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EAC... how perfect? How does it work?, Redundant, but more detailed questions
post Mar 10 2003, 01:55
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I've been reading HydrogenAudio for a couple of weeks now and think
this place is a real gem for audio nuts. wink.gif

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

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? smile.gif

Thanks for your time and patience ! :-)
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post Mar 12 2003, 14:50
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QUOTE (yourtallness @ Mar 12 2003 - 05:04 AM)
Let me rephrase: in digital audio, a 1 that should be a 0 can result in entirely different sound, or not? I can't see how errors could add/remove bass, depth etc. from a song...

1. If errors are detected but the original information is not restorable (by e.g. using error recovery information) interpolation will be done.

Some (theoretical) example on the consequences:
1.1. Imagine, every 2nd sample is erroreous (1st correct, 2nd wrong, 3rd correct, 4th wrong ...) (and detected correctly). If best possible interpolation for this case is done, the result is the same as resampling a 22.05kHz signal to 44.1kHz. It's the same as applying a 11.025kHz lowpass. If the interpolation is not ideal for this case, e.g. linear: valueX=1/2(valueW+valueY), frequencies > 11kHz won't be cut away but "modified", causing aliassing and distortion. This is an extreme example, but basically it's the same if a few samples get interpolated. High frequency content is modified.

1.2. Imagine, you have a sharp transient, e.g. digital silence and suddenly a sample value of x000. If some samples before the 1st x000 sample are interpolated, the sharpness of the transient will be damaged, similar to pre-echo.

2.If errors are not detected e.g. because error detection information is not used, random errors can occur.

This will result in a single sound, described as "click", "pop", "digital kiss" wink.gif , depending on the error pattern.

You can try these things yourself using a hexeditor and/or a wave editor.

Corrections are welcome. smile.gif

Let's suppose that rain washes out a picnic. Who is feeling negative? The rain? Or YOU? What's causing the negative feeling? The rain or your reaction? - Anthony De Mello
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Posts in this topic
- Radetzky   EAC... how perfect? How does it work?   Mar 10 2003, 01:55
- - Mr. Mulder   The ETA for the next version of EAC is the same as...   Mar 10 2003, 09:00
- - Pio2001   Interesting questions indeed B) No ! As ...   Mar 10 2003, 13:21
- - tigre   Great answer, Pio2001 - You should add this thread...   Mar 10 2003, 14:49
- - AtaqueEG   QUOTE (tigre @ Mar 10 2003 - 09:49 AM)Great a...   Mar 10 2003, 18:40
- - NumLOCK   QUOTE (Pio2001 @ Mar 10 2003 - 01:21 PM)It is...   Mar 10 2003, 19:16
- - BadReligionPR   QUOTE (NumLOCK @ Mar 10 2003 - 10:16 AM)I per...   Mar 10 2003, 19:58
- - ben   QUOTE (Pio2001 @ Mar 10 2003 - 12:21 PM)No, t...   Mar 10 2003, 21:52
- - Pio2001   QUOTE (NumLOCK @ Mar 10 2003 - 09:16 PM)I per...   Mar 10 2003, 22:25
- - Pio2001   QUOTE (AtaqueEG @ Mar 10 2003 - 08:40 PM)Seem...   Mar 10 2003, 22:30
- - Radetzky   Thanks Pio2001. Your answers sure shed light on m...   Mar 11 2003, 04:06
- - Mr. Mulder   QUOTE (Pio2001 @ Mar 10 2003 - 06:25 PM)[]try...   Mar 11 2003, 07:42
- - tigre   QUOTE (Radetzky @ Mar 10 2003 - 07:06 PM)Fina...   Mar 11 2003, 09:06
- - tigre   QUOTE (Mr. Mulder @ Mar 10 2003 - 10:42 PM)...   Mar 11 2003, 09:57
- - Mr. Mulder   Thanks tigre.   Mar 11 2003, 12:00
- - Patsoe   QUOTE (Radetzky @ Mar 11 2003 - 04:06 AM)But ...   Mar 11 2003, 13:14
- - Pio2001   QUOTE (Radetzky @ Mar 11 2003 - 06:06 AM)EAC ...   Mar 11 2003, 13:33
- - EmDub   QUOTE Finally, EAC detects the following features ...   Mar 11 2003, 17:02
- - Radetzky   Pio2001: Hmm.. so to my question "if I rip a...   Mar 12 2003, 02:17
- - Patsoe   Radetzky: you're somewhat repeating your same ...   Mar 12 2003, 10:51
- - Pio2001   QUOTE (Radetzky @ Mar 12 2003 - 04:17 AM)Also...   Mar 12 2003, 12:43
- - yourtallness   QUOTE What do you mean by quality? Quality as in t...   Mar 12 2003, 13:27
- - Patsoe   QUOTE (yourtallness @ Mar 12 2003 - 01:27 PM)...   Mar 12 2003, 13:48
- - yourtallness   Let me rephrase: in digital audio, a 1 that should...   Mar 12 2003, 14:04
- - KikeG   I doubt error interpolation can result in less bas...   Mar 12 2003, 14:40
- - Patsoe   QUOTE (yourtallness @ Mar 12 2003 - 02:04 PM)...   Mar 12 2003, 14:44
- - tigre   QUOTE (yourtallness @ Mar 12 2003 - 05:04 AM)...   Mar 12 2003, 14:50
- - Radetzky   I understand I've been somewhat redundant with...   Mar 13 2003, 02:01
- - Patsoe   Usually, deleting silence does the job, yes. You c...   Mar 13 2003, 02:43

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