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  #1  
05-01-2012, 06:20 PM
moxiecat moxiecat is offline
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Today I ran into a strange situation. I burned three DVDs in a Pioneer drive (one of the older, good ones) using the same authoring process I've been using for years.

When I tried the DVDs in two set-top DVD players, all three discs played with errors: freezing at the same points in the video, freezing when jumping from one chapter to the next, etc. These are two DVD players that I use all the time and have no reason to believe they aren't working.

Then I tested out the discs to see what was wrong with them. I tried (using a different drive than the drive that burned the discs):
- Copying the Video_TS folder from the DVD to the hard drive
- Running the DVD through CD Check
- Playing the DVD on the computer via Power DVD, through the same "bad" spots
- "Prescanning" the DVD on my USDM duplicator tower (a reading process the duplicator tower uses to determine whether a disc can be successfully duplicated)

The discs passed all four of these tests with no trouble whatsoever! The only item that CD Check found is called "For at least one file only file readability was tested because no valid hash file was found (code 54)"--but I have no idea what that means, and CD Check also noted that no actual issues were found on any of the discs.

So do the discs have a problem...or not? If there was no problem, then why would two completely different DVD players--a Sony and an LG--have trouble reading the same spots on the discs? And if there ARE problems at those spots, why didn't any of these programs/processes find them?

Does anyone have a clue as to what might be going on? I am going crazy trying to figure out if these discs really do have playback problems--and how to determine that, when none of the regular programs can find them!
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  #2  
05-01-2012, 07:06 PM
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Quote:
  • Copying the ... DVD to the hard drive
  • CD Check
  • Playing the DVD
  • a reading process the duplicator tower uses
None of those are overly useful tests.

Those are what you'd refer to as a layman's test. Playback and non- bit-for-bit reading of an optical disc can be misleading. CD players and DVD players will generally just play a disc with a video/audio booger, as opposed to forced re-reads. A lot of hardware and software copying tools will do the same.

The reason some hardware sees an error, and some do not, is generally due to differences in quality and/or age of the reader/burner devices.

To actually test the condition of the disc, you'd want to use some more advanced tools:
  • ScanDisc (surface test) in Nero DiscSpeed 4 --- no, not "that" Nero.
  • Benchmark (TRT scan) in Nero DiscSpeed 4.
  • Disc Quality (PIE/PIF/PO testing**) in Nero DiscSpeed 4, though understanding this is not necessarily useful information, and works with few drives.
** Important: Scanning media should be done on an idle computer, with nothing else running. Not even background/phantom processes, unless required by the core OS. Therein lies the problem with most amateurs who scan media and forge false ideas on what is or is not a quality disc. It's rather easy to create lots of weird results. Even on an ideal system, the information may only have limited value. It has to be interpreted, as opposed to literally read. The numbers alone mean zilch.

Anyhow, there's really no evidence yet to either blame the media, nor to clear the players of wrongdoing.

Ask yourself this:
  • Are the two players the same age?
  • From the same manufacturer? (Not the brand, but the manufacturer!)
  • Under the same humidity and temperature? Humidity affects the playback quality of an optical device! You'll probably notice discs may skip at certain times of the year more than others. It's currently the beginning of the wet season in North America.
  • If you equally "use [these players] all the time", then there's a very good chance they're burning out at the same time. I've done that quite a bit myself. DVD players tend to only work for a few thousands hours max (2-5 years), and then die a slow death. The ability to read burned RW media goes first, followed by write-once burned media. Then pressed media goes last.
I'm also assuming that you're using quality media?

A lot of people adore Taiyo Yuden, but that's not always wise. As decent as it is, there are know readability issues with the discs in a small percentage of players. It's a mix of issues that causes it, be it age or whatever else. Mitsubishi discs have no such problems. A DVD player has to literally be near-useless to not read a MCC/MKM disc, as they tend to play/read almost as perfectly as pressed media, due to the metal AZO dye.

Old pre-"F" Ritek were common sources of issues, too. Since Ritek switched to oxonol (Fuji dye), this isn't really an issue anymore.

