Fast transmission distortion estimation and adaptive error protection for H.264/AVC-based embedded video conferencing systems

This paper presents the design and implementation of an error-resilient H.264/AVC-based embedded video conferencing scheme over Internet. We first develop a fast recursive algorithm to estimate the decoder-side distortion of each frame in the presence of packet loss. The algorithm operates at block level, and considers the impacts of different intra prediction modes, the unrestricted intra prediction, and the skip mode. We then design a family of very short systematic forward error correction codes with linear encoding and decoding complexity, which runs across the slices of each frame to recover lost packets. An optimization problem is then formulated to minimize the decoder-side distortion by allocating a given channel coding redundancy among a group of frames. Various techniques are introduced to speed up the algorithm without sacrificing too much accuracy, in order to meet the hardware and real-time constraints of the system. As a result, the proposed scheme can run on a real-time embedded video conferencing system with resolution up to 1024x576 pixels, 30 frames per second (fps) and 4megabits per second (Mbps).