Information Technology Reference
In-Depth Information
very high-speed transmission lines or high-speed disks that operate at 3 - 24 Giga
bit/sec. SHR video compression schemes are thus needed to reduce the transmission
and recording costs.
We have already developed a CODEC system[1] for SHR, it consists of multi-
ple conventional MPEG-2 HDTV CODECs[6] and a frame synchronizer. The main
benefit of this system is its ability to handle SHR video of various resolutions. This
system can adapt to many kinds of SHR images by increasing or decreasing the
number of encoders and decoders used. However, it is difficult to equalize the encod-
ing quality among multiple encoders, and it is also difficult to record and playback
the SHR stream because it consists of separated multiple HDTV streams.
In this chapter, first, we describe the basic idea behind our CODEC system, which
is spatial image division and multiple stream output. Section 3, we explain the video
shift and padding function, which solves the boundary distortion problem caused by
spatial image division. Section 4, we show switchable cascade multiplexing that
enable to increase the flexibility of the combination of SHR video programs in mul-
tiplexing mode. Section 5, we show how to synchronize the multiple outputs in
multiplexing mode and in non-multiplexing mode. Section 6, we explain the strat-
egy of the adaptive bit-allocation in multiplexing mode. Sections 7 and 8 discuss
our evaluations of the CODEC system. A few trials with transmission and recording
using our system are described in Section 9. Section 10 is a brief conclusion.
2
Basic Concept
2.1
Basic Concept of SHR CODEC
SHR image transmission using parallel encoding and decoding architectures con-
sists of several HDTV encoders, a transmission network and several HDTV decoders.
SHR image is represented using several HDTV images in such architectures. An SHR
camera outputs several synchronous HDTV images, and they are input to HDTV en-
coders. In HDTV encoders, all HDTV images are encoded independently and gen-
erated bitstreams are transferred to HDTV decoders through the network. Decoded
images decompressed by the decoders are output to an SHR display system.
2.2
Spatially Parallel SHR CODEC System
This CODEC system adopts the spatial image division and multi-stream output
approach. In spatial image division, the input image is divided into multiple sub-
images and the encoder modules encode them in parallel, as shown in Fig. 1.
This approach is reasonable in terms of cost performance and scalability and
has been used in some HDTV CODEC systems that use multiple SDTV CODEC's
[6, 8]. We used it when we constructed the SHR CODEC system based on mul-
tiple MPEG-2 HDTV CODEC LSIs. Spatial image division can use a one-stream
output system, in which the sub-streams generated by the encoder modules are re-
constructed into one SHR elementary stream (ES), or it can use a multiple-stream