More on testing media here: Software for Media ID and Quality Scans [DOWNLOADS + GUIDE]
And the blank media reviews here: http://www.digitalFAQ.com/reviews/dvd-media.htm

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  #3  
05-02-2012, 07:25 AM
moxiecat moxiecat is offline
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Thanks! I downloaded from your DiscSpeed link and ran one of the discs through the three tests you mentioned. Great tool.

First, the Scan Disc test was 100% green/good, so I won't bother posting the graphic.

Here is the Benchmark test. I can't find any instructions as to what this means, so hopefully someone will be able to help.

benchmark.png

And here is the Disc Quality test. I did find online where a disc shouldn't have more than 280 PIE max per DVD specs (this disc has 1081) or more than 4 PIF max (this disc has 270).

Although I don't quite know how to read these graphs, I do see that both of them seem to go haywire and change sharply around the 3.25 mark on the disc. That would fit with the "freezing" spot I encountered on that particular disc, which occurred around 3/4 of the way through the video.

So what does it mean that the Scan Disc test passes with flying colors, but these other two tests show errors?

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I am now burning the same project via a different Pioneer burner and running the disc through the same three tests, just to see what happens. I'm thinking that the first burner is having problems. Also, while I still think that my two DVD players are fine, it was quite humid here yesterday, and maybe they were just overly sensitive to the errors that DiscSpeed found. (Just a theory. :-)


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  #4  
05-02-2012, 07:50 AM
moxiecat moxiecat is offline
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Just noticed the "disc quality" score for that first disc was a big fat 0! Ha!

The results seem to be drastically better for the second disc, burned with a different burner. Again, the Scan Disc result was 100% good.

Benchmark - and can someone explain what the green line and yellow line are indicators of?

benchmark-2.png

Disc Quality - now I've got an acceptable PIE max of 161 and a PIF max of 11 (which is higher than the "4" that is supposedly recommended, but maybe that's not too important).

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The disc quality score on this disc is 94.

So I guess the lesson learned is that drive #1 is dying and needs to be replaced. Other thoughts on these tests are most welcome.


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  #5  
05-02-2012, 09:39 AM
moxiecat moxiecat is offline
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I looked at the excellent thread: Verify after burning with ImgBurn? What's a TRT scan? PIE/PIF?
and have a few questions on these graphs and what constitutes a good disc.

Our friend Lord Smurf posted graphs that are similar to the graphs from my "good disc" and writes in that thread: "This scan doesn't really tell me anything different than the TRT, in a general sense. That is, that this disc is good. All of the values are within norms, and there shouldn't be any playback or reading errors when the disc is played or read. Jitter is good, PI failures are good, PI errors are okay."

Questions:
1.) Do you know from the TRT that the disc is good because the green line slopes upward continuously and the yellow line remains flat? Is that the mark of a good disc?

2) "All of the values are within norms" (from the Disc Quality graph). What are the norms that you are using for PIE and PIF? And what number is acceptable for the Quality Score?

Thanks for your help with this.
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  #6  
05-02-2012, 10:58 AM
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The first graph in post#3 -- the one that look like our stock market from 2000-2010 -- reveals a fubar disc read. While this can point to issues in the reading drive, let's quickly unscientifically assume the drive is fine. This would show a disc that is hard to read. As such, it's going to give problems in devices. The errors are on the outer 1GB worth of the disc, which is a common side of a bad disc/burn.

Disc jitter is supposed to be 8% or less. Jitter of 9-12% may be tolerable, but is undesirable. That huge pink section on your second graph in post#3 essentially means the disc is screwed. The burned data is way, way, way out of spec. I'd put that disc right in the trash. This also assumes the Optiarc AD-7206S is capable of giving reliable scan results, which I'm not sure if it does off-hand. But given the three problems thus far (skips in players, bad TRT, and now a bad jitter report), I'd more readily believe in a flaky disc.

The TRT is post#4 is what a TRT scan should look like -- a smooth uphill line.

