Understanding the different 3D TV Formats

3D TV formats span from the Side-by-Side 3D as used by DirecTV and Sony’s PlayStation Top/Bottom 3D, to the latest Blu-ray 3DTM format.

Some may think that this may lead to a format war; but do not worry, this is not the case as all 3D TV makers had stated during their debut in 2010 that their 3D HDTVs comply with practically all 3D TV standards in use today.

In this article, we look at the different 3D formats to better understand the differences. We also explain why not all 3D Television formats need the latest HDMI 1.4 to deliver 3D content.

3D HDTVs: Support for different 3D TV Formats

Panasonic VIERA TC-P55ST60 55-Inch

Prior to discussing the different 3D TV formats, I think it is significant to note that during the 3D TV debut in CES2010, all TV makers made a clear statement that their new 3D HDTVs support practically all 3D TV formats in use today.

It was extremely important that these confirmations came at such an early stage of deployment of 3D TV technology in the home. It seems that the manufacturing industry had learned from the mistakes of the recent past that led to format war between Blu-ray and HD DVD, a war which led to waste of resources by both the manufacturing and entertainment industries.

This means that unlike early adopters who went for a 3D-ready HDTV with the hope of future-proofing their TV purchase between 2007 and 2009, buying a 3D TV now should still give you a usable 3D TV for the years to come.

We have to admit that with all the different 3D TV formats in use today, understanding the terminology and the way these formats work can seem to many like an impossible task.

One major difference however between the different formats in use today is that of the effective resolution of the final 3D image. While the latest Blu ray 3D supports full 1080p content at source, formats like those used by DirecTV and PlayStation 3-D are reduced resolution 3D TV formats, displaying two simultaneous images at half the resolution for each eye in a single frame. This is practically the same as with passive 3D-TV glasses technology, which cuts the full HD 3D image resolution by half.

Full HD resolution 3D TV systems require two full streams of 1080p content to be able to display a full 1080p HD image to each eye in a field-sequential manner. It is this reduced resolution that in effect allowed both Sony’s PlayStation 3 and DirecTV’s existing satellite receivers to be able to handle 3D TV through a simple firmware upgrade; the electronics inside these systems are not designed to handle two simultaneous streams of full 1080p content.

This guide to 3D TV formats has been written with the aim of providing an easy-to-follow overview on the subject. Having a basic understanding of the 3D TV formats in common use and how these relate to HDMI 1.3 and HDMI 1.4 devices is important to foresee possible compatibility issues that may arise with non-compatible HDMI 1.4 devices.

Most common 3D TV Formats explained

The picture presented here depicts the main 3D TV formats in use today. We discuss each of these formats in detail below.

This diagram depicts how these different 3D TV formats store the left and right sub-frame images; these are then processed so that irrespective of the way the information is stored in the 3D content frame, the final presentation would be a full size image for the left eye and a full size image for the right eye.

Picture credit: Cineramax Next Gen 4-D Cinema Systems

Side-by-Side 3D

We have already noted that DirecTV and PlayStation 3D TV formats are not full resolution 3D formats.  DirecTV uses a 3D TV format referred to as Side-by-Side 3D where the horizontal resolution of the HD image is reduced by half in order to store the left eye and right eye images on a single frame. This means that the left-eye sub-frame and the right eye sub-frame are stacked side by side, as implied by this format name itself.

To display Side-by-Side 3D, a 3D TV will have to split the frame into its left and right sub-frames; these sub-frames are then up-scaled to the set native screen resolution and displayed in a Frame Sequential manner – a process also referred to as page flipping – to achieve the 3D effect.

The most common Side-by-Side 3D TV format is the Side-by-Side Half where each sub-frame occupies just half the horizontal resolution of a full HD frame, resulting in a 3D image with 960pixels by 1080 lines instead of the 1920×1080 required for full 1080p content. This simplifies the electronics while making it compatible with HDMI 1.3 devices.

It is interesting to note that Side-by-Side 3D may also be used to stack two full 1080p frames in a side-by-side fashion, thus delivering full HD 3D; this requires HDMI 1.4. However, it is not a mandatory for HDMI 1.4 devices to carry full 1080p HD sub-frames in Side-by-Side 3D format.

