2D-plus-depth

2D-plus-Depth or also called 2D + Z format (not to be confused with 2D plus Delta or 2D-plus-DOT) is a Stereoscopic Video Coding format that is used for 3D displays, such as Philips WOWvx. Philips discontinued work on the WOWvx line in 2009, citing "current market developments". Currently, this Philips technology is used by SeeCubic company, led by former key 3D engineers and scientists of Philips. They offer autostereoscopic 3D displays which use the 2D-plus-Depth format for 3D video input.

The 2D-plus-Depth format is described in a Philips' white paper and articles.

Each 2D image frame is supplemented with a greyscale depth map which indicates if a specific pixel in the 2D image needs to be shown in front of the display (white) or behind the screen plane (black). The 256 greyscales can build a smooth gradient of depth within the image. Processing within the monitor used this input to render the multiview images.

Supported by various companies across the display industry, 2D-plus-Depth has been standardized in MPEG as an extension for 3D filed under ISO/IEC FDIS 23002-3:2007(E).

There is also an extension on the 2D-plus-Depth format called the WOWvx Declipse format. It is described in the same Philips' white paper "3D Interface Specifications". In this advanced format, two more planes are added to the original 2D image and its depth map for each frame: the background areas covered by foreground objects and their respective depth map. So, each frame in the Declipse format is described with an image containing four parts, or quadrants. This extension improves potential visual quality by providing data for more correct and precise filling of the uncovered occlusion areas created by shifting foreground objects during the multiview generation process.

2D-plus-Depth has the advantage that it has a limited bandwidth increase compared to 2D (compressed greyscale increases bandwidth 5–20%) so that it can be used in existing distribution infrastructures.

2D-plus-Depth offers flexibility and compatibility with existing production equipment and compression tools.

It allows applications to use different 3D display screen sizes and designs in the same system.

Another advantage is that depth maps are created in the course of 2D-to-stereo 3D conversion using almost any approach to this video transformation. That is why there is the respective 2D-plus-Depth representation of a converted stereo footage in almost all cases. Considering the lack of 3D content shot in stereo and the number of converted 3D films, this is a big benefit.

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