aits.uillinois.edu/glossary/glossaryc.html
A ROM medium that typically holds up to 1 GB of information.
199.247.245.42/afoster/Comp125/Term/Win2000Glossary.html
A relatively small optical disk on which text, data, sounds, visual images, and the like can be recorded digitally and then scanned, decoded, and transmitted by a laser beam to a computer monitor, television set, or playback device. See also AUDIOVISUAL RECORDS, OPTICAL DISK.
www.epa.gov/records/gloss/gloss02.htm
A nonerasable disk that stores digitized audio information.
web.umr.edu/~subra/cs235/files/Glossary.html
A small optical disk, normally 120mm across used to store audio. When used as a backing storage device to computer systems it is called CD-ROM which can contain audio, text and video.
www.highlandschools-virtualib.org.u...um/glossary.htm
a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser
www.cogsci.princeton.edu/cgi-bin/webwn
Notice the overlap between the two definitions?
Can I use a CD-ROM to hold DA? Absolutely!
| quote: | | A CD-Rom is NOT writable. |
Yes it is.
| quote: | | The File a CD-ROM is damaged if a large enough number of data blocks are not recoverable and if the redundancy data fails to allow correction. |
Not a single byte of redundant data is actually written to a CD-ROM. I do say : DATA.
| quote: | | The File a CD-ROM is damaged if a large enough number of data blocks are not recoverable and if the redundancy data fails to allow correction. |
The only "redundant" data a DATA file contains is the CRC cheksum, a checksum which was there before the file was actually written to CD and only serves as a verifier. A datafile with a wrong CRC can't be copied unless the CRC checksum error is deliberately ignored as in a byte to byte copy. The resultant file would be mostly unusable unless a data recovery program succeeds in recovering the error(s). Most of the time it isn't successful plainly because there is no redundancy to speak of and you could just as well win the lottery trying to guess.
| quote: | | It seems you are erronously refer to the Writable CD-ROM, or more accuratly CD-WORM.... |
No I'm not.
| quote: | | I may to re-read, however I remember the standard for DATA Files on CD-Rom to include reduant data. |
I strongly advise you to do so, starting with a glossary of terms would be nice.
Cheers,;) |
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| ALW |
Frank,
You shouldn't believe everything you read on the Web. Note none of those definitions come from the standards documents.
The blank discs are CD-R(W) or CD-R(W) Audio, a blank CDDA doesn't exist.
Well, it may, but it's useless, like this discussion ;)
Andy. |
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| fdegrove |
Hi,
| quote: | | You shouldn't believe everything you read on the Web. Note none of those definitions come from the standards documents. |
That doesn't make them false per se.
I already gave a link to where to get the standards and some of the links I provided contain links to the IEC.
| quote: | | The blank discs are CD-R(W) or CD-R(W) Audio a blank CDDA doesn't exist. |
Precisely. They're all Compact-Disks anyway.
| quote: | | blank CDDA doesn't exist. |
They do exist but they're in no way different than the others, other than the price you'd pay for them as it already includes a fee that goes to the RIAA.
At least that how it goes down here. Some of them are of higher quality and optimized for audio use but that's all there's to them.
Cheers,;) |
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| sauuuuuce |
| Yeah so if you read the patent info it mentions a permanent maget. Also the only claim that is made on the patent is that it reduces EMI. It's no mystery that a field will effect EMI. I have been on service calls plenty of times where a chuches choir mic lines pick up radio stations. I didn't use Shakti stuff but little cylenderical magnets that clip around the wire and the noise is gone. I simply used that as a demonstration to upgrade the wiring from cheap belkin install stuff to more expensive kanari stuff with a better sheilding. This is not "improving audio resolution" as Shakti would have you believe, but reducing EMI. |
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| serengetiplains |
| quote: | Originally posted by sauuuuuce
Yeah so if you read the patent info it mentions a permanent maget. Also the only claim that is made on the patent is that it reduces EMI. It's no mystery that a field will effect EMI. I have been on service calls plenty of times where a chuches choir mic lines pick up radio stations. I didn't use Shakti stuff but little cylenderical magnets that clip around the wire and the noise is gone. I simply used that as a demonstration to upgrade the wiring from cheap belkin install stuff to more expensive kanari stuff with a better sheilding. This is not "improving audio resolution" as Shakti would have you believe, but reducing EMI. |
Alas the Randi thread comes full circle ..... again. Sau..ce, I commend you for reading the patent. And thanks for your note about EMI. Sorry, guys, demonstrating the audibility of EMI reduction does not constitute demonstrating the paranormal. No million bucks.
