DCT/DPCM Processing of NTSC Composite Video Signal

This paper describes two different schemes of DCT/ DPCM processing of digital NTSC composite video signal. The first scheme (line processing) is based on applying the discrete cosine transform (DCT) along each horizontal line and then implementing the differential pulse code modulation (DPCM) in the vertical direction on the semitransformed image. The second scheme (block processing) involves DCT of (4 × 4) subblocks followed by adaptive DPCM to reduce intersubblock correlation. Based on the statistics of the prediction error, variable bit quantizers optimized for minimizing the mean-square quantization error are developed. These techniques lead to reduced bit rates for transmitting the color video at broadcast standards. Both original and processed color images in composite form are displayed for subjective evaluation. The effects of channel error on block processing are also investigated.