Recent Advances in Region-of-interest Video Coding

Abstract

Recently, the content distribution network industry has become exposed to significant changes. The advent of cheaper and more powerful mobile devices having the ability to play, create, and transmit video content and which maximize a number of multimedia content distributions on various mobile networks will place unprecedented demands on networks for high capacity, low-latency, and low-loss communications paths. The reduction of cost of digital video cameras along with development of user-generated video sites (e.g., iTunesTM, GoogleTM Video and YouTubeTM) have stimulated the new user-generated content sector. Growing premium content coupled with advanced video technologies, such as the Internet TV, will replace in the near future conventional technologies (e.g., cable or satellite TV). The relatively recent ITU-T H.264/AVC (ISO/IEC MPEG-4 Part 10) video coding standard (Wiegand & Sullivan, 2003), which was officially issued in 2003, has become a challenge for real-time video applications. Compared to others standards, it gains about 50% in bit rate, while providing the same visual quality. In addition to having all the advantages of MPEG2, H.263 and MPEG-4, the H.264 video coding standard possesses a number of improvements, such as the content-adaptive-based arithmetic codec (CABAC), enhanced transform and quantization, prediction of "Intra" macroblocks (spatial prediction), and others. H.264 is designed for both constant bit rate (CBR) and variable bit rate (VBR) video coding, useful for transmitting video sequences over statistically multiplexed networks (e.g. asynchronous transfer mode (ATM), the Ethernet, or other Internet networks). This video coding standard can also be used at any bit rate range for various applications, varying from wireless video phones to high definition television (HDTV) and digital video broadcasting (DVB). In addition, H.264 provides significantly improved coding efficiency and greater functionality, such as rate scalability, “Intra” prediction and error resilience in comparison with its predecessors, MPEG-2 and H.263. However, H.264/AVC is much more complex in comparison to other coding standards and to achieve maximum quality encoding, high computational resources are required. Due to the recent technological achievements and trends, the high-definition, highly interactive networked media applications pose challenges to network operators. The variety of end-user devices with different capabilities, ranging from cell phones with small screens and restricted processing power to high-end PCs with high-definition displays, have stimulated significant interest in effective technologies for video adaptation for spatial formats, consuming power and bit rate.