27 Nov 2004 7:35 AM
|1. An IFO file is a roadmap to a DVD, whether it is a DVD-5 or a DVD-9
2. DVD-5's are simple to backup and in fact can be done quite simply.
3. DVD-9's are much harder to backup and I will try to explain why:
Let's suppose that a DVD-9 is composed of 10 title sets. Some are less, but many are more, but for this example, we'll use 10.
The actual movie is only contained in 5 of these title sets, with the other 5 being menus, trailers and special features.
Let's say the IFO file instructs the DVD Player to begin playing at title set 1. This is the FBI disclaimer. Now, the IFO instructs the player to play the second title set (2) which is another disclaimer. When that's finished, the IFO instructs the DVD Player to play the third title set (3). This third title set is a trailer of some upcoming release. At the end of this third title set, the IFO file instructs the DVD Player to play the fifth (5) title set. (No, I didn't skip over # 4) This is the menu title set. Now when the user presses the play button in the menu, the IFO file instructs the DVD Player to play the fourth (4) title set which is a THX trailer. At the end of the THX trailer, the IFO file instructs the player to play the sixth (6) title set which is the beginning of the main movie.
Did you follow that? 1->2->3->5->4->6 (the IFO file instructs the PGC or program chain in a series of events, which by the way in many cases can be interrupted by the user, like when you press the menu button on your remote)
A DVD-9 is actually two pressed (not burned) layers of media with a physical break in between them. You can't see the layer break, but it is there. Each layer can hold approx 4.7 billion bytes of data.
Your DVD Player sees these individual layers and can access them instantaneously. So when it needs to jump between title sets it can do so very easily.
This is a simplistic example but nonetheless, can be quite revealing, once you understand it.
Let's say that title set five (5) the main menu, is on the first layer, BUT title set four (4) (the THX trailer) is on the second layer. And then title six (6) the main movie, begins back on the first layer. Your DVD Player can easily jump between these two layers and bridge the IFO instructions to play these in sequence.
NOT SO EASY for DVD X COPY. DVD X COPY must follow (walk) the PGC (program chain) and in some cases make best guess determinations as to which title is which. And in fact, we have to re-author the IFO file, so that it doesn't jump to title four (4) WHICH IS NOW on disc 2 (because we want to fit as much, if not all of the movie on disc one).
But as a user, you expect to select PLAY on the menu and have it start the movie.
And here's where it gets really complicated. We can of course code this for each DVD title, because once you see the title (let's say in IFOEDIT) it becomes quite obvious which title sets need to be re authored. BUT, when you're trying to do this ON THE FLY, and let the program decide, it becomes VERY COMPLICATED.
Add to that, some players will ignore obvious IFO errors and others will not. That is why some of you can play a backup in your player perfectly, while others will experience wild and erratic playback behavior.
The good news is, we've managed to come up with a code base that will address most of the DVD titles on the market. And we will continue to refine the code base and make it smarter over time.
Someone once posted in this forum that DVD X COPY just needs to do ONE THING and ONE THING ONLY! Why can't it just do that ONE THING PERFECTLY?
Put simply, DVD X COPY is NOT doing just one thing. It is actually doing many things. It has to proactively adapt to hundreds of DVD authoring techniques and split movies, titles, features, and menus over two PHYSICALLY separate layers. And re author in such a way that the IFO file is interpreted by every compatible player on the market.
This might look something like this in a mathematical formula:
DVDXCOPY * DVD TITLES * DVD PLAYERS (The * means multiplied by) If you take just 5000 (five thousand) DVD titles and 100 (one hundred) players, the possible permutations that DVD X COPY must proactively adapt to are 500,000 (five hundred thousand) possibilities.
This is like trying to make an engine part for a car, which would automatically fit every car, make and model on the street today.
NOW ADD all the possible computer configurations, hardware and OS configurations and user error possibilities, and maybe you can begin to understand why it didn't work for everyone out of the box.
BUT, we ARE going to accomplish this massive feat. It's already in the works to develop a massive global database that will pre-define title sets for a specific DVD title and will allow DVD X COPY to work flawlessly, for everyone, first time out of the box. This is part of the foundation of our code base for the platinum edition.
Until that time, we will continue our efforts to provide the best quality DVD backup product on the market and will not rest until we achieve that level of distinction and excellence.
Thanks for reading a very long post :)
Chief Mod of DXC forums. YE RAG-TAG (#4)