New Design Considerations
Like all new formats, 3D Blu-ray authoring introduces new technical considerations into the author’s workflow. 3D is unique among technologies, however, in that it introduces physiological considerations as well. Put simply, poorly implemented 3D can make your audience sick — and we are not speaking metaphorically.
The issue of Z-depth position, the measurement of how deep into or how far in front of the screen an image is perceived to be by the viewer, becomes an important consideration for disc structure, menu design and subtitle implementation. This is because it is very taxing for the human eye to repeatedly refocus on objects that are displayed at different Z-depths.
To demonstrate this, hold your finger about a foot in front of your face, and then in rapid succession, look at your computer screen, then back to your finger, and so forth. Your eye re-focuses each time. If you display pop-up menus or subtitles over 3D video, you need to display those graphics in the same depth as the dominant visual on the screen or else your viewer will have to refocus on them quickly. For pop-up menus this can be disorienting and unpleasant. In the case of subtitles, this will cause a headache or worse.
Since the action on screen is likely changing depth all the time, you really need to adjust the z-depth of your graphics throughout the duration of the shot or scene. This adds a new element to your authoring process and requires you to consider the best overall design for your disc: Will I create 3D menus? Do I wan to implement a pop-up menu? If so will I choose a single Z-depth or will it track throughout the entire show.
While you mull over these new design considerations, here is some basic technical info to get you started.
Blu-ray Disc Profile 5
The 3D Specification for Blu-ray Disc is designated as “Profile 5″ (the previous Blu-ray disc profiles are Profile 1.0, Profile 1.1 “Bonus-View” and Profile 2.0 “BD-Live”). Profile 5 allows a maximum data rate of 72Mbs (up from 48Mbs for BD-Live players), requires HDMI 1.4 (a higher-speed version of HDMI), and supports 3D video, 3D menus and 3D subtitles.
BD3D discs are backwards compatible with earlier profile Blu-ray players
Frame rates/sizes
The Blu-ray 3D specification defines a more limited number of frame size and frame rate combinations than standard Blu-ray. The allowable frame size/rates for BD3D are as follows:
- 1920×1080 @ 23.976 fps progressive
- 1280×720 @ 59.94 fps progressive
- 1280×720 @ 50 fps progressive
You can mix 2D Blu-ray and 3D Blu-ray on the same disc. When you do so, you can use all of the allowable frame sizes and frame rates for 2D Blu-ray Disc.
3D Encoding - the MVC Format
Blu-ray 3D uses a new file format, called Multi View Coding, or MVC, which is an extension of the MPEG-4 AVC format used by standard Blu-ray discs. There is not VC-1 or MPEG-2 codec for BD3D. To encode your video in 3D, you will need to create two full-frame HD streams and use a BD3D-compatible encoder.
MVC streams are backwards-compatible with earlier (non-Profile 5) Blu-ray players. In this case, only the base view (2D) is displayed. It is still full 1080p. For more information about the MVC format and 3D encoding, please read this page.
3D Menus
There are two ways to implement menus in 3D. You can design 2D menu graphics and assign an overall Z-depth value for the menus (all menu elements will display at the same depth). Or you can implent 3D menu graphics in which each menu element has its own Z-depth value.
Each approach has advantages and disadvantages. For more information, please read this page.
3D Blu-ray Authoring tools
Support for 3D Blu-ray authoring has been announced by the major Blu-ray authoring tools companies. A 3D authoring module will be available for NetBlender’s DoStudio in June.