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Title: Complexity management of H.264/AVC video compression.
Authors: Kannangara, Chaminda Sampath
Supervisors: Richardson, I. E. G.
Zhao, Yafan
Miller, Tony
Issue Date: Oct-2006
Publisher: The Robert Gordon University
Citation: KANNANGARA, C.S., RICHARDSON, I.E.G., BYSTROM, M., ZHAO, Y., SOLERA, J., MACLENNAN, A. and COONEY, R., 2006. Low complexity skip prediction for H.264 through Lagrangian cost estimation. IEEE Transactions on Circuits and Systems for Video Technology, 16(2), pp. 202-208
RICHARDSON, I.E.G. and KANNANGARA, C.S., 2004. Fast subjective video quality measurement with user feedback. IEE Electronic Letters, 40(13), pp.799-800.
KANNANGARA, C.S., RICHARDSON, I.E.G. and MILLER, A.J., 2008. Computational complexity managemen of real-time H.264/AVC encoder. IEEE Transactions on Circuits and Systems for Video Technology, 18(9), pp. 1191-1200.
KANNANGARA, C.S., RICHARDSON, I.E.G. and MILLER, A.J., 2006. Computational management of an H.264 encoder. In: PCS 2006, Beijing, China, 24-26 April 2006.
KANNANGARA, C.S. and RICHARDSON, I.E.G., 2005. Computational control of an H.264 encoder through Lagrangian cost function estimation. In: VLBV 2005, Sardinia, Italy, 15-16 September 2005
KANNANGARA, C.S., RICHARDSON, I.E.G., BYSTROM, M., SOLERA, J., ZHAO, Y., MACLENNAN, A. and COONEY, R., 2005. Complexity reduction of H.264 using Lagrange optimization methods. In: IEE VIE 2005, Glasgow, 4-6 April 2005.
KANNANGARA, C.S., RICHARDSON, I.E.G. and ZHAO, Y., 2004. H.264 complexity management using macroblock skip-mode prediction. In: PGNet, Liverpool, 28-29 June 2004
RICHARDSON, I.E.G. and KANNANGARA, C.S., 2005. Encoder control system. UK Patent application 0524663.2, December 2005.
RICHARDSON, I.E.G. and KANNANGARA, C.S., 2005. Subjective video quality measurement with user feedback. European patent application EP20050252018, 2005.
Abstract: The H. 264/AVC video coding standard offers significantly improved compression efficiency and flexibility compared to previous standards. However, the high computational complexity of H. 264/AVC is a problem for codecs running on low-power hand held devices and general purpose computers. This thesis presents new techniques to reduce, control and manage the computational complexity of an H. 264/AVC codec. A new complexity reduction algorithm for H. 264/AVC is developed. This algorithm predicts "skipped" macroblocks prior to motion estimation by estimating a Lagrange ratedistortion cost function. Complexity savings are achieved by not processing the macroblocks that are predicted as "skipped". The Lagrange multiplier is adaptively modelled as a function of the quantisation parameter and video sequence statistics. Simulation results show that this algorithm achieves significant complexity savings with a negligible loss in rate-distortion performance. The complexity reduction algorithm is further developed to achieve complexity-scalable control of the encoding process. The Lagrangian cost estimation is extended to incorporate computational complexity. A target level of complexity is maintained by using a feedback algorithm to update the Lagrange multiplier associated with complexity. Results indicate that scalable complexity control of the encoding process can be achieved whilst maintaining near optimal complexity-rate-distortion performance. A complexity management framework is proposed for maximising the perceptual quality of coded video in a real-time processing-power constrained environment. A real-time frame-level control algorithm and a per-frame complexity control algorithm are combined in order to manage the encoding process such that a high frame rate is maintained without significantly losing frame quality. Subjective evaluations show that the managed complexity approach results in higher perceptual quality compared to a reference encoder that drops frames in computationally constrained situations. These novel algorithms are likely to be useful in implementing real-time H. 264/AVC standard encoders in computationally constrained environments such as low-power mobile devices and general purpose computers.
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