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  • PFS
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Gap detection accuracy levels in EAC
Sorry for starting so many threads...but this one is important.

I've just ripped about 150 CDs of my collection with EAC, and I just realized that my gap detection was set to method B, inaccurate.  I've done some searches and found that secure and accurate are about the same, but I couldn't figure out how bad inaccurate is in comparison.

I tried re-reripping a few discs, and noticed no difference in the cuesheets.

So how bad is inaccurate?  If there's much risk that my rips are off, I'll probably redo the whole thing...I'm kind of nuts that way (want as close to perfect rips as possible) and I've got lots of time this summer....

  • AtaqueEG
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Gap detection accuracy levels in EAC
Reply #1
Depends on your drive, really.

Most modern drives will extract gaps accurately the first time around.

That is the difference between the three methods, IIRC. "Innaccurate" extracts only once, "Accurate" twice and (this is my guess) "Secure", three times.
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  • dewey1973
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Gap detection accuracy levels in EAC
Reply #2
From The Coaster Factory:

Quote
The Detection accuracy is the number of times EAC counterchecks the detected gaps. In the Inaccurate mode the gaps will be retrieved only once while the Accurate and Secure modes retrieve the gaps several times to verify the gap positions. It is possible that your drive does lock up when using the more accurate detection accuracy. Thus some experimenting is required.

  • PFS
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Gap detection accuracy levels in EAC
Reply #3
Awesome, thanks for the replys....that was just what I needed to know.  Somehow all the discussion of accuracy I turned up just mentioned differences in performance without saying exactly what was going on behind the scenes.  My drive is only 6 months old, and so far I've only done rips on discs I rip without errors, so if the entire disc was read properly, I'll assume the TOC was too.  Whew...saves a lot of reripping.  Cheers again.

Gap detection accuracy levels in EAC
Reply #4
I've seen some differences between Method A - Accurate and Method B - Inaccurate.  I keep the setting at A - Accurate on my NEC NR-7800A.
"Have you ever been with a woman? It's like death. You moan, you scream and then you start to beg for mercy, for salvation"

  • PFS
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Gap detection accuracy levels in EAC
Reply #5
Quote
I've seen some differences between Method A - Accurate and Method B - Inaccurate.  I keep the setting at A - Accurate on my NEC NR-7800A.
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Were the discs you were ripping damaged at all?  Or were the differences strictly due to the different methods and security levels used in detecting the gaps?

Right now I'm just hoping that different methods and security levels will return the same info so long as the disc is clean and readable...

  • Pio2001
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Gap detection accuracy levels in EAC
Reply #6
The gap information is not in the TOC AFAIK. It is retrieved from the subcode channels at the real position, into the CD.

Gap detection accuracy levels in EAC
Reply #7
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The gap information is not in the TOC AFAIK. It is retrieved from the subcode channels at the real position, into the CD.
[a href="index.php?act=findpost&pid=283989"][{POST_SNAPBACK}][/a]

That's why a separate gap detection is necessary at all.
I know that I know nothing. But how can I then know that ?

  • Supacon
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Gap detection accuracy levels in EAC
Reply #8
Kind of unrelated, but I noticed that Plextools' cuesheets were about a frame off from the ones I made with EAC for many tracks in the early part of some CDs.  It sort of bothered me, but... it's only a frame.  Whether you get 1/75 of a second of silence one way or the other doesn't make a big deal to me.

I'm not sure why it would be different though.  As far as I can remember I was even using the same drive, although it'd make more sense if I was not.

  • PFS
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Gap detection accuracy levels in EAC
Reply #9
Man, I know what you mean.  It's the kind of thing that makes absolutely NO impact on the listening experience, but you still want to know that what you have is a perfect copy of the CD...that feeling is what prompted me to start this thread in the first place, so it's not that unrelated at all. 