Whoa! There's a UFO outside my work window! Holy cow it's HUUUUUUGE! |
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| fdegrove |
Hi,
| quote: | | Whoa! There's a UFO outside my work window! Holy cow it's HUUUUUUGE! |
That's normal.
They always send the big ones to North-America.
Cheers, ;) |
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| serengetiplains |
| quote: | Originally posted by fdegrove
That's normal.
They always send the big ones to North-America.
|
Actually, that's true. Now that I think of it, probably the biggest UFOs on record blew up parts of Los Angeles and the White House etc not so many years back. Actually, was that in a movie?
I actually saw into the window of the one that hovered outside my work window. I swear to The Deity I saw Shakti stones on top of Parasound amplifiers inside the control room. But here's the hitch: there were no speakers. Is that freaky or what? |
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| sauuuuuce |
| You would think that with all of the adavanced technologies that aliens would a have a far superior method of reducing EMI. What does intergalactic shipping run these days any way? Probably more than the shakti stones are worth...............if only we could get inside and remove the stones we could conquer these aliens once and for all. |
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| geewhizbang |
| quote: | | Try it, look at the eye pattern in a CDP with mastered and different copied discs - the difference is visible on a 'scope. |
I think you are getting confused again. A few variables, such as a bad pit, or a different disk brand, or positional changes caused by the multi-speed disk drive are going to cause the positions of the pits to vary quite a bit on copies.
But the data is read in from a source disk, the error correction bits do their thang, and a perfect digital data stream is created. It then gets written back to the disk with new error correction code and this can also also be different, but as long as the pits are written in a format that is understood by the target player the data on the copy is an identical perfect copy.
The DAC will receive exactly the same digital stream from either disk. No matter how many times you copy the disk, unless one off the copies is so bad that an outright, nasty error is made that the error correction cannot fix.
As far as the time dependent nature of the stream, the first generation players could barely keep up with the data stream. Memory was shockingly expensive, so they have very small buffers. These days, I would suspect that even rather cheap players have plenty of extra disk speed and memory buffer so it can read the disk several times where an error is detected and very often fix it. That is essentially how skip control works on a Walkman or a automotive CD player. They just have a 1 meg buffer.
The only thing you have left is the effect of vibrations on the quartz crystal inside the unit. I remain very dubious about this explanation but it could be possible.
Everything else, including the better sound of cry'oed CD, cannot be explained the way you are attemping here. You are greatly misunderstanding the process of CD writing and reading if you don't understand that copies are either perfect or have gross mistakes when the error correction fails.
There is no way to explain the slight changes you are describing other than Psychoacoustics, if you continue to try to explain this as errors in reading the pits. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by geewhizbang
As far as the time dependent nature of the stream, the first generation players could barely keep up with the data stream. Memory was shockingly expensive, so they have very small buffers. These days, I would suspect that even rather cheap players have plenty of extra disk speed and memory buffer so it can read the disk several times where an error is detected and very often fix it. That is essentially how skip control works on a Walkman or a automotive CD player. They just have a 1 meg buffer. |
No consumer CD Player Chiset works like that. All CD-Players (excluding some for mobile use) operate SYNCRONOUS. There is no re-read, no memory buffer, no nothing. You keep making assumptions and you keep a shocking ignorance of facts.
Please make sure you know what you are talking about before you do.
So, we are back to one pass trying to correctly identify "Pit" or "Land". If at that exact point the disk surface is somewhat out of focus (because the disk is vibrating more than allowable) this reading of the "Pit" or "Land" will give inaccurate results. The inaccuracies may very be enough to exceed the very basic and primitive error correction, forcing the Error Correction circuitry to switch to error concealement.
Simple, straightforward and plain.
