Open GOP's? How do I close them?! Are they causing problems...?

[Littlerich]

Hi there.

I am trying to create a multi-menu DVD with individual short clips from an already existing DVD.

I am using DVD Lab Pro 2.0. todo the authoring.

So far, I have imported the video from a DVD which had no menu, and joined the VOB files to create one which I am using for the new DVD.

I have 24 diferent chapters, each with a minute of black between them.

I want to be able to play the chapters individually without playing any black, so I have created chapter points at the start and end of each section of video I want to use, with a start and end point.

I have then created branches, with chapers 1, 3, 5, 7, ect (the actual video, without any black) in them. In the menus I have created the links.

When I try to encode the DVD however, no matter HOW i try it, I always come up with it aborting.

I get a message stating that the file has Open GOP's and that I should re-encode it with closed GOP's...

What IS an open GOP and ow do I close it?

[manono]

Why are you reencoding? Can't you just cut out the black places? These clips you're using come with a minute of black each? Sounds kind of strange to me.

If you insist on reencoding, then:

When I try to encode the DVD however, no matter HOW i try it, I always come up with it aborting.

Did you say anywhere just how you're reencoding this thing; how you're getting the video into the encoder, what encoder you're using, and at what settings? Any helpful error messages when it aborts?

There's nothing really wrong with Open GOPs. It's just a warning and a useless one at that, in my opinion. If you're joining clips together, depending on how you acquired them, I suppose Closed GOPs could be helpful, but I don't usually do it. Open GOPs means that the individual frames can get decoding info beyond the GOP boundary. You close them by reencoding and setting Closed GOPs in your encoder.

[DRP]

In DLP2 go into Project Properties|Advanced and uncheck the option "Warn if Open GOP detected". Problem solved.

If the compile is aborting, it's not because of Open GOPs. Cut the black bits you don't want off with Womble MPEG-VCR.

[Cornucopia]

Why are you reencoding? Can't you just cut out the black places? These clips you're using come with a minute of black each? Sounds kind of strange to me.

If you insist on reencoding, then:

When I try to encode the DVD however, no matter HOW i try it, I always come up with it aborting.

Did you say anywhere just how you're reencoding this thing; how you're getting the video into the encoder, what encoder you're using, and at what settings? Any helpful error messages when it aborts?

There's nothing really wrong with Open GOPs. It's just a warning and a useless one at that, in my opinion. If you're joining clips together, depending on how you acquired them, I suppose Closed GOPs could be helpful, but I don't usually do it. Open GOPs means that the individual frames can get decoding info beyond the GOP boundary. You close them by reencoding and setting Closed GOPs in your encoder.

It's not USELESS.

The problem comes when you try to do what I'm pretty sure he's trying to do: Merge/Concatenate. He's got: individual clips He wants: Chapters of one long clip
To do that, he's going to have to merge the clips into 1 big clip (you kinda mentioned that anyway, manono). If you try to edit Open-GOP material AND merge, unless you're cutting on the I-frame AND butting clipA end I-frames next to clipB start Iframes, you'll have unreferenced frames. That leads to picture corruption (if it allows it at all).

Scott

[Littlerich]

Why are you reencoding? Can't you just cut out the black places? These clips you're using come with a minute of black each? Sounds kind of strange to me.

This is done like this because it's a showreel for a friend. Instead of getting a DVD authored, all they have done is a digibeta-dvd transfer without any menus.

The original DVD just played through 1 hour 17 minutes without stopping between each clip.
(that includes the minute of black between short clips).

I have taken the original Video_TS folder and copied it onto my HDD then used DLP2 to re-author it from the original VOB files.

Did you say anywhere just how you're reencoding this thing; how you're getting the video into the encoder, what encoder you're using, and at what settings? Any helpful error messages when it aborts?

I have tried several different methods:
1. Importing VTS01-1/2/3.VOB files straight into DLP2 and allowing it to convert to elementary streams and re-joining it to one VOB file. (Then made the menu, ect...)

2. I also used an encoder called SUPER (by a company called eRightSoft) to re-encode the VOB. (I've always had good results with this program)

3. I also tried DLP2 to join the VOBS without converting to elementary streams.


Whatever method I use, I still have the same problem.


------ UPDATE -----

I have tried re-doing the chapters and encoding during various stages... Whenever I encode 5, 10, 15 or 20 movie clipsit encodes properly... HOWEVER, when I try to encode the DVD with all 27 chapters it seems to bomb out after it does 21... Is there a limit on how many chapters I can have??

[manono]

It's not USELESS.

But it is. If he reencodes, then I agree he should use closed GOPs. I think we agree, though, that reencoding is to be avoided if possible. To prevent any kind of corruption when the video is decoded, he only has to leave a minimum of 2 frames of black at the end and at the beginning of each clip. Then there won't be any decoding difficulties. For an authoring app to warn in every instance (the way that TMPGEnc does, and the way this DLP does by default, evidently) that open GOPs are by their very nature something to be avoided, scares the neophyte unnecessarily into thinking he's done something wrong, and is itself wrong, as Open GOPs are, in most instances, preferred.

Yes, what he's doing is a prime case where Closed GOPs would be better, but, as I said, it's an easy matter to cut out the black and avoid any possible problems. I've done it before with no problems (merged open GOP video, making sure there were black frames at the join, like when reencoding end credits to be joined to the main body of a movie).

