Development

Building DVD discs with Bombono

DVD authoring can be a deceptively tricky business. Though it can take some time to convert source video to the proper MPEG format, the technical requirements for the various regions are standardized, so it is at least possible to configure the conversion tools and do it right, once and for all. What cannot be automated is building the disc structure that distinguishes a user-friendly disc with chapters, eye-pleasing menus, and a file hierarchy that makes sense from a down-and-dirty, technically-it-plays-but-it-looks-awful amateur job.

There are several actively-developed DVD authoring tools for Linux desktops and command-line environments today, including QDVDAuthor, DeVeDe, ManDVD, and DVDStyler. They vary quite a bit in ease-of-use and the number of disc-building options they support. We have covered several of these alternatives in the past.

One of the newest options is called Bombono, a GTK+-based disc authoring application that focuses on simplicity. The project provides packages on its download page for many Linux distributions and FreeBSD. The most recent release is 0.6, from April 16. No special dependencies are required; mjpegtools, the TwoLAME MP2 encoder, and dvdauthor are the only packages needed outside of standard GNOME components.

Of course, one reason Bombono has so few dependencies is that it makes no attempt to tackle one of the key tasks involved in producing a DVD from arbitrary video and audio content: preparing the media. Bombono requires that you convert your videos to compliant MPEG-2 format in an external tool; it recommends nonlinear video editors such as Kdenlive or stand-alone FFmpeg frontends such as WinFF. Which of these options works best in practice is a matter for individual exploration; it often depends greatly on the format of the source video. In any event, Bombono has zero margin for error for acceptable MPEG formatting, but it does at least prevent you from adding non-compliant video, and warns you about which file properties constitute the problem.

Getting started

With compliant MPEG video in hand, you can launch Bombono and immediately start working on a new disc project. The interface splits the application into three tabs, one for each of the three sequential steps in the process. "Source" allows you to add all of the media you will use (including video content and still images for menus) and to bookmark chapter divisions in the video media if desired. "Menu" provides a canvas on which you compose menu screens, and link individual menu items to videos or to other menus. "Output" controls writing the final disc image or directly burning your creation to an optical drive.

The interface is simple to understand; it is uncluttered and clearly labeled. It does, however, incorporate some peculiarities that stray from the normal GNOME human interface guidelines — most notably, the menu bar includes not only menus ("Project," "Go," and "Help"), but a tab-selector for the Source / Menu / Output mode tabs, and a drop-down listbox for selecting the disc capacity. Neither element impedes the application's usability, but they look out of place, as do several UI elements rendered in non-default font sizes and weights.

Nevertheless, with a disc needing to be crafted, one can overlook such things and concentrate on the task at hand. Bombono includes a file browser for adding video and image media, but also supports drag-and-drop from the system file manager. It can also extract video from a physical DVD or a DVD image, courtesy of a guided wizard found in the Project menu as "Add Videos from DVD...", and save single video frames as still images. Everything added is listed together in a project-wide "media list" which makes another appearance in the menu-creation process.

Apart from simply adding the relevant files, the Source tab's main feature is the ability to mark chapter break-points in video media. A simple timeline and preview window allow you to seek to the break-points you wish to add, then mark them with a right-click. A full video player is not built in, although you can open the selected video in GNOME's Totem player from the right-click menu.

Menu building

The menu-building interface is sparse, but again, easy to work with. First, you add a new menu via the plus-sign button in the Menu List. Selecting a menu in the list does not make it editable, though; to do that you must click the "edit" button, which is a green circle.

You can then build the menu design on the canvas, adding a background color, text elements, and dragging images or videos from the media list. All of the project media added in the Source tab is accessible in the media list, and video chapters are selectable as distinct elements, which allows you to build a "chapter menu" without much effort. Videos and images that you place on the canvas will be rendered as fixed-size thumbnails; chapter videos use the first frame of the chapter as their thumbnail image.

To make menu elements do something, you must add a link to them via the right-click menu. There, the Link submenu is populated with both the video content of the disc (chapters included) and the existing menus. Linking an image or text element to a video will cause it to play the video (or video chapter); linking to a menu will cause it to jump to that menu.

Those are the basics. Bombono offers a handful of layout tools, including the ability to align selected elements to each other, and bare-bones font options. It does not, however, check your links for a proper hierarchy, so if you forget to add "return to main menu" links to your submenus, you are on your own. Similarly, the image support is bare-bones; you can scale but not crop images, and you cannot change the z-ordering of any page elements — the order they are added to the page is the order in which they stack vertically.

By default, videos and stills are placed on the canvas in rectangular frames. To create a slightly more complicated look, you can change the frame shape from the drop-down menu in the toolbar. Hexagons, rounded rectangles, and alpha-transparent border fades are supplied. The project's documentation includes some incomplete instructions about creating your own frames; hopefully that will be expanded in the future.

On the other hand, Bombono's right-click linking is very difficult to get wrong. Working with the application might remind those old enough of Apple's Hypercard; Bombono keeps track of the linkable elements for you, and makes it impossible to create a semantically invalid link, which is something it is possible to do with more complex DVD authoring tools that take a scripting-like approach.

Outputting

The actual DVD image creation is handled by the external dvdauthor tool. Bombono lets you burn a disc directly, write out an ISO image, or write a DVD content folder than can be burned to disc by another application. Dvdauthor's output is written to a "Details" window as the authoring process proceeds; if it fails you can inspect the output there to try and determine the cause of the problem.

Tracking down an error caused by a moved file might be easy, but it is also possible for Bombono's menu editor to produce invalid intermediate XML that will throw an error when fed to dvdauthor. I encountered this problem when producing a test ISO. The DVD failed to burn, reporting that one of the buttons attempted to link to a chapter that did not exist in the video. How that happened is still a mystery; it isn't possible in the GUI to link to a chapter that doesn't exist, so the erroneous reference obviously had some other cause.

In such a situation, the only recourse is to open up Bombono's XML project file and look for empty attributes. This is made more difficult because the application assigns automatic names (such as Media.0.0) to disc elements, rather than using the source element's name, and because there is some ambiguity in the way non-video elements are treated. For example, a still image can be added to a menu directly, in which case it is automatically created within a frame, or the frame can be added first and the image added to it as a "Poster" element. The two appear identical, but in the former case the image is added to the frame as "Ref" element instead of a "Poster" and evidently produces different behavior when linked to a video. A little trial-and-error time is probably a wise idea before starting work on the big Annual Report DVD.

Once the kinks are worked out, however, you can open a DVD ISO image in VLC Player (or any other media player with full DVD support) to test its playback and menu functionality, without burning it to a physical disc.

Closing credits

DVDs can support a lot of non-essential features (such as alternate audio tracks, animated menus, multiple subtitles, and the rarely used "alternate angles"); most authoring tools start out supporting a small subset and slowly add more features as they progress. Looking at the support forum and issue tracker for Bombono, it appears that developer Ilya Muravjov is resisting the temptation to add too much too soon.

That is certainly wise. Some of the more feature-laden DVD authoring suites, such as QDVDAuthor, become tricky to use by virtue of supporting complex menu structures and DVD features. Although it is good to have the options available, for the majority of Linux users crafting a DVD is an occasional task at best. Still, it would be nice to see Bombono add one or two more features to help in the editing process — such as better layout tools, perhaps rulers and z-ordering, and some support for subtitle tracks.

For right now, though, if you are asked to put video content onto a disc that will play in a typical consumer DVD player, Bombono is a quick and straightforward solution.

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