[Kees]

Quote:

Originally Posted by wlai /img/forum/go_quote.gif No, that's a terrible terrible analogy. One, he assumes that bits are pants. You may get by comparing pants to analog vinyl, but they are not the same as digtal bits. Bits are either on and off. and there are no wrinkles to them. On top of that, the error correction code does two things: 1) Tells you when there is an error, and 2) In *some* instances when error occurs, it can recover from the error. The instances where it can detect error is much greater than instances where it can fixes it. And when the ECC tells you the error is not correctable, then you've lost all hopes of recovering the original audio signal from that CD. Your CD player either gives up, or its DAC translates the bad bits into bad analog waveform. You may hear the problem, or you may not. But the same problem exists when copying that disc onto CDROM. When copying the disc with the bad section, there are only three things that the PC can do: * Tell you there is an error and gives up, stop copying * Realizes the error, but faithfully copies everything, error and all, exactly onto your new CDROM * Realizes the error, and makes up the answer, as in: "Is it a 1 or 0 at this position? Hmm, since the original can't tell me, I'll just always assume it's a 0 and continue on" The whole premise of this thread is that #3 above somehow magically corrects the error. There is no magic. If it's broken, and that's all you've got access to, then half the time guessing the bits will be right, and half the time it'll be wrong. Average over all the errors on a disc, you are no better off. No fairy godmother will come out of your PC to tell you what the correct bit is at that location. The only way to "fixes" that error is to get a new original disc and copy from that disc, but then what's the point of copying the bad disc in the first place? The only way to get out of the jam, is to compare it to other people's original disc. If most discs have no errors, then you can say most people have this bit to be a 1, while I have a 0 (and the ECC alarms went off), so I'll assume it's a 1 because most people has it as a 1. And if you use CDEx to extract a CD into lossless format, that's exactly what it does.

I still think it is a good analogy:
The correction of errors on a CD is as you describe I guess, but the difference is that in the copied CD the player does not have to think "hmmm, what is this, I don't know, let's make it a zero..." , it just reads the zero that is already written there, without any interruption.
On top of that the reading of the original will lead to more "hmmm, what is this, I don't know, let's make it a zero..." - situations than the reading (more evenly spaced writing) of the copy.
The data is exactly the same, but there will be less reading-interrupts while reading the copy. You sort of do the error handling off-line.
And I think (my personal opinion) that playback with less interruption for error handling may result in better perceived sound quality.

 

[wlai]

Quote:

Originally Posted by Kees /img/forum/go_quote.gif I still think it is a good analogy: The correction of errors on a CD is as you describe I guess, but the difference is that in the copied CD the player does not have to think "hmmm, what is this, I don't know, let's make it a zero..." , it just reads the zero that is already written there, without any interruption. On top of that the reading of the original will lead to more "hmmm, what is this, I don't know, let's make it a zero..." - situations than the reading (more evenly spaced writing) of the copy. The data is exactly the same, but there will be less reading-interrupts while reading the copy. You sort of do the error handling off-line. And I think (my personal opinion) that playback with less interruption for error handling may result in better perceived sound quality.

Well, the ECC is happening at all times. It doesn't assume that there is an error before computing the ECC. It is always computing the ECC at every passage on the disc, and the data is instantenously available. There is no "thinking" delay.

Further, when you play back the CD-RW that you copied, it's computing the ECC as well, because it can't assume any disc is ever perfect.

In other words, nothing is gained.

 

[Kees]

Quote:

Originally Posted by wlai /img/forum/go_quote.gif Well, the ECC is happening at all times. It doesn't assume that there is an error before computing the ECC. It is always computing the ECC at every passage on the disc, and the data is instantenously available. There is no "thinking" delay. Further, when you play back the CD-RW that you copied, it's computing the ECC as well, because it can't assume any disc is ever perfect. In other words, nothing is gained.

I may be wrong, but computing the ECC is not the error handling, is it?
How could the reading of a disc otherwise ever fail?
On top of that, that would mean every DAC would alltimes (from the same disc) output exactly the same bitstream (and at the same speed) as any other DAC?
Because that would mean speed stability would play no role whatsoever, as long as the ECC can be computed the output will be delivered bit-perfect?

