CHAPTER 5
1. 3D IMAGES
The 3D video is a continuous succession of moving images by applying a particular filter, it allows
observing three-dimensional images giving them a sense of depth and producing an effect similar to
projecting images on the screen.
There are several types of 3D video:
 3D Video based on stereo television
 Stereoscopic 3D Video.
 3D Video based on auto stereo television
These different types of 3D video correspond to the technology used to create the illusion of depth as well
as the necessary technology for viewing.
The process of giving depth to a video and get a false sense of three dimensions has its bases in the double
capture of a sequence of images with an angular variation between them. Each sequence of images is
intended to be viewed by one eye so that the human brain interprets the two images and reconstruct a
third one offering the illusion of depth.
1.1
KINDS OF 3D VIDEO
Next, it will be described the different kinds of 3d video, according to the technology required for viewing.
The following summary description of the different types of 3D video technology basis required for
viewing.
1.1.1
3D VIDEO BASED ON STEREO TV
With this technology the 3D sensation is based in the angular variation of the beam of light from each pixel
of the screen. To achieve this change in the beam of light, a small circular and thin membrane composed
of silicon nitride, and aluminum coated is used suspended above electrodes.
When it applies a voltage variation over the electrodes that support this membrane is deformed in a
parabolic shape and allows changing the wave front of the light beam. This allows switching between the
sequences of images for each eye. If, however, the membrane remains flat, the images correspond to
video broadcast in two dimensions, so that both video systems are made compatible on the same screen.
IMAGING CAPTURE
ILLUSTRATION Error! No text of specified style in document.-1 SCHEME FOR VIDEO-BASED 3D STEREO TV
As shown in illustration 5-1, each eye interprets a sequence of images, which to the membrane of the
pixels of the screen has to deform and project the light beam toward the position of each eye
This system has the advantage of compatibility between the two video formats: Two-dimensional and
three dimensional.
On the other side, its main drawback is that only allows a single viewer can view the images
simultaneously, and the need to know at every moment the direction in which the viewer looks to produce
adequately the variation in the beam produced by the deformation of the membrane.
1.1.2
STEREOSCOPIC 3D VIDEO
The stereoscopic 3D video is an improvement of 3D video system based on stereo televisions.
The stereoscopic video is based on obtaining two different sequences of images for each eye, sequences
that should possess a number of similar characteristics and be perfectly synchronized in both shooting and
in their projection. There are variations of this type of video that allow the creation of 3D stereoscopic
video from a single image sequence that contains the images for each eye.
1.1.3
3D VIDEO BASED ON AUTOSTEREO TV -
The 3D video based on auto stereo television is just a stereoscopic video presented on a special display
type called WOWvx developed by Philips and is an evolution of the previously explained "3D video based
on stereo TV”, because this system is based on principles similar to the deformable membrane of that
model to represent three-dimensional images on an LCD screen without special glasses. This will look in
more detail in section 3D video issue.
º
To get the image sequences that enable the production of stereoscopic video there are two possibilities:
1. Obtain two separate image sequences, one for each eye.
2. Getting a single image sequence containing a sequence for each eye.
Next, it will be described the first process, including an overview of the means to carry it out. The second
process is based on the first one except that to carry out pre-extraction of the two image sequences
Stereoscopic video production from two different image sequences requires at least two imaging systems,
usually video cameras.
1.1.4
MULTICAMERA
By the method of multi-camera is allowed to capture video from various perspectives (and are not
necessarily two, may comprise a number n of viewing angles).
In this method, n number of video cameras should be placed in an orderly manner in an observation area
around the place in which the scene it will be recorded. These cameras must be timed perfectly (either in
carrying out the recording or performing a synchronization of video signals later in the production process)
and calibrated so as to maintain a common axis that allows the subsequent image overlapping.
ILLUSTRATION Error! No text of specified style in document.-2 VIDEO CAPTURE SCHEME USING MULTIPLE CAMERAS
TIME OF FLIGHT
Time of Flight is a system which allows getting depth information of a single image, and with that, forms a
stereoscopic image in the production process.
This method uses a depth plane (similar to the plane that in an image provides information on the
luminance or chrominance) obtained by a camera that emits a signal modulated by infrared at a frequency
higher than 20MHz. This signal projected onto the scene being recorded, bounce back over the camera
and so each pixel of the camera can demodulate the signal and detect the distance of objects through the
phase of the signal, leading to a signal in gray scale.
ILLUSTRATION Error! No text of specified style in document.-3 GETTING VIDEO THROUGH TIME OF FLIGHT
ILLUSTRATION Error! No text of specified style in document.-4 IMAGE AND RELATED DEPTH MAP
In Illustration 5-4 it can see a time in capturing a video sequence using Time of Flight, and an example of
an image signal obtained and the corresponding depth plane.
1.2
PRODUCTION AND DISTRIBUTION
The process of producing a 3D video greatly depends on the technology used for imaging and the system
will be used for display.
1.2.1
THE AVATAR CASE
To illustrate this section it will be taken as reference the production process of the film "Avatar" in its
three-dimensional version, which has become the highest grossing and seeing film in 3D in the history of
cinema.
