What is Frame Sequential 3D?
While the 3D TV market is set to take off in a big way, one of the annoyances at the moment is that there is still no standardized method for transmission and encoding of 3D content. Thankfully however, this isn’t akin to the typical format wars because even though there are a number of different techniques that are in use for encoding 3D videos, all 3D HDTVs can process this incoming 3D signal and re-encode it on the fly to a specification and format that allows it to display the 3D content.
One of the primary formats is what is called Frame Sequential 3D. 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.
Thus, ultimately, frame sequential content work well with frame sequential displays. However, you can be reassured that there is nothing much to worry about when it comes to the encoding format for 3D content as almost all 3D ready TVs released in 2010 will be capable of handling multiple 3D formats and converting it to a suitable form so that they are able to display it on screen.
More Information – JVC: 3D Video Technology
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about 5 months ago
We are told that 3d tv’s are all 120Hz so that each eye will receive 60 frames per second. As only 60 full frames can currently be transmitted per second, does this not mean that each eye is only truly seeing 30 distinct frames, with the other 30 being interpolations ?
about 5 months ago
Hey Richard,
That is a great question. Unfortunately, many of the specifications that will be used for 3D broadcasts are still not set in stone. However, I should clarify one important thing. 60fps is not necessary for smooth viewing. If that were the case, you and I could never enjoy any of the Hollywood movies in the cinemas or when watching Blu-ray discs.
This is because Hollywood still uses 24fps for shooting movies, and that works perfectly fine for the most part. Blu-Ray 3D will mostly utilize frame sequential 1080p at 24fps, that is 24 frames for each eye, or 48 total frames at 1080p. This should provide excellent quality.
When it comes to 3D broadcasts, depending on how you are getting your video, you might be bandwidth or cablebox limited. There are techniques such as “Side by Side” 3D, where the left and right eye image is squeezed into a single 1080 or 720 frame, and then processes and separated out by the TV. It does halve the horizontal resolution of the image but initial tests by ESPN with 720p side-by-side content at 60fps has gotten very positive feedback.
We’ll have to wait and watch a bit to see what framerate and specifications 3D content providers go with, but for the most part, you don’t have to worry too much about it as all the 3D TVs should be able to process these different specifications and display it correctly on the TV screen.
I will be including a couple of articles on the different frame packing and display methods that are going to be incorporated in 3D displays. So stay tuned!
about 5 months ago
Thanks for the reply, it’s rather as I thought. I take your point about the lack of a set stndard, I was really thinking of the frame sequential format rather than side by side.
The thought behind my question is that there is really no fundamental reason why a 3d tv should have to be 120Hz. The systems currently available have been configured thus – the glasses only operate at 120Hz as I understand it – but a 60Hz set delivering 30fps to each eye would in theory still be better than movie film.
about 5 months ago
Richard,
While you are indeed correct in that there is no specific reason that television sets needed to be 60Hz or 120Hz back in the day, the truth is that 60Hz at 30fps for 3D wouldn’t work as well. While the video itself would display correctly, due to the nature of the active shutter glasses, a 1/30 second shuttering per eye (for a 60Hz 3D Display) would be too jarring and noticable, leading to flickering and a poor viewing experience.
Of course, that is independent of the actual ability of the TV to display the content, but is more a limitation imposed by active shutter technology. Historically, the different framerates chosen by different media/countries has made the whole framerate system a bit messy. It certainly would be ideal if everyone could agree on a single FPS so that we wouldn’t have to worry about uneven pulldown and judder associated with incompatible display refresh rates.
As mentioned in our Panasonic Plasma 3D TV reviews, the new panasonics had to also be modified to handle 120Hz. This was purely for the sake of active shutter to work, as Plasma TVs don’t inherently need the bump to 120Hz refresh rates for ghosting, etc due to the ultra-fast response time of plasma panels.
about 4 months ago
Thanks for the info!
I am looking for info on how to create 3D animation for the Panasonic screens (or other brands)
I already make 3D for autostereoscopic screens and really would like to try to make images for those new screens!
Is there a special codec to use ?
It seems that it have to be 60fps for a frame sequencial, am I right?
thanks for your help
Chris
about 4 months ago
Hi Chris,
I don’t think I’d be the best person to advise you on 3D content creation. However, I’d certainly be glad to point you in the right direction. Have you tried the 3D Yahoo Group?
http://groups.yahoo.com/group/3dtv/join
Excellent group, with some very knowledgeable folk including a few industry veterans. Feel free to post your question there and I’m sure that someone on the group should be able to give you a much better answer than anything I could come up with =)
about 3 months ago
HDMI 1.4a Spec/Standard for HDTVs was done with mandatory of 3D formats. Find it and see what actually CE vendors must have manufactured.