  • hdarwen
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Gap detection accuracy levels in EAC
Reply #10
Have noticed the same thing with differences in Plextools & EAC CUE sheets ... First noticed it on a mix CD which (normally) would not have any gaps but Plex detected a 1 frame gap on every track. I checked further with EAC and got no gaps with Method A Secure. Interestingly though, using EAC Method B & C Secure, the 1 frame gaps came back. So am guessing that EAC Method A Secure is more accurate than anything else.

  • Supacon
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Gap detection accuracy levels in EAC
Reply #11
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...am guessing that EAC Method A Secure is more accurate than anything else.

Of course, this would only apply to your particular drive, I assume.

I've been ripping hundreds of CDs recently, and one of the drives I'm using is an old Plextor Plexwriter 12/10/32A.  In EAC, I've got to keep alternating between modes A,B, and C because most of the time one of them will just kind of freeze and sit for hours on one track, making no progress.  It's a little odd...

  • markanini
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Gap detection accuracy levels in EAC
Reply #12
Quote
Quote
...am guessing that EAC Method A Secure is more accurate than anything else.

Of course, this would only apply to your particular drive, I assume.

I've been ripping hundreds of CDs recently, and one of the drives I'm using is an old Plextor Plexwriter 12/10/32A.  In EAC, I've got to keep alternating between modes A,B, and C because most of the time one of them will just kind of freeze and sit for hours on one track, making no progress.  It's a little odd...
[a href="index.php?act=findpost&pid=293550"][{POST_SNAPBACK}][/a]

I have the same problem with my Plextor Premium drive.

  • hdarwen
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Gap detection accuracy levels in EAC
Reply #13
Quote
Of course, this would only apply to your particular drive, I assume.


Seems to depend more on the CD for me. Most times I get A to work, but not all. Essentially same behaviour as you - some A, most of the rest B, and a few on C only. Interesting thing is I can get slightly different results using the different methods on the same CD (for CDs that work with all 3).

  • toNka
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Gap detection accuracy levels in EAC
Reply #14
Well, I've done a little testing and came up with some conclusions.
I have a Plextor PX-708A and I have noticed differences between Method A/Secure and Method B/Secure.
Have a look at the following pictures.

Detection Method A / Secure:


Detection Method B / Secure:


Here they are 100% cropped side-by-side.
Method A......../.......Method B
         


Posting CUE sheets would be a little messy but trust me, they reflected the same differences you are seeing in these pictures.

So I did a bit compare against the ripped tracks with different methods of gap detection with foobar2000.
I don't know how accurate this test is but here's my results:
Quote
Comparing:
"D:\Detection Method A Secure - 05 - Donkey Rhubarb.flac"
"D:\Detection Method B Secure - 05 - Donkey Rhubarb.flac"
No differences in decoded data found.


So if foobar2000 is correct then the files are the same.
But if we used the two different CUE sheets to burn them, wouldn't the burned CD be slightly different?
I'm not sure about the accuracy of this bit compare because if EAC is appending the pre-track gap to the end of the previous track and the pre-track gaps are different, then the files should be different.

I compared the files with EAC's wave compare function and that came out a perfect match too.

Let's see what Audition 2.0 has to say about it.
So now I have both files open in Audition and I am staring at the sine waves with my own eyes at the beginning and end of the tracks at the same zoom level.
They look identical when I Ctrl+Tab between the two.

Hmmmm....
Three different tests.
foobar2000 bit compare = pass
EAC wav compare = pass
Audition visual compare = pass

There is no doubt in my mind that these files are exactly the same.
So why would EAC show two different pre-track gaps using different methods?
And since the CUE sheets are different, how would that effect the CD being burned?

Anyone care to take this to the next level?
I'm exhausted.

  • JunkieXL
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Gap detection accuracy levels in EAC
Reply #15
The tracks will not be affected by a difference in gap length unless you have EAC set to append gaps to previous or next track.

The only resulting difference would be in the length of the gap between tracks if you used the resulting cue sheets to play the files or burn them.

