MPEG-4 Video Encoder Optimization
The MPEG-4 standard has been adopted as the solution for mobile multimedia communications and Internet streaming. To improve the quality of video transmission, we consider techniques that optimize the coding efficiency. Additionally, we focus on developing techniques that reduce the complexity of the video encoding process and ensure robust delivery to client devices over time-varying heterogeneous networks.
Background & Objective: The topic of encoder optimization has been studied extensively within the context of previous coding standards, such as MPEG-2. In MPEG-4, new coding methods allow for much greater flexibility and the possibility to optimize compression efficiency in different ways.
Technical Discussion: Rate-Distortion (R-D) models are extensively used to solve various encoder optimization problems. We have developed novel R-D models that provide a relationship between the quantizer and rate for coded frames, as well as models that estimate the distortion for coded and non-coded frames. These models have been used by our rate control algorithm to ensure that the encoded video bitstream satisfies various constraints, while maximizing the quality of the reconstructed video. MPEG-4 is the first object-based coding standard and we have developed algorithms to perform bit allocation at the object level. Also, MPEG-4 provides support for variable frameskip; an algorithm that considers optimal spatio-temporal trade-offs has been developed, i.e., code more frames with less quality or fewer frames with higher quality. Finally, new scalable coding techniques in MPEG-4 require advanced methods of modeling, bit allocation and transport; such techniques are currently under investigation.
Contact: Anthony Vetro
Publications:
Jun Xin, Jianjun Li, Anthony Vetro, Huifang Sun, Shun-ichi Sekiguchi, "Motion Mapping for MPEG-2 to H.264/AVC Transcoding", IEEE International Symposium on Circuits and Systems (ISCAS), May 2007 (TR2007-085)
Technology Areas:
Audio Video Processing
Digital Communications
Modification Date: September 12, 2007