Abstract: A motion vector calculating device receives horizontal and vertical components of a motion vector and calculates the magnitude of the motion vector. A motion estimating device then compares the magnitude of the motion vector with stored reference values. A quantization level modifying device in turn provides a real quantization level signal taking into consideration man's visual perception characteristic and the fullness of a buffer in the data transmission path. Accordingly, the quantization level is enhanced for larger moving parts of the picture while the quantization level is reduced for parts of the picture containing less motion, thereby allowing the signal being quantized to be further compressed.

Abstract: An encoding method and apparatus uses energy characteristic of discrete cosine transform (DCT) domains for determination of a quantization level. The DCT domain is divided into for sub-domains. The energy characteristic of each macroblock is represented as one among the four domains such as simple, complicated, edge and plain domains. The buffer generates a first quantization level which is varied according to the buffer fullness in units of a slice. The energy characteristic information and the first quantization level of the buffer are used for determination of a second quantization level supplied to a quantizers. The quantizers quantize the transformation coefficient data according to the second quantization level generated in units of the macroblock. Thus, the viewer can feel less quantization error in sight.