Image encoding method and apparatus thereof

Abstract

An image encoding apparatus according to the present invention effectively encodes an image without its degradation, at a low price. A block division circuit receives image data , dividing it into several blocks. An orthogonal transformation circuit orthogonally transforms each block of divided image data into transformed coefficients. A code amount control circuit calculates a quantization step value and a quantization number , which will restrict the number of coefficients in a macroblock to be quantized, using both the sum of the absolute values of the transformed coefficients of respective blocks and a code amount cumulative value output from a variable-length encoding circuit , and then outputs them to a quantization circuit . A delay circuit delays the coefficients for the necessary number of clock pulses. The quantization circuit quantizes the delayed coefficients , using the quantization step value and the quantization number . The variable-length encoding circuit encodes the quantized transformed coefficients, and then outputs them as encoded data . It also outputs a cumulative code amount for a frame to the code amount control circuit