Creating a Dual-layer DVD
[ This article was first published in the December, 2008, issue of
Larry's Final Cut Pro Newsletter. Click here to subscribe. ]
While I’ve been teaching DVD Studio Pro for a long time, I haven’t had the need to create a dual-layer DVD until recently.
In doing so, I learned techniques that I’ve never covered in training before, so I thought I would share it with you here.
First, though, a quick review.
DVDs are measured in storage capacity. A single-sided, single-layered DVD holds 4.3 GB of data if you burn it, and 4.7 GB of data if you replicate it (take it to a disc manufacturing facility).
A single-sided, dual-layer DVD holds 8.5 GB of data, whether burned or replicated.
While double-sided discs exist, they have generally fallen out of favor as there is no place to put a label. As well, the costs of manufacturing a DVD have fallen so much that it is more cost effective to release multiple discs than to use both sides of the same disc.
For those of you old enough to remember, a DVD (or CD) is like a vinyl record. There is only one track that slowly spirals from edge to edge. With a record, the track starts at the outside and spirals in. With a DVD, the track starts at the center and spirals out.
With a single layer disc, burning is easy. The laser starts at the center of the disc and lays down data until it either runs out of data or runs out of disc.
With a dual-layer disc, things get a bit more complicated.
A dual-layer disc has two layers; one stacked on top of the other. First the laser focuses on the lower layer, then, when it reaches the end, it refocuses on the upper layer.
There are two ways the laser will write multiple layer data to the disc: OTP or PTP. OTP (Opposite Track Path) means that when the laser reaches the end of the bottom layer it refocuses, then starts spiraling back to the center. PTP (Parallel Track Path) means that the laser zips back to the beginning of the DVD, then starts spiraling out from the center.
The advantage to OTP is that the track changeover is very fast, less than half-a-second. The disadvantage is that the upper track can’t be any bigger than the lower track.
The advantage to PTP is that the upper track can be bigger or smaller than the lower track. The disadvantage is that it takes a long time for the laser to reset back to the middle — several seconds.
My recommendation is to use OTP – setting the break point is harder, but the overall performance of your DVD is much better.
Finally, while DLT tape has been the traditional means of mastering your DVD for delivery to replication, increasingly DVDs are used as source masters. For a single layer disc, all you need to do is burn your material to the disc and the replicator will make a copy of it.
However, as you might suspect, dual-layer discs don’t make it that easy. Instead, you need to create a master using DDP (Data Description Protocol). While DVD Studio Pro supports DDP, it isn’t easy to find, nor is it intuitive to select what you need to know to create it properly.
With that as background, let’s take a look at the steps to creating a dual-layer DVD that are different when compared to a single-layer DVD. These fall into three areas:
- Creating a break point
- Creating the DDP master files
- Burning the DDP files onto a DVD
CREATING A BREAK POINT
Before you spend any time worrying about creating a dual layer disc, finish all the rest of your authoring. Because setting the break point accurately depends upon working from a completed DVD; by that I mean that you need to build the VIDEO_TS folder first.
For this example, I was working on a two-disk set on horse training, where each disc was a dual-layer disc.
To start, choose the Outline tab and select the name of your DVD — its at the top of the list.
Then, in the Inspector, change the Layer Options to Dual. Make sure the Track Direction remains at OTP and don’t worry about the Break Point pop-up menu quite yet.
Note: Leave the Seamless option UNchecked. Although this is supposed to allow smoother transitions between the two layers, in real life it causes more problems than it solves.
According to the DVD Spec, there are two rules that govern where a DVD changes layers:
- first, the lower layer (Layer 0) needs to be as close to 4.1 GB as possible
- second, the top layer can not be bigger than the lower layer
These are easy to state, but there is not an easy way to determine this without a lot of trial and error.
If your DVD has lots of chapter markers, you may be able to leave the Break Point pop-up menu set to Automatic. But, frankly, I don’t think you’ll be that lucky.
