Overdose
Well-known member
davedotco said:
Until the disc is damaged and then it is. Error correction is a selectable option when ripping.
Until the disc is damaged and then it is. Error correction is a selectable option when ripping.
To put it simply well ill try, when you RIP a CD the software makes sure it writes to the HD exactly what it read from your Fleetwood Mac CD if makes a mistake it will try again untill it gets it right.
If your playing the same CD on your music CD player you may hear a skip or somthing which you dont want to record.
So yes in theory its Snake oil!! You wont actually get better music quality as we know it.
If your playing the same CD on your music CD player you may hear a skip or somthing which you dont want to record.
So yes in theory its Snake oil!! You wont actually get better music quality as we know it.
Al ears
Well-known member
davedotco said:
Whatever, back to the OP.
When I get my nice new CD and put it in my cheap Taiwanese DVD-RW mechanism and use my favourite software to rip it to a flac file it does so first time (reporting no errors as usual) and I'm a happy bunny.
So when i then play this flac file back through the same DAC that I have my CD transport connected to I am not at all surprised to find it sounds no better. I just have the data in a different format.
busb
Well-known member
Thompsonuxb said:
You ask a question & folk here answer either directly or with links. You seem to go into denial however. You can lead a horse to water but sure as hell, can't make it drink. If playing a CD always resulted in exactly the same stream of ones & zeros, why would the process need pretty sophisticated error correction? It's not a case of ripping adding to the original data but recovering more of the original data. Well, so goes the theory - some ripping programs are supposedly better than others: EAC has a reputation for extracting that stream of ones & zeros better than others by repeatedly reading the same sequence until the checksum matches or is as close to the original as it can get. It may be a slower rip but more accurate.
Some say that some transports seem to be better than others (feeding the same DAC). I don't know but most ripping is done by PC or laptop transports anyway. However, these transports are able to read data at 25 - 50x normal playback speed.
Overdose said:
I rip without, normal discs used and abused in the normal manner, and get around a couple of percent failure.
Given the redundances in the data on the disc I find my ripping software digs out sufficient data to achieve an accurate checksum, I can recall having to use error correction on one, maybe two occasions.
Alears said:
This is how it should be, and with new discs, usually is.
On older, less than perfect discs there is an advantage in ripping the disc as you may get more of the data, that is pretty straightforward.
Whether or not it makes an audible difference or not, that is another matter and can only really be determined by testing.
Covenanter
Well-known member
I'm not sure if people are aware how "checksums" work but what you do is to split a signal into chunks, say 8 bits, then you add up the "1s" (or "0s") and add an extra "1" or "0" to the signal so that each set of now 9 bits is always even (or odd). So for example 01010101 for an even checksum becomes 010101010 (four 1s) and for an odd checksum becomes 010101011 (five 1s). Checksums are as old as computing and indeed if you get a memory problem on your pc you will often get an error message "Checksum error".
However, to be 100% clear, if a checksum error is identified there is no way that anyone can know which of the bits is wrong, indeed it can be more than one bit and even the checksum bit itself. There is absolutely no way that this can be corrected except by repeatedly reading the signal and hoping the error will go away. Read errors on CD drives ahould be very infrequent anyway because, as another poster has pointed out, they are only looking for a pit or the absence of a pit.
To summarise, whilst in theory it is possible that a ripped version of a track would be better than a "played" version, in practice the difference will be marginal at best.
Chris
PS It always amuses me when people quote HiFi firms in terms of technical expertise. The link that CNo posted reads like it was written by somebody who has just read a childrens' encyclopaedia which indeed is about the level of expertise I would expect. (I was no circuits man myself but none of the good ones ever went into HiFi.)
However, to be 100% clear, if a checksum error is identified there is no way that anyone can know which of the bits is wrong, indeed it can be more than one bit and even the checksum bit itself. There is absolutely no way that this can be corrected except by repeatedly reading the signal and hoping the error will go away. Read errors on CD drives ahould be very infrequent anyway because, as another poster has pointed out, they are only looking for a pit or the absence of a pit.
To summarise, whilst in theory it is possible that a ripped version of a track would be better than a "played" version, in practice the difference will be marginal at best.