That's why I prefer to leave gaps out and use Non-Compliant Cue Sheets with multiple files and gaps generated by EAC.
JXL
  • Last Edit: 29 March, 2007, 03:16:38 PM by JunkieXL

  • elpres
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Gap detection accuracy levels in EAC
Reply #16
What you are comparing are the waveforms of the images, which are independent from the cuesheets / gaps. The gaps are not periods of silence, but simply a sorf of marks, which still may contain audio data. I've got (at least) one CD which is gapless (a DJ mix), but nonetheless has "gaps".

If you take a look at a cuesheet, you'll notice that it has "TRACK" entries, and they have "INDEX" entries. "INDEX 01" is the position where the player jumps to when you choose this track. But these can also be an "INDEX 00" indicating the start of the gap between this track and the one before. This period between "INDEX 00" and "INDEX 01" is the "gap" (the pregap, to be precise), but noone forces the manufacturer of the CD to set the gaps in a way that they contain only silence.

  • greynol
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Gap detection accuracy levels in EAC
Reply #17
The tracks will not be affected by a difference in gap length unless you have EAC set to append gaps to previous or next track.
If you tell EAC to append gaps to the previous track (or rip without detecting gaps which results in exactly the same thing) the tracks will not be affected by a difference in gap length.  It is only when you tell EAC to leave gaps out or prepend them (append them to the next track) when you will see the difference.

The only resulting difference would be in the length of the gap between tracks if you used the resulting cue sheets to play the files or burn them.

That's why I prefer to leave gaps out and use Non-Compliant Cue Sheets with multiple files and gaps generated by EAC.

You don't seem to know what you're talking about here.  You must detect gaps in order to leave them out.  If you do not detect gaps they will be appended to the previous track.  If you leave gaps out and try to use a noncompliant sheet you will get an error.
Your eyes cannot hear.

  • toNka
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Gap detection accuracy levels in EAC
Reply #18
I append gaps to the previous track (EAC Default) and use non-compliant CUE sheets.
From my understanding, this is the only way you can use seperate tracks and preserve a bit perfect way to record to CDR later.

What throws me off is, if track 2 has a 2sec pregap then EAC puts that 2sec at the end of track01.wav but if it then detects a pregap of 1.76sec then it only adds the 1.76sec to the end of track01.wav.
Then wouldn't these two wav files be of different lengths?
I'm I missing out on how this works?

  • greynol
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Gap detection accuracy levels in EAC
Reply #19
I append gaps to the previous track (EAC Default) and use non-compliant CUE sheets.
From my understanding, this is the only way you can use seperate tracks and preserve a bit perfect way to record to CDR later.
Actually it isn't.  In fact, this method won't always be able to give you all the available data since it doesn't extract the pregap before the first track when it exists.

What throws me off is, if track 2 has a 2sec pregap then EAC puts that 2sec at the end of track01.wav but if it then detects a pregap of 1.76sec then it only adds the 1.76sec to the end of track01.wav.
Then wouldn't these two wav files be of different lengths?
No.
I'm I missing out on how this works?
I'm afraid so.

When EAC detects gaps it's detecting the locations of 00 index points which are found in the subchannel data.  The location of each 01 index is instead found in the TOC and specifies an absolute position.

When EAC appends gaps to the previous track, it is the same as if it does nothing at all.  The tracks get ripped from one 01 index to the next 01 index.  The placement of the 00 index in this situation is nothing more than a marker behind the next 01 index.  If you were to have gaps prepended to the next track then you're telling EAC to rip from one 00 index to the next 00 index unless one doesn't exist in which case it will be substituted with the 01 index.  If you tell EAC to leave gaps out, it will rip from the 01 index to the 00 index (or next 01 index if the 00 index doesn't exist).
Your eyes cannot hear.

  • toNka
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Gap detection accuracy levels in EAC
Reply #20
So, is there a better way, more bit perfect, to rip with EAC to separate tracks?
I understand that CDs with Track 00 need special attention but they are few and far between, and when I come across one I rip it accordingly.
So, with the exception of a CD that has a "hidden song" in the Track 01 pregap (Track 00), shouldn't appending gap to previous track plus non-compliant cue sheet be perfect?