A Two-Channel Overlapped Block Transform for Image Compression

In this correspondence, a new two-channel overlapped block transform is introduced by prefiltering the Haar transform. The prefiltering employs plane rotations with one single rotation angle to achieve high computational efficiency. The resulting transform is equivalent to a periodically time-varying (PTV) filter bank. The proposed transform or PTV filter bank has several advantages for image coding. First, symmetric extension is very easily performed at the boundaries in spite of the fact that the filters are asymmetric. Second, arithmetic complexity can be reduced to simple shifts and adds. Finally, the performance for image compression is shown to be high, both in terms of visual quality and PSNR. As a result, the proposed transform is a competitive alternative to the 5/3 and the 9/7 filters, which are currently popular for subband/wavelet image coders.