Filming
On the set of Avatar it were present a number of factors: on one side they must record taking into account
the 3D effects that would be displayed by the spectator, on the other hand being a sci-fi movie, they had
to introduce virtual sets and special effects computer made, and finally they also had to keep intact as
possible the scenes shot by the actors.
Thus, to carry out the filming, the actors that shaped "Na'vi" beings had a series of sensors throughout his
body to capture their movements and expressions. These sensors, connected to a receiver, allowed in the
postproduction process through technology "performance capture", move such movements to the CG
characters.
ILLUSTRATION Error! No text of specified style in document.-5 ACTORS WITH MOTION SENSORS
ILLUSTRATION Error! No text of specified style in document.-6 CHARACTER OBTAINED FROM "PERFORMANCE CAPTURE"
This technology solves the problem of moving scenes of the actors to the characters made by computer.
To capture the 3D image sequences they had to use double-lens cameras that captured footage with an
angular variation (as explained in section "image capture"). Thus in the post process would comprise the
video with the two sequences.
ILLUSTRATION Error! No text of specified style in document.-7 3D RECORDING CAMERA, LENS LEFT
ILLUSTRATION Error! No text of specified style in document.-8 3D RECORDING CAMERA, LENS RIGHT
In the scenes with special effects, those in which effects are produced "startling" to the spectator; they
used multiple cameras to capture the scene from different angles.
ILLUSTRATION Error! No text of specified style in document.-9 3D RECORDING CAMERA CAPTURING A SEQUENCE
ILLUSTRATION Error! No text of specified style in document.-10 ACTION SCENE RECORDED FROM THREE ANGLES
Postproduction
After obtaining all the material of the film, in the postproduction process is done the video anaglyph
mount. This process, also called digital intermediate process, was monitored on a HD LCD monitor JVC GD463D10U that enables the display of 3D video in real time while adjusting the three-dimensional effect.
The three-dimensional effect adjustment was carried out using the Quantel Pablo 3D Stereo System, which
is a technology that lets you manipulate 3D stereo streams of two sequences of high resolution images
simultaneously in real time.
ILLUSTRATION Error! No text of specified style in document.-11 3D VIDEO EDITING BY QUANTEL PABLO STEREO 3D
The main advantage of this system compared to other existing as Telecine 3D, is that this system can
correct the timing of the images while conducting the video editing, integrating a display option for both
sequences.
However, subsequent to the video editing process in 3D should be a process of adjustment to suit the
sequence of images obtained by the display format which will be projected (brightness, contrast, and
especially size and proportions).
1.2.2
TDT 3D, TV3 CASE
Similarly to the 3D video production for cinema, 3D video can be produced for broadcast on television.
Currently there is no channel that broadcasts his programming entirely in 3D, but in the coming months
will be launched Canal+ 3D, integrated in the channels package of satellite TV Digital+. In addition, the
Catalan regional television TV3 has announced that tests 3D broadcast via DTT, becoming the first Spanish
network in to do it.
But aside from these first future broadcastings, in Spain there is a television channel has broadcast 3D TV
via DTT locally in Seville during the "International Congress on Digital Terrestrial Television", held in the
Andalusian city in March 2010.
These emissions using the method side-by-side, in which two images are sent in parallel to the receiver,
the receiver flap it forming the three-dimensional image displayed on the screen. In this case it is not
necessary to have glasses for viewing, but a specific type of screen.
Codecs
Today the TV channels broadcasting tests in 3D (such as the Madrid local channel 'Canal 33') are based on
anaglyphic system, so that the transmission of the image is based on the fundamentals of transmission
for a sequence 2D video image
ILLUSTRATION Error! No text of specified style in document.-12 EMISSION TESTING FOR MADRID DTT CHANNEL 33
Therefore have not developed specific codecs for encoding / decoding of 3D images.
1.3
ISSUANCE AND DISPLAY
Once analyzed the process of recording, production and distribution of 3D video, this section presents a
summary of the available display systems for viewing of content produced.
At this point, it is therefore necessary to differentiate between various displays systems for stereoscopic
images:
 Anaglyph




Polarization
Field sequence.
WOWvx.
Other systems.
1.3.1
ANAGLYPHS SYSTEM
The anaglyph system for viewing stereoscopic images uses filters of complementary colors for each eye.
These colors are usually red, blue or red and green.
The sense of depth is achieved when viewing two parallel images (one for each eye) with glasses having
each lens of a complementary color. Thus, the projected image in red is only seen by the eye with the red
lens but not the other eye, allowing the brain to interpret a third image "virtual" three-dimensional.
ILLUSTRATION Error! No text of specified style in document.-13 ANAGLYPHS IMAGE
This system has been the most widely used until now because it allowed for a negligible cost (cardboard
glasses video and film) to enjoy the 3D effect to the masses without having to perform any adaptation.
In contrast, negative effects such as loss of light and altered colors, plus being able to have visual fatigue
after long exposure.