Chris
PS It always amuses me when people quote HiFi firms in terms of technical expertise. The link that CNo posted reads like it was written by somebody who has just read a childrens' encyclopaedia which indeed is about the level of expertise I would expect. (I was no circuits man myself but none of the good ones ever went into HiFi.)
Overdose
Well-known member
davedotco said:
If you use error correction and there is a problem with the disc, the rip will potentially stall or at least slow down. This is an indication of a potential uncorrectable error that will result in an audible artifact, such as a click on playback. Leaving error correction off, leaves in these clicks and pops and they are there to tick you off when you are least expecting it. I have (much to my annoyance) got some of these non EC'd lurkers in my collection and weed them out occasionally.
Some discs have the data on the surface under the label print and even minor scratches to this layer will destroy the data and make it unreadable. I have had several of these discs and make sure that they are replaced first and then reripped. The damage is not always easily evident and can be present without damage to the shiny/read side of the disc.
As ever on this forum, a little knowledge.....
Data Is stored on a CD using a redundant self correcting encoding sceme known as a hamming code. The specific system is called Reed-Solomon encoding. Data is stored as blocks, and depending on the level of redundancy in the data, a given number of errors can be detected, and a given (smaller number) or errors corrected. The enthusiastic student should look up Reed - Solomon on Wikipedia.
The more redundancy in the data, the more robust the disk, but the less data can be stored. That's why yellow book CDroms (which have a higher data redundancy) store less data than redbook music CDs.
So, for a CD player doing a one pass 'on the fly ' read, the hardware error correction in the drive will attempt to correct any errors encountered. If the level of corruption is too high, it will be able to detect the error, but not fix it. In this case, the drive will either leave the value of the errored sample the same as the previous sample, or perform a linear interpolation to the next known good sample and make the missing data up (too old to remember which).
This is where a rip and a CD player differ. If the hardware error correction can't fix the error, a CD player has to move on, in contrast, if the controlling software of a rip receives an error flag from the drive, it can ask the drive to have another go. CD drives are mechanical systems, in particular the stepper drive to the laser head has backlash, and 'having another go' can place the laser in a slightly different position relative to the disc which allows a successful read to take place. This is why you sometimes hear a drive on a PC sawing away as repeated attempts to read an errored section are made by repositioning the laser read head.
So, it is quite possible for a rip to be able to extract more correct data from a cd than a CD player, doesn't make the music from the rip any better than the original recording, just less wrong than the CD player.
A note about the 'checksum'. This has nothing to do with the error correction on the drive, but is an overall test of the entire track calculated by the ripping software. It's a lot more complicated than Chris's example above - (google cyclic redundancy check) but it performs the same function. If two rips have the same checksum, then it is likely that the data is the same - this is a final test of accuracy of the rip, and if in error, some ripping program's will have another go at the entire track.
Data Is stored on a CD using a redundant self correcting encoding sceme known as a hamming code. The specific system is called Reed-Solomon encoding. Data is stored as blocks, and depending on the level of redundancy in the data, a given number of errors can be detected, and a given (smaller number) or errors corrected. The enthusiastic student should look up Reed - Solomon on Wikipedia.
The more redundancy in the data, the more robust the disk, but the less data can be stored. That's why yellow book CDroms (which have a higher data redundancy) store less data than redbook music CDs.
So, for a CD player doing a one pass 'on the fly ' read, the hardware error correction in the drive will attempt to correct any errors encountered. If the level of corruption is too high, it will be able to detect the error, but not fix it. In this case, the drive will either leave the value of the errored sample the same as the previous sample, or perform a linear interpolation to the next known good sample and make the missing data up (too old to remember which).
This is where a rip and a CD player differ. If the hardware error correction can't fix the error, a CD player has to move on, in contrast, if the controlling software of a rip receives an error flag from the drive, it can ask the drive to have another go. CD drives are mechanical systems, in particular the stepper drive to the laser head has backlash, and 'having another go' can place the laser in a slightly different position relative to the disc which allows a successful read to take place. This is why you sometimes hear a drive on a PC sawing away as repeated attempts to read an errored section are made by repositioning the laser read head.
So, it is quite possible for a rip to be able to extract more correct data from a cd than a CD player, doesn't make the music from the rip any better than the original recording, just less wrong than the CD player.