Now you could rip the CD to a Hard Disk with EAC set to "paranoid" and then compare the same data streamed from a CD player into the S/P-DIF input of your card and record that to HD. Then compare the files and note just how much the ripped CD differs from the one played via a syncronous opertaion CD Player.
You could then start scratching a CD burned for test purposes and play that and do the same process....
How about you do some actual research instead of asserting how things should be based on your irrational believe?
Sayonara |
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| TNT |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
No consumer CD Player Chiset works like that. All CD-Players (excluding some for mobile use) operate SYNCRONOUS. There is no re-read, no memory buffer, no nothing. You keep making assumptions and you keep a shocking ignorance of facts.
Sayonara |
Well ...
From :http://www.marklevinson.com/product...=cd&prod=no390s
"Each bit of the digital audio signal is stored momentarily just prior to its transmission to the digital processor. The reference clock determines the precise moment when each bit is released from this memory buffer. This purely electronic process virtually eliminates transport-related jitter, whether of mechanical or electrical origin. Of course, another bit must be ready to be loaded into the buffer as the current bit leaves on its way to the processor. For this reason, the same crystal oscillator that controls flow of information out of the memory buffer also directs the digital servo that sets the rate at which data flows into the buffer.
By placing the all-important reference clock in the final stage of the transport section, and slaving the mechanical subassemblies to it rather than the other way around, the signal presented to the digital processor section of the No.390S is uncontaminated by electrically- or mechanically-induced jitter. The sonic advantages of this design are immediately apparent in the stunning clarity, warmth and dynamic contrasts exhibited by the No.390S."
KYW, one day I thing You will find Your self confidence a burden.
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| geewhizbang |
Someone has already explained over and over that the error correction on CDs is not as "basic" as your theories allow.
Secondly, even small errors in reading the CD data are very audible. You know a lot of stuff, but it is mostly wrong.
I would suspect that most home audio players have buffers and at least 2x readers, because a player that reads a lot of disks well without problems is going to sell better than one known to be picky. These days, a 1 meg buffer and a 2x motor are not going to add anything to the cost of the drive. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by TNT
Well ...
From :http://www.marklevinson.com/product...=cd&prod=no390s
"Each bit of the digital audio signal is stored momentarily just prior to its transmission to the digital processor. The reference clock determines the precise moment when each bit is released from this memory buffer. This purely electronic process virtually eliminates transport-related jitter, whether of mechanical or electrical origin. Of course, another bit must be ready to be loaded into the buffer as the current bit leaves on its way to the processor. For this reason, the same crystal oscillator that controls flow of information out of the memory buffer also directs the digital servo that sets the rate at which data flows into the buffer.
By placing the all-important reference clock in the final stage of the transport section, and slaving the mechanical subassemblies to it rather than the other way around, the signal presented to the digital processor section of the No.390S is uncontaminated by electrically- or mechanically-induced jitter. The sonic advantages of this design are immediately apparent in the stunning clarity, warmth and dynamic contrasts exhibited by the No.390S."
|
Yes, this "Buffer" stores each bit after read. Nevertheless the data extraction is still sequential and essentially syncronous.
The Buffer is usally a few kB. Please peruse the datasheets for any funloving standard CD Processor, evaluate how much memory is on board and how it works.
| quote: | Originally posted by TNT
KYW, one day I thing You will find Your self confidence a burden.
|
Hardly. Contrary to believers I happen to KNOW. As I know proof can be supplied easily. Here a link to a Datasheet of a standard CD processor for your personal eludication and to reduce the degree of your shocking ignorance:
http://www.semiconductors.philips.c...s/SAA7327_2.pdf
This among other notes also lists the difference between standard operation and use with external memory and how this afffects reads and operation. It also covers the error correction operation in detail.
Basically, as they used to say in the old Millenium - **** and shut up till you have.
