Offset-adaptive quantization in DCT-based low-bitrate video coding

Band effect is one of the most annoying visual artifacts in digital video, and is especially obvious in low-bitrate applications, such as mobile video. This paper discusses the cause of band effect and proposes an improved quantization method, which can reduce band effect effectively in DCT-based video coding. This offset-adaptive quantization method adjusts the quantization results of every block according to adjacent blocks. The method can improve video subjective quality with ignorable additional computing cost. The method need not change standard bitstream syntax, so it can easily be applied to many DCT-based video codecs. Experimental results on practical video sequences prove that the method is valuable.