Complexity Control for Real-Time Video Coding

A methodology for complexity scalable video encoding and complexity control within the framework of the H.264/AVC video encoder is presented. To yield good rate-distortion performance under strict complexity/time constraints for instance in real-time communication, a framework for optimal complexity allocation at the macroblock level is necessary. We developed a macroblock level fast motion estimation based complexity scalable motion/mode search algorithm where the complexity is adapted jointly by parameters that determine the aggressiveness of an early stop criteria, the number of ordered modes searched, and the accuracy of motion estimation steps for the INTER modes. Next, these complexity parameters are adapted per macroblock based on a control loop to approximately satisfy an encoding frame rate target. The optimal manner of adapting the parameters is derived from prior training. Results using the developed scalable complexity H.264/AVC encoder demonstrate the benefit of adaptive complexity allocation over uniform complexity scaling.