Simple question on layer breaks with pgcedit/imgtool

[jamos]

When I am browsing the title for layer breaks on the original disks (and the ripped versions from decryptor) I see they are marked as 00. I notice after a burn using imgtool they are 20 (meaning discontinuty). Just wondered why the breaks are different, and does 20 cause a small skip as 00 would not? (I would think it does not matter)

Also where exactly does the break occur (at the start or the end of the sector checked)?

thanks

[r0lZ]

What do you mean by "marked as 00" and 20? Is it the cells flags value? In hexadecimal? Or is it "0 0" and "2 0"? (The second value is the representation of a second bytes containing the access restricted and VOBU still flags, not related to the layer break.)

The layer break must have the Seamless Joint flag (value 8) clear, and generally, it has also the STC discontinuity set (value 2). The other flags are not related to the layer break.

The layer break occur between the previous cell and the checked cell. The image that will be visible during the pause is the last image of the previous cell.

[jamos]

What do you mean by "marked as 00" and 20? Is it the cells flags value? In hexadecimal? Or is it "0 0" and "2 0"? (The second value is the representation of a second bytes containing the access restricted and VOBU still flags, not related to the layer break.)

The layer break must have the Seamless Joint flag (value 8) clear, and generally, it has also the STC discontinuity set (value 2). The other flags are not related to the layer break.

The layer break occur between the previous cell and the checked cell. The image that will be visible during the pause is the last image of the previous cell.
Yes to all of the above, thanks.

It seems best when remastering a dual layer output to just pick a good area where you can split a cell where there is little motion and sound to make the layer break almost non noticable. Takes a bit of work but can be done.

[frank]

...to make the layer break almost non noticable. It's very hard or not possible without smart encode!

[r0lZ]

What's "smart encode"?

[ron spencer]

I think they mean smart/lucky recording of the movie...that is making sure the scene where the layer break is is black...so you never notice anything

[jamos]

Funny thing is on all my dvd writers I never notice the break even in the middle of a action scene. They must have very fast laser tracking compared to home units or the dvd player software reads ahead and buffers. Wish home units would do the same I have a very good one though and its a barely noticable blip.

[r0lZ]

I think they mean smart/lucky recording of the movie...that is making sure the scene where the layer break is is black...so you never notice anything
Hum, to be unnoticeable, the LB must be in a black shot, and there must be no sound! Those two conditions are rarely met at the same time!

I don't notice the LB on any on my PC drives, too. I think it's not hardware related, but due to the buffering Windows does.
But who like to watch a movie on a computer monitor?

[jamos]

I think it's not hardware related, but due to the buffering Windows does.

Exactly why couldn't home dvd players buffer like a computer could, I think cost factors of adding memory to do this.

I need to try my xbox360 and some dvds and see if it buffers..:D
edit: 360 doesnt buffer dvd playback either :p

[frank]

What's "smart encode"?Real reencoding of the splitted location as good MPEG editors or Nero Vision Express do.
AFAIK you'll get closed GOPs and on the second layer video and audio packets will restart synchronous (with new Cell ID).

[jamos]

Real reencoding of the splitted location as good MPEG editors or Nero Vision Express do.
AFAIK you'll get closed GOPs and on the second layer video and audio packets will restart synchronous (with new Cell ID).
Jdobbs at dvd rebuilder is looking into doing this I beleive..or hope.

[jamos]

By splitting the last part of the cell right previous to a chapter break, I have gotten the best results as far as not noticing the layer break. the last frame pauses just for a smidge before the next chapter starts..works better than putting the break right at the start of a chapter.

[r0lZ]

You mean that you split the cell just one GOP before an existing chapter entry point? I wonder why that makes a difference.

[jamos]

You mean that you split the cell just one GOP before an existing chapter entry point? I wonder why that makes a difference.
Not sure I am guessing because the chapter points are not as frame accurate as they should be or maybe home dvd players tracking are not all that accurate?? when I leave it at a chapter break the new scene starts for a very short bit pauses then starts again. at the last gop of the previous chapter (ie new cell split) it just pauses for a tiny bit at the end of the chapter then the new chapter starts.

[r0lZ]

I don't understand why, but it's a good tip. Thanks!