Konnichiwa |
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| RHosch |
I have compared an EAC ripped track with a track streamed from a transport during low, moderate, and high levels of vibration after removing all frame and subcode data (i.e., comparing .wav files without any headers). It wasn't completely scientific in that I didn't document my procedure, try to isolate all variables, or have others review my result, but it surely satisfies KYW's criteria of knowing rather than believing. And from that test, I KNOW that it takes rather high levels of vibration to produce read errors beyond the error correction ability of the transports I used, and I KNOW that it is vastly more likely that when such errors occur they produce large time blocks of muted signal. Not once did I find single bit errors in the stream due to vibration. To suggest that vibration could cause a subtle (which usually means correlated) change in the subjective quality of a CD is really stretching things, and to me sounds like the musings of someone who hasn't done an experiment themselves.
From my experience, vibration issues result in muted output, as the threshold of error correction is surpassed simultaneously for a large number of frames, while small smudges and scratches can result in the single bit interpolations that KYW speaks of. Microphony induced quality change is something I categorizes as impossible when related to disc vibration. As for clock jitter, as always I remain skeptical but open minded. |
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| TNT |
Using faul language will not strengthen Your case !
I rest mine ....
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by geewhizbang
Someone has already explained over and over that the error correction on CDs is not as "basic" as your theories allow. |
Someone deliberated upon his personal pet delusions as to what he thinks should happen.
The FACTS are as suggested (from the Philips SAA7327 Datasheet):
| quote: | Philips SAA7327 Datasheet
The SAA7327 has a ±8 frame FIFO. The error corrector is
a t = 2, e = 4 type, with error corrections on both C1
(32 symbol) and C2 (28 symbol) frames. Four symbols are
used from each frame as parity symbols. This error
corrector can correct up to two errors on the C1 level and
up to four errors on the C2 level.
The error corrector also contains a flag processor. Flags
are assigned to symbols when the error corrector cannot
ascertain if the symbols are definitely good. C1 generates
output flags which are read after (de-interleaving) by C2,
to help in the generation of C2 output flags.
The C2 output flags are used by the interpolator for
concealment of uncorrectable errors.
|
| quote: | Philips SAA7327 Datasheet
A 1-sample linear interpolator becomes active if a single
sample is flagged as erroneous but cannot be corrected.
The erroneous sample is replaced by a level midway
between the preceding and following samples. Left and
right channels have independent interpolators. If more
than one consecutive non-correctable sample is found, the
last good sample is held. A 1-sample linear interpolation is
then performed before the next good sample (see Fig.11).
|
So, please get your facts right. I have corrected you at least ten times on the subjects actual facts and suggest you remedy your ignorance of them before posting again, clearly you refuse such good advise. It seems that your insistance on the results of you counterfactual thinking borders on clinical. I repeat, you may wih to seriously evaluate your position in general. I cannot suggest anything more usefull as the moderator suggets my good advise is namecalling, so please look up the older post on more far reaching recommendations.
| quote: | Originally posted by geewhizbang
Secondly, even small errors in reading the CD data are very audible. |
Nope, the whole point of error concealement is to make them as little audible as possible. The scheme of interpolating missing samples from adjecent samples is quite effective. If there are too many interpolations the signal is distorted to a certain degree, not neccesarily one that is notable as drastic audible distortion or skipping, merely as a degradation in quality.
| quote: | Originally posted by geewhizbang
You know a lot of stuff, but it is mostly wrong.
|
Funny. Please list one specific point where I am wrong in this discussion. ONE will do, but make sure you research it well, you may find I have the full backup for my point ready at hand.
| quote: | Originally posted by geewhizbang
I would suspect that most home audio players have buffers and at least 2x readers, because a player that reads a lot of disks well without problems is going to sell better than one known to be picky. |
You suspect a lot of stuff and if you worked for police Squad with Frank Drebbin you would still find it very hard to keep your job.
| quote: | Originally posted by geewhizbang
These days, a 1 meg buffer and a 2x motor are not going to add anything to the cost of the drive. |
But you will not find them anyway.
I make you an offer. List at least 3 Consumer CD Players (eg not High End gear from Meridian or the other few exceptions) that allow multiple reads and use a large buffer (eg more than 16 to 64 Frames) and I will actually admit that you may actually have a point.
Sayonara |
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| TNT |
If it had a buffer it would not be used for re-reads of the disk, only for jitter suppression like in the ML.
Those things are for Discmans !