Top-Bottom 3D

Another reduced resolution 3D TV format is the Top-Bottom 3D used by Sony’s PlayStation 3; this format is also at times referred to as Over-Under 3D format.

In concept, this is very similar to the Side-by-Side 3D but with the Top-Bottom 3D format, it is the vertical resolution that is reduced by half as the images for the left and right eye are stored on top of each other in a single frame, hence this format name.

As with the Side-by-Side 3D, it is the 3D processor inside the 3D TV that will expand the corresponding half frame image into a full-size image for each eye in accordance with the native resolution of the HDTV.

How the actual half frame in both the Side-by-Side and in the Top-Bottom 3DTV formats is expanded into a full size image to cover the entire screen area, may differ between different TV makers. But systems may either work out the missing pixel data, like when upscaling image resolution to display a lower resolution image at the HDTV native screen resolution, or simply fill in adjacent blank lines in the case of top/bottom 3D systems and alternative pixels in the case of side-by-side 3D images.

In other words, with these formats, the displayed images will still be field sequential but the 3D enjoyed in this manner will be of a lower resolution than that possible with Full HD 3D TV. Again, this is practically the same as with passive 3D glasses TV systems. Despite the lower resolution, the resultant 3D image will still look great on the average size screen, though some image softness will start to become noticeable as one moves towards 55-inch screen sizes and above.

Reduced resolution Top-Bottom 3D is compatible with HDMI 1.3 and is supported under the HDMI 1.4 specifications. It is a popular choice for displaying sports in 3D at 720p 60fps.

As with Side-by-Side, lossless Full HD 1080p 3D using Top-Bottom frame stacking requires HDMI 1.4. This Top-Bottom stacking is also the standard format of stacking the Full HD high definition 3D standard for 3D-enabled Blu-ray players.

Blu-ray 3D, also known as Full High Definition 3D (FHD3D Format)

As indicated above, Blu ray 3D, or FHD3D, supports full 1080p content at source. This means that the images intended for the left and right eye are already at 1920×1080 pixel resolution at source. These images are then displayed in the usual field sequential order to render the effect of a 3-dimensional image.

This is the only loss-less 3D TV format that provides true HD. Each full HD sub-frame for each eye is stacked using the Top-and-Bottom 3D format. This format requires HDMI 1.4 and is incompatible with HDMI 1.3 devices since these cannot handle the extra bandwidth required to support a 3D frame containing two stacked full 1080p HD sub-frames.

One important difference between this Blu-ray 3D format and the lower resolution 3D formats is that FHD3D uses a process referred to as ‘Frame Packing’ to build up the combined loss-less single 3D frame from the two full HD sub-frames. This means that Frame Packing is used only with full resolution Top-Bottom and Side-by-Side 3D formats without any halving of the vertical or horizontal resolution of individual sub-frames in each format respectively.

Instead, lower resolution 3D TV formats use a process known as ‘Frame Compatible’ to build the 3D frame from the two lower resolution sub-frames. In the case of Frame Compatible 3D content, the net resolution and size of a given 3D frame is the same as a single frame of regular 2D HD content, thus making it compatible with regular 2D HD. This compatibility is achieved by halving the net resolution for each sub-frame, either by halving the pixels in each horizontal line or by halving the number of vertical lines.

Checkerboard 3D Format

One 3D TV format we did not refer to above is the checkerboard format used in DLP HDTVs. Some may think that DLP rear projection TV technology is dead, but if you were thinking so, you are in for a surprise! Just check our latest rear projection TV review update for 2012 to see why.

3D DLP TVs and 3D Digital cinema systems use a format based on checkerboard technology, which in itself is a by-product of the wobulation process used by DLP HDTVs to build up the 1080p image from the 960×1080 pixel Texas Instrument Digital Micro-Mirror Device (DMD). This uses a small optical actuator to offset (wobulate) the 960×1080 pixel image by ½ pixel 120 times a second, generating 120 sub-frames/s to create a full 1080p 60Hz image.

This half-pixel displacement not only helps soften the pixel edges for a seamless more film-like image with no visible pixel structure as instead is the case with large plasma and LCD TVs, but also renders itself ideal for the implementation of high quality 3D imaging on DLP RPTVs through the use of the 3D checkerboard format.