[ron spencer]

Hum, to be unnoticeable, the LB must be in a black shot, and there must be no sound! Those two conditions are rarely met at the same time!

actaully I do this all the time. I know how I like to encode, etc so I know what fits where, so if I NEED to use dual layer I can pretty much ensure I get black and silence @ slayer break, but this is with home movie stuff and being anyal about how much I have recorded....a bit of a pain actually

[jamos]

actaully I do this all the time. I know how I like to encode, etc so I know what fits where, so if I NEED to use dual layer I can pretty much ensure I get black and silence @ slayer break, but this is with home movie stuff and being anyal about how much I have recorded....a bit of a pain actually
When I author Weddings that I record (ones that take more than 2 hours :rolleyes: ) I usually will put the layer break on a still title without music so it is not noticable (usually I put the reception on the second layer for long weddings).

But for merging movies tv shows etc. it is harder to dictate how and where to encode setting layer breaks before hand (unless you are barely going over 4.5 gig which then you have a wide range of places to put the layer break).

[frank]

...you split the cell just one GOP before an existing chapter entry point:rolleyes: That's commonly nonsens. The reason are the chapter points itself! When you reencode mpeg then the chapter points mostly not sitting on an I-frame of a closed GOP! I don't trust encoders, DVD-RB...
But if you shrink with DVD-Shrink, Nero Recode, then the chapter points are untouched!

Authoring programs like DVD-lab Pro index the video and then snap-in to the next I-frame. That's good but not the best.

Nero Vision Express reencodes the video and audio tracks around the LB to get closed GOPs and new video and audio packets from the beginning of the second layer! (Smart encode) The muxed packets must not overlap the LB! They have to end on L0 and restart at L1. L1 starts with a new VOB Id.
CELL Ids start at VOBU (I-frame) but it's not a guarantee for a new video/audio packet (time stamp). So cheap hardware players get a buffering problem.

[jamos]

:rolleyes: That's commonly nonsens. The reason are the chapter points itself! When you reencode mpeg then the chapter points mostly not sitting on an I-frame of a closed GOP! I don't trust encoders, DVD-RB...
But if you shrink with DVD-Shrink, Nero Recode, then the chapter points are untouched!

Authoring programs like DVD-lab Pro index the video and then snap-in to the next I-frame. That's good but not the best.

Nero Vision Express reencodes the video and audio tracks around the LB to get closed GOPs and new video and audio packets from the beginning of the second layer! (Smart encode) The muxed packets must not overlap the LB! They have to end on L0 and restart at L1. L1 starts with a new VOB Id.
CELL Ids start at VOBU (I-frame) but it's not a guarantee for a new video/audio packet (time stamp). So cheap hardware players get a buffering problem.
Problem with shrink is it doesnt do a good enough job for me..i would rather use Procoder2 or CCE SP than shrink, to resize though so I am stuck with rb-pro. Shrink doesn't do encoding but transcodes and the results are not as good.

I do not think the problem is open GOPs, as much as home dvd players not as accurate as they should be.

Frank what do you use to remaster dvds into a dvd-9 and create a layer break that works good? If I use visionexpress to do this, that means I will have to use recode to it to size right? Also I do not want to lose the existing chapters if i use vision express to reauthor.

[jamos]

I am going to try nero recode after I am done messing with the dvd (ie using dvd rebuilder and use pgcedit to manually set the layer break) to see if it closes the open GOPs then try mksifos.exe and imgburn to burn.

[setarip_old]

Problem with shrink is it doesnt do a good enough job for me...If you haven't tried DVD Shrink with both "Deep Analysis" and "AEC" selected, you may be pleasantly surprised.

You might also want to check out DVD2One (commercial software) in "Variable Ratio" Compression Mode...

[frank]

...what do you use to remaster dvds into a dvd-9 and create a layer break that works good?Buffer problem is a problem of old hardware players. An original mastered LB on DVD stutters too, if the player has a poor buffer management!
I only use Nero Recode and then PgcEdit (chapter points used). No cell splitting or reencode. My new Philips player has no LB stutter problem - buy a new one. :)

[jamos]

If you haven't tried DVD Shrink with both "Deep Analysis" and "AEC" selected, you may be pleasantly surprised.

