Compression of HDTV signals for low bit-rate transmission using motion compensated subband transform coding and a self-organization neural network

The quality of visual communications has greatly improved with HDTV. Due to the advantages of digital communications, and the trend towards it, it is desirable to develop a cost effective digital codec for HDTV signals. One of the criteria in the transmission of digital signals via satellites is the transmission bandwidth which dictates the transmission costs. Apart from development of good compression schemes, due consideration should also be given to the ease of hardware implementation, which is crucial in deciding factors like processing delay and the level of encoder/decoder complexity. With the above mentioned factors in mind a cost-effective HDTV codec is proposed. Few US organizations have addressed the problem of HDTV distribution via communication satellites. The majority of efforts in the development of an HDTV codec have been aimed at the 100 to 140 Mbits/sec data rate. To facilitate cost effective satellite transmission, the DS3 rate of 45 Mbits/sec, is desirable. The purpose of the present research is to compress the HDTV signals to around 20 Mbits/sec so that 2 HDTV channels can be transmitted through the DS3 rate channel. To achieve this degree of compression a new scheme is proposed. First subband coding is used to decompose the image into different frequency bands. Next motion compensation is applied to the low band, and the resulting interframe difference is discrete cosine transform (DCT) coded. The high bands are also DCT coded. The DCT coefficients of the difference signal of the low band and the DCT coefficients of the high band are then vector quantized