| With the rapid development of wireless networks and consumer electronics, and the development of VLSI, hand-on devices become more and more popular. Our mobile phones, Pocket PCs and PDAs nowadays, changed revolutionarily, compared with 5-10 years ago, no matter in computational power or in memory capacities. Therefore, various mobile applications have emerged. Video application, as one of the hottest, transferred from traditional PC to mobile devices. However, compared with PC, the computational power, memory and display screen are still limited, so traditional video coding applications can not work well on mobile devices.Many efforts have been done in this area. They are presented in chapter four. However, there are some disadvantages of the current work, one of them is the lack of universality, and some implementations focus on one special encoding and decoding standard, such as MPEG-4 or H.263 only or focus on one hardware platform, such as the ARM chips.In this paper, we proposed a software-based video codec framework and its implementation which is suitable for real-time video coding applications on mobile devices. The framework is available for most of the mobile platform and the coding standard. Furthermore, some key optimizing techniques, such as stationary block prediction and fast predictive motion estimation and compensation (ME&MC), zero-coefficients prejudgment, multiplierless integer discrete cosine transform (DCT), 16-bit colorspace, ABS function optimization, etc are used in our codec. Experimental results both on simulator and real equipment demonstrate the flexibility of our framework and the good speedup we achieved while video quality degradation is negligible. According to test result on real PPC, for QCIF(176*144) format test sequences, we can reach 20fps in encoding speed. The codec is suitable for scenarios where low-complexity computing is required, especially fit for mobile video conference and video surveillance. |
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