I recently bought a new optical drive, a BenQ DW1620, to replace my old Lite-On LTC-48161H. According to the AccurateRip database (and verified by me) the BenQ has a much larger read offset than the Lite-On: +618 vs. +6.

I realize that neither of these makes a huge difference when it comes to ripping, but is one better than the other? I want to know if I can safely discard the Lite-On drive, or if I should keep it around for ripping. (It also rips much faster than the BenQ, so that would be a bonus.)

Thanks!

I'm honestly not sure if the read offset value makes a difference if you're using software to rip that will correct the read offset. However, I would keep the faster drive around for ripping as long as it is faster ripping in EAC's Secure mode.

Hopefully someone else can give you a more definitive answer as to whether the difference in read offset values has an affect on ripping quality.

I think you mean read offset correction. If both drives support overreading into the lead-out, you should get the same results. However, AFAIK, none of the devices supports that.

Edit: Grammar.

Regardless overreading issues, offset shift surely doesn't make any difference if the offset correction works properly (and you've detected the correct ofset). It's just a small time shift of the extracted audio data (to the beginning of the CD, if your positive offset values are correction values and not actual ones (say, yout Liteon has a read offset of -6))
If your drives aren't capable of overreading into the lead out, than a higher read offset correction means more loss of samples at the end of the last track of the CD (the only disadvantage)
(Maybe if the offset was very very high (>several thousands of samples) then it'd be possible that EAC's offset correcton doesn't work correctly any more.)
In any case, keep your Liteon drive to get second rips for verification or if you want to rip the last track of a CD.

Thanks for the advice. I think I've been leaning toward keeping both drives, but I was hoping that one could do everything. (Besides, the Lite-On commonly rips at 35X, while the BenQ can't get much better than 13X!)

@Sebastian Mares, is there a way to test the drives' ability to overwrite/overread into the lead-out (or lead-in)? Or can I find that information somewhere?

Thanks again!

Install EAC -> go to drive options (F10) -> Offset / Speed -> Detect read offset correction.
The detection also determines the ability of your drive to overread into lead-in/out...
But as Sebastian Mares have written "AFAIK, none of the devices support that."
I know only about Plextors which can overread into both lead-in and out...

I think many writers do.

@boombass: You can manually test your drive's overreading capability. Take a CD with noise at the end of the last track (old AAD-CDs...), enable the correct read offset correction you've detected, enable "fill up missing offset samples with silence" in the EAC options and extract the last track.
-the offset number of samples as silence (perfect null samples, open the file in a wav editor with vertical zoom ability) at the end of the file=>drive can't overread into lead out
-no null samples at the file's end=>drive can overread into the lead out
"Fill up missing offset samples with silence" has no effect if drive can overread. This manual detection is more secure than the automatic test.

I hope boombass doesn't like boomy bass ...

Thanks all. I'm probably worrying about nothing, but it's what I do best!

@precisionist: I'll try what you suggest this weekend. I've got lots of old AAD CDs, but could you recommend one or two that might be common?

As for my BB name, boombass was the first thing I could think of when I registered - it's from an old TV show. I kind of like it, so it sticks! (Short for Saul Boombass. Bonus points if you know where it came from!)

I think there aren't "common CDs" for this, just try...

Another method would be to make (=burn) such a test CD yourself.

EDIT: I suddenly realize that this method will only work under certain conditions: your read offset correction must be greater than your write offset and they must have the same sign.

What you want is a leadout that is not silent. How to achieve this:

1. The last track of your CD must end with noise or music (no silence). You can create such a by cutting in the middle of a song (somewhere where there is no silence) with a WAV editor.
2. Burn without correcting the write offset, so that the end of the last track will be written in the leadout.

To do the test with this test CD, EAC must read with combined offset (not just read offset correction). In your case this is +6 + 0 = +6. If EAC extracts the last track completely, you can conclude your drive overreads, whereas if the last extracted samples are silence, EAC doesn't overread.

This is an interesting idea. I used EAC to make a write-offset test CD, and determined that my Lite-On's write-offset is 0. So I could use that to test both drives.

A zero write-offset should be good for this, no?

The only problem is I have no time now. I'll try it soon and report back!

35X is quite impressive. Are you sure EAC is set-up for secure mode with the Lite-On?

