Projector Reviews

First Blog – Moving to 3D

Greetings to all existing and future home theater owners that have made the decision to use front projection at the means of achieving the cinema experience in their own home.  For my first blog, as well as the next several here at Projector Reviews, I have decided to focus a little on the history and more on the technology for bringing 3D into the consumer home theater environment.  Pete Connolly’s “The Art of Gaming” blog will cover 3D gaming while my focus will be on 3D for viewing movies and video programming.

 

Over the next several blogs I will be talking a little about the history of 3D video with some discussion of how 3D video has evolved into its current state.  I also plan to get into some the technical aspects of 3D video with discussions of the alternative 3D approaches for providing consumers with 3D in their projector-based home theaters.  My focus will not be limited to just 3D-ready projectors but also to projection screens, 3D glasses, video processing and to some extent to 3D sources. 

 

To start off this first blog I would like to summarize where we are with the HDMI version 1.4a standard for 3D video.  The HDMI version 1.4a specification was released on March 4, 2010 and includes a section on “Extraction of 3D Signaling” that defines the 3D formats that are mandatory for 3D displays. Note that there are a number of 720p DLP projectors being sold as being ”3D Ready” that do not have HDMI 1.4a input(s) and do not support the 3D video formats required by that specification.   Any 3D display/projector that claims to be certified to HDMI 1.4a must accept all of the mandatory 3D signal formats (listed below) at their HDMI input then internally apply video processing to put the 3D video into a format appropriate for that specific display. Therefore, the 3D video source (e.g., Blu-ray 3D disc player) is not required to adapt its output signal format to the unique capabilities of the connected 3D display nor is the 3D source device required to support more than just one of the approved 3D signal formats. Note that the rules for which 3D formats are required to be supported applies only to those sources and displays that claim to be compliant with the HDMI 1.4a specification. The Blu-ray 3DTM specification (released in December 2009) specifically requires support for the Frame Packing 1080p/24 and 720p/60 formats as defined by the HDMI 1.4 spec. Below is a brief summary of the mandatory 3D video formats that are defined by the HDMI 1.4a specification. There are 3 basic formats defined (in table 8-15 and associated figures and text of the HDMI 1.4a spec.) and then there are specific resolution and frame rate variations required/allowed under each.

Frame Packing 3D Format (Blu-ray 3D required full resolution formats)  

  • full 1080p resolution for each right/left images with refresh rates of 23.98/24 Hz
  • full 720p resolution for each right/left images with a refresh rate of 50Hz* or 60Hz.

The Frame Packing structure used for delivering full resolution 1080p 3D video at 24 frames per second (for each the right and left image streams) is illustrated in the figure below:

 Note:    Frame Packing is capable of placing two full resolution HD images into one “super sized” frame as shown above for transmission across HDMI. Frame Packing provides full resolution 3D and when used for 1080p 3D video, the right and left images are placed one above the other into a “super sized” frame that is 2205 pixels vertical by 1920 pixels horizontal with a 45 x 1920 pixel active blanking area separating the two images.

 

Side-by-Side 3D Format – (e.g., satellite or cable 3D broadcast)

  • half horizontal resolution 1080i (i.e., 960h x 1080v pixels) for each right/left image with refresh rates of 59.94/60 Hz or 50 Hz*.

Top-and-Bottom 3D Format – (e.g., – satellite or cable 3D broadcast)

  • half vertical resolution 1080p (1920h x 540v pixels) for each right/left images with refresh rates of 23.98/24 Hz.
  • half vertical resolution 720p (1280h x 360v pixels) for each right/left image with refresh rates of 59.94/60 Hz or 50 Hz*.

 

Note:    All 3D displays conforming to the HDMI 1.4a spec. must accept 3D signals with a 23.98/24 Hz refresh rate as well as either 50Hz (e.g., Europe) or 60Hz. (e.g., North America) refresh rates for all of the mandatory 3D signal types as listed above. However, the actual resolution and refresh rate the 3DTV uses to display the 3D images to the viewers is entirely up to the specific 3DTV design.

 

Please post you comments and/or suggested future discussion topics.

 

RonJ  (Ron Jones)