Subband coding of NTSC color images and HDTV images

This research investigates a sub-band coding scheme to reduce the transmission bandwidth of the digitized composite television images and HDTV images. These images are decomposed into seven bands. The base band is DPCM encoded and the high bands are encoded by using non-uniform Laplacian quantizers with a dead zone. By selecting the dead zone on the basis of energy in the high bands an acceptable image quality is achieved at an average of 1.3028 bpp and at an average SNR of 35.02 dB.; To encode the composite signal at bit rate close to 1 bpp and yet maintain acceptable visual quality for all simulated images and with lower complexity, the fixed rate sub-band coding scheme FRSBC is developed. In this algorithm, the overall target bit rate can be assigned and the algorithm will optimally quantize the sub-bands to give the best possible SNR. The bit rate of 1 bpp is obtained with an average SNR of 34.17 dB. This rate is comparable to some very hardware intensive schemes such as the DCT or VQ.; This algorithm is also tested on a monochromic image. The standard picture Lena is used to compare the performance of FRSBC with other algorithms. At the bit rate of 0.6840 bpp with SNR of 35.3219 dB, the FRSBC compared very favorably with these computationally intensive algorithms.; A modified version of the FRSBC algorithm is implemented to compress the HDTV signal in the component form. The modification is required to make the algorithm optimum for the component signals and simple for implementation. It is found that the goal of 45 Mbps rate for the HDTV is easily accomplished with the application of this algorithm on an intraframe basis. The bit rate of the adopted scheme is 0.8759 bpp with an average SNR of 30.9481 dB. The subjective quality of the reconstructed pictures is also acceptable.