Most recent NU drives supports not only PI/PO but also Jitter measurements. After using the latest Nero CD-DVD Speed v2.97.4beta we got scans ,from already measured DVD recordable discs with SA300 system, of various discs.

* Reference Scans

MCC 4X @ 4X with BTC 1108IM

* NU DDW-082 scan @ 8X (CAV) reading speed



* NU DDW-082 scan @ 6X (CAV) reading speed



* NU DDW-082 scan @ 4X (CAV) reading speed



- Some thoughts

* The reading speed mainly affects the sampling rate and probably accuracy. The 4X (CAV) reading speed, returns the highest number of samples with average scanning interval 8.06ECC, very close to the specs (8ECC).

* The PI error rate trend seems to be more or less the same at all three reading speeds. The good news is that despite the selected reading speed, the PI error rate trend line at the end is present, even at different absolute values compared with SA300. The bad news is that the drive didn't reported (at any speed) the increased error rate at the inner area of the disc as SA300 did.

* The PIF error rate is low especially at the end, which however comes in direct conflict with SA300.

* No POF errors reported from the drive (not to sure if can report such errors after all).

(in reply to emperor)

MCC 4X @ 4X with BTC 1108IM Jitter Tests

* Reference Scan



* NU DDW-082 scan @ 8X (CAV) reading speed (no modification)



* NU DDW-082 scan @ 6X (CAV) reading speed (no modification)



* NU DDW-082 scan @ 4X (CAV) reading speed (replaced left axis with right one)



- Some thoughts

The Jitter as reported from the NU drive seems to comply with the SA300 series. The reading speed does affect the max and average values, the 4X gave the highest average, while the 6X the max absolute values.

(in reply to emperor)

Just a quick question ... are the SA300 scans carried out with a reading speed of 1x or does the "@ 4x" refer to the reading speed ?

(in reply to emperor)

I just got the info so forget about that last posting ... ;-)

(in reply to JeanLuc)

All SA300 scans are at 1X, the "@4x" means burned at 4X

(in reply to JeanLuc)

I see ... I asked because I thought that the appropriate ECMA document states that PIPO measurements should be carried out at 1x speed.

(in reply to emperor)

Yes 1X, but also testing equipement manufacturers allows 2X with some testers...

(in reply to JeanLuc)

PI/PO are causal measures, i.e. they don't represent errors on the disc - as we know.

As such, it is IMHO, more useful to scan at speed that the disc is going to be used at AND/OR using a speed that (based on testing) gives a rough estimate of readability on other drives.

Usually higher scanning speed (as demonstrated by Emperor) can result in hopefully more generalisable PI/PO results across various drives. Scannint at too low speed (using a superior reader) can give falsibly too low error results, considering the actual day-to-day read speeds AND the inferiority of many other readers.

Now, about NuTech/Philips drives:

It is quite disturbing, that the minimum scanning interval is over 8 ECC blocks.

This makes it impossible to scan PO values per 1 ECC block AND calculate true PiSum8.

If the scanning interval is 8 ECC block or more, then the drive reads as follows:

1st read sample: blocks 1 - 8
2nd read sample: blocks 9-16
3nd read sample: block 17-24
etc.

OR WORSE (Philips has a scanning interval of 32 ECC blocks currently)

For true PO/1ECC block and true PI/ _running_ 8 block consecutive window one needs the drive to read:

1st read sample: blocks 1 - 8
2nd read sample: blocks 2-9
3nd read sample: blocks 3-10
etc.

Using this latter read method (something which LiteOn drives almost upport), one can actually calculate PO values per 1 ecc block and running PiSum8 window.

I wonder if this "feature" can be fixed on the Nexperia chipset drives?

Also, I'm really itching to get Nec/Pioneer onboard with CD DVD Speed / DVDInfoPro. We need more chipset/drive mechanisms for testing.

regards,
halcyon

(in reply to emperor)

Halc, i also have those questions myself, we will continue posting test results...

(in reply to Halc)

Halc, "PO" for you is PO1 or PIF, right ?

As for the reading speed ... personally, I think that some 50% of all recorded (burned) DVD's will make their way into a standalone player that reads them at 1x speed so IMHO, scanning at 1x is a valid methodology.

Of course, there is a high probability that reported PIPO errors will rise with higher reading speeds as we have seen many times before (even with K-Probe) - the impact of present "hardware" disc errors upon the drive's error correction circuitry includes read/rotational speed as a parameter. Maybe scanning at 4x CLV should be added to the CATS procedure as a sensible addition.

Most PC drives will slowdown when the PI/PIF values become too high an re-read at lower speed ... so mostly, the disc is readable at last. Video playback, on the other hand, might be "choking" on a PC drive if this happens (assuming no speed limiter like CDBremse is active).

(in reply to emperor)

In fact, most DVD players in the future (if not already) will use 2x or higher reading speeds. This is due to anti-skip, FF/RW, etc.

The validity of reading discs at 1x is for the reason of testing the disc and NOT the drive!
In this case, even 0.1x reading might be appropriate. Unfortunately, there is no commercial drive able to run at this speed.
Besides, the required amount of time, in this case, would be anormous.

