Some fundamental experiments in subband coding of images
Sven Ole Aase, Tor Audun Ramstad · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1991
The paper describes some basic experiments for analyzing the origin and character of the noise in subband coders. A new tool introduced in this paper is an ideal filterbank which guarantees that no interband noise contamination will occur. The coding results are compared with a subband coder based on a standard FIR filterbank. It is found that interband contamination does not play any significant role in the subjectively perceived noise in an image subband coder. Further experiments show that the noise in the decoded image, which subjectively manifests itself as ringing noise in smooth areas close to higher activity regions, is due to the thresholding to zero of a large number of small amplitude subband samples, which takes place in the quantization procedure. It can be thoroughly removed by the dithering technique. The article presents some image material demonstrating the cited results.