This 3D TV format is used to pack the left and right images into one frame, with one sub-frame of the DLP image containing the right image and the other sub-frame containing the left image. Unlike other 3D formats, this is a ‘static’ format – implying there is no need for page-flipping. Instead, the two views are overlaid and appear as a left and right checkerboard pattern to form a single 3D image as further explained in the short video clip above.

The resultant 3D image is at half the resolution supported by the 1080p HDTV format in a similar manner to 1080p 3D TVs using passive 3D glasses technology. However, the use of wobulation/checkerboard technologies to implement 3D in DLP displays helps render superior 3D images that are virtually free from 3D image crosstalk and closer to what one enjoys in 3D movie theaters.

The checkerboard DLP 3D TV format requires active shutter glasses, with the shutter glasses using a special synchronization protocol called DLP Link, developed by Texas Instruments.

3D TV Formats and 3D Glasses

The three 3D TV formats referred to above are not the only 3D TV imaging formats in use today. It is interesting however that all 3D TV systems in the home use some form of 3D glasses for the viewer to be able to see the two 2D images displayed by the 3D TV as a single 3D image. The type of 3D glasses to use depends on the 3D technology itself.

For example, in the past, we have seen two-color Anaglyphic 3D―viewed using anaglyph 3D glasses; these have two differently tinted lenses, often one in red and the other in cyan, though other anaglyphic 3D system come in either green and magenta, or yellow and blue. These 2-colored 3D glasses are used to combine two color-modified images – which when seen through the color correcting glasses, would supposedly produce a 3D image in the correct color.

The result is inevitably a somewhat discolored 3D image than that supported by the latest 3D TV technology using the field-sequential 3D TV formats.

The latest 3D formats use either active or passive 3D glasses technology. Active 3D glasses technology makes use of the more expensive active 3D shutter LCD glasses; these work by synchronizing the LCD ‘shutter’ on the 3D glasses with the image displayed on the screen – thus allowing each eye to see only the image it is intended to see. Active glasses 3D systems support the full 1080p 3D resolution but the glasses are somewhat less comfortable in use than passive glasses systems.

Passive 3D glasses systems use circular-polarized glasses to separate the two sub-frames being shown on the TV screen at the same time; another polarized filter is placed in front of the TV screen. The screen filter is invisible to the viewer but when you look at the screen through the polarized 3D glasses, the screen filter ensures that each eye sees alternate lines on the displayed image, thus creating a separate image (sub-frame) for each eye. This means these systems do not rely on field sequential as active shutter glasses 3D technology; in addition, displaying the two sub-frames at the same time on the screen means that passive glasses 3D systems have to cut the Full HD 3D resolution by half. However, passive 3D glasses are more comfortable and much less expensive than active shutter 3D glasses.

What about no-glasses 3D TV Technology?

We said that all present 3D TV formats use glasses; currently, there is no mass market technology for 3D in the home that lets a TV displays 3D content without glasses. However, we have been seeing no-glasses 3D TV prototypes since CES2009. In particular, the prototype presented by Toshiba during CES2012 did achieve impressive results even though work is still necessary to perfect this technology.

These systems use an autostereoscopic display, where the image is doubled up so each eye perceives a slightly different view, and you get an illusion of depth perception without the need of 3D glasses.

These displays are extremely expensive to produce and have their downside as well. To view these displays, viewers have to stand at one of several points in the viewing area―otherwise the image will look doubled up and blurred. The Toshiba no-glasses 3D HDTV presented during this year CES did support up to nine such different viewers positions.

This is a major limitation with 3D TV viewing at home even though the larger number of viewing positions with the latest prototypes significantly reduces the problem. As with most autostereoscopic displays, the Toshiba 3D prototype incorporates a camera in the display to track the viewer’s head and adjust the image parallax accordingly so that the viewer can sit anywhere. But once it locks on a viewer, the other persons in the room will have to stay at specific positions within the viewing area to be able to see the 3D image.

These systems are still not ready for the mass market but it is encouraging to see TV makers working to eliminate one of the biggest hurdles 3D TV has to overcome―the 3D glasses.

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