You might also want to check out DVD2One (commercial software) in "Variable Ratio" Compression Mode...
Yes I have tried those options they do a pretty decent job but not even close to the same as using procoder2 or CCE SP :p

[jamos]

Buffer problem is a problem of old hardware players. An original mastered LB on DVD stutters too, if the player has a poor buffer management!
I only use Nero Recode and then PgcEdit (chapter points used). No cell splitting or reencode. My new Philips player has no LB stutter problem - buy a new one. :)
hmm just bought a new Sony HDMI upconverter dvd player http://www.circuitcity.com/ssm/Sony-DVD-Player-DVP-NS75H-/sem/rpsm/oid/146242/catOid/-12873/rpem/ccd/productDetail.do, I am thinking it is a issue with using the HDMI cable as that is known to slightly delay video audio signals. My older sony player using just video out does not stutter so who knows?

[jamos]

hmm preliminary tests show that using Nero Recode using advanced analysis and slow recode (probably uses smart encode like Frank says) with no compression to create the image file causes no pauses or breaks in playback on the layer break burned then with imgburn. So it may be after all DVD-Rebuilder not closing its GOPs properly or something to do with its mastering. On my sony it plays back flawlessly right by the layer break. Recode put the layer break in the correct spot also right at the start of a chapter over 50% of the dvd and in a correct divisable by 16 sector (it pads it some way). Imgburn burned the .nrg flawlessly.

I will test a couple other remastered titles through this process. I do not think mkisofs.exe is doing this (using the latest version that does not need the .dll) as I am thinking it is dvd-rebuilder but really can not pinpoint that it is. Has anyone else used the latest version of mkiosfs.exe and done dual layer disks and see if it pauses a bit on playback at the layer break?

[jamos]

I can confirm after using recode2 with the above method on another title the pause is removed also. It is probably dvd-rebuilder but who can tell? I am bypassing using pgcedit for setting the layer break and creating the iso. I guess my next test should be using recode2 to generate a folder instead of a image file and use pgcedit to set the layer break then burn with isoburn to confirm that it is not pgcedit.

[r0lZ]

Thanks for your tests, jamos. As you can imagine, I am very interested by this thread!

[jamos]

Ok output the same title to folder using Recode2 and then set the layerbreak with PGCedit then burned with imgburn. There is a noticable pause at the layer break. Recode must be doing something to the layer break (syncing etc.) when it creates the image file.

[r0lZ]

Could you have a look at the cell flags used by Recode? Is the STC discontinuity flag set? Is it a change in the VOB ID?

[jamos]

ok I will look into that.
First nero doesnt seem to pad to do the layer break. but the layer break is ok.
first shot is nero
http://img230.imageshack.us/img230/3366/nero1ex.th.png (http://img230.imageshack.us/my.php?image=nero1ex.png)
Second is pgcedit
http://img109.imageshack.us/img109/5273/pgcedit6ll.th.png (http://img109.imageshack.us/my.php?image=pgcedit6ll.png)

[jamos]

here is what the layer break looks like from the nero created DVD (acutal dvd burned):
http://img66.imageshack.us/img66/7659/pgcedit0hz.png (http://imageshack.us)
But before I burned it with imgburn, this is what imgburn reported where the break would be im sure that is the absolute sector
http://img455.imageshack.us/img455/2992/imgburn1tm.png (http://imageshack.us)
Looks ok and it looks like Nero splits the cell where it needs to when it creates a dual layer image.

[r0lZ]

Well, I see that recode doesn't set the STC discontinuity flag and doesn't change the VOB ID. Exactly like PgcEdit. Therefore, it must be something in the VOB files.

I don't understand why ImgTool displays this information. Anyway, I wouldn't use it to burn, especially when it's a DL DVD.

Could you confirm that you have burned both ISO/NRG files with ImgBurn?

Thanks for your help. I will do some tests, too, but I don't have recode2! Maybe I'll install a trial version...

[jamos]

Ok after finding out what nero really does is just create a new cell randomly where a layer break is legal (ie cell 42 is a newly created cell in the middle of a action scene and not the cell I was browsing before creating the image) I browsed the dvd to THAT spot and indeed a very short pause does occur there as did the output from pgcedit at its layer break (but with pgcedit i could control where).

