Comparison of Video Coding Standards Used in Mobile Applications

Introduction

Although already designed and enhanced for high data rates and flexible communication capabilities, today’s modern mobile telecommunication systems are experiencing growth of mobile user requirements for delivering of high quality multimedia information. Mobile users are used to being able to access different kind of rich multimedia content such as pictures, moving clips, movie trailers, animations or real time video streaming on their mobile terminals. Provision of this high quality multimedia information puts more demanding requirements on planning and designing of mobile communications systems for improving throughput, transfer delay, and data error rate.

Important issues arise from this situation. The first one is cost of services that forms and affects the acceptance and attractiveness of certain mobile applications, the second is the capacity of modern mobile communication channels, and the third is storage capability of mobile terminals. Access to rich multimedia content through the mobile network is very expensive since it requires high data rate point-to-point connection for each mobile user. The importance of mobile terminal storage capacity lies in the possibility to allow the time of information transmission to be decoupled from its time of use, thereby enabling the best possible economy of use of the available spectrum. Furthermore, large number of users and limited bandwidth capacity can cause system congestion that can lead to poor quality of service requiring network operators to carefully balance network traffic (Holma et al., 2007). Concerning the real time video distribution as an alternative to point-to-point oriented, limited and expensive mobile networks such as 3G (Kumar, 2007), new point-to-multipoint mobile systems were developed to enable and allow reception of video for a number of mobile users simultaneously without consuming limited channel resources (Kornfeld, 2004). Additionally, Faria (2006) describes how representatives of these new mobile networks employ techniques and spectrum of digital terrestrial broadcasting technology. There are several standards around the world designed for broadcasting to mobile terminals such as DVB-H (ETSI EN 302 304, 2001) and T-DMB/DAB (ETSI EN 102 427, 2005; ETSI EN 102 428, 2005). Probably a combination of technologies will be used together in order to provide interactivity and high quality of delivered rich multimedia content on mobile terminals as depicted in Jordan et al. (2006).

Nevertheless, regardless of used mobile system for efficient utilization of available transmission channel capacity and improvement of the quality of service, the appropriate coding method needs to be selected for mobile systems. Since video signal is composed of successive frames alternating in time domain, there is a high correlation present between neighboring image elements (pixels) inside and between successive frames. This means that the video has a large amount of spatial and temporal redundancy, which can be removed in order to reduce the irrelevant information and achieve the required transmission bit rate. Furthermore, while human visual system is less sensitive to higher spatial frequencies, these higher frequencies can be eliminated without any effects on subjective picture quality degradation (Zovko-Cihlar et al., 1998; Bauer et al., 1998).