Higher reading speeds are necessary for testing the drive, not the media.
Taking this into account, it is no surprise to me that some drives, as reported by our emperor lately, report PI/PO errors correctly only at higher reading speeds.

This argument can be used for supporting the use of cats and other related equipment for checking the quality of a disc with repsect to a particular drive. Otherwise, the results seem to be indicative more of the reading abilities and optimizations of a particular reader, than the quality of the media/recorder combination.

(in reply to JeanLuc)

Actually, even testing at 1x is also testing the drive.

There is no way to test the disc and only the disc, unless one uses electomicrophotography or some other non-rotational imaging technique. At least not for indirect measures like DC jitter and so.

Causal errors are not, of course, measure of what is on the disc itself. They are not disc errors nor disc characteristics.

Why do I think testing at various speeds (including highest speeds) is useful?

Because:

1) I don't believe we will ever be able to measure the disc (and mostly only the disc) alone with consumer gear.

Even if we were able to do it, it's important to remember that errors are not on the disc.

The PI/PO scans done with CATS are a combination of what number of errors does the Pulsetec drive see when scanning at the selected scanning speed (1x or 2x) using the disc under scanning? Change any of those three variables: pulsetec/calibration, scan speed or disc, and the figures will change. That's why they are causal measures. In fact, other scan parameters are a fourth variable and there could be more, I don't know of.

2) If our aim is to measure _compability_ in other drives, overall probable _readability_, then we need to also consider the worst case scenario.

The worst case scenario is more likely at higher rotational speeds when the jitter that the drive sees increases, along with some other lower level indirect measures.

Of course, it is possible to get "artificially high" measures by scanning with the worst reader at 8x read speed.

This won't probably tell us too much about the overall readability by itself. We need various scans from various drives at various speeds. Those combined will probably tell us a better picture of what the disc compatiblity/readability is going to be like. However, if a disc reads within specifications of error rates at 8x in various drives, then it's highly likely it will remain compatible/readable in most drives (excluding dvd+r/bit-setting problems for now).

But scanning at only 1x (especially with a drive that has superior jitter tolerance) will most likely result in "artificially low" results of PI/PO (i.e. a number of errors that only a very small minority of drives will be able to see, because they are worse readers AND because they read at a higher speed).

I do however think you are right that the lower the speed, the more we are testing the disc and less the drive. Or at least, that is a fair assumption (hasn't really been experimentally proven as of yet).

Still, the point is:

What are we trying to find out and which scans will give us decent estimates of that?

- Overall compatibility/readability estimates of a certain burn -> Scan at various speeds (including 8x and higher) in various drives
- Disc/burn quality of a certain disc type/burn (in a certain burner) -> Scan at lower speeds in various drives (in order to not to stress the drive too much)

That at least is my working hypothesis as of know. Of course, I'd need a CATS scanner and a few hundred tests to prove it, so that's why it's merely a hypothesis.

regards,
halcyon

(in reply to sp)

When readers run at over 16x, scanning at 1x on a device which is known to always reproduce statistically significant results, leads essentially to the proof of this proposition: 1x reading on a well calibrated device (kat) is able to test the quality of the disc.

There are two more ways to prove this. The first is to check the same disc with more than one drive. (This is what media makers frequently do in order to check the reproducibility of their own tests.) The other is that drive makers use their own drives on prerecorded (and/or premanufactured) discs instead. They rely less (if any at all) on special equipement.

(in reply to Halc)

Err... can you rephrase? I don't understand, sorry.

The facts as I've understood them for dvd testing are as follows:

1) Indirect measures are not true characteristics of the disc. They are ALWAYS the measure of both the disc and the reader. Of course, at slower reading speeds the drive does not have to stress itself as much and the true disc characteristics show through more easily when looking at indirect measurement data.

2) For DVD Indirect measures include (but are not necessarily limited to): asymmetry, reflectivity, push-pull (tangent.), radial noise, tracking signal, dc jitter and of course PIE/POE error rates.

3) For DVD true disc characteristics include: Track pitch, scanning velocity, information diameters, birefringence, substrate thickness, index of refraction, etc.

4) There is no "DVD metric standard reader" as there is one for CD measurement. As such, the Pulsetec drive is based on averages from various manufacturer's input. Is is not "the ultimate in drive performance" that all other readers/analyzers should aim for. It is just a very reasonable average. The best in the industry at the moment.

As such, regardless of the reading speed, indirect measures are always measures of both disc low level characteristics and the reader (even in CATS/Falken with current Pulsetec drives).

best regards,
halcyon

Refs: DVD Testing Principles and Practices, Gerger. S., ODS 7-8/1998
Universal Disc Measurement, ODS tech papers,
Replication & Duplication, ODS News, 1-2/2004
How to interpret the CATS test protocol, AudioDev, 2003

(in reply to sp)

To test a disc you need a rotating device.
There is practically no other way to obtain results within a bounded timeframe.

(in reply to Halc)