How Frame Sequential 3D Works

Frame sequential 3D, as the name implies, consists of a sequence of alternating frames wherein each successive frame carries the image meant for one or the other eye. This means that if Frame number 1 contains the image for the left eye, then frame number 2 carries the image meant for the right eye, with frame number 3 again carrying the image for the left eye, and so on and so forth.

Frame Sequential 3D content consists of alternate frames that are meant for each eye.

This format is quite popular and is part of the 3D Blu-Ray specifications. The reason it is popular is because it lends itself very well to Active shutter based 3D capable TVs since these 3D TVs rely on the alternate display of the left and right eye images in quick succession. Thus, in the case of Active shutter displays, the frame sequential 3D video is directly displayed on the 3D screen. The only tricky bit is to sync the active shutter glasses with the 3D TV so that the active shutter glasses allow the left eye to view the screen at exactly the same moment when the frame corresponding to the left eye is being displayed on the television screen. Subsequently, the active shutter glass will turn opaque and switch the eyepiece for the right eye from opaque to transparent so that the viewer can now view the next frame intended for the right eye.

How Side by Side 3D Works

In side-by-side 3D, a full 1080p or 720p frame consists of two halves on the left and right, with the entire frame for the left eye scaled down horizontally to fit the left-half of the frame, and the entire frame for the right eye scaled down horizontally to fit the right side of the frame. Thus, in the case of 720p content (resolution of 1280 x 720), each frame will actually consist of the horizontally scaled frame for the left eye with a resolution of 640 x 720 and adjacent to it, the corresponding frame for the right eye at the same 640×720 resolution.

Each frame of side-by-side 3D consists of a horizontally scaled combination of the frames for the left and right eye.

Side-by-side 3D results in a halving of the horizontal resolution of each frame intended for the left and right eye. When the 3D ready TV receives this side-by-side 3D signal, it splits each frame to extract the frame for each eye, and then rescales these individual frames to a full HD resolution using upscaling algorithms. It then displays these upscaled individual frames alternately in a frame-sequential manner (see the second image below) that is in sync with your active shutter 3D glasses.

Conversion of side by side 3D content to frame-sequential 3D

Almost all 3D TVs that are being released in 2010 rely on the frame sequential 3D display method. However, this doesn’t mean that the input 3D signal to the TV has to be in a frame-sequential format. In fact, pretty much all 3D HDTVs can process 3D signals in a variety of different formats and perform on-the-fly conversion of the incoming 3D video signal into a frame sequential format. While frame-sequential 3D is part of the blu-ray 3D spec, when it comes to airing 3D content over cable/air, Side by Side 3D is proving to be a popular choice. In fact, DirecTV has announced that it will be airing 3D programming by using the side-by-side 3D format. ESPN will also be airing 3D content using a 60fps, 720p side-by-side format.

Side-by-side 3D is a popular choice for 3D broadcast content at the moment because it uses the same bandwidth as regular HD content, so it can be transmitted in the same way that current HD signals are transmitted. As a result, you won’t need an expensive set-top-box replacement for viewing 3D content. Instead, your cable service providers can upgrade the firmware of the set-top-box to enable the transmission of side by side 3D content to your 3D TV. It should be noted that ESPN has already done some testing with 720p side-by-side content for sporting events and the feedback from initial testers has been extremely positive.