Crazy talk about CD v Rips....

[manicm]

As far as I was aware data is stored on the CD as a series of 'pits' . These are read by the laser mechanism in either a CD player or in a CD-ROM drawer of a computer.

How exactly a 'read head' decides what is 'bad' data that shouldn't be there is something else altogether but if I had to trust something to read the data off an audio CD I know it wouldn't be attached to a computer.

Right.......

So.

A cd player that has to read all the data in one pass, irrespective of damage, misalignment, dust or other factors, then apply error correction circuitry to interpolate (informed guesswork) for missing data is, better than a computer drive that makes multiple passes, collects all the data and then performs a 'checksum' calculation to veryfy that the data is 100% accurate.

Just because the optical drive is in a cd player rather than a computer.

Got it...!

And how does that checksum know that the data is 100% accurate?? Oh I get it - AccurateRip. The truth is, if parts of a CD are scratched beyond repair, no amount of error correction is gonna recover the music, be it through software or otherwise.

Remember, audio on CD is stored as PCM, not WAV format, so to an extent comparing a rip to the CD is comparing apples to oranges. Some may shoot me, but things like AccurateRip are ultimately a red herring.

In all of this I'm not saying rips don't sound good. They do, and my personal preference audiowise is uncompressed WAV.

 

[andyjm]

As far as I was aware data is stored on the CD as a series of 'pits' . These are read by the laser mechanism in either a CD player or in a CD-ROM drawer of a computer.

How exactly a 'read head' decides what is 'bad' data that shouldn't be there is something else altogether but if I had to trust something to read the data off an audio CD I know it wouldn't be attached to a computer.

Right.......

So.

A cd player that has to read all the data in one pass, irrespective of damage, misalignment, dust or other factors, then apply error correction circuitry to interpolate (informed guesswork) for missing data is, better than a computer drive that makes multiple passes, collects all the data and then performs a 'checksum' calculation to veryfy that the data is 100% accurate.

Just because the optical drive is in a cd player rather than a computer.

Got it...!

And how does that checksum know that the data is 100% accurate?? Oh I get it - AccurateRip. The truth is, if parts of a CD are scratched beyond repair, no amount of error correction is gonna recover the music, be it through software or otherwise.

Remember, audio on CD is stored as PCM, not WAV format, so to an extent comparing a rip to the CD is comparing apples to oranges. Some may shoot me, but things like AccurateRip are ultimately a red herring.

In all of this I'm not saying rips don't sound good. They do, and my personal preference audiowise is uncompressed WAV.

A checksum is not error correction, it is error detection - just a way to get confidence that the data is correct. The usual way to do this is to embed the checksum in the data iteslf - a real world example is your credit card number where a basic checksum is included to spot obvious mistakes and transposed numbers. If the checksum isn't embedded in the data, then it can be sent separately - but both these techniques require the checksum to be calculated from known good data before the data is sent.

In the case of a CD, there isn't a checksum available from known good data. Accuraterip (and similar programs) build a database of the checksums from users rips. When you rip a CD, your checksum is compared with other peoples checksum for the same CD. The chances that your rip is in error if (say) 30 people have ripped the same disk, got the same checksum as you are vanishingly small.

There is no red herring here - absent a checksum from known good data, having a common checksum from multiple separate rips is a good second best test.

As for different formats, that is a red herring. Data gets transposed losslessly from format to fomat all the time. As I have already posted, there isn't a bit for bit relationship with the data on a CD and the output of a CD drive - the error correction hardware has to strip out all of the additional error correction bits and reformat the data before it leaves the drive. When calculating a checksum, it does have have to be on the same data, but whether that data is in FLAC, OGG Vorbis, PCM or whatever doesn't matter.

 

[chebby]

So AccurateRip is reliant upon your CD being popular enough for it's database to hold multiple results from many others having ripped the same disk? (And the same version of the disk.)

Is there any way of searching for your CDs on their system before buying AccurateRip? (Or at least a trial version.)

 

[andyjm]

So AccurateRip is reliant upon your CD being popular enough for it's database to hold multiple results from many others having ripped the same disk? (And the same version of the disk.)

Is there any way of searching for your CDs on their system before buying AccurateRip? (Or at least a trial version.)

I use dBPoweramp (which I would recommend) - it certainly shows how many rips there are of your CD when it has finished a rip, but I can't remember if it shows you how many are in the database before the rip. I have never ripped a CD where there wasn't at least two or three other rips of the CD already in the database - but maybe my tastes are very mainstream. I dont know if you can interrogate the system before you buy.

Absent an existing rip, dBPoweramp will do a multi pass rip - rip the CD twice and compare the checksum from the two rips. This is less useful as it will catch unstable errors (a bit was read as a 1 on the first rip, but a 0 on the second), but if the errors are stable (a 1 is read as a 0 both times), then the checksums will agree but will both be wrong.

 

[chebby]

I have never ripped a CD where there wasn't at least two or three other rips of the CD already in the database - but maybe my tastes are very mainstream.

Put it this way, Gracenote doesn't recognise the vast majority of my BBC Radio drama / comedy / documentary / history etc.. CDs (about 250 or more I think).

An example was the 9 CD set of The Diary of Samuel Pepys that I ripped last week. I had to paste in art work, type in artist, album title, volume numbers, disk numbers myself.

I sort of doubt much of my (non-music) collection is going to benefit from EAC, AccurateRip or DbPowerAmp or whatever.

I'm not missing them, I am entirely satisifed with the ALAC and 320K AAC rips (error correction always on) that I have already done. Just curious really.

