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Old 25th April 2006, 01:17   #1  |  Link
jamos
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PGCedit Seamless layer break discussion..

I am a bit confused. looking at the dual layer images created from PGCedit 7.0 it seems the discontinuty flag is not set. Is this normal as I see other programs such as nero sets it?
Image of a iso from PGCedit


note: I can manually set the discontnuity flag, but that kind of defeats the purpose of letting PGCedit choose the layer break doesn't it or does it really not matter?

Last edited by jamos; 1st May 2006 at 11:07.
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Old 25th April 2006, 05:12   #2  |  Link
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The STC discont does not need to be set unless there is an actual discon in the system time clock. You would typically see this happen when a VOB ID changes (cell 36 should have been a 10), and in other cases.

For the LB, it is important that the cell is marked as seamless. I would suspect that the orig LB was on 36 but you manually moved it to 34. It is correctly set up to break at cell 34.

As for Ner0, I wouldn't trust it at all.

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Old 25th April 2006, 11:34   #3  |  Link
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Quote:
Originally Posted by blutach
The STC discont does not need to be set unless there is an actual discon in the system time clock. You would typically see this happen when a VOB ID changes (cell 36 should have been a 10), and in other cases.

For the LB, it is important that the cell is marked as seamless. I would suspect that the orig LB was on 36 but you manually moved it to 34. It is correctly set up to break at cell 34.

As for Ner0, I wouldn't trust it at all.

Regards
Thanks, that makes much sense!

No the reason 36 is not a chapter cell is because this is a merged DVD I get this because of the extra vobs it adds when I merge them (ie start of a new vob has to be a new cell) I did not know that it should be a 10 though I manually changed it back to 8 guess I should of left it a 10 (although it plays fine so maybe I am ok).

Last edited by jamos; 26th April 2006 at 00:18.
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Old 25th April 2006, 22:00   #4  |  Link
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I suppose that, theoretically, it is better to have a STC discontinuity in the VOB files at the LB. But if you select a cell that has not the STCD flag set, I don't think it's a good idea to force it, since it will not reflect the reality. Anyway, I haven't read reports on playback problems when the STCD flag is not set. Maybe the pause is a little bit longer to let the player resynchronize the audio and the video?
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Old 25th April 2006, 22:50   #5  |  Link
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Quote:
Originally Posted by r0lZ
I suppose that, theoretically, it is better to have a STC discontinuity in the VOB files at the LB. But if you select a cell that has not the STCD flag set, I don't think it's a good idea to force it, since it will not reflect the reality. Anyway, I haven't read reports on playback problems when the STCD flag is not set. Maybe the pause is a little bit longer to let the player resynchronize the audio and the video?
In all the pressed dvds that I have looked at the flag is not set at the layer break, it looks like the above screen shot. As far as the pause I have not noticed any difference either way. I would say unless the break is at the starting cell of a new VOB that it should not be set.

Last edited by jamos; 25th April 2006 at 23:11.
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Old 25th April 2006, 23:01   #6  |  Link
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Thanks. That confirms what I've seen, and that PgcEdit is not faulty.
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Old 25th April 2006, 23:38   #7  |  Link
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Quote:
Originally Posted by r0lZ
Thanks. That confirms what I've seen, and that PgcEdit is not faulty.
Don't you love when I answer my own questions..
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Old 25th April 2006, 23:48   #8  |  Link
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Yeah!
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Old 26th April 2006, 00:10   #9  |  Link
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Also looking at the Phantom Menace DVD they have a layer break on a new VOB cell. Discontinuity is set at the layer break. I would assume that is the best way to do a layer break as Frank stated. But, for a break that is NOT the first cell of a VOB, discontinuity should be set off.

Last edited by jamos; 26th April 2006 at 00:18.
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Old 26th April 2006, 00:46   #10  |  Link
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Yes, it's a good method, also recommended by mpucoder.