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| runebivrin |
So there is error correction on CD:s, and the signal to the DAC does not come synchronuosly from the laser, but passes through a FIFO.
The question then is: Are the error rates on good CD:s high enough that reasonable vibration could cause the error correction to fail? I don't know.
And if the error correction is sufficient, does jitter from the laser affect sound?
Rune |
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| motherone |
On this whole subject of CD Audio versus CD Data formats.. My jaw hit the floor on the past couple of pages. The sheer lack of knowledge on how even basic ECC functions by KYW blows my mind.
So far, the only person who's stated things correctly was the one (ALW? sorry, i'm lazy and don't want to reread those pages.. my stomach can't handle it) who referred to them by their proper formats (Red Book, Yellow Book, etc).
How CD's are made:
http://www.ee.washington.edu/consel...daudio/95x6.htm
CD Error Correction along with the Alogrithm:
http://www.ee.washington.edu/consel...audio2/95x7.htm
Various CD Standards:
http://www.ee.washington.edu/consel.../cdrom/95x8.htm
If these links aren't enough, some googling for the IEC 908 standard can give you more information that validates these links.
The second link covers how Error Correction works and how Error Concealment works. Error Correction != Error Concealment. They are two separate functions. From this page:
"CD players use parity and interleaving techniques to minimize the effects of an error on the disk. In theory, the combination of parity and interleaving in a CD player can detect and correct a burst error of up to 4000 bad bits -- or a physical defect 2.47 mm long. Interpolation can conceal errors up to 13,700 or physical defects up to 8.5 mm long."
Also:
"SO! The final frame (which started at 6*16*2 = 192 data bits) now contains:
1 sync word 24 bits
1 subcode signal 14 bits
6*2*2*14 data bits 336 bits
8*14 parity bits 112 bits
34*3 merge bits 102 bits
GRAND TOTAL 588 bits"
ECC is a function of hardware. This happens in real time, most at the controller level. In order to correct these errors, I would assume that ALL cd chipsets employ at least a small buffer to verify the parity information and then correct it. This would not be audible as it most likely happens as a function of the chipset before the data is output to the next stop in the signal chain.
If someone here has actually worked with CD Chipsets, it'd be great if they'd post something here. If someone here has information contrary to what I've posted, please feel free to correct me. Heck, if someone knows where I can read datasheets on CD Chipsets, please post a link! I did some cursory googles for it and came up empty (too much CD-RW stuff screwing up the results). |
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| motherone |
| Hmm.. Looks like there were a number of replies while i was constructing my post.. Sorry if my information is redundant or points that I made have already been answered. |
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| serengetiplains |
| quote: | Originally posted by runebivrin
And if the error correction is sufficient, does jitter from the laser affect sound? |
Hi Rune, Meitner states in the article referenced above on cryogenics that laser movements modulate the power supply, causing jitter. Extrapolating from what he said, any vibrations causing movement in the spinning disc theoretically could cause jitter.
I should add that Meitner's statements in the article regarding jitter are almost certainly based on actual measurements of jitter. I recall reading an interview of him where he discussed developing jitter measuring devices in-house to sensitively probe the many sources of jitter and track them to their source. FWIW, Meitner is probably among the best experts on jitter, and probably owns highest calibre jitter measurement devices. |
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| john curl |
Keep on Truckin! Thorsten.
This is like going back 20 years and hearing it all over again. As I remember, CD was "Perfect sound forever!". Dr. Doi's book 'Digital Audio Technology' 1983 should have set us straight. It is virtually all there! Why bother listening, or 'improving' perfect sound already?
Unfortunately, for me, it didn't sound 'perfect' far inferior to a record, analog tape, or even an FM tuner broadcast.
Then, among other things, we discovered 'jitter'. But, how to measure it, and why should such a small change in the time domain of micro, nano, or even picroseconds make any difference? Impossible? Well, I don't think so. In recent years, primarily do to the efforts of hi end designers like Meitner and Bob Stuart, we have seen CD reproduction 'improve' beyond 'Perfect sound forever'.
I guess that these improvements were there all along. :) |
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| serengetiplains |
| quote: | Pappas: Do the same issues about jitter apply to DSD as they would for PCM?
