K. K. Loo

Semi-hierarchical motion estimation for the dirac video codec

In this paper, a semi-hierarchical way of motion estimation for the Dirac video encoder is proposed. The algorithm requires fewer numbers of SAD calculations per block while the compression efficiency and PSNR remain the same. There is huge saving in terms of SAD calculation per block especially in moderate level motion sequences. Moreover, the proposed algorithm has the ability to increase or decrease the search range depending upon the complexity of the motion in order to maintain the accuracy of the motion estimation to a certain level and can be use in any type of standard video encoders.

Field trials and test results of portable DVB-T systems with transmit delay diversity

This paper describes work carried out by Brunel University and Broadreach Systems (UK) to quantify the advantages that can be achieved if transmit diversity is applied to systems employing the DVB standard. The techniques investigated can be applied to standard receiver equipment without modification. An extensive and carefully planned field trial was performed during the winter of 2007/2008 in Uxbridge (UK) to validate predictions from theoretical modeling and laboratory simulations. The transmissions were performed in the 730 MHz frequency band with a DVB-T transmitter and a mean power of 18.4 dBW. Transmit delay diversity has been observed to deliver significant reception improvement in automotive and indoor- non line of sight situations.

Measurement results of transmit delay diversity for DVB-T networks

This paper describes work carried out by Brunel University and Broadreach systems (UK) to quantify the advantages that can be achieved if transmit diversity is applied to systems employing the DVB standard. The techniques investigated can be applied to standard receiver equipment without modification. An extensive and carefully planned field trial performed during the winter of 2007/2008 in Uxbridge (UK) is described. The transmissions were performed in the 730 MHz frequency band with a DVB-T transmitter and a mean power of 18.4 dBW. Transmit delay diversity has been observed to deliver significant reception improvement in automotive- non line of sight situations.

A Novel Rate Control Algorithm for the Dirac Video Codec Based upon the Quality Factor Optimization

In this paper, we propose a novel rate control algorithm for the wavelet-based open source Dirac video codec by using the quality factor (QF) optimization method. We derived a mathematical model which we call Rate-QF (R-QF) model to generate the optimum QF for the current coding frame according to the target bitrate. The proposed algorithm is completely one pass process and does not require complex mathematical calculation. The process of calculating the QF is quite simple and does not require calculating for each and every frames being coded. The experimental results show that the proposed algorithm can control the bitrate precisely (within 1% of the target bitrate in average). Moreover, the bitrate fluctuating which is the variation of bitrate over each and every group of pictures (GOPs) is lower than that of H.264, which is one of the desirable features to avoid buffer over flow and under flow in real time broadcasting.

Motion estimation using partial cost function calculation

Having fast and efficient motion estimation is crucial in todays advance video compression technique. In this paper, a method which we call partial cost function calculation is proposed for faster cost calculation in finding the exact match for any type of block matching algorithms. It is based upon the reduced number of operations which follows a certain pattern, instead of calculating the cost for all points within a block. The experimental results show that the proposed method gives two to eight times reduction (depending upon the block size used) in the computational load with the motion estimation accuracy loss which is negligible compared with full cost function calculation and can be used in conjunction with any type of fast block matching algorithms.