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Digitalized video and audio system has become the trend of the progress in multimedia, because it provides
great performance in quality and feasibility of processing. However, as the huge amount of information is needed
while the bandwidth is limitted, data compression plays an important role in the system. Say, for a 176 x 144
monochromic sequence with 10 frames/sec frame rate, the bandwidth is about 2Mbps. This wastes much channel
resource and limits the applications. MPEG (moving picttre ezpert groip) standardizes the video codec scheme,
and it performs high compression ratio while providing good quality. MPEG-i is used for the frame size about
352 x 240 and 30 frames per second, and MPEG-2 provides scalibility and can be applied on scenes with higher
definition, say HDTV (high definition television).
On the other hand, some applications concerns the very low bit-rate, such as videophone and video-conferencing.
Because the channel bandwidth is much limitted in telephone network, a very high compression ratio must be
required. ITU-T announced the H.263 video coding standards to meet the above requirements.8 According to
the simulation results of TMN-5,22 it outperforms 11.263 with little overhead of complexity. Since wireless communication
is the trend in the near future, low power design of the video codec is an important issue for portable
visual telephone.
Motion estimation is the most computation consuming parts in the whole video codec. About 60% of the
computation is spent on this parts for the encoder. Several architectures were proposed for efficient processing of
block matching algorithms. In this paper, in order to meet the requirements of 11.263 and the expectation
of low power consumption, a modified sandwich architecture in21 is proposed. Based on the parallel processing
philosophy, low power is expected and the generation of either one motion vector or four motion vectors with
half-pixel accuracy is achieved concurrently. In addition, we will present our solution how to solve the other
addition modes in 11.263 with the proposed architecture.
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