Meitner: Of course.
Pappas: Okay, there are no disadvantages or advantages in terms of jitter performance?
Meitner: No. Jitter is still an important issue. The way I see it, the problem with jitter is that very few people — almost none out there — have an analyzer for it. I think we were about the only ones who, for the past five or six years — from the moment when Stereophile adopted our jitter analyzer — actually measure this stuff. And we measure it in such a way that you don’t only know how much jitter you’ve got, but you also know what your frequency components are in that jitter.
Pappas: That’s the LIM device?
Meitner: Yes.
Pappas: Can you give us a little background on it? Because I think it’s important.
Meitner: Basically, it is a face demodulator that you can look at any sample frequency within a digital system from 2FS to 768FS. In a 20 kHz bandwidth, it gives you your jitter components and your frequency components in the jitter, which is more important than just knowing what the actual value of the jitter is. Because if it’s just noise, it’s not so bad, but if you have components in there that are alien to audio, well, that’s a different story. What are these "components"? Well, typically, it’s artifacts coming from a CD drive, a deck; you have components in there that are jitter components that come from the focus adjustment, tracking adjustment, motor speed adjustment, and all sorts of other staff that have nothing to do with audio. So this device shows you what those components are. |
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| fdegrove |
Hi,
| quote: | | So there is error correction on CD:s, and the signal to the DAC does not come synchronuosly from the laser, but passes through a FIFO. |
Basically, yes.
Now what is a FIFO? Ooopsie...That's a buffer.
| quote: | | The question then is: Are the error rates on good CD:s high enough that reasonable vibration could cause the error correction to fail? I don't know. |
Vibration of the spinning disc causes laser scatter which in turn leads to other problems.
Let's not forget this is optical media storage.
The data on the CD (after all it's just a file) includes already a substantial amount of extra information to be used by the error correction mechanism provided it can be read by the laser.
The laser uses the lands on the disc to position itself so if high vibration occurs the laser will see a scattered reflection and will have difficulty reading where it should position itself.
The pits contain the actual data.
To answer your question: it takes quite a large amount of vibration (does anyone know how much?) alone to make the entire ECC system trigger the mute transistors.
But it's not that simple: ideally a laser transport should operate as independently from the rest of the system as possible. In reality it hardly does so it causes interference (jitter) and all kinds of spuriae.
| quote: | | Unfortunately, for me, it didn't sound 'perfect' far inferior to a record, analog tape, or even an FM tuner broadcast. |
Same here but the guys in my backyard are working overtime to "Make Things Better"...
I wish they told us what those things are...maybe just their bankaccounts...Who knows?
Cheers,;) |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by runebivrin
So there is error correction on CD:s,
|
As I have claimed. And the error correction covers up to samples (bits) out of a whole frame. Not much.
| quote: | Originally posted by runebivrin
and the signal to the DAC does not come synchronuosly from the laser, but passes through a FIFO. |
The Signal at the DAC passes through any number of digital stages. What is read of the CD by the laser is an analog pattern which is then passed through a trigger circuirt to derive "pit/land" or one/zero symbols. These are then held in a small FIFO buffer, usually no more than 64 Bytes, often less, 16 Bytes in the case of my example consumer CD Player Chipset.
BTW, I never denied that a buffer is present, I KNOW one is present. However it is a VERY small buffer and does not allow multiple attempts on reading the same data (which EAC and other Ripper Software CAN do).
| quote: | Originally posted by runebivrin
The question then is: Are the error rates on good CD:s high enough that reasonable vibration could cause the error correction to fail? |
They are high enough to shift from error correction to concealement readily on absolutely immaculate CD's, freshly pressed. Adding micro surface scratces and vibration to the mix would make a switch to concealement on a pretty regular basis more or less mandatory.
In other words, a microscratch that might not cause an error if the CD is not exposed to vibration might cause a read error if vibration is present. Equally, a pressing imperfection which might just pass on it's own may cause an unrecoverable sample f combined with microscratches and/or vibration.