I may be seriously wrong, I am by no means an expert in this, but that seems not very plausible to me. Because there are in fact differences in the output of different DACs.

I actually suppose (I don't know!) that the "thinking" / interpreting of the read data has to be done before the computing of the ECC. I find it difficult to believe that the ECC computing algorithm accepts a "dunno" as input.

Anyway, that is how I picture how it works, and that is why I think it might make a difference. But I am no expert in how these processes are actually implemented, so I don't claim to be right. It just seems possible to me.

But feel free to correct my reasoning if I went wrong somewhere.

 

[wlai]

Computing ECC is error handling, and is part of the CD "transport". The transport's job is to get all the bits it can off the CD. The transport here (more accurately, the reading of the reflection of the laser and error detection and correction) always start with the assumption that there may be errors in the reading of the disc. That's why you are always computing ECC, nonstop. The simplest form of ECC is just parity bit calculation. It can detect errors that are 1, 3, 5, ... odd number of bits off. It only detects, however, and doesn't corrects. And then there are ECC algorithm like Reed-Soloman coding that detects and then can fix some % of errors. They are more time consuming to calculate, but all that is done on hardware and is *always* done before the next stage, again, because you can never assume there are no errors.

The Digital Analog Converter (DAC) only comes in the picture after you read the bits off the disc and ECC'ed it. It's not what we are talking about in this thread. Different DACs indeed have differences, but its job is not to correct disc errors.

Bit-perfect is something else entirely, usually used in the PC software situation, not in CD player that we are talking about.

 

[Some geek]

I let this thread die a few days ago, but this reply was so silly, I felt compelled to reply if only because some newbie might read it and believe it....

Quote:

Originally Posted by Audiofiler /img/forum/go_quote.gif Kind of sad is this thread....as elephas has already eluded to a very good point..There is some truth to the general process that the OP speaks to...

No there is not. Using a lossy compression technique and resampling at random will NOT make your music sound better. PERIOD. it is simply a falsehood.

Quote:

Originally Posted by Audiofiler /img/forum/go_quote.gif ..and even recently, a well respected member markl on the boards here has perhaps a clearer conception of the basic proponents that help to drive this theory within his thread. Also, there is also some really great information on the steve hoffman site as well.

Either you misread what they where saying or there respect is misplaced. (I suspect the former) There is no "theory" here. It is gibberish.

Quote:

Originally Posted by Audiofiler /img/forum/go_quote.gif Although unclear may have been the attempts of the OP to communicate this process, there still bears just as much relevance to this forum

No it does not. It is the responsibility of this community to separate fact from fiction from option. This is fiction. It doesn't even rise to opinion.

If I got on here and said, "The way to make you music sound better is to build a $20 AM radio kit from Radio Shack and use it to send your music to an AM radio" that would deserve no respect... I guess you could say it is an opinion but I might be of the opinion that I'm Teddy Roosevelt too. That wouldn't make it so.

Taking your CD data and throwing a bunch away won't make it sound better.

Quote:

Originally Posted by Audiofiler /img/forum/go_quote.gif and to those interested to warrant proper replies or clarification; however, the dialogue and posts in this thread, unfortunately, are as useless as its initial confusion and seem drafted rather poorly and lacking couth

We'll you are correct some of the replies to this thread are useless. But I'm doing my best to debunk them.

Davesrose said it best... This whole thread is absurd. The only thing useful about this thread is that it shows when it comes to the audio world some people will believe anything.

In case you missed the point, I'll close with it again:

Taking your CD data and throwing a bunch away won't make it sound better. Period.

 

[m_memmory]

Except that when the OP got his talk straight he wasn't really on about using any compression. he talks about ripping the tracks to wav - upsampling to 192Khz from the 44.1 CD default and then burn that back to a CD-R.

Now whether this would give any audio benefits - well I'm not going to attempt it myself as I like my music as it is - but it doesn't involve compressing anything.

 

[LFC_SL]

If CDs are only 44.1 though, would there be any point in upsampling to 192, then back down again? By that I mean would it make a difference? I'm leaning towards "no"