A note about the 'checksum'. This has nothing to do with the error correction on the drive, but is an overall test of the entire track calculated by the ripping software. It's a lot more complicated than Chris's example above - (google cyclic redundancy check) but it performs the same function. If two rips have the same checksum, then it is likely that the data is the same - this is a final test of accuracy of the rip, and if in error, some ripping program's will have another go at the entire track.
Covenanter
Well-known member
Thanks Andyjm, as concise a summary as I have seen.
I have to say that my maths is no longer good enough to follow all the nuances of this subject, but a basic understanding, particularly of what can and can not be achieved, can be of great help to the enthusiast in helping him understand what he is hearing and why.
One thing not mentioned in the above posts is the audibility or otherwise of error correction. I used to think that it was a possible cause for some of the differences heard between different real time transports, but now, having done a little more research, I am less sure. The suggestion is that the errors from the error correction are not correlated, ie they are not directly related to the signal, so the idea that it might cause the harshness or other identifiable traits in some players may well be misguided.
There is however one undisputed fact about digital music reproduction that applys to all 'amature' enthusiasts and music lovers, and it is this.....
"The moment you think you understand what is going on in digital audio, you are wrong".
This must be the most counter intuitive subject that I have ever come across in real life.
I have to say that my maths is no longer good enough to follow all the nuances of this subject, but a basic understanding, particularly of what can and can not be achieved, can be of great help to the enthusiast in helping him understand what he is hearing and why.
One thing not mentioned in the above posts is the audibility or otherwise of error correction. I used to think that it was a possible cause for some of the differences heard between different real time transports, but now, having done a little more research, I am less sure. The suggestion is that the errors from the error correction are not correlated, ie they are not directly related to the signal, so the idea that it might cause the harshness or other identifiable traits in some players may well be misguided.
There is however one undisputed fact about digital music reproduction that applys to all 'amature' enthusiasts and music lovers, and it is this.....
"The moment you think you understand what is going on in digital audio, you are wrong".
This must be the most counter intuitive subject that I have ever come across in real life.
chebby
Well-known member
Well, after all the fur and feathers have settled, I am not going back to CD replay as the only digital source. My current set-up has CD replay as an option (and so might whatever I upgrade to) but I don't use it much because my CD collection is boxed and stored in a cupboard under the stairs!
I bought (and ripped) nine CDs yesterday - a box set - and will continue to buy (and rip) CDs in favour of downloads. I am not bothered if my ALAC and 320K AAC rips upset anyone here because I use technology to suit my purposes rather than to do battle in futile arguments about 'ultimate quality' that have going on since the (equally stupid and futile) CD vs vinyl arguments that started in back in 1983 (or thereabouts).
Interesting (in relation to the discussion of cheap PC drives) to note that some £5000+ CD players are using cheap, OEM, CD-ROM drives with noisy loading mechanisms...
http://www.whathifi.com/review/halo-cd1
... it runs at 4 X normal speed and uses an embedded Intel based computer (running Linux) to read/re-read the data and run error correction as necessary.
So what is the essential difference between a CD rip and a CD played by this $5000 machine? One is stored permanently as a file and played on demand, one isn't stored permanently after being played.
I bought (and ripped) nine CDs yesterday - a box set - and will continue to buy (and rip) CDs in favour of downloads. I am not bothered if my ALAC and 320K AAC rips upset anyone here because I use technology to suit my purposes rather than to do battle in futile arguments about 'ultimate quality' that have going on since the (equally stupid and futile) CD vs vinyl arguments that started in back in 1983 (or thereabouts).
Interesting (in relation to the discussion of cheap PC drives) to note that some £5000+ CD players are using cheap, OEM, CD-ROM drives with noisy loading mechanisms...
http://www.whathifi.com/review/halo-cd1
... it runs at 4 X normal speed and uses an embedded Intel based computer (running Linux) to read/re-read the data and run error correction as necessary.
So what is the essential difference between a CD rip and a CD played by this $5000 machine? One is stored permanently as a file and played on demand, one isn't stored permanently after being played.
