Probably a touchy subject, but WHY?? (1 Viewer)

[Holadem]

quote: for instance, if all you've heard is a grainy amplifier[/quote]
What the heck is a "grainy" amplifier?
[EDIT]Oops, I just realised the question has been asked, never mind...
[EDIT 2]... And now that I read the whole thing, I see no one answered it, so back to square 1.
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Holadem
[Edited last by Holadem on November 13, 2001 at 09:33 PM]
[Edited last by Holadem on November 13, 2001 at 09:57 PM]

 

[Holadem]

Someone back there even said PCs can only play audio CDs at 1x because the data stream is so special. Another CROCK. If that were true, it would take 74 minutes to make a copy of a CD.

...Assuming the copy ends up being exactly the same as the original, which from what I read, is not always true of audio CDs. I have heard crappy CDRs.
About audio cables:
While I might still need some convincing that jitter is audible, I do not think it is a myth at all after this discussion: Scientific arguments were made, scientific documents were shown. While I did not read the links, I will trust these gentlemen who did. This is not comparable at all to the audio cable discussions: The expensive cable advocates had ZERO DATA to back up their claims, and seem unwilling to do anything that might challenge their perceptions, even with the very real possibility that the results turn out in their favors.
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Holadem

 

[John Morris]

You know, sometimes I wonder why I bother. Does anybody actually read the links that are posted? All the information you need to understand was posted and is readily available.As a self-described "mid-audiophile", you are willing to admit that there are things that you do not fully understand right? Not everything that you don't understand is "mythical". You are free of course to believe what you wish, but when it flies in the face of scientific documents that have been posted, well...that's a little silly..

I read, err, skimmed the articles that were linked and not in any place did I find an example of where I could actually listen to a modern commercial CD player which exhibited audible jitter and another one which did not when playing back the same CD. All the scientific evaluation of ones and zeros and timing errors in the nanoseconds, simply are inaudible and thereby audibly mythical, IMO. It seems that the jitter arguement is like saying that the amp which specs out at .004 distortion is twice as bad as the one which specs out at .002. Scientifically that statement is true... but so what. Neither distortion spec is anywhere near audible. I don't usually take this side in the boutique cable arguement but it is starting to make more sense to me everyday. If one unit sounds better to me, then that's all that really matters...
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Take Care,
merc
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Link Removed
God Bless America!!!

 

[Saurav]

quote: Someone back there even said PCs can only play audio CDs at 1x because the data stream is so special. Another CROCK. If that were true, it would take 74 minutes to make a copy of a CD.[/quote]
That someone was me, and I remember reading that most CD-ROM drives play at 1x when you put in an audio CD. That's not quite the same thing as "can only play ... because the data stream is so special", which would be "crock" if anyone actually said that.
Also, if the CD-ROM drive were reading at faster than 1x, then the software would have to store the data in RAM, because it surely takes 74 minutes to play an audio CD on a computer, it wouldn't be much fun to hear the music going by at 32x. So, now you need 650 MB of buffer space on your hard drive/RAM. Of course, the software could read the CD in chunks, one song at a time, or something - that would work too, but it seems like it would be much easier to just have the drive run at 1x when playing audio.
Anyway... like I said, I could be wrong, but I have read somewhere that that is how it's done, which is different from saying that is how it has to be done. As long as we're clear on that
quote: CD audio is two 16 bit samples at a piddling 44,100 times a second. Period. No ifs, ands, or buts. Reading that data rate and delivering it reliably out of a digital cable is TRIVIAL.[/quote]
Agreed. No one said anything about the data getting corrupted. There is a difference between bit errors and timing errors.
quote: This discussion sounds EXACTLY like those about cables and how those $1000 cables make a difference.[/quote]
Very true. Someone always barges in and starts telling the others how stupid they are
And anyway, if digital audio were only about bits, then CDR's could never sound different from their originals, could they? Plenty of people have experienced CDR copies sounding different from the original, Holadem included. Of course, that could be the placebo effect too, i.e., maybe he imagined it all.
quote: What the heck is a "grainy" amplifier?[/quote]
Stereophile once ran an article with an audio glossary. Search their archives if you want to, you might find the article and see what the term 'grain' means when referring to a component's sonic characteristics.
quote: If one unit sounds better to me, then that's all that really matters...[/quote]
I totally agree
Edit: OK, here's what I'd said:

However, when you play an audio CD, the bits are read off the CD at a constant rate, and the CD-ROM drive is also forced to spin at 1x speed.

