Human Visual System Based Adaptive Inter Quantization

Block effect is one of the most annoying artifacts in digital video processing and is especially visible in low-bitrate applications, such as mobile video. To solve this problem, we propose an adaptive quantization method for inter frames that can reduce visible block effect in DCT-based video coding. In the proposed method, a set of quantization matrices are constructed before processing the video data. Matrices are constructed by exploiting the temporal frequency limitations of human visual system. The method is adaptive to motion information and is able to select an appropriate quantization matrix for each inter-coded block. Based on the experimental results, the proposed scheme can achieve better subjective video quality compared to conventional flat quantization especially at low-bitrate application. Moreover, it does not introduce extra computational cost in software implementation. This method does not change standard bitstream syntax, so it can be directly applied to many DCT-based video codec. Potential application could be for mobile phone, palm computer and other digital devices with low-bitrate requirement. Keyword: video coding, quantization, human visual system, discrete cosine transform (DCT)