The Process
As with all media projects, the first things that must be determined in the high-definition video process are the content, audience, and goals of a project. The planning process is the time to brainstorm the most dynamic and inventive ways to present your content on Blu-ray Disc.
Planning
As this format is still relatively young and its potential largely untapped, the planning process is an opportunity to discuss the possibilities that Blu-ray can provide. The first step is taking an asset inventory to catalog the number of video clips and their running time, as well as any chapter points needed. Next, the menu structure needs to be laid out, and a few questions need answering. Are still images or text graphic screens to be included? Will the disc use advanced features such as motion menus, multiple audio tracks, subtitles, or multiple camera angles?
These questions help us calculate a bit budget which determines the amount of material that can fit on a single disc. A flowchart is then created to guide the creation process. This document includes all content structure, menu branching and interactive navigation of the disc.
Encoding
Encoding is the process of digitizing and compressing video and audio assets. Blu-ray supports a multitude of video and audio codecs:
Video |
• AVC |
Audio |
• Linear PCM |
Audio |
• DTS HD
|
The disc format, content duration, and content style (i.e., static video, fast camera motion, etc.) will determine the encoding bit rate and the amount of video that can fit on your disc (see charts). Source video must be master quality in HDCAM or HDV tape formats, or a high-definition digital source provided on external HDD storage.
Disc Type |
Layers |
Capacity |
Approximate Video Capacity |
Blu-ray Disc 25 |
Single |
25 GB |
128 min |
Blu-ray Disc 50 |
Dual |
50 GB |
256 min |
Authoring
Authoring for Blu-ray is much more involved than standard DVD. In addition to familiar tasks such as laying down audio, video, and subtitle assets, and creating chapter points, this format engages a customized “BD-J” layer (an interactivity layer using a form of Java). This language allows for an unprecedented amount of menu interactivity and increased functionality spanning the whole disc. If you can imagine it, it can probably be done: the sky is literally the limit!
However, the BD-J layer is still being developed and only just beginning to reach mainstream hardware compatibility. Until it becomes widely supported, the authoring is done in “HDMV” mode, which provides a much more robust set of commands and programming freedom than DVD, but still faces similar limitations.
Pre-mastering
Pre-mastering involves several steps: formatting, imaging, and proofing. Formatting multiplexes (joins) the video and audio tracks into a single track, then organizes the files into the proper configuration. Imaging copies these files to BD-R, or hard disk for proofing and, later, replication. Proofing (also called simulation) is the quality assurance step of the process. Carefully viewing the content and checking navigation will insure that a disc is ready for release. A BD-R “one off“ disc is burned to test the program in different players to assure universal acceptance.
Mastering
Mastering is the actual physical fabrication of the disc. A DLT containing the data files is sent to a replication facility. In a process similar to standard definition DVDs, a glass master is created and used to press replicated copies. The replication process usually requires one to two weeks depending upon the quantity and lead-time.
