Encoding And Delivering 3D Video Content
The highest-quality method to encode and deliver a 3D video program is to store and deliver it as a dual-stream synchronized video program, with one full-quality video stream for each eye. This is how Blu-ray 3D works, storing the video for each eye as a full “Blu-ray quality” video program.
The HDMI 1.4 specification provides for 3D stereoscopic video to be delivered in several different ways, including over/under-formatted frames that are 1920 pixels wide and 2205 pixels high. The frame for the left eye and right eye are delivered together, to assure that synchronization is always maintained, even if the signal is momentarily lost and then restored.
Compressed 3D Encoding
For compatibility with existing equipment and video standards, 3D video content can be compressed to fit in a standard video signal. There are several ways that this can be done.
Side by Side encodes the video for each eye in half of a standard video frame (with the right eye picture on the right side of the frame). Thus, the video for each eye is stored with half of the horizontal resolution (960x1080 pixels in a standard 1080p video frame).
Interlaced stores the video for each eye in alternate horizontal lines. The odd lines store the picture for one eye, while the even lines store the picture for the other eye. The picture for each eye has full horizontal resolution, but half of the normal vertical resolution (1920x540 in a 1080p video frame).
Over/Under is a format that encodes the picture for each eye with half the vertical resolution stacked on top of each other in a single video frame. The picture for the left eye is stored in the upper half of the frame, and the right eye is stored in the lower half. As with the Interlaced format, the picture for each eye has full horizontal resolution, but half of the normal vertical resolution (1920x540 pixels for a 1080p video frame).
Displaying 3D Video
A stereoscopic 3D video contains two time-aligned video channels (one for each eye). To view 3D video, the display technology and the 3D glasses must assure that the left eye sees only the video meant for the left eye, and so on for the right eye. There are a number of different technologies that are designed to accomplish this, and each technology has its own benefits, drawbacks, and costs.
Mention 3D video and the image that comes to mind for many people is that of the familiar 3D glasses, with one red and one blue lens. These glasses use the anaglyphic method of displaying a 3D image.
Anaglyph images are created by using color filters to remove a portion of the visible color spectrum from the image meant for each eye. When viewed through the color filters in the 3D glasses, each eye only sees the image that contains the portion of the color spectrum not filtered out by the lens. The benefit of the anaglyphic method is that no special display is needed; any standard 2D display or TV can display an anaglyphic 3D image. The drawback of anaglyphic 3D is obvious. The overall image quality suffers as a large portion of the color spectrum is filtered out of the image for each eye.