 

[Thompsonuxb]

.............. :roll:

you engineers and scientist..... I swear.

 

[davedotco]

.............. :roll:

you engineers and scientist..... I swear.

I know, I know......

Next time your car doesn't start in the morning, call a poet.

When your broken leg needs setting try a barman.

 

[MakkaPakka]

You lot must have really been mistreating your CDs. I've ripped loads and hardly any had any errors at all. Those that did had one error. One error would effect what, a couple of seconds of a song? This topic seems to be obsessing over something that shouldn't really be a problem.

 

[Thompsonuxb]

.............. :roll:

you engineers and scientist..... I swear.

I know, I know......

Next time your car doesn't start in the morning, call a poet.

When your broken leg needs setting try a barman.

Dave, don't get me wrong... I mean, I myself have phd's in engineer & scientist its just some of the stuff its clear some just ....lol..... lets move on.

 

[Thompsonuxb]

You lot must have really been mistreating your CDs. I've ripped loads and hardly any had any errors at all. Those that did had one error. One error would effect what, a couple of seconds of a song? This topic seems to be obsessing over something that shouldn't really be a problem.

The topic was about the quality of the copy.....and while an exact copy maybe possible a better copy than the orignal is impossible.

 

[steve_1979]

...I myself have phd's in engineer & scientist..

That's interesting. I hadn't realised that you had a PhD. Out of interest what was your thesis about?

 

[CnoEvil]

The topic was about the quality of the copy.....and while an exact copy maybe possible a better copy than the orignal is impossible.

Of course you can't get better than the original, but you can certainly get worse......which is why CDPs themselves differ in ability; and why playing a perfect rip through a streamer, helps solve some of the inherent problems that CDPs suffer from.

 

[Al ears]

The topic was about the quality of the copy.....and while an exact copy maybe possible a better copy than the orignal is impossible.

Of course you can't get better than the original, but you can certainly get worse......which is why CDPs themselves differ in ability; and why playing a perfect rip through a streamer, helps solve some of the inherent problems that CDPs suffer from.

When you suggest CDPs differing in ability are you putting that down to the quality of the drive / read mechanism?

I hope you are not suggesting they are inferior to that cheap DWD-RW drive I have in my home PC.

 

[CnoEvil]

When you suggest CDPs differing in ability are you putting that down to the quality of the drive / read mechanism?

Yes, along with the quality of the power supply, isolation of components (from internal / external vibration, mitigation of unwanted resonance and quality of wiring and DAC.......but what do I know. :?

 

[BenLaw]

...I myself have phd's in engineer & scientist..

That's interesting. I hadn't realised that you had a PhD. Out of interest what was your thesis about?

He used the plural, so it seems he has at least one PhD in 'engineer' and at least one in 'scientist'. So the question is, what were his theses about? And who did the spelling and punctuation for them?

 

[chebby]

...I myself have phd's in engineer & scientist..

If I had a "phd" (sic) I would be sure to write it correctly as PhD.

Also I wouldn't describe the discipline/disciplines as 'engineer & scientist'.

Which branches of engineering and science? Mechanical? Civil? Electronics? Physics? Biology? Organic chemistry?

 

[Al ears]

When you suggest CDPs differing in ability are you putting that down to the quality of the drive / read mechanism?

Yes, along with the quality of the power supply, isolation of components (from internal / external vibration, mitigation of unwanted resonance and quality of wiring and DAC.......but what do I know. :?

[/quote}

A right, so not just the read mechanism then, this is the only thing likely to effect the quality of a ripped CD.

 

[Al ears]

...I myself have phd's in engineer & scientist..

If I had a "phd" (sic) I would be sure to write it correctly as PhD.

Also I wouldn't describe the discipline/disciplines as 'engineer & scientist'.

Which branches of engineering and science? Mechanical? Civil? Electronics? Physics? Biology? Organic chemistry?

Has he got an 'ology?? or two?

 

[MajorFubar]

I'm not a scientist and I don't have a PhD, but I can grasp that a computer which is able to make mutiple passes at ripping a CD is at a great advantage compared to a CD player which does it on-the-fly. You don't need to know the science behind it for that to be obvious.

 

[Al ears]

I'm not a scientist and I don't have a PhD, but I can grasp that a computer which is able to make mutiple passes at ripping a CD is at a great advantage compared to a CD player which does it on-the-fly. You don't need to know the science behind it for that to be obvious.

Quite so Major. However, whether it needs to make multiple passes or not, you are not going to end up with a rip that is better than the original.

 

[MajorFubar]

Yep, obviously that would be impossible.

 

[steve_1979]

Has he got an 'ology?? or two?

I can think of a few characters on this forum who could have a PhD in psilology.

 

[CnoEvil]

A right, so not just the read mechanism then, this is the only thing likely to effect the quality of a ripped CD.

IME. A CDP's performance is the sum of its design, with the best I've heard being the £45k DCS Scarletti 4 box system (Transport / DAC / Clock / Upsampler). They make a big issue of their bespoke (and expensive) Ring Dac.

I linked to a concise view on the advantages of ripping and streaming, on the first page of this thread.

 

[BenLaw]

Has he got an 'ology?? or two?

I can think of a few characters on this forum who could have a PhD in psilology.

Nice. Obscure.

 

[Al ears]

Has he got an 'ology?? or two?

I can think of a few characters on this forum who could have a PhD in psilology.

Had to look that one up I did.

Obviously not 'ology material!