compressed video communications

[...]... video communications Firstly, the effects of transmission errors on the decoded video quality are analysed in order to provide the reader with an understanding of the severity of the errors problem and a feeling of the importance of error resilience schemes, especially in mobile video communications The sensitivity of different video parameters to error is then analysed to determine the immunity of video. .. implications on the video quality of service are pinpointed and analysed The video quality is then put into perspective with a view to analyse the QoS issues in mobile video communications The effects of some QoS elements such as packet structure and size (mainly for real-time video communications using RTP over IP), channel coding and throughput control using time-slot multiplexing, on the perceptual video quality... allow different video coding algorithms to interoperate, a heterogeneous video transcoder must be employed to modify the bit stream generated by the source video coder in accordance with the syntax of the destination coder Some heterogeneous video transcoders are enabled to operate in two or more directions allowing incompatible streams to flow across 2 or more networks for inter-network video communications. .. levels, image size and spatial resolution, also influence the video quality and the bit rate provided by a particular video coding scheme The perceptual quality in video communications is a design metric for multimedia communication networks and applications development (Damper, Hall and Richards, 1994) Moreover, in multimedia communications, coded video streams are transmitted over networks and are thus... layer coder for both quality and bit rates achieved Chapter 3 analyses the flow control mechanisms used in video communications The factors that lead to bit rate variability in video coding algorithms are first described and alternatives to variable rate, fixed quality video coding are examined Fixed rate video coding is then discussed by explaining several techniques used to achieve a regulated output bit... mechanism The multi-layer video coding, described in Chapter 2, is then presented as a bit rate control algorithm commonly used in video communications today The video scaleability techniques are also a point of focus in this chapter with particular attention given to the Fine Granularity Scaleability (FGS) technique recently recommended for operation under the auspices of the MPEG-4 video standard Chapter... acts as consultant on image /video compression and mobile video communications to potential companies in the UK Telecommunications industry He is well supported by the industry in the form of research projects and consultancy contracts He runs a private consultancy company VIDCOM Dr Sadka is the instigator of numerous funded projects covering a wide spectrum of multimedia communications He has been serving... his researchers have pioneered work on various aspects of video coding and transcoding, error resilience techniques in video communications and video transmissions over networks His work in this area has resulted in numerous novel techniques for error and flow control in digital video communications He has contributed to several short courses delivered to UK industry on various aspects of media compression... audiovisual communications, such algorithms have been employed to compress video signals at high coding efficiency and maximum perceptual quality In this chapter, an overview of the most popular video coding techniques is presented and some major details of contemporary video coding standards are explained Emphasis is placed on the study and performance analysis of ITU-T H.261 and H.263 video coding... principles of the ISO MPEG-4 standard video coder are also explained Extensive subjective and objective test results are depicted and analysed where appropriate 12 2.2 OVERVIEW OF DIGITAL VIDEO COMPRESSION ALGORITHMS Why Video Compression? Since video data is either to be saved on storage devices such as CD and DVD or transmitted over a communication network, the size of digital video data is an important issue .