So here’s one manual method:
- Calculate the total number of video minutes in your DVD.
- Figure out which track holds the half way point.
This won’t actually help, but it will make you feel better. Instead, let’s use DVD Studio Pro to help us figure it out. To do that, we need to burrow deep into the technical side of how files are stored.
1. Click the Outline tab to display the structure of your DVD.
2. Grab the small two-line slider about half-way down on the right side between the Outline window and the Menu window. Drag the slider to the left to reveal a new column who’s header reads “By VTS.”
3. Video is stored in VOB’s (Video Object Blocks) which, in turn, are stored in VTS’s (Video Title Sets). Find the VTS that is closest to the middle of the list and twirl it down. The track listed in the middle VTS is where you need to put your Break Point.
Note 1 : A Break Point is a special track marker that tells the DVD player when to switch from the bottom layer to the top layer on your DVD. There is only one Break Point marker per DVD.
Note 2: This method assumes that you have a reasonably full DVD. If you have a disk that has less information, you’ll need to figure out, based on the list of tracks in the VTS column, which track is likely to fill the disc to the 4.1 GB level. That, then, becomes the track that holds the layer break point.
4. A break point should be set somewhere in a track where a half-second pause in the audio and video won’t cause a problem for your views. I try to set mine at the end of a paragraph, when the action is fairly stationery. I’m not always able to use that point, but its always where I start.
5. Put your timeline playhead where you want to set the marker and press the letter M. A standard green chapter marker appears at or near the position of your playhead.
6. Click the marker to select it, then, in the Inspector, select the Dual-Layer Break Point check box. The color of the marker changes to purple with a heavy black dot in the center of the marker. This is now the point where your DVD changes layers.
7. If you select your DVD in the Outline tab and look in the Inspector, the Break Point menu now indicates the name of the track where your break point marker is set.
Note: So far, this is really easy. The problem is that you won’t know if your marker is set properly – remember those two placement rules I mentioned earlier? – until you build the DVD. This is why I always recommend getting all the rest of your DVD authoring done first. Setting a break point is always a process of trial and error and requires that all tracks and menus be completed first.
CREATING THE DDP MASTER FILES
In order to test whether your break point is set properly, you need to build your master file. In the process, you’ll also build the DDP folders that the replicator needs to create the glass master disc for manufacturing.
To build the DDP master files:
1. Choose File > Advanced Burn > Build and Format. You will be building four folders at this point:
2. In the Source section, indicate where you want the VIDEO_TS and AUDIO_TS folders stored. I usually create a folder on my second drive, named the same as my DVD. Inside that is where I store the two _TS folders.
3. Then, since the Destination pop-up menu defaults to burning a DVD, I change the Output Device to Hard Drive.
4. Here’s a potential problem: check with your replicator to determine what DDP format they want. DiscMakers, for example, wants DDP v2.0 files. This may vary by replicator so be SURE to check. Be careful not to select IMG or CMP.
5. A dialog will pop-up asking where you want the DDP folders stored. I generally put then in the same folder as the _TS folders – just so I know where they are – however, you can store them anywhere.
Note: DDP files are ONLY for mastering, you can not play them on your DVD player. If you don’t replicate your discs, you don’t need to create DDP folders.
6. Click Build & Burn to create your files. This will take a while, so don’t be impatient.
WHEN THE BUILD FAILS
Notice I didn’t say “IF the build fails….”
When the build fails, you’ll get one of two error messages. The first states that Layer 0 is too big. It exceeds the 4.1 GB limit. In which case, you need to go back to your break point marker and move it closer to the beginning of the track.
The other error message says that Layer 1 can’t be bigger than Layer 0. (Remember, since the laser starts at the end of Layer 0 and spirals back to the beginning at the center of the disc, we have a limited amount of room here.) In this case, you need to move the marker closer to the end of the track.
After moving the marker, repeat the process of building your files.
