A Low-Rate Video Coding Based on DCT/VQ
Joon Gyu Maeng, D. N. Hein · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1989
The Discrete Cosine Transform (DCT) is an efficient coding method to compress the video-conferencing images. It has well-known artifacts, blocking effects and mosquito effects. These artifacts are very visible at the low bit rates such as 56 Kbps and 112 Kbps. A coding method based on the Discrete Cosine Transform and Vector Quantization (VQ) is presented in this paper. The incoming image is split into two bands of frequencies. The low frequency band is coded by the 8x8 DCT with motion compensated inter-frame coding and the high band is coded by the 4x4 Vector Quantization. The decoder filters the low band after construction and combines it with the high band to restore the image. The simulation results show a great improvement in subjective picture quality. No blocking effects are visible and the mosquito effects are greatly reduced. Since only the low band is filtered by the low pass filter, no high frequency components are lost in the process of filtering. The combined image of high and low band maintains edge sharpness and has a smooth texture.