I guess that could have been misunderstood - I meant "forced" as in forced by the application software, not forced because of anything special in the data. I apologize for the confusion.
[Edited last by Saurav on November 14, 2001 at 12:37 AM]

 

[Saurav]

Paul,
If you want scientific articles on jitter, please try this link: http://www.aes.org/publications/preprints/search.html
Enter "jitter" in the search field, and you should get a fairly long list of documents discussing jitter in the Audio Engineering Society journal. Of course, you'd need to pay to read any of these, and honestly, I don't expect you to do so. All I'm trying to say is, this isn't some BS that people are making up, this is actually stuff that is discussed in a relatively scientific community. I've copied and posted titles and abstracts from the AES search results in the past, and I'm not going to do it again. The combination of this site's search feature and peoples' tendency to ask questions without first trying to look for answers is pretty frustrating.
And I think I'm done with this discussion now.

 

[RicP]

What's honestly surprising to me is the "fact" that everyone thinks he/she has the same level of gear and the same hearing sensitivity. It's completely inane to state "If I can't hear it, it's mythical." Unless of course you deem yourself to be the be-all and end-all of audio listening sensitivity.
Somehow I doubt that the AES would spend time and money researching a "myth". You may choose to believe anything you want, but don't pretend that your opinion is the only one that matters. I have papers and a multitude of documentation from the AES to back up the claim that jitter is indeed real and does affect the sound that is delivered form different transports.
But of course YOU can't tell a difference, so that means emphatically that none exists.

Someone back there even said PCs can only play audio CDs at 1x because the data stream is so special. Another CROCK. If that were true, it would take 74 minutes to make a copy of a CD.

Thank you for proving here that you have no idea what the discussion is about. You clearly, like so many others, fail to be able to distinguish between ripping digital "data", and playing a PCM stream in real-time. When you play an audio CD on a computer, it cannot spin faster than 1x, that is a fact. When you copy data from an audio CD, which is what happens when you copy a CD, timing is no longer an issue because there is no Digital to Analog decoding being done, just a copy of bits to bits. That is the difference, and you've clearly shown that you do not understand such a difference, so isn't it possible that you do not yet understand what jitter is and why it is indeed a concern? Food for thought.
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Ric Perrott - My DVD's

 

[Jack Gilvey]

Everyone should just grab a turntable and a beer. Wither, oh dither?

 

[Rick_Brown]

Here' an interesting article on jitter, unfortunately I've lost the link or author's name. I've edited out some lines to make it shorter:
I'll try to explain this. A digital audio signal has two components to it - one of them is the actual data itself, the 1s and 0s. These do have an "all or nothing" character to them - if an error in the data occurs, a 1 will be read as a 0, or vice versa
All of these features are characteristics of the data itself. However, there is another equally critical component to a digital audio signal, and that is timing. Perhaps you've seen the term "16/44.1" somewhere. This is how audio is encoded in regular CDs. What this means is, the original analog audio signal (which is essentially voltage on a line) is sampled at a frequency of 44.1 Khz (44,100 samples a second), and then each sample is encoded into a 16 bit value (this gives 2^16 possible values), a process known as quantization. This should be pretty clear so far - first sample the continuously varying analog signal at certain regular instances of time; and then for each sample, pick the closest value out of the 2^16 values discrete available to you to represent it. Quantization introduces its own noise, because you are approximating a continuous range of values into a set of 2^16 discrete values, but that is an inherent compromise of any digital system.
The job of the playback system, now, is to read 16 bits at a time, 44,100 times a second, and generate the corresponding voltage value on the output line. This is where timing becomes important. 44,100 samples a second means 1 sample every 1/44,100 seconds, or (approximately) every 23 microseconds. This means that once the electronics has generated one voltage value, it expects to receive 16 bits in 23 microseconds, at which point it will generate the next value. If the 16 bits arrive a little bit early or late, the next value will be generated at the wrong instance in time. Since no bit errors have occured, the value generated will be the correct one, but it will be generated at the wrong moment.
What will be the physical effect of this? The playback system isn't generating the same signal that was recorded, that is for certain. The output signal has the same values as the input signal, but they occur at the wrong instances of time. What this will sound like is still the subject of debate...

 

[Lewis Besze]

quote: I have papers and a multitude of documentation from the AES to back up the claim that jitter is indeed real and does affect the sound that is delivered form different transports.

Goodie!
Can you post this info or get link to it?
I don't deny the fact that jitter exist,but it's audiability,is highly questionable,in the scientific sense.
What I'm looking for is "scientific" validation,not "audiophile" anecdotes.
Does your AES papers stand up for that?
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"You Hungarians always disagree"
[Edited last by Lewis Besze on November 14, 2001 at 09:34 PM]

 

[RicP]

Can you post this info or get link to it?

Try reading an entire thread next time. There have been numerous links posted and mentioned. Do your own leg work.
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Ric Perrott - My DVD's

 

[Saurav]

I don't think Ric can post the contents of an entire AES paper here, because that would be a gross copyright violation, and could get this site into trouble. These documents aren't available freely to the public. However, the website is www.aes.org and I've posted a link to the search page - if you're really interested, you could pay the necessary fees and download the documents that you find interesting. I would guess that Ric didn't get them all for free either.

