As previously mentioned, a DVD can have up to 32 different subtitle streams in a VTS. Although they're called subtitle streams, they actually are implemented as overlaid picture files rather than as a text representation, so they can do other things as well. An example of this is the “White Rabbit” feature seen on The Matrix DVD. Subtitling is fairly easy, as it's essentially the same process as creating menus, only without the background layer. Figure 5 shows an example subtitle picture, providing a title for a photo. A sample submux description for this title that keeps it onscreen for two seconds would be:
sub1.png 00:00:00.00 00:00:02.00 0 0 0 255 0 255
In this application, I'm working with separate, short MPEG-2 clips, so each has to have a separate submux description. For longer clips, a submux file probably would have multiple entries.
Having made the video slides, subtitling them and creating the menus, the only thing left to do is assemble everything together using dvdauthor. dvdauthor works in two modes, one for normal titles and another to define the VMGM menu; the VMGM can't have any video information apart from the menu. Let's start with the first title:
dvdauthor -o tmp -m -P \ -b 239x397-489x457,subtitle32+vts1 \ -b 239x500-489x560,vmgm1 \ -b 27x223-127x263,subtitle32+vtsm.2 \ -b 165x184-325x305,subtitle32+vts1.1 \ -b 352x184-512x305,subtitle32+vts1.2 \ -b 539x184-699x305,subtitle32+vts1.3 \ \ title2/titlemenu1.mpg -m -P \ -b 239x397-489x457,subtitle32+vts1 \ -b 239x500-489x560,subtitle32+vmgm1 \ -b 27x223-127x263,subtitle32+vtsm.1 \ -b 165x184-325x305,subtitle32+vts1.4 \ -b 352x184-512x305,subtitle32+vts1.5 \ -b 539x184-699x305,subtitle32+vts1.6 \ title2/titlemenu2.mpg -t -P \ \ title2/v1.mpg title2/v2.mpg title2/v3.mpg \ title2/v4.mpg title2/v5.mpg title2/v6.mpg \ -i post=3Dvtsm
This code defines two title menus with six buttons each, six MPEG video clips (dvdauthor defines the transition from one clip to another as a chapter point) and a post-video instruction that returns the DVD player to the title menu. The coordinate system is the same as The GIMP's, so you can use that to get the necessary regions. A button can perform various actions (see dvdauthor --help for a list of possibilities). In the example above, the first button sets the audio track to zero, sets up the required subtitle stream (stream 0 is bizarrely numbered 32, stream 1 is 33 and so on) and plays the video associated with the title. The second button returns the player to the main VMGM menu, and the third button moves the DVD player to the second title menu. The other three buttons move to specific chapters within the video stream, corresponding to clicking on one of the thumbnail pictures. The -o option is for an output directory, in this case the image/ subdirectory. The program works incrementally, so running the same command line twice creates an additional title set rather than updating the original.
For the main menu, you need to pass the -T option to dvdauthor so it knows it should create the required VMGM information. Then, link in the VTS files it already has created:
dvdauthor -o tmp -T -m \ -b 497x89-693x136,vtsm1 \ -b 497x138-693x187,vtsm2 \ -b 497x189-693x239,vtsm3 \ -b 497x240-693x289,vtsm4 \ -b 426x405-490x474,vts5 \ -P mainmenu/mainmenu.mpg
It's a good idea to test the DVD image before burning it onto disc. This can be done using xine; all you need is to give xine an argument like this:
and xine should act as though it is playing the information from a DVD. As dvdauthor is incremental, you should be able to use xine after creating each separate title to ensure that you're doing things properly.
Once you're happy with your DVD, it's time to burn. I used the cdrecord-prodvd application for DVD-R burning. The operation is the same as cdrecord, so first you need to create an ISO image using mkisofs:
mkisofs -o <output_filename> -dvd-video \ <path_to_dvd_root>
Then use cdrecord.prodvd to burn it:
cdrecord.prodvd dev=3D0,0,0 -pad -dao \ <path_to_DVD_image>
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