A bandwidth and memory efficient MPEG-4 shape encoder

Abstract

-We have developed a shape encoder hardware for MPEG-4 video coding. On the one hand, the alpha component is compressed and therefore, the size and memory access of alpha frame memory can be reduced to 50% and 56.25% respectively. On the other hand, an efficient data transfer scheme combining the run length coding and addressing mode can reduce average data transfer time to 9.39% and accelerate the shape encoding process. The shape encoder can support MPEG-4 Main Profile at Level 4 in real-time. In addition, verification and testing methods are also considered. I. IntroductionMPEG-4's object-based scene description allows the transmission of arbitrarily shaped video objects [1][2]. The purpose of using shape is to promote a better subjective picture quality, a higher coding efficiency as well as more user interaction. These advantages make this standard best suited for the needs of mobile applications or browsing multimedia databases on the Internet. Therefore shape coding can be utilized in lots of consumer electronics devices, such as video telephony, PDA, and video surveillance. However, these flexible and high-efficient coding features are based on the complex decision process and high computational tasks that demand the high computing and high data traffic properties. For example, the analysis of MPEG-4 Core Profile at Level 2 performed on a Ultra Sparc RISC indicated that MPEG-4 shape encoding requires giga scale operations and hundred mega byte scale memory access per second. To meet the stringent requirements on low cost and low power for the embedded system market, there is a clear need of the optimized VLSI architecture for MPEG-4 shape encoding.Some works [3][4] have been presented on hardware designs of MPEG-4 shape encoder. In this work, we present a more efficient hardware design for the MPEG-4 shape encoder in terms of bandwidth and memory usage. In addition, the proposed design can also support higher level of MPEG-4 standard. We have successfully implemented the hardware shape encoder and ported the design on the ARM-based platform. The chip is fabricated using UMC 0.18µm CMOS 1P6M process. The design can support MPEG-4 Main Profile at Level 4, i.e., 489,600MB/sec with a frame size of 1920×1088.