The thing to remember most about PIE/PIF/PO/jitter reporting is that it's not so much a test of the disc, as it is the report of how the disc is interacting with the drive, based on data sent from the drive. Some drives are rather lousy at reading media, and most drives misreport values to a certain extent. So that's one reason you have to evaluate and interpret the data, as opposed to reading literal information.

(In some ways, it's comparable to the Bible, where literal reading shows that man is 5,000 years old. However, read with scientific scrutiny, it contains very little useful information on the origin of our species, or of the universe. Taken into context with other archaeological evidence, it does nothing but confirm our presence and an attempt by our ancestors to understand the universe. And there very much is a religious cult-like following surrounding DVD media testing amongst some amateurs, who insist on truths and facts that simply are not there in the graphs.)

The disc "quality score" is entirely useless. Don't even bother reading it. It's a weak attempt to help novices interpret data, but it generally does nothing more than mislead them further.

I don't see any evidence of burner #1 dying yet. Maybe if it had issues reading RW or -R/+R discs, reading/writing CDs, or reading/writing other non-TY blanks, then I'd jump to a quick conclusion of drive=bad. However, that all said, I'd probably still look to either replace the drive, or even just add another one. These days, with drives costing $25-40, depending on store, it's not worth the effort to re-burn media, or to waste blanks.

It may be some sort of variation in the batch of media you currently have. Understand that a "batch" is anywhere from 10,000 to a million discs, depending on manufacturer. And then this particular burner does not properly calibrate to the needs of the disc. Generally speaking, that's not good -- the disc is to blame here. Consistency is tantamount in optical media. Blank CD/DVD/Blu-ray media is supposed to fit a spec, and when it doesn't, you have problems.

I've never been a fan of burning TY DVD-R in Pioneer drives. I've seen this happen before, as far back as 4x and 8x TY DVD-R blanks, when used in Pioneer drives. So for me, this isn't anything unusual or unexpected.

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  #7  
05-02-2012, 11:05 AM
moxiecat moxiecat is offline
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Thanks--only one more question before I put this to bed...

What are the values you use to determine good PIE and PIF?I know that the spec for PIE is max 280, but some people online want it to be 100 or less. I've seen that PIF max can be anywhere from under 16 to under 32--so I'm particularly confused on that point.

And one last, LAST question!....if you run the disc through the benchmark TRT check and get that smoothly sloping uphill green line, is that a decent reason to conclude that the disc is probably OK?

Thanks again for your help.
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  #8  
05-02-2012, 11:22 AM
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Think about going to do the doctor. He/she looks on the outside, on the inside, and then takes fluids for further testing. Sometimes you have to have MRI, x-ray, CAT, PET, etc. Each test that passes is simply one more sign that you're healthy. Or in this case, each successful test of a disc tends to infer it's healthy. A single test is not a test, but several tests together can give an acceptable picture on condition. A sample of one is not a sample at all.

From a general sense, I would agree that a good TRT tends to point to okay media.

I don't have a rigid number system for determining what is good/bad. For example, if you scan the same disc 2-3 times in the same drive, you'll get 2-3 different results. Even TRT can be this way. What you don't want do is violate the DVD specs, which means having more than 280 sum8 PI errors, or average PI failures above 4.0. (Honestly, 4 for PIF is ridiculous, and 1 is what I'd consider a max.) An ideal situation is to get the values as low as possible. Lower is better for PIE, PIF and jitter.

This isn't something that can be learned overnight or even in a single read. You're getting into optical media theory now.

For example, software-based tests don't analyze reflectivity, which is a primary factor in media quality. That requires optical measurement hardware, or an ability to measure with secondary means. For example, Taiyo Yuden reflectivity is inconsistent, because of the dye they use. It's not bad, but it's not as good as metal AZO. Most TY fans are unaware of this.

Attached is the ECMA-337 specs that outline acceptable values for discs. It's a heavy read.


Attached Files
File Type: pdf ECMA-337 2e Optical Media Specs.pdf (2.97 MB, 1 downloads)

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