Bit rate reduction apparatus

Claim 1

A bit rate reduction apparatus comprising: block forming means for dividing input samples of a video signal into blocks, wherein each of said blocks is composed of a specific number of the input samples; transforming means for transforming the input samples in each of said blocks to obtain transformed components; quantizing width selecting means for selecting a quantizing width from a plurality of quantizing widths each being expressed as 2 i , where i is an integer including 0, said plurality of quantizing widths including at least one quantizing width which is expressed as 2 i satisfying such a condition of that i is larger than 0; offset value generating means for generating an offset value determined by a value of i, wherein the offset value generating means generates an offset value which is a maximum one of integer values not larger than both a value (2 i- 1)/2 and a predetermined value t; quantizing means for quantizing each of the transformed components by using the quantizing width selected by the quantizing width selecting means and the offset value to obtain a quantized value, the quantizing means shifting a value of (c+the offset value) by i bits to obtain the quantized value, where c denotes a value of a transformed component inputted to the quantizing means; and encoding means for encoding the quantized value to obtain a bit rate reduction coded data.