Understanding Mainstream 3D Formats

We still await the final release of the HDMI 1.4 specification. But the 3D portion of the spec has been finalized and available for a few weeks. This important document details four standards by which 3D content can be formatted and delivered on 3D-capable displays.

We are certain these standards will also find their way into commercial applications. Any manufacturer producing displays intended for the viewing of mainstream 3D content will need to support each of these four 3D formats.

Each of the four 3D standards is different, and those differences are worth understanding, as they define the framework by which our future 3D sources and displays will connect with one another.

Members of Digital Projection International's engineering team have analyzed and condensed the 3D portion of the HDMI 1.4 spec to the following.

Frame Packed 3D

This is the standard for 3D Blu-ray players now entering the market. This format retains 1920 x 1080 pixels for both the left and right eyes, but vertically packs two normal 1080p frames within the same time period as each of the 24 frames normally presented by a Blu-ray player. The result is a frame packed with 1920 x 2160 pixels that is split by a few black lines defining the left and right images.

Features
Out of the four 3D standards, Frame Packed 3D provides the highest native resolution from the source – true 1080p for each eye.

Although the native frame rate of the source is only 24p (per eye), Triple-Flash Processing this signal is the same approach used in commercial cinemas, and produces a very good 3D experience.

It is also possible for 1280 x 720 native 3D formats to be delivered in a similar "Frame Packed" format, but at 60 frames per second per eye. This may be an interesting approach for 3D delivery mechanisms that have lower system bandwidth than Blu-ray.


Click image for graphical breakdown of Frame Packed 3D

Top/Bottom 3D

This standard uses a 720p HD format, employing the top 360 lines for the left eye content and the bottom 360 lines for the right eye content. The content for each eye is half the vertical resolution of a 720p signal (360 lines tall), but the full 720p horizontal resolution (1280 pixels) is captured at a full 60 fps.

Features
Out of the four 3D standards, Top/Bottom 3D provides the lowest native resolution from the source, although the native frame rate is 60 fps.

A variant on the Top/Bottom standard could employ a 1080/24p format to dedicate 540 vertical lines and 1920 pixels of width to each of the left and right views. This variant delivers the full top-bottom data set at 24 fps.

As of today, we are not aware of any consumer 3D sources using this standard.


Click image for graphical breakdown of Top/Bottom 3D

Side-by-Side Progressive

This standard applies a 1080p HD format, with the left and right eye perspectives packed into each 1920 x 1080 frame, side by side. Each eye perspective is 960 pixels wide, which is half the horizontal resolution of a 1080p frame, but benefits from the full 1080 lines of vertical resolution.