ILLUSTRATION Error! No text of specified style in document.-14 ANAGLYPHS GLASSES
1.3.2
Colorcode 3D
Is a variation of anaglyphic system that allows anaglyph viewing on any screen using blue and yellow. Its
main advantage over systems that use other colors anaglyphic is that in this case we get the full
chromatic range.
ILLUSTRATION Error! No text of specified style in document.-15 ANAGLYPHS IMAGE WITH COLORCODE 3D
TECHNOLOGY
1.3.3
POLARIZATION SYSTEM
This system uses for display glasses with special lenses that allow the use of polarized light to
separate the sequences of the right eye and left eye.
Its rationale is as simple as the recording of two image sequences that will be shown later
synchronized. Each sequence will be applied to a given filter (horizontal and vertical in one
another) and this will produce two beams of light with a phase difference of 90 degrees.
ILLUSTRATION Error! No text of specified style in document.-16 IMAGE PROJECTION WITH POLARIZATION FILTER PROYECCIÓN DE IMÁGENES CON FILTROS DE POLARIZACIÓN
These light beams projected to the screen bounces back the spectator's glasses composed of
two lenses, a polarizing filter with a vertical and horizontal with a filter, allowing to obtain
three-dimensional image.
ILLUSTRATION Error! No text of specified style in document.-17 IMAGE DISPLAY FOR POLARIZED SYSTEMS
The polarized image display system improves the system by not producing anaglyphic
alteration of three-dimensional color images, but has other issues such as loss of brightness.
To solve this problem should increase the sources of light but this can cause other effects such
as ghosting due to the high contrast images.
1.3.4
SEQUENCE FIELD SYSTEM
Sequence Field is the most efficient 3D video display system of the three described.
This system uses a pair of LCD glasses to separate images for each eye, which will be shown
sequentially. To accomplish this it is necessary to multiplex the images and the glasses are kept
synchronized with the layout of each of the two fields that make up an image, for showing the
image on the right pane the left pane is covered and vice versa.
ILLUSTRATION Error! No text of specified style in document.-18 LCD GLASSES FOR 3D DISPLAY USING FIELD
SEQUENCE
1.3.5
SISTEMA WOWVX
WOWvx is a 3D video display system developed by the company Philips. Actually it is an auto
stereoscopic TV, that is, capable of representing three-dimensional images without auxiliary
glasses.
It is based on a screen that contains layers with an array of multi-view lens, transparent and
cylindrical. These lenses are fixed on the screen and make it possible with an eye to observe a
portion of the screen while the other shows a different part.
As result of the application of the layer with the lens array is diminished the brightness and
contrast of the screen.
The sense of depth and three-dimensional image is achieved by representing the visual
information about the sub-pixels in which each lens is divided. When a source overlaps a subpixels group, this information is sent in a different direction to the observer, which interprets
them as separate images.
ILLUSTRATION Error! No text of specified style in document.-19 WOWVX 3D VIDEO DISPLAY SCREEN
1.3.6
OTHER SYSTEMS
This subsection includes all the systems display stereoscopic images that complement those
already explained above.
Free Vision parallel (Magic Eye)
Each eye observes a sequence of images maintaining the same optical axis parallel, is valid for
images less than 65mm between their centers.
ILLUSTRATION Error! No text of specified style in document.-20 STEREOGRAM CONTAINING 3D IMAGE
Free cross Vision - Visión libre cruzada
The three-dimensional image it seen crossing the optical axes of the eyes. It is valid for images
larger than 65 mm between their centers.
Head Mounted Display
System similar to steps in the field-glasses that are composed of two LCD screens, one for each
eye.
ILLUSTRATION Error! No text of specified style in document.-21 GLASSES DISPLAY BY HEAD MOUNTED DISPLAY
Another key element to the three-dimensional video display, are the home screen currently
being introduced in the Spanish market.
These screens are based on the polarized stereoscopic imaging projection, thus requiring the
use of special glasses, and must have support for high refresh rates of images (currently found
in about 200Hz) so that projects to 100 images for eye and second.
ILLUSTRATION Error! No text of specified style in document.-22 SAMSUNG LED 3D 3000
ILLUSTRATION Error! No text of specified style in document.-23 SAMSUNG GLASSES FOR VIEWING VIDEO 3D
In addition to the display, the fact to need specific glasses for viewing 3D video is an important
point in this technology. The current lack of consensus among TV manufacturers today do we
find ourselves in an uncertain scenario.
On the one hand is Panasonic, one of the first manufacturers to market 3D television and,
therefore, to launch their own glasses. Moreover, Samsung, currently leads the sales of this
type in television, has refused to adopt the same standard as Panasonic for making glasses
and, therefore, has made its own incompatible with the former.
Recently, the web portal specializing in multimedia publication "Home Cinema" published an
article which reveals the system to use for compatibility with Panasonic Samsung glasses. This
method is simply rotated 180 degrees glasses.
Samsung, meanwhile, has had to admit this fact, and has already committed to reaching an
agreement for the marketing of standard glasses by all manufacturers.