Compressing moving pictures using the APEX neural principal component extractor

An application of the optimal Karhunen-Loe`ve transform (KLT) in place of the traditional discrete cosine transform (DCT) for compressing intra-frames in the MPEG protocol is proposed. The I-frames attain the smallest compression ratio since they are coded without reference to any other frames. The difficulty of KLT (additional bit-rate is required to make the image-dependent transform basis known to the decoder) is overcome by using the KLT basis of the previous I- or P-frame which, the authors argue, is very similar to the basis of the current frame. The previous frame is already known to the decoder. Therefore, no additional information needs to be sent out. Paying attention to the nonstationary statistics of image they propose to split the I-frames in N parts and use a dedicated transform basis for each part. Since the KLT basis must be updated continuously they use the adaptive principal component extractor network (APEX) that can incrementally estimate the new basis for the next frame