Though it is true that a cell at the beginning of a new VOB must have the STC flag set, I'm not sure a cell that is not at the beginning of a new VOB cannot have the STC discontinuity (and its flag.)
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Old 26th April 2006, 02:07   #11  |  Link
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Just look at the SCR values, if they do not reset (or change by a large amount in either direction) then the flag should not be set - and is unaffected by the layer break. In general cells within a vob are continuous and seamless, a new vob should reset the clock (and may be seamless or not).
I've been researching the "seamless layer break" and seen recomendations to make the layer break either between cells of the same vob or between seamlessly joined vobs to yield a smooth playback. Jim Taylor, in DVD Demystified, says "A cell cannot be spread across both layers of a disk. This rule is also supposed to apply to a pair of cells intended to play seamlessly, but so-called seamless layer changes can be made by violating this rule." (2nd ed, p 264)
I believe he is trying to say that the rule is "a pair of cells intended to be played backed seamlessly should not be spread (or split?) across both layers" and that by violating this rule, ie making the layer break between 2 cells intended to be played back seamlessly, a seamless layer break will result.

Last edited by mpucoder; 26th April 2006 at 15:39.
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Old 26th April 2006, 09:16   #12  |  Link
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Great info, mpucoder!

So, it should be possible to leave the seamless flag set on the LB cell! Do you think this rule violation is compatible with all players, or is it a risk of crash/freeze, especially with old standalone players? I thought the player need some time to switch from a layer to the other one...
I might add an option to leave the seamless flag on the LB in the burn setup dialog of PgcEdit. Is it safe?
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Old 26th April 2006, 09:44   #13  |  Link
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http://forum.doom9.org/showthread.php?t=102185
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Old 26th April 2006, 09:51   #14  |  Link
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Thanks, bigotti5. So, it appear that this seamless LB technique requires a special muxing. Difficult for PgcEdit to analyse the VOB file to be sure the seamless flag can be set. Pity!
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Old 26th April 2006, 11:29   #15  |  Link
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Well so far out of 15 pressed dvds I have never seen the seamless flag set (several had a discontinuity flag set because its break was at the start of the first cell of a VOB). So I am guessing that even if there is a standard to set seamless and multiplex it, it is rarely done. Maybe with older dvds setting seamless was done more often as the older dvd players took more time on layer breaks?

pressed dvd with discontinuity at start of new VOB:

pressed dvd with discontinuity not set (not at new VOB):

Last edited by jamos; 26th April 2006 at 11:51.
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Old 26th April 2006, 11:42   #16  |  Link
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take a look at Superbit DVD
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Old 26th April 2006, 12:09   #17  |  Link
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Thanks, Jamos.
BTW, your second screenshot is a good example of several cells that are not used for chapter points. In this case, it is difficult for PgcEdit to guess which cell was used for the LB (unless the seamless flag is left unchanged during the rip.)

@bigotti5
I haven't analysed a superbit DVD yet.
Do you think superbit really offers a better quality than a good traditional DL DVD? Unless the movie is really long or full of action scenes, I think a perfect quality can be archived without having to use the full DVD size for the main movie. Anyway, the bitrate is limited by the standard. Is it true that the main movie occupies (almost) the full space of the DL DVD?
Honestly, I suspect a commercial trick instead of a real improvement.
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Last edited by r0lZ; 26th April 2006 at 12:18.
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Old 26th April 2006, 12:24   #18  |  Link
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Perfect quality imo is always subjectively.
I have only one Superbit DVD ("Das Boot") in my Collection and I have not compared with other releases of this movie.

It is the seamless layer change that initiates me drawing attention to Superbit, not the quality (quality is good though).
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Old 26th April 2006, 12:51   #19  |  Link
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I don't think I will ever use the seamless layer change - it's just too risky ATM. Many studios are getting smarter about where they put the LB so it is aesthetically pleasing (a scene which fades to black for example, or one where there is no audio or movement for a couple of seconds).

I do like superbit - I have one or 2 (Hannibal I think is one) and it is very good - avergae BR is very high around 7-8Mbps (which doesn't give much room for low BRs - it is almost like CBR encoding). And, r0lZ, the movie occupies ALL the DVD, there are no extras just wasting space.

In any event, as we know, it is a "psychvisual" experience r0lZ, as "perfect quality" is in the eye (literally) of the beholder.

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Old 26th April 2006, 13:30   #20  |  Link
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Quote:
Originally Posted by blutach
And, r0lZ, the movie occupies ALL the DVD, there are no extras just wasting space.
I know there are no extras. But that doesn't mean that the main movie occupies the whole DVD. Have you verified that the VOB files of the main movie are really around 7GB?
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