Yes that will do.

P.S. I have edited my previous post, but the change doesn't make a difference in your case.

Good point. Offsets are much less important than a correctly configured EAC.

I don't suggest burning own CDs, because then it soon gets very complicated. The thread has gone far enough to quote myself to clear up some facts:

We should also define that a negative value or number is always lower than a positive one (like it is in mathematics). I think liekeloo is talking about absolute (always positive) values of read offset correction and write offset. edit: Maybe I'm wrong. I don't understand liekloo's post because I don't know which values he means.
Anyway, EAC can't write any CD properly (in terms of offset) without the correct write offset entered in the according box on the "writer" tab.
So
1. Detect the writer's read offset correction either using CDs from the EAC key CD database or from the accuraterip key CD database (or even better both).
2. Calculate and enter your writer's write offset using my formulas given above. If you use EAC's "make offset test CD" function, your writer will then write a CD which is equivalent to a CD from the EAC or the accuraterip key CD database. (EAC will report the read offset correction for any drive with this CD)
If you enter write offset 0 instead of the calculated value, this CD will then report the combined read/write offset correction of the writer is has been written with and any drive it is used with (the writer's write offset and the reader's read offset-can be the same drive).
3. If you want to write a CD like liekloo's describing, you need to have an actually (used) positive write offset. Say, your actual (hardware) write offset is -6. Enter write offset -12=>EAC uses write offset correction +12=>The written write offset is +6=>The resulting CD will have 6 non-null samples in the lead out (if the wav had no null samples) edit: regardless of overwriting capability...
You see why I don't recommend writing...

@Boombass:
Precisionist is right: writing and offsets are really tricky.

The problem is, I don't know a good, easy method.

The simplest method (EAC offset reference CD) was explained earlier in this thread. But for this to work, you need such a CD.

Precisionist's method (AAD CDs) might work if you've got enough CDs. With the last track of each CD, look at the track end for either a silence of exactly [read offset correction] samples (that indicates NO overread capability in the leadout), or no silence at all (indicating overread capability in the leadout). Zoom in with your WAV editor to be sure the silence is perfect ("digital silence").

Another method would be setting overread to yes in EAC, and ripping a number of CDs and waiting for a sync error to appear on the very end of the last track (which happens with many CDs on drives that don't overread but have the option "overread" set to "yes" in EAC). If I recall correctly, the sync error only appears if you rip the CD as a whole (all tracks, not only the last).

P.S. most similar liteons have write offset -6, so chances are that your value is -6 as well (not 0 as you now think). In that case, my 'write' method needs a change (see part 3. in Precisionist's last post)

A really hard task, ripping that much. Doesn't the appearance of the error also depend on the "fill up missing offset samples with silence" option ?


CD written with write offset correction 0 => CD has -6 write offset because hardware write offset is supposedly -6 => ripped with -6 hardware read offset and +0 software offset correction, so the rip starts at the same position like the burned audio, 6 samples to early => software (EAC) reports offset shift 0:
read offset - write offset = combined read/write offset
read offset - combined read/write offset = write offset
-6 - 0 = -6
This is the way write offsets should be determined.
Probably something is wrong because he got 0. Check signs, formula and settings, boombass.

There are excellent offset explanations (and especially illustrations) in the EAc tutorial:
http://users.pandora.be/satcp/eacoffsets00.htm#-

liekloo, I just saw your 'essential ripping guide' (link in the faq)...respect

If you are interested, I could test this (so far I have never used EAC without that option).
Thanks for your appreciation .

No, if the write offset is -6, there will be no data at all in the official lead-out, and the 6 official last samples of the last track will also be silent. What the writer believes to be the 6 last samples of the last track (officially the 6 samples before) will have data. These data will be the 6 samples before the 12 last ones of the wav file. EAC will discard the rest, unless you can overwrite. But you know that EAC only overwites with some old Teac burners.

Anyway, you don't want to overwrite into the lead-out. All you want is to get a reader that believes that your burner overwites. It does if their combined offset is positive.

edit: regardless of overwriting capability...:
This actually meant "under the condition that the writer + EAC can overwrite",
not "no matter if the writer + EAC can overwirte or not"
Probably bad English, bad expression.Sorry.

