DVD physical defects: where do they affect the movie?

[casejustin80]

Hi!
Suppose I know the radius and layer of a physical defect on a DVD.
Or: I know its block address thanks to ISO Buster.
Now, I must evaluate its impact on the movie (pixelates?, freezes?, etc.).
How can I know the exact moment within the movie so I don't have to watch all of it?.
Thanks in advance!

[guns1inger]

Some authoring tools can tell you where they are burning the files to, so you can re-arrange the layout before burning. However this is before the burn.

After the fact I suspect you pretty much have to watch it find out where it breaks, and not go there next time. You could try to rip the disc, find out which VOBs fail, and make an educated guess from that information as to what titles, and where in those titles, the problem will occur.

[tinker]

It can be calculated, but the problem is you will have to know exact recording strategie.
Read this.
http://en.wikipedia.org/wiki/Constant_linear_velocity
After that few math formulas should do the trick.
That will be OK for physical defects, you can see.
The other problem and a worse one is burning defects, which will show only after disc is burned and are really unpredictable.

[bendixG15]

Stick it in your DVD player, play at fast foward speed, and when it crashes, the DVD player will freeze and give you the play time. (Mine does that.) Takes maybe 3 or so minutes.

[casejustin80]

Many thanks for all these answers!.
- guns1inger: you are right, an "educated" search is what I am doing in these cases. But many times I was given a false alarm becuse of defects or artifacts created during authoring, so I need a more precise clue.
- BendixG15: unfortunately, I can't just fast-forward the disc and wait for the crash because sometimes the visual defect will be just some momentary random squares but won't crash.
- Tinker: you are thinking in terms of elapsed time since start of recording, that would be useful for analyzing aborted recordings. But my main interest is to analyze a pressed DVD.

So... suppose I know sector 1,200,000 is unreadable. And "something" tells me chapter 4 on title 2 lies between 1,100,000 and 1,500,000. Voilá!, now I know the player will step on the bad sector at about 25% of that chapter! (supposing steady bitrate and no branching). What utility would provide this data?. Woud it learn it from the IFOs?. I took a glance at IFOEdit but doesn't seem for this.
Thanks again!

[tinker]

I think IFOEdit can do it.
If you open Ifo for VTS title, like VTS_01_0.IFO, you can find out chapter ID, than VTS cell address table will give you Start Sector and End Sector for each chapter.

[guns1inger]

unfortunately, I can't just fast-forward the disc and wait for the crash because sometimes the visual defect will be just some momentary random squares but won't crash

This can also be caused by a problem during the source decoding/ encoding process, and may no come from a detectable media or authoring error. These can only be found by a visual scan of the image.

[bendixG15]

Okay, so the DVD player "freeze" solution won't work all the time, but it will work some of the time. which is more than you got so far.

[casejustin80]

Yesss!. I gave IfoEdit 0.971 a 2nd and a 3rd try (I tried PgcEdit in the meantime, another good app), and finally I found its usefulness. Can you believe I just couldn't make it do anything useful... until I found the bottom buttons were hidden by my taskbar?!?.
Ok, now my search is easier thanks to you. It will be over when I find the "source code" of the IFOs so I can read them with a homebrew program so it presents just the data needed in a convenient format.

Now I will abuse of your gentleness and will ask another question: in an old thread, a suggestion to find the layer break with IfoEdit was "open the movie ifo. Look in the lower window for 'Layer Br' after V/C Id". I did so, both with the Video_ts.ifo and the Vts_xx_0.ifo that I do know contains the break, the "V/C Id" is there but I couldn't find the LB info. I browsed every "folder" in the tree. Do I need to update my glasses? o_o
Best regards!

[tinker]

Open VTS_01_0.IFO, if that is a title you are looking at. Once in IfoEdit, click on first line which show location of your file (top of the tree). In lower window you will see chapter info.
Than under the same tree go down to (VTS_C_ADT) "Video Title Set Cell Address Table",click on that, there is the info you are looking for.

[casejustin80]

Dear Tinker:
I've finally found the LB (on top of the tree for the file, not in VTS_C_ADT Video Title Set Cell Address Table).
My 1st attempt had failed because I was analyzing a DVD with a peculiar behavior at the LB: makes a Panasonic S35 freeze forever (unless pressing Next), and Nero ShowTime (the only player I know it tells you the layer) keeps showing layer=bottom until next chapter change. Now I know the reason: the LB info is not explicitly coded into the IFO in this particular product.
Then I tried another DVD9, yes it shows the LB (yet I have some doubts as to correlation with physical location). But yet another one shows Layer Break in 15 out of 16 chapters!!!. I will make some more exploring and probably come back for more of your fine assistance.
Thank you!