Frame skip encoding apparatus for moving images

Abstract

In a moving image encoding apparatus, an image signal is converted into a digital image signal by an A/D converter and is stored in frame memory 110. In addition, a movement vector detector 300 detects a movement of the output of the frame memory 110. In an orthogonal transformer 130, a difference signal between a present frame image which is stored in the frame memory 110 and a previous frame image which is stored in a variable delay frame memory 210 is supplied, in which the difference signal is converted by orthogonal transformation. The orthogonally transformed transformation signal is quantized into a linear or nonlinear discrete level on the basis of a step width of quantization from a step size controller 600 in a quantizer 140. Then, the quantized data is encoded into a variable length code in a variable length encoder 150. A movement vector detector 300 detects movement of the image by pattern matching processing between the present frame and the previous frame. A movement vector/encoding mode judger 310 generates the movement vector 3 and the encoding mode 4. The variable length code is transmitted to the transmission circuit after adding a movement vector 3 and encoding mode 4. In these operations, a frame rate controller 700 controls the processing rate of each frame image in the entire apparatus. Frame rate controller 700 calculates a total frame skip number S.sub.T which corresponds to the total number of frames that are not transmitted after a frame has been transmitted. The total frame skip number S.sub.T is calculated by selecting a smaller sum of an externally set signal S.sub.min, signal S.sub.M which is calculated from the degree of movement compensation and S.sub.S which is calculated from the degree of quantization, and an externally set signal S.sub.max.