[manono]

Littlerich-

I still have no idea why you're reencoding. Maybe convert the vobs to mpg using VOB2MPEG, and use one of the tools in this list of guides to cut out the black (leaving a very small amount at the beginning and end of each section). Pretend it's commercials:

https://www.videohelp.com/guides.php?searchtext=&tools=&madeby=&formatconversionselect=...or+List+Guides

Some are free and some are commercial. Some of the commercial ones have a period of free use for you to try it out. Then when done, demux , add to your authoring app as elementary streams, create chapters, and author.

Mpeg2Schnitt and Cuttermaran are free utilities for this. If demuxing is required, DGIndex, among other free tools, can easily do the job.

[guns1inger]

Follow Manono's advice. VOB2MPG to get back to elementary streams. Once you have the streams loaded into DLP, frameindex the video, then add your chapters.

You can have more than 27 chapters, and you can use playlists with vidoes with open GOPS. You cannot use open GOPS with multi-angle, but you aren't doing this, so it should not be an issue.

[Cornucopia]

It's not USELESS.

But it is. If he reencodes, then I agree he should use closed GOPs. I think we agree, though, that reencoding is to be avoided if possible. To prevent any kind of corruption when the video is decoded, he only has to leave a minimum of 2 frames of black at the end and at the beginning of each clip. Then there won't be any decoding difficulties. For an authoring app to warn in every instance (the way that TMPGEnc does, and the way this DLP does by default, evidently) that open GOPs are by their very nature something to be avoided, scares the neophyte unnecessarily into thinking he's done something wrong, and is itself wrong, as Open GOPs are, in most instances, preferred.

Yes, what he's doing is a prime case where Closed GOPs would be better, but, as I said, it's an easy matter to cut out the black and avoid any possible problems. I've done it before with no problems (merged open GOP video, making sure there were black frames at the join, like when reencoding end credits to be joined to the main body of a movie).

Yes, I think we mostly agree (certainly on the hope of not re-encoding).
However, let's assume for a moment that these clips are encoded VBR. If you cut out 2 B-frames off of each end, and merge at P-I or I-I boundaries, you could run the risk of causing the remaining bitrate to have a SPIKE, maybe enough to mess with the buffers or go over the max allowable (since the B-frames are the efficient/lower-bit-per-frame and you'd be taking those out).

I think there's enough of a case where things COULD go wrong, that it IS a good idea to warn--hence, not useless.

Scott

[guns1inger]

Can the OP clarify the source. My reading is that these clips were already compiled into a DVD, but without menus etc., and that the project is simply taking the existing VOBs to create a new disc. I'm not convinced he is joining 27 clips together. If it is coming from an existing disc then VOB2MPG should be enough to get the video out without issue, as there really is nothing to join.

[Cornucopia]

That's possible. My last take on this got me to thinking that one could just as easily create a playlist that SKIPPED the bulk of the black sections.
I mean, if the VOB is contiguous anyway and obviously must have ORIGINALLY fit on a DVD, you're probably not gonna save much of anything on the new disc(unless you were cutting from multiple discs and then merging).

Does that make any sense?? It's been a long day...

scott

[manono]

He already has a DVD created from the 27 clips. There is a minute of black in between each clip, and no chapters. His convoluted idea is to reencode the whole thing, at the same time creating chapters at the beginning and end of each clip. That way, when he authors, he can create nav commands that will allow him to skip over the black and go directly to the next chapter.

For 3 reasons, this makes no sense to me:

1. Reencoding degrades the quality and wastes time.
2. He doesn't even have to reencode to accomplish what he wants. He can just demux, send the elementary streams to the authoring app, create the chapters there (one at the beginning of each clip, and the next at the end), and then make sure that after the end of each clip, it jumps over the black and goes directly to the next clip. I don't know if this is easy to accomplish or not, using DLP. It sounds pretty easy to me, though. Instead of each chapter following the next consecutively, he'll be playing every other chapter.
3. He can cut out whatever he wants, using the methods described earlier, and then author.

Edit:

That's possible. My last take on this got me to thinking that one could just as easily create a playlist that SKIPPED the bulk of the black sections.

I think while I was writing, you came up with the same idea as my point number 2, Cornucopia.

[Cornucopia]

I concur.

[Littlerich]

As an update to this - I have managed to put together the DVD with menus and compile it without any problems. That was AFTER i had cut down on the number of videos I wanted to include...

I had 13 different videos, each with a 3 minute version and a 1 minute version. (i.e. 26 in total...)

I had on the menu an option to play them individually, as well as a link to a "play all" option.
This was spread over 3 menu pages and a contact information page (It was a showreel on DVD).

However, whenever I tried to compile the DVD it kept getting to Title 21 and aborting... Is there some limit to the number of Links you can make on a DVD with DLP2?

(My workaround incidentally was simply to have a "PLAY" for each of the 13 videos, which took the viewer to a chapter which had the 3 minute followed by the 1 minute versions..)

[rayden54]

I also have a problem with open GOPs, however unlike Littlerich, I already have to re-encode my movie AND because I'm attempting to create a multi-angle DVD, I do actually need to have closed GOPs.

Can this be done with Super or do I need to purchase a different program to do my encoding with? Or is there a freeware program that can close GOPs?

[manono]

Or is there a freeware program that can close GOPs?

HCEnc

[Cornucopia]

If you're doing multiangle, there are other restrictions on how you encode your stuff (or re-encode in your case). I wrote about this pretty extensively in a previous post (you can do a search for it on this site -- "multiangle" "Cornucopia").

Good luck,

Scott

>>>>>>
edit: This means, you may have to narrow your choices of encoder to be able to set things correctly--maybe even not using freeware...?