Video has become a key part of our daily digital lives. An increasing number of people are using video to document their lives and share their experiences through , sites such as YouTube and Facebook. Due to this ever increasing quantity of video content, it is clear that more efficient and robust video compression algorithms are needed. In this thesis video compression and transmission are investigated, specifically focused on High Definition (HD) video coding and wireless transmission. Unfor- tunately, the techniques relied upon for efficient compression are the same tech- niques that hinder robustness. This is because conventional video compression relies on inter-frame prediction (motion estimation), intra frame prediction and variable- length entropy encoding to achieve high compression ratios but, as a consequence, produces an encoded bitstream that is inherently sensitive to channel errors. There- fore, in order to ensure reliable and robust delivery over lossy channels, it is necessary to invoke various additional error detection and correction methods. In this thesis a technique called Pyramid Vector Quantisation (PVQ) is investig- ated. In contrast to the other methods, Pyramid Vector Quantisation has the ability to prevent error propagation through the use of fixed length codewords. This thesis introduces an efficient Rate Distortion Optimisation (RDO) algorithm for intra- mode PVQ which offers similar compression performance and visual quality to intra H.264/ AVC, intra VC-I, VC-3 and Motion JPEG 2000 while offering outstanding inherent error resilience. The results are reported for a range of representative 1080p HD video sequences. The error resilience performance of the enhanced PVQ codec is then evaluated for HD content in the context of a realistic (IEEE 802.11n) wireless environment. The impact of both uncorrelated and correlated channel errors is investigated. It is shown that PVQ provides high tolerance to corrupted data compared to the state-of-the- art H.264/ AVC while obviating the need for complex encoding tools. PVQ (without explicit error resilience tools and without error concealment) is able to significantly outperform H.264/ AVC (with error resilience tools and with error concealment) by up to I3.3dB PSNR for the same wireless simulation scenario. The benefit obtained by employing a Gaussian Markov Random Field (GMRF) based wavelet domain error concealment algorithm to post process erroneously re- ceived PVQ bitstreams is also investigated. It is shown that this algorithm leads to a further 2.5dB performance gain thus outperforming H.264/ AVC by up to 15.8dB PSNR. Overall, it is hoped that the results of this thesis demonstrate PVQ's feasib- ility for in-home HD video coding and transmission.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:559487 |
| Date | January 2012 |
| Creators | Bokhari, Syed Mohsin Matloob |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0151 seconds