This becomes a time-consuming balancing act to get the layer point exactly where both rules are met and you have a layer transition that doesn’t totally destroy the flow of your movie.
It generally takes me four or five attempts before I get it right. When you get it right, no error dialogs appear and DVD Studio Pro happily builds all your files.
BURNING THE MASTER FILES ONTO A DVD
When everything is done, you’ll have a folder with the name of your DVD, with an AUDIO_TS, VIDEO_TS, and two Layer folders inside it.
The one thing you DON’T want to do is send your replicator a dual-layer DVD — it won’t work for a master. They will yell at you. It will be awful.
Also, according to the replicators I’ve spoken to, while DVD Studio Pro is excellent for creating DVDs, it is not a good choice for burning the masters. A much better choice is Roxio Toast. Specifically, the latest version of Toast – v.9.0.4.
That’s because the DVD needs to be burned using the UDF file system (um, UDF is not Mac and not Windows – its Unix.)
So, after your Layer folders are created, open Toast and select DVD-ROM (UDF). Drag the entire Layer folder into Toast and burn it. Don’t rename anything.
Each Layer folder is burned to its own DVD.
Then, you ship the DVDs off to the replicator and sit back and relax – knowing that you’ve done everything possible to make your masters as accurate as possible.
Note: There’s one more thing you need to pay attention to, and that’s the media you are burning your DVDs onto. Again, based on my own experience and the experts I’ve talked to, I recommend three brands: Taiyo-Yuden, Verbatim, and MAM-A. Never, ever, buy DVDs on price. The cost of the disc is nothing compared to the cost of losing your data.
For more on this, see my next story on picking the right optical media.
The process of creating a dual-layer disc was more complex than I expected. And it took a number of phone calls and false starts before I got it right.
Remember to finish authoring your DVD before setting your break point. And be patient, don’t expect to get your break point setting right on the first try.
Oh, and one other thing. Talk to your disc replicator BEFORE you start creating the masters to be sure you are creating something they can work with.
UPDATE – Dec. 21
Uli Plank, a long-time reader and contributor from the Institut für Medienforschung added:
While VOB’s are limited to 1 GB in size, VTS’s are not directly related to any specific size. One VTS can hold the whole movie on a DVD in a row of VOB’s or there can be lots of small VTS’s. So, it doesn’t help very much to choose one in the middle. To take some of the guesswork out of finding a good layer-break and avoid multiple tries on time-consuming multiplexing, let DVD SP do some of the work.
First make a duplicate of your whole project and work on that!
With your VTS list open and keeping an eye on the size of your DVD, start deleting VTS’s from the end (they’ll be arranged on the DVD physically in that order). When the size falls below the size for layer 0, undo the last delete. Now get into the timeline for that VTS and start pulling back the video from the end while watching the size again. You don’t need to care too much about sound, since it’s size is small in relation to the video.
When it gets below the layer 0 size, take note of that position. Start to look for a convenient layer- break (LB) point forward from there and set the marker. BTW, the marker doesn’t need to be checked as a chapter marker as in your screenshot, it can be a LB only. You can set several potential LBs for DVDSP to choose from.
This method works pretty well with projects where video and audio are already encoded, as I’d typically do it for professional work. In most cases I don’t need more than one try to get a valid LB.
While DLT is still the industry standard for DVD authoring, you can send masters for the two layers on separate Data-DVDs as you wrote, but I’d suggest to make duplicates for each layer (clearly marked as backups) if your deadline is close, for the rare case that even high-quality DVDs can’t be read correctly at the replicator’s plant. Plus, check with the replicator if they want DDP or CMF.
Larry replies: Uli, thanks for the additional information. Keep in mind that most DVD recorders can’t create a CMF disc, that generally requires special equipment. Second, your approach assumes the size indicator is accurate. While I have serious questions about the visual thermometer in the toolbar, the size of the DVD as indicated numerically in the Inspector I’ve found generally accurate.