A new quantizer selection scheme for digital VCR

Consumer-Use Digital VCR selects a quantizer for each DCT block based on CLASS and QNO. CLASS is determined for each DCT block according to the characteristic of the block, for example, the maximum value of AC coefficients. Six DCT blocks comprise a macroblock for which a QNO is determined. All of the quantizers defined in the specifications are numbered from 0 to 15 by QNO. Different quantizers can be referenced by the same QNO and are discriminated by CLASS. In this paper, we propose a new method to determine these parameters, QNO and CLASS, for the selection of a quantizer per each DCT block. We first determine QNO for a macroblock and then fine-tune the quantizers by adjusting CLASS of each DCT block. For this we propose a modified quantizer map with a reduced set of quantizers, which preserves the compatibility with the conventional one. The results of our experiment show that our method outperforms the conventional method.