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Topic: Small understanding problem according to the overread-feature (Read 4482 times) previous topic - next topic
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Small understanding problem according to the overread-feature

Hi

It's not clear to me when the overread-feature takes effect for splitted rips O_o''

Just an example:

Imagine I have a drive with a negative offset of 30, which supports "Overread into Lead-In and
Lead-Out" - I'm aware of the fact, that it's enough for the drive to support Lead-Out-overreading because
of it's distinctive offset.

Of course, I'll make use of this in the EAC configurations by using "Read offset correction : 30" and
"Overread into Lead-In and Lead-Out : Yes" - I mean, who doesn't want to get the maximum out of
one's CDs ? ^^ ...

When I'm ripping an album with these settings as a CD_image, the whole album will be shifted 30 samples
forward, which, in fact, erases the offset => it starts at 0 samples. The 30 "more" samples will be overread
into the Lead-Out.

Okay, but how about splitted rips then ? What happens to the 12 tracks in detail, when one rips with
such settings ? The idea of it transfered from a huge file to many small files, which are nothing but the
huge file in splitted form, confuses me  ...

Does that mean that the first track will be shifted 30 samples forward. All following files as well.
And the last file is (also) shifted 30 samples forward AND is overread 30 samples into the lead-out ?
Or does that mean that every single track is shifted 30 samples forward and overread 30 samples
into the next passage of the CD ?



For the one's who are interested what made me so thoughtful:
I've seen a log-file of a rip, which only extracted track no. 4 (of 12 tracks). It was made with an offset
correction of 30 and activated "Overread into Lead-in and Lead-Out". And I've asked myself what effect
the two mentioned options have on this track - the effect on a whole album is clear to me. What would be
the difference of this specific rip, and a rip of track no. 4 without the two mentioned options (?)  ...

Paralysed greetz,
arctic

Small understanding problem according to the overread-feature

Reply #1
Since your offset correction is a positive number, overreading will be done from the lead-out.  The lead-out is at the end of the disc, therefore the overreading setting only makes a difference with the last 30 pairs of (stereo) samples of very last track on the disc.  Overreading has no bearing on any other track.  So for your example, track 4 of 12 does get shifted based on the offset correction but it does not lose any samples if overreading is not checked.

I'm not sure what you mean by splitting since it sounds like you're talking about ripping separate tracks.  In EAC splitting specifically refers to taking an image file and cutting it up into separate tracks based on a CUE sheet.  When EAC performs this function nothing is ripped so offset correction and overreading do not apply.

Small understanding problem according to the overread-feature

Reply #2
First of all thank you for the feedback
And yes, I meant seperated tracks.

Okay, I think I get it now:
All tracks are shifted due to offset correction. The only practical use of this is, that all tracks exactly
start there, where the tracks of the Original-CD start, as we've erased the "error source", offset.
So, ripping with offset correction simple causes complete ripped tracks with the right beginnings, nothing
else, BUT, if you want to have the last track to be ripped completely and from the right starting point,
you should have overreading into the Lead-Out activated  ...

Small understanding problem according to the overread-feature

Reply #3
Yes, but only if the drive is capable of reading from what it thinks is the lead-out (or lead-in if the offset correction is a negative number).

For drives that can't overread:
It's important to check to "fill up missing offset samples with silence" so that the first or last track comes out to be the right length.  If the correction is negative, the first track will also be positioned correctly; otherwise when burning to CD-R, silence will be appended to the end of the track (rather than padding the beginning where it should be!), that will create a gap betwen it and the second track.

Edit: Where are my manners today?  You're welcome!   

Edit #2: "when burning to CD-R" placed earlier for better clarity.

Small understanding problem according to the overread-feature

Reply #4
Well, thank you for the welcome ^^ ...
but to be honest your passage just confused me ^.^
So, to find back to the line:

1. Knowing one's offset and appling an adequate correction of such
2. Having a drive which supports both Overread-features or only the specific overread-feature which is mandantory
3. Activating "Overread into Lead-In and Lead-Out" in EAC

=> Maximum of extraction with EAC, no matter if ripping as CD_images or in seperated tracks

If you don't have the opportunity for the overread stuff and are forced to fill up missing offset
samples with silence, the only difference between two different rips - one with overread, one without -
will occure either at the very beginning of the first or at the end of the last track; where the difference
will be depends on the direction in which the offset correction shifts everything.
So, it's possible to rip perfectly within the scope of the first and last track for drives, which don't
support Overreading features, BUT as soon as it comes to the first or last track the feature lack would
take effect...

Small understanding problem according to the overread-feature

Reply #5
So, it's possible to rip perfectly within the scope of the first and last track for drives, which don't
support Overreading features, BUT as soon as it comes to the first or last track the feature lack would
take effect...

Actually in most cases there won't be a difference, as most CDs beginns/ends with null samples, and then it dosen't matter if the null samples are really read of the disc, or simply generated by EAC. In the rare cases where the CD dosen't beginns or ends with enough null samples, then you are of course absolutely right

 

Small understanding problem according to the overread-feature

Reply #6
...and for those that don't end or begin with digitally silent samples, the samples that may be lost will still be practically silent, or at least they should be.  With 30 pairs of samples, we're only talking about 680 millionths of a second.  Such a small amount of data that is practically silent should hopefully seem trivial enough not to worry about.

Arctic, from what you've said I'd say you understand this stuff very well.  What seemed to be your biggest concern was that data may be lost between tracks.  Luckily this isn't the case.

There are instances where being able to overread can come in handy.  I've seen pressings of discs where the first track starts in the lead-in.  One album in particular was Sammy Hagar's Three Lock Box.  The track begins with him saying "Suckers walk, money talks, but it can't touch my three lock box."  Well the pressing was so bad that the track started like "-kers walk, money talks..."

The offset was so bad that EAC's offset limitation of 20 frames wouldn't allow the entire beginning to be extracted so the setting in the registry had to be tweaked.  On top of that, the adjustment, which is given in hexidecimal, required a negative number.

 
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