 

[Zbigniew]

Saurav,
Microsoft Media Player 7.+ used digital extraction to play audio CD - data is read from CD very fast (*more on it later), and converted into analog signal on your sound card with adition of software DAC. That allows them to use all visualisation/equalization tools in digital domain.
SOme better sound cards (M-Audio Audiophile 2496, whole M-Audio Delta class) does not have analog connecot for a CD; the card contains very good DAC to do it much better than cheapie DAC included in a 68$ CD in your PC.
About reading CD as data - you do not need to read whole CD at once. You do not need to read it even a track at a time - you read few sectors/tacks ahead, stop and wait; when software drains the buffer, it requests OS to read again some more data. Technology for read-ahead, buffering, disk optimisation is fairly advanced - it was developed for HD, and applied to CD.
In order to do DAC conversion via CPU/audio card, something in system has to act as a referece clock - usually it would be your system clock. It should be stable enough, because even if it drifts, it has a monotonous (unidrectional, and steady slope) drift.
_zjt

 

[Saurav]

Thanks for the update.

 

[RicP]

What Zbigniew says is indeed true. These were developed for two reasons:
1) To combat read errors.
2) To eliminate Jitter.
Why would companies spend time and money to develop a reclocking, buffered CD player for a computer if Jitter was a "myth"? Answer: They wouldn't.
The fact still remains though that if you play a CD in a computer using a "regular" CD player program, and not one of the advanced buffering ones, the CD will spin at 1x, no faster. In that case jitter is an issue because the data needs to be sent digitally and decoded by the sound card.
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Ric Perrott - My DVD's

 

[Zbigniew]

RicP,
open your computer.
Do you see a two wire cable rom CD player to your sound card ? That is analog signal. You ae using DAC in a CD, and only processing it as analog input on your sound card.
if you disconnect this cable, your sound card will no longer deliver music from CD.
In this mode, cd-player acts as music CD player. Analog signal (generated with a DAC inside CD) is pased to sound card. New Soundblaster cards can accomodate 2 players - for folks with CD/RW and DVD players. When using this mode, your CD is using 1x speed, and clocking is internal to CD.
Back to main topic: jitter impacts voice transfers seriously-that is why ATM, not FR is used for voice transmissions. That is also why QoS is so critical to transer voice over data network. THat is one of reasons why quality of streaming media is so lousy under congestion. It is not because of packet loss - we can drop up to 5-6% of voice transfer without noticeable degradation for phone conversations(no doubgt golden ears will find it much faster), but variation in arrival of packets of 5 % degrates call below toll quality.
To experience a jitter, set up on a semi-loaded network connection using Netmeeting, connect headphones and mike - then stat heavy browsing or file transfers to saturate network.
If you have a record player with off-balance plate, it will simulate jitter nicely - touching a record platter in a DJ-style will only increase this effect...
_zjt

 

[RicP]

Do you see a two wire cable rom CD player to your sound card ? That is analog signal. You ae using DAC in a CD, and only processing it as analog input on your sound card.

That depends on the type of CD Drive that you're using. Some pass the signal analog to the sound card, some higher end ones pass it digitally. But for the most part you are correct, most consumer level CD-ROMS use less than high-end DACS and pass the signal to the sound card via analog lines for amplification.

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Ric Perrott - My DVD's

 

[Lewis Besze]

Zbigniew,
the type of jitter we're talking about here is not the "extreme" ones you site,but rather,extemelly small timing difference,that measured in nano and pico seconds.
I've yet to come accross any reliable data that proves ,that the human brain can ,pick up such miniscule timing differences.
Ric P,

quote: Try reading an entire thread next time.

I have!
But a small section of the forum rules,namely "How to treat others" should be on your must read list!

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"You Hungarians always disagree"
[Edited last by Lewis Besze on November 16, 2001 at 09:28 AM]

 

[Zbigniew]

Lewis,
are you sure you are quoting me ?
The line "Try reading an entire thread..." is not from my post. Please check your attribution.
YOu are correct that we are not talking about jitter causing errors on single bit level, existing on optical cables. The level of jitter you are talking about is noticeable on packet level errors - like IP based traffic.
Take care,
_zjt

 

[Lewis Besze]

Zbigniew
No I wasn't quoteing you,sorry for the confusion,I'll edit my post.
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"You Hungarians always disagree"

 

[RicP]

I have! But a small section of the forum rules,namely "How to treat others" should be on your must read list!

PLease. If you're that sensitive, then perhaps you should look into a book entitled "Developing a thicker skin".
You asked for something that was pointed out repeatedly over the course of the thread. If you indeed read the entire thing as you claim to have, then that says something about your reading comprehension or your antagonistic nature. Either way, I will not be dragged into an argument, the literature is out there if you care to read it.
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Ric Perrott - My DVD's