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From: Urs Thuermann on 5 Jul 2010 16:50
When I rip audio CDs, I typically use both cdrdao and cdparanoia and
compare the results to make sure that I really really have the correct
digital audio data. I run Debian testing with current versions of
cdrdao 1.2.2 and cdparanoia III release 10.2.

For each CD I run

cdrdao read-cd --datafile data.cdr --device /dev/sg0 toc
and
cdparanoia -d /dev/sg0 -B

where /dev/sg0 refers to an Plextor Ultraplex 40max SCSI CDROM drive.

Then I use my own small program to split the data.cdr file into wav
files <n>.wav according to the toc file. I then compare these wav
files with the track<n>.cdda.wav files from cdparanoia.
Alternatively, one could run

sox track<n>.cdda.wav cdda.cdr

and then compare data.cdr to cdda.cdr. I most cases the results of
cdrdao and cdparanoia are the same but for roughly 1 of 4 CDs one or
more tracks differ. Sometimes this is the case for CDs with scratches
but sometimes also for CDs with no obvious scratches where both,
cdrdao and cdparanoia don't give any error message and do not seem to
have any problems ripping the CD. I can run cdrdao and cdparanoia
repeatedly, say 10 times, and I get deterministic results, i.e. all
runs of cdrdao give the same result and all runs of cdparanoia give
the same result but the results of cdrdao and cdparanoia differ.

Now my question is where these differences come from and which results
are the correct (better) ones. From the output to stdout I see that
cdrdao uses the Paranoia DAE library and Joerg Schilling's SCSI
library to actually read the audio CDs. With ldd I see it is not
linked dynamically to these libraries. So one question is, do cdrdao
and cdparanoia use different library versions?

Regards,
urs


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From: Andrei Popescu on 5 Jul 2010 17:30
On Lu, 05 iul 10, 22:43:44, Urs Thuermann wrote:

> Now my question is where these differences come from and which results
> are the correct (better) ones. From the output to stdout I see that
> cdrdao uses the Paranoia DAE library and Joerg Schilling's SCSI
> library to actually read the audio CDs. With ldd I see it is not
> linked dynamically to these libraries. So one question is, do cdrdao
> and cdparanoia use different library versions?

Maybe it's just me, but after reading the cdparanoia FAQ[1] I wouldn't
use anything else for CD ripping ;)

[1] http://xiph.org/paranoia/faq.html

I doubt (but have no proof) cdrdao can handle all errors that cdparanoia
can handle.

Regards,
Andrei
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From: Mark Allums on 6 Jul 2010 03:30
On 7/5/2010 3:43 PM, Urs Thuermann wrote:
> Now my question is where these [CD-rip] differences come from and which results
> are the correct (better) ones.


Audio CDs live in a world where there is no guarantee that any two
passes across a "sector" will ever give the same result. For one thing,
there is no error correction. Give up the idea of getting a correct, or
"perfect", rip; it's theoretically impossible.

In fact, that's why cdparanoia exists. In the days of CD-ROM drives,
the drives were not very good at ripping audio discs, and cdparanoia
compensated for the problems. It was also unbelievably slow. Today,
DVD drives have a much better disc transport, etc., and a lot of
software is smarter than it used to be, so ripping is only a real
problem with copy-protected CDs, and very damaged discs.



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From: Mark Allums on 6 Jul 2010 03:50
> On 7/5/2010 3:43 PM, Urs Thuermann wrote:
>> Now my question is where these [CD-rip] differences come from and
>> which results are the correct (better) ones.


Here is a nice web site about CDs. It is about CD-Rs, but it has a lot
of general info that anyone can benefit from, including about audio CDs.
It is a good starting point.

http://www.cdrfaq.org/


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From: Mark Allums on 6 Jul 2010 04:00
> On 7/5/2010 3:43 PM, Urs Thuermann wrote:
>> Now my question is where these [CD-rip] differences come from and
>> which results are the correct (better) ones.
>
>
> Audio CDs live in a world where there is no guarantee that any two
> passes across a "sector" will ever give the same result. For one thing,
> there is no error correction. Give up the idea of getting a correct, or
> "perfect", rip; it's theoretically impossible.


Oh, I forgot. One more thing (and sorry to keep flooding the list
replying to myself): There is an analog output and a digital output,
and they are not equal. Your CD-drive or DVD-drive will treat them
differently, and that conceivably may make a difference for you.

I'm sorry, I cannot offer advice about what, if anything, to do with the
analog output, but since you are probably only interested in the digital
output, anyway, it's just as well.


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