BigH
Well-known member
chebby said:
:rofl: good god, and people wonder why hifi bods get called gullible. there has to be about 500-800 quid worth of parts in that maximum, so the mark up is astronomical, and the advertising bumf is unbelievable, given they've basically taken a pc and now called it "a new method for playing cd's" :help:
steve_1979
Well-known member
andyjm said:
Thanks for that post. I didn't know that computer CD drive mechanisms could try rereading the data from different angles when necessary. I've learnt something new today already.
steve_1979
Well-known member
cheeseboy said:
Some audiophiles refuse to believe (or understand) how a £15 CD drive in a dirt cheap PC using a digital output into a competent DAC will play CDs better than an expensive audiophile CD player.
Ironically the WHF review of that Parasoiund Halo CD player explains why perfectly. Although why they need to charge £5000 for a cheap Linux PC in a fancy case I don't know.
"The Halo disc drive runs at four times normal speed, allowing it to read sections of the disc many times to minimise reading errors. Every data sector is initially read twice; those two reads are then compared. If they match, the data is sent to a large memory buffer. If they don’t, the process is repeated until the buffer (which stores around 30 seconds of music) is about to run out. Only at that point is error correction employed"
Errr...
look after your CD's and none of this BS ever becomes an issue?
Look. Digital data is just that. If it is in tact it doesn't matter if it's read off a sterile aluminium spinning disk, solid state memory or a friggin' squashed marshmallow.
My £10 PC CD reader can rip a disc, in ONE PASS at 40x speed with NO ERRORS! NONE. ZIP. ZERO ERRORS. Sorry to shout but some ppl just aren't getting the memo.
Now. If anyones CD player is having trouble with a clean disc, that it needs to keep applying all this error correction, I suggest you take it back, because it's not working to spec.
look after your CD's and none of this BS ever becomes an issue?
Look. Digital data is just that. If it is in tact it doesn't matter if it's read off a sterile aluminium spinning disk, solid state memory or a friggin' squashed marshmallow.
My £10 PC CD reader can rip a disc, in ONE PASS at 40x speed with NO ERRORS! NONE. ZIP. ZERO ERRORS. Sorry to shout but some ppl just aren't getting the memo.
Now. If anyones CD player is having trouble with a clean disc, that it needs to keep applying all this error correction, I suggest you take it back, because it's not working to spec.
chebby
Well-known member
ReValveiT said:
Exactly. Buy the CD. Unwrap the CD. Rip the CD. Put the CD back in it's case and store in a cool, dry, safe place. It can't get damaged. (Don't forget to back up the music library now and then.)
In fact "Stand upright in a cool place" is not a bad code for life. (And for bleach bottles.)
ReValveiT said:
Well no, not BS actually.
There may well be no errors on the output of the drive after the error correction has worked its magic, but no physical medium is 100% error free. It is extremely unlikely that a CD or CDROM is 100% bit perfect. Same is true of hard drives, its not that the physical medium is 100%, it is the smart error correction encoding that is used that allows the bit errors to be corrected.
eggontoast
Well-known member
steve_1979 said:andyjm said:
Thanks for that post. I didn't know that computer CD drive mechanisms could try rereading the data from different angles when necessary. I've learnt something new today already.
It doesn't re-read from a different angle, but shifting the mech back and forth will position the laser head in a slightly (nats ****) different position due to it being a mechanical system. This maybe enough to get a good read though.
steve_1979
Well-known member
Understanding the capabilities of digital audio, even if the method by which these capabilities are achieved is beyond you, as it is me, requires a bit of grounding in science and how science works.
Since science, particularly the science of digital audio, is quite clearly the work of the antichrist it is to be avoided at all costs.
Since science, particularly the science of digital audio, is quite clearly the work of the antichrist it is to be avoided at all costs.
ReValveiT said:
I'd love to see that CD drive that can read the inner edge of a CD at 40x speed with disintegrating to bits from the vibration.
(If you going to shout, please make sure that you are not shouting non-sense.)
Also from my experience, even with a new audio disc the experience you describe is rare. More often than not the rip will slow down at some point or other due to a relatively high level of read errors. For example due to the disc not being perfectly centered. In most case though, slowing down the read speed is enough to still achieve a 100% accurate rip. (Due to redundancy of the data.)
Similar threads
Facebook
Twitter
Instagram