Current Projects

Rate-Distortion Optimal Rate Control for Video Coding Key Words: Rate-distortion optimization, rate control, bit allocation, rate and distortion modeling

Project Members

• Osman G. Sezer

Project Description

Most video encoder applications require a controlled output bit rate, in which large deviations from a target rate are avoided at any time instant because of video buffer regulations set at the decoder. A rate-control method at the encoder ensures that by intelligent selection of encoding parameters, the video buffer constraints are met, while at the same time a best possible video quality is achieved. The optimal solution to the rate-control problem requires explicit knowledge of the video source properties and the encoder operation effects. If we could know the rate-distortion characteristics of each coding block as a function of its properties and the coding parameters, we would be able to solve the rate-control problem in an optimal way. Since we do not have this knowledge, either we approach the solution gradually by making several encoding/ decoding passes to meet our targets, or use mathematical models that estimate the rate and quality of the output of the video coder as a function of the encoding parameters. The first choice of a multi-pass system is not desirable for most applications that demand a very fast encoder. This is why many conventional rate control algorithms use rate and distortion models for their operation. The performance of a rate-control algorithm greatly depends on its ability to estimate the rate and the distortion. In this project, our we aim is to develop novel rate-distortion models for the next generation video coders such as H.264/AVC and develop a more efficient rate control algorithm than the existing state-of-the art algorithms.

Related Publications

• N. Kamaci, Y. Altunbasak, and R. M. Mersereau, “Frame Bit Allocation for the H.264/AVC Video Coder Via Cauchy-Density-Based Rate and Distortion Models” IEEE Transactions on Circuits and Systems for Video Technology, Volume 15, Issue 8, Aug. 2005 Page(s):994 - 1006 [pdf]
  (The IP in this paper is patented. For more information, contact yucel@ece.gatech.edu)
• N. Kamaci and Y. Altunbasak, "Frame Bit Allocation for H.264 Using Cauchy-Distribution Based Source Modelling", IEEE Int. Conf. on Acoustics Speech and Signal Processing, Philadelphia, PA, March 2005 [pdf]
• N. Kamaci and Y. Altunbasak, “Rho-domain rate-distortion optimal rate control for DCT-based video coders,” IEEE Int. Conf. on Acoustics Speech and Signal Processing, Montreal, Canada, May 2004 [pdf]
• Y. Altunbasak and N. Kamaci, “An analysis of the DCT coefficient distribution with the H.264 video coder,” IEEE Int. Conf. on Acoustics Speech and Signal Processing, Montreal, Canada, May 2004 [pdf]
• N. Kamaci and Y. Altunbasak, “Performance comparison of the emerging H.264 video coding standard with the existing standards,"  in IEEE Int. Conf. Multimedia and Expo, Baltimore, MD, July 2003 [pdf]