So it is not pgcedit. the pause is shorter though using recode2 to master it still than without using it so rebuilder is not doing something correct with timing or whatever.
So Rolz, pgcedit is fine..looks like just a normal thing with dual layer dvd playback.:rolleyes: I think i have a older sony that handles the breaks better, and I will experiment with that player tommorow (new player may be going back to circuit city).

So what I will do now is create a folder with recode2 to make sure all gops are closed then create the layerbreak with pgcedit and burn with imgburn.:p

[jamos]

Well, I see that recode doesn't set the STC discontinuity flag and doesn't change the VOB ID. Exactly like PgcEdit. Therefore, it must be something in the VOB files.

I don't understand why ImgTool displays this information. Anyway, I wouldn't use it to burn, especially when it's a DL DVD.

Could you confirm that you have burned both ISO/NRG files with ImgBurn?

Thanks for your help. I will do some tests, too, but I don't have recode2! Maybe I'll install a trial version...
You wouldnt use Imgtool to burn?? you mean you wouldnt use Recode to create the image file right? I agree with you there..putting the break just randomly the way they do it is bad.

And ImgTool is right 2053360 is the absolute sector - 656(start of VTS_01_1.VOB) = 2052704 is exactly where the layer break was set.

[r0lZ]

Well, I use PgcEdit to select the layer break cell and to create the ISO. ImgTool Classic is only a frontend over mkisofs, like PgcEdit. Therefore, what can be done with ImgTool can also be done with PgcEdit, but PgcEdit offers more possibilities.
I have never used ImgTool Burn (based on Nero) because... it is based on Nero!


The LB cell must have the seamless playback clear, which means that a pause will occur.
I don't think it is possible to create a shorter LB in some conditions. The duration of the pause depends on your hardware, your media, and the quality of the burn. It may be shorter or longer also if its position is near or far of the outer edge of the DVD, but I'm not sure.
My Sony pauses approx 2 seconds, even with commercial DVDs, while my KISS (a computer based standalone player) pauses less than one second with burned DVDs. There are also some large buffers on some recent and relatively expensive players (and, of course, on all software players) to avoid the pause completely.

Theoretically, the LB cell must have the STC discontinuity flag set, and, according to mpucoder, it must start with a new VOB ID. However, I have seen many commercial DVDs with only one VOB ID for the whole movie, and no STC discontinuity at all.
Anyway, since the STC discontinuity flag reflects the way the streams are multiplexed, it is probably useless to force it on the LB cell with PgcEdit.

[jamos]

Well, I use PgcEdit to select the layer break cell and to create the ISO. ImgTool Classic is only a frontend over mkisofs, like PgcEdit. Therefore, what can be done with ImgTool can also be done with PgcEdit, but PgcEdit offers more possibilities.
I have never used ImgTool Burn (based on Nero) because... it is based on Nero!



If I said imgtool I meant imgburn, sorry.

[jamos]

Theoretically, the LB cell must have the STC discontinuity flag set, and, according to mpucoder, it must start with a new VOB ID. However, I have seen many commercial DVDs with only one VOB ID for the whole movie, and no STC discontinuity at all.
Anyway, since the STC discontinuity flag reflects the way the streams are multiplexed, it is probably useless to force it on the LB cell with PgcEdit.
Yes setting the flag before running it thorough nero does nothing, nero ignores it because nero will not pad (it just splits a cell). But running it through nero just to recode it does close gops then outputting to a directory (file mode) allows me to use PGCedit to set the layer break and burn with IMGburn.

Only other thing I could try is to rip to a directory a img that was padded with mksisofs.exe and then use recode2 to recode it to see if it picks up the discontinuity flag and maybe will multiplex it correctly (im thinking probably not)?

As to commercial dvds yes I do notice a slight pause on many of my home dvd players.

[r0lZ]

In my understanding, a new cell always starts with a closed gop, unless that cell has been cut by a tool like VobBlanker, in which case it should be a broken gop. But I may be wrong.

[bigotti5]

...a new cell always starts with a closed gop, unless that cell has been...