I would be interrested knowing which transport RHoch employed in his test. Associates of mine found problems when comparing ripped and burned CD's to their originals played on consumer grade CD Players and originally argued extensively that the Copies made where not bitidentical to the original, when in reality the "originals" where actually compromised through the poor error correction of standard CD replay and ripped and copied very accuratly on PC Hardware.
But that as they say is another story.
| quote: | Originally posted by runebivrin
And if the error correction is sufficient, does jitter from the laser affect sound? |
IF the error correction delivers accurate data from the FIFO prior to the interpolator, the Jitter source is only the clock and the PSU line noise induced jitter (IIRC a single cmos gate with 50mV PSU noise translated to around 5ps additional jitter) from all the circuitry between FIFO and the DAC chip.
If the PSU feedthrough can be minimised and the clock lines are reclocked prior to the actual DAC the Jitter on the DAC should depend only on the Clock Jitter and any induced through the PSU in the reclocker and internally to the DAC.
These are many IFs.
My personal preference would be ripping the CD to a (PC) Hard-Drive and replay from there or asyncronous replay using multiple re-read attempts and the using a large buffer, that then combined with a system that provides a clean conversion master clock to the DAC (preferrably from a seperate clock generator also clocking the interface in the PC or the output of the Transport, basically studio style.
However we look at it however, using conventional CD Player systems suffer from many hidden problems that are usually not divulged to the great unwashed. These problems result at least potentially in audible differences where it would seem they should not exist. To pelicanise these problems will NOT DO and to attempt to argue them away if ignorant of facts causes egg all over faces.
Sayonara |
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| TNT |
"Yes, this "Buffer" stores each bit after read. Nevertheless the data extraction is still sequential and essentially syncronous."
I would argue that when we are talking ps jitter, the data can not be seen as even "essentially" syncronous. In this realm, its, at is best, pleisynchronous.
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| janneman |
| quote: | Originally posted by john curl
[snip]In recent years, primarily do to the efforts of hi end designers like Meitner and Bob Stuart, we have seen CD reproduction 'improve'[snip] |
John,
Indeed. Due to better filtering, higher interpolation and DAC bit rates, better understood and implemented analog post-processing and a few other bits and pieces. It has NOTHING to do with the discussion on error correction and the subtle effects that purpotedly are caused by the lack of pointy feet. It is bad enough that Thorsten tries to pull the discussion off-track to save whatever he can.
But can I ask you, in the interest of actually lesarning something, NOT to confuse us and try to introduce irrelevant issues thereby muddling the discussion? Thanks.
Jan Didden |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by TNT
"Yes, this "Buffer" stores each bit after read. Nevertheless the data extraction is still sequential and essentially syncronous."
I would argue that when we are talking ps jitter, the data can not be seen as even "essentially" syncronous. In this realm, its, at is best, pleisynchronous. |
Granted. Where jitter is concerned the Buffer forms a barrier that simple Eyey Pattern Jitter cannot pass.
My point about syncronous, sequential extaraction related to the general operation, compared to using DAE modes or other such "read ahead & reread when error" strategies that some people seem to think are inherent to CD, when they are not.
At any extent, PSU current related crosscontamination is difficult to stop. Once you have managed to deal with that on both Ground and Supply lines you will have to wipe a lot of swaet of your brow in standard consumer CD players.
Sayonara |
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| Steve Eddy |
| quote: | Originally posted by john curl
This is like going back 20 years and hearing it all over again. As I remember, CD was "Perfect sound forever!". |
Don't drag out that old canard again. "Perfect sound forever" was nothing more than a marketing blurb coined my the marketing deptarment. Not by engineers and researchers.
| quote: | | Then, among other things, we discovered 'jitter'. |
No, "we" didn't discover "jitter." As is too often the case in high end audio, what "we" did was rediscover something which had been known of decades before Compact Disc ever hit the market.
*sigh*
se |
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| janneman |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
[snip](I lump error corrction and error concealement into one mechanisms as this is how audio CD handels it).[snip]Sayonara |
Clever, but you are not getting away with this. You clearly stated that subtle component changes like vibrations can lead to subtle audible changes because it would cause misread bits and influence the error correction. This is not true as noted by several. As long as error correction can cope, there are NO audible differences due to this because THERE ARE NO MISREAD BITS. Once error correction cannot cope anymore, error concealment tries its best to limit the damage, but it will generally be gross errors and be VERY audible.
