EAC... how perfect? How does it work?, Redundant, but more detailed questions Options

[Radetzky]

I've been reading HydrogenAudio for a couple of weeks now and think
this place is a real gem for audio nuts.

I am about ready to proceed to backup about 250 CDs of mine on a
RAID-1 setup. I plan to rip all the CDs using a LGE HL-DT-ST RW/DVD
GCC-4240N drive and EAC 0.9b4.

Though, before doing do, I would love to have your input regarding a
couple of points I have a hard time with. I hope you won't find these
questions redundant. I know some, or most, have already been asked
but I never was satisfied with the answers (*not* that I think anybody
_has_ to provide an answer I will be happy with...).

So here goes for the questions :

1. Is it true that (at minimum) in any of the Secure modes EAC will
read at least twice every thing it reads? I ask so because there
are no confirmation anywhere in the software that it is doing so.
It would be nice if during the rip process a little string saying
"currently reading each sector twice" or something would appear.

When, if ever, does EAC perform only one read of the audio?

2. Exactly what does it read twice? How big is the chunk of data that
is being read? 10x2352 bytes? 2352 bytes? 1 bit?

3. I know this has already been asked at digital-inn.de, but I don't
think I understood the answer fully. How sure can we be that EAC
really does detect and "correct" errors?

I mean, lets say there is a minor scratch on one of my CDs. My
drive reads through the scratch.. the returned data is, say 0x2431.
It reads again and the data is still 0x2431. EAC thinks this is
fine. But the scratch is done in such a way that the reflected
information is always the same, AND wrong. How could EAC deal with
this physical anomaly?

I remember Andre (the author of EAC) said something like it was
very unlikely that the same data could be read from a scratch or
spot (or whatever damage there is) on the CD. But how sure are we
of that?

4. If I intend to keep all the ripped music on my computer and not
duplicate it on, say, CD-R media, should I go nuts with the
offsets?

I did tests myself and I tried to inject a -10000 offset and then a
+10000 offset and it didn't mater at all sound wise. I checked
with a WAV editor (Audacity) and the difference (the time-offset)
was really minimal and only cutting or adding silence (haven't
found a CD that starts with music too soon).

If I want to extract all the tracks as one big WAV file, am I right
to say that the digital extraction is successful anyway, that the
offset only induces a time-shift (a very, very small one)? Or is
there a subtlety I didn't grasp?

5. A very important (to me) question. When EAC commands the drive to
read whatever amount it has to during its rip process, what error
correction is performed by the drive? Is it using the Reed Salomon
ECC error codes from the disc?

In DAE mode (... is it a 'mode' ?), if the drive detects a problem
on the disc (scratch, etc.) will it try to interpolate between two
points or will it just send the data back unmodified?

Asked differently, in DAE mode does the drive treat the audio data
as audio or as data?

Reading http://www.roxio.com/en/support/cdr/cderrors.html leads one
to believe there are many more problems to deal with that "only"
scratches and finger prints. The actual CD might have errors
injected during its pressing (!).

6. I have a HL-DT-ST RW/DVD GCC-4240N drive. It is a low-profile
combo (DVD + CD-RW) drive. When I perform a rip using EAC and this
drive, will it be of the same quality from a rip performed from,
say, a Plextor Ultraplex drive?

7. Last question... what is the ETA for the next release of EAC?

Thanks for your time and patience ! :-)

[Patsoe]

But if the drive always provide the same value
from it's interpolation technique... we have a problem, no?

Yes and no. Yes, because you will not have read the right value at that position. No, because the drive can't do any better so interpolation is the best option available.
If C2 reporting by the drive is done properly, though, EAC will still be able to suspect that interpolation has been done at that position.

I saw _ben_ questionned the term 'quality'.  I too have a
problem understanding what you mean (even with the explanation you
gave him)...
....................will I have the _exact_ same .wav file on my
hdd (not taking into account the potentiel different offsets) ?

"Quality" concerns the whole drive. That is, e.g. a better laser pickup will read flawlessly where other drives would be needing interpolating, and so on. On a bad CD, with difficult positions, EAC-rips can thus be different with different drives.

Ofcourse, if there are such positions, you want to know.

My method is to use a drive with good C2 report. Then, rip in secure mode with C2 setting enabled, no cacheflushing, and offset correction, and do test+copy. Then, if there are C2 errors you'll have a less than 100% track quality, so even if test and copy CRCs match, you'll know there is a possibly interpolated position.

If this occurs, take a second drive: different brand, different chips. (this is why you need offset correction; to compare with the second drive). If it returns the same rip CRC, all is fine. Else, since interpolation values of different drives will probably be slightly different, you can see the problem spot from wav-compare.

Why do I set no-cache mode? Because in my experience, less read errors occur with that setting; EAC doesn't flush the cache every 2MBs, and the pickup thus does less work. Ofcourse, this setting makes error correction by EAC useless (because re-reads will come from cache). But that's why you do test+copy. And besides, I don't want error-correction the EAC-way if not necessary. I just want to know if there's a troublesome scratch and if there is, I'll get another disc to rip from...

Edit: tried to make last paragraph more readable.

This post has been edited by Patsoe: Mar 11 2003, 13:32