No - cant be - that would require to set chapters at encoding or force the authoring program to reencode GOPs after setting cells

[r0lZ]

OK, in this case, is it possible that the open gop at the beginning of the LB cell forces the player to go back to layer 0 to read some pictures? I suppose it's the case if you jump directly to the LB cell, but if the PGC is read sequentially, the last images are kept in a buffer, right? So, how do you explain that the pause is longer in some cases?

[bigotti5]

..gop at the beginning of the LB cell forces the player to go back to layer 0 to read some pictures..

no - these B-Frames are discarded

imo it is a result of muxing and seamless flag does not fit
if the flag is set by pgcedit as NSM the muxing itself is not changed, so there are audio packs in the first cell of layer 1 belonging to last cell of layer 0

[r0lZ]

I agree, but though this can cause a little sound desynchronisation, I don't understand why the pause should be longer.

[bigotti5]

Maybe mpucoder can clarify

[jamos]

OK, in this case, is it possible that the open gop at the beginning of the LB cell forces the player to go back to layer 0 to read some pictures? I suppose it's the case if you jump directly to the LB cell, but if the PGC is read sequentially, the last images are kept in a buffer, right? So, how do you explain that the pause is longer in some cases?
Delay Seems shorter when i close the cell I am putting the layer break on. Vobblanker says the cell is open when i split it. If I put the break at that new open cell I get a noticable longer delay, than I would if I reencoded it with recode2 and subsequently closed the cell.

[jamos]

Follow up to putting layer breaks on Chapter Start positions. Sometimes that works ok, but in many instances the chapter (cell) start points are actually several frames after a scene starts. (ROlz this is why I was having a scene start then pause then resume because the chapter start was not exactly on the scene transition). I have checked several pressed dvds and find this is the case often. Also many layer breaks do not occur at chapter breaks on pressed dvds (most occur where there is a pause in action). Therefore it is not always best to assume that putting a layer break on a chapter break will result in a good pause between one scene and another when your dvd player reaches the layer break. It is best to preview the cell prior to where your layer break is to occur and make sure that a scene transition occurs (ie last cell of previous chapter is a previous scene) and a pause in action and mainly DIALOG occurs.

If you need to change the layer break, find on the dvd where the suggested layer break occurs by using PGCedit to burn (do not actually burn though). then from that cell go a small ways before or after the recommended chapter break point (PGCedit will actually tell you the relative sector range that the break can occur in) using vobblanker and split the cell using cells then split on the cell you want the layer break to occur (if you get a this cell is open/broken message then you should reencode the dvd to close the vob after blanker is finished with it). Then when you choose PGCedit to choose a layer break again you should have a better alternative choice to choose from.

[r0lZ]

I have never noticed a chapter point that is not exactly at a scene change. Strange, since it is possible to place it accurately. Since the commercial DVDs are very expensive, I think it's not admissible!

I agree that there are many layer breaks that are not placed at a chapter point. It is often easier to find a still shot within a chapter than at the end of a chapter. PgcEdit tries to locate such non-chapter cells to place the default LB position. However, in some cases, it's really not easy.

Thanks again for your investigations. But honestly, I think that your "cut" method is too complicated and time consuming for the vast majority of users.

[jamos]

I have never noticed a chapter point that is not exactly at a scene change. Strange, since it is possible to place it accurately. Since the commercial DVDs are very expensive, I think it's not admissible!

I agree that there are many layer breaks that are not placed at a chapter point. It is often easier to find a still shot within a chapter than at the end of a chapter. PgcEdit tries to locate such non-chapter cells to place the default LB position. However, in some cases, it's really not easy.

Thanks again for your investigations. But honestly, I think that your "cut" method is too complicated and time consuming for the vast majority of users.
Title that has chapter break not at a scene change for example: Two Towers Extended Version Disk 1 Chapter 30. It's not common though you are right, but can happen.

Most users will not care as long as that the layer break is not during dialog I agree, but splitting cells is pretty easy with blanker and takes about 4 minutes on my computer to do (recoding is optional). Most user will probably never need to worry about this unless they are compiling lets say tv episodes from two disks to one dual layer..thats where they will care:p I believe that now that dual layer media is becoming more inexpensive that layer break issues will start to be more of a issue with users in the future. I know on CD freaks we get many questions on it.

I have rarely seen non chapter break cells in a movie except for where the original layer break was at.