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transmitted in parallel. In the multiplexing mode, the pre-encoder analyzes the in-
put images and each encoder module in the main-encoder outputs a variable bitrate
(VBR) ES, and these are multiplexed into one CBR TS. The multiplexing mode has
the advantages of available transmitters and efficient coding. The other advantage
of the multiplexing mode is that it is easy to record and playback the TS because
the TS to be handled is single. However, it is difficult to record and playback in the
non-multiplexing mode due to synchronization problems among multiple TSs.
3
Video Shift and Padding Function
Generally, SHR or over-HDTV image camera systems output divided images by
using conventional HDTV video-signal interfaces, such as HD-SDI's. There are
1080 active lines in a conventional HDTV system[10]. Here, this system is called
a 1080-HD in this chapter. However, some SHR systems use the old HDTV signal
system[11], where there are 1035 active lines, we call this the 1035-HD.
There are two problems in connecting SHR equipments that has a different num-
ber of active lines. The first is the black line problem. If 1035-HD system signals
are received by a conventional 1080-HD system, the received image data do not
fill the active line, e.g., 1920 x 1035 image data on 1920 x 1080, and the remain-
ing lines are filled with black or zero data. A 3840 x 2160 projector, which uses the
1080-HD system, will display three horizontal black lines on the screen, as shown in
Fig. 3, when the projector is connected to a 3840 x 2070 camera that uses a 1035-HD
system. It seems that an effective solution is to vertically shift the SHR image data
with the SHR projector to overcome this black-line problem; however, this solution
is insufficient rectify to the second problem.
The second problem is distortion caused by mismatch between the image bound-
ary and the DCT block boundary. Because MPEG-2 encoders transform 8 x 8 image
blocks by using DCT and cut off high-frequency components, if the edge of the im-
age and the DCT block boundary do not match, the border will not be sharp and the
image data will be eroded by black data. Thus, coding distortion will be visible at
the boundary of the divided images. Although this problem also occurs at the border
of ordinary coded images, it is more visible in SHR systems because the boundaries
of the divided images are positioned at their center.
The video shift and padding function modules in our encoder system are placed
in front of the encoder modules to solve the mismatch problem. These modules can
Fig. 3 Black line problem
causedbymismatchbe-
tween active lines
SHR projector
(1080-HD system)
SHR camera
(1035-HD system)
Black lines
1035
1035
1035
1035
HDSDIx4
2070
2160
Black lines
1035
1035
1035
1035
Black lines
3840
pixels
3840
 
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