ICSPO2 zyxwvuts Proceedings zyxwvutsr Wireless Video Communication on Embedded System zyx Wu Dajun, Lim Keng Pang, Yu Rongshan, Pan Feng, Zhu Ce Centre for Signal Processing School of EEE, Nanyang Technological University Singapore 639798, Singapore Abstract In this paper, a PDA-based wireless communication system adopting MPEG-4 video compression techniques is introduced. The key implementation and op$mization issues are described such as multithreading, buffer design, wireless communication, encoder and decoder. The results indicate that the system proposed and developed has successfully reached the aim of real-time video coding and communication through the wireless channel. Keywords: Video Compression, MF’EG-4, Embedded System, Communication System, Multithreading, Buffer 1. Introduction In recent years, Personal Digital Assistants (PDA) have attracted the attention of more and more people. Contrast to the bulky notebook computers, these electronic devices enable users to carry them much more easily and run application programs including taking notes, sche$ding plans, surfing the Net, accessing email-boxes and many more. In a general sense, these PDAs such as Palm, Jornada, iPac and etc can be considered as embedded systems. The reason is partly because the underlying software platforms inside are the embedded operating systems like Windows CE and Palm OS. As the embedded processors inside PDAs get faster, smaller and consuming less power, there is a growing trend towards a strong demand for better multimedia applications “on the move”. With the added dimension of broadband networks such as zyxwvutsrqp 2.5G or 3G communication network, there will be no doubt of the proliferation of embedded multimedia applications on PDA devices in a very near future. Of particular interest, video communication is becoming a viable application on PDA devices. This is because of the improvement in embedded processor’s speed and the availability of wireless broadband network services (GPRS) in Singapore recently. However, the video stream content involved in a video communication system contains so much data that compression techniques should .be utilized to transmit video data through the narfow transmission channels. In another word, codec which stands for compression /decompression techniques is dispensable in this--kind of video communication system. In addition, in a video communication system, data exchange should be performed in real-time. Thus real- time is also a necessity in codec here. MPEG-4 [ I] is one of the best compression standard suitable for low bit-rate compression. Thus it is adopted in the system. The paper consists of six parts. Part I gives an introduction to this paper. Part 2 gives a systematic view of the developed video communication system. Part 3 explains the main idea of video compression techniques. Part 4 presents some implementation and optimization details. Part zyxwv 5 shows the result of the system: Part 6 gives future plans and concludes the paper. 2. System description The PDA-based wireless video communication system developed is mainly related to software. The encoder side of the system consists of a HP Jornada 568 PocketPC with Intel StrongARM SA-I 110 processor inside, Socket Low Power CompactFlash (Type 1) 802.11b Wi-Fi wireless LAN Card and the encoder application software. The decoder side consists of the similar configuration with the exception of the decoder application software. The two sides are connected through Wireless LAN and Internet. The MPEG-4 compressed video bit stream is transmitted from the encoder side to the decoder side. A schematic diagram of the system is shown below in Figure I. A video camera and a video capture card should be plugged into the slot of encoder PDA. However, there is no known video camera (including SDK) for PocketPC in the market by the time of writing this paper. Thus, instead of reading video signal from a video capture card, the encoder reads a raw YW format video file stored locally. The encoder developed is then able to compress it and send out the data to the wireless channel before it is decoded on the remote side in the end. 0-7803-7488-6/02/$17.00 zyxwvutsrq 0 2002 IEEE. 1371