Casually remarking that you lump the two together is really an insult to all of us who read your posts.
Jan Didden |
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| serengetiplains |
| quote: | Originally posted by janneman
It has NOTHING to do with the discussion on error correction and the subtle effects that purpotedly are caused by the lack of pointy feet. |
Jan, if pointy feet reduce vibrations reaching the spinning cd, won't we also see reduced jitter?
Am I reading you right here?
Tom |
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| serengetiplains |
| quote: | Originally posted by Steve Eddy
No, "we" didn't discover "jitter." As is too often the case in high end audio, what "we" did was rediscover something which had been known of decades before Compact Disc ever hit the market.
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Allow me to suggest John was saying we discovered that jitter creates audible effects. Sigh back. |
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| diy_audio_fo |
| quote: | Originally posted by john curl
Then, among other things, we discovered 'jitter'
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Not exactly.
Back in the early '80 our research group bought several digital scope Tek and LeCroy. Their specs were 8bit - 100Ms/s (Megasample per second)
Their cost (each) was about 35,000,000 Italian lira (about 20,000 USD)
With the LeCroy we got a lot of literature and there was an amazingly well written white paper about time base jitter and its relation with vertical resolution.
If the CD players were built by LeCroy nobody had to worry for the jitter since the '80 :-) |
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| janneman |
| quote: | Originally posted by john curl
Folks, I can't address every comment and criticism concerning me, but let me state my position:
First, I have been in this business a long time, about 40 years in the serious study of audio. My colleagues are and were: Paul Klipsch, Richard Heyser, Matti Otala, Walt Jung, Michael Gerzon, John Meyer, Dick Marsh, Dr Hawksford, etc, etc. This means that have I talked extensively with, shared dinner with, drank with, visited, and was visited by, worked on research with, wrote papers, and was continually on the phone with, etc, etc. [snip]
Jan, I'm sorry that I push your buttons when I mention my colleagues, but they know better than you appear to know about audio problems.
Hang with Steve Eddy if you must. |
Yes John, it DOES completely turn me off. It is a deliberate attempt to introduce issues that have nothing to do with an intellectual discussion. I am afraid that I am not accustomed to forming my opinion on hearsay from someone who was on the phone with someone who knows somebody he had dinner with. Sorry.
As for the SE bit, I am not sure how to react. Is this another attempt to discredit one or the other or both? Fot the life of me, I cannot detect anything constructive in that last part. But maybe I just missed it?
Jan Didden |
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| RHosch |
| quote: | Originally posted by Kuei Yang Wang
They are high enough to shift from error correction to concealement readily on absolutely immaculate CD's, freshly pressed. Adding micro surface scratces and vibration to the mix would make a switch to concealement on a pretty regular basis more or less mandatory. |
What experiments have you done and/or what sources back up this claim? In my personal experience, new CD's of reasonable quality typically produce bit-identical streams on multiple reads and through multiple transports. Vibration does not change that behavior until a substantial level is reached, after which large errors (muting and long sample hold times) are observed, not single bit interpolation errors.
Do your experiments show otherwise? Are there any easily pointed to sources that confirm your assertion that good quality new CD's routinely produce read errors beyond the ability of the CIRC error correction scheme to rectify? My observations are consistent with the theoretical scratch limits on correction and concealment. I'd be interested to read the data showing that redbook CD is fundamentally incapable of producing bit-perfect playback, even with absolutely immaculate freshly pressed CD's, as you state.
| quote: | | I would be interrested knowing which transport RHoch employed in his test. |
Over the past few years I have performed versions of this experiement using a first gen Denon DVD player, a low-fi consumer Sony DVD player, the Marantz SACD player, a Marantz 300-disc DVD changer, and a ten year old 5-disc CD carousel player (either Yahama or Panasonic, I don't recall now). If you really must know I'll provide model numbers. I once even performed such an experiment using a 1984 Technics CD player, and was surprised at how often successive plays of a track were bit-identical using quality discs. |
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