Hi all. It's been a while since I posted to this thread, and I've had some time to do some investigating. To recap, I bought a new optical drive, a BenQ DW1620, to replace my old drive, a Lite-On LTC-48161H. I started ripping with the BenQ and was disappointed to find out that it ripped about half as fast as the Lite-On. It also had a larger read offset correction (+618) than the Lite-On (+6), and I wanted to find out which would be the best drive for quality rips.

Now I have both drives installed in my system, and I've run some tests to try to figure out what is going on. I've also re-configured EAC, and I think I've done it right this time. (@evereux, you are quite right: I didn't have it set up correctly when I was getting 35X rips! Now it's more like 13X or so. I followed the Coaster Factory guide extremely carefully.) I've determined the correct read offset corrections for each drive (as stated above, and confirmed by AccurateRip), and determined that the write offset correction for my Lite-On is -6 (not 0 as I thought before: I did the test wrong...). I can't get the write offset correction for the BenQ, because EAC crashes when reading a disc to determine offset.

OK, so here are my results. I ripped the same track on a disc with each writer, with the "Overread into Lead-In and Lead-Out" option in EAC checked or unchecked. Then I did a "Bit-compare tracks..." test with each track (ripped by a different drive) to check if it was identical or not.

When the track was in the middle of the disc, or at the beginning of the disc, I got bit identical tracks from both drives. This was true if the Overread box was checked or not checked. So neither of my drives has a problem with the first track of a disc, but that is now fairly obvious since the read offset corrections are both positive!

When I ripped the last track, I got different 'bit-level' tracks with each drive and each setting of the "Overread" option. Here's a summary:

BenQ vs. Lite-On:
Overread into Lead-In and Lead-Out checked: differences found: 30 sample(s), starting at 246.706 second(s), peak: 3.051758e-005 at 246.706 second(s), 1ch
Overread into Lead-In and Lead-Out unchecked: differences found: 56 sample(s), starting at 246.8553 second(s), peak: 6.103516e-005 at 246.8601 second(s), 1ch

BenQ drive, Overread checked vs. unchecked: differences found: 3606 sample(s), starting at 246.706 second(s), peak: 6.103516e-005 at 246.7075 second(s), 2ch

Lite-On drive, Overread checked vs. unchecked: differences found: 3632 sample(s), starting at 246.7065 second(s), peak: 6.103516e-005 at 246.7075 second(s), 2ch

It might also be helpful to know that the ripped song is 4:06 long (246 seconds and change), so all the differences happened at the very end.

So, what does all this mean?? Well, it seems that I won't be able to rip the final track in a CD perfectly - no big loss, really. I mean, missing 30 samples is perfect enough! (More like 6 samples, in the case of the Lite-On. All of my tests are comparisons, and so I can only infer how many samples I am missing.) It also means that neither of my drives can overread into the lead-out. Again, no big loss. I can try to force EAC to overread, but then I get sync errors, and it looks like worse results (based on the bit compare).

If anyone wants to analyze this further, I'd be interested to see what you have to say.

For now, I'm happy with what I've found. My Lite-On drive is just over twice as fast when ripping, and I've come to believe that a smaller magnitude read offset correction is better (or preferable) to a larger one. And so now I'm not going to worry about it any more!

Thanks for your time!

edit: as per Precisionist's post following

At first:
If you want to do such comparisons, it's best to use EAC's "wav compare" feature. It tells you only a number of samples which the two rips are off or a time amount one is longer etc. Numbers of samples is the only thing that matters here.



I think zou should correct something:
You're right, read offset correction positive=>actual read offset is negative, reading starts before the beginning of the disc=>the disc's beginning is read correctly no matter if drive is able to overread into lead-in or not.

Results confuse me. I think they can only be explained by both drives being not able to overread into the lead-out. In this case a smaller read offset correction is indeed better than a large one.
For example, your LiteOn starts ripping 6 samples too early. If it could overread into the lead-out, the difference in LiteOn vs. LiteOn: overread ckecked vs. unchecked should result in 6 samples missing at the end of the last track in the "unchecked" version (if "fill up missing offset samples with silence" is unckecked), because in the drive's 'mind' the last 6 samples belong to the lead-out.

If you check overread on a drive that doesn't overread, you can get several sectors of wrong data at the end. I think that the whole last read command must be wrong : invalid adress -> null samples are returned.