HIGHLY EFFICIENT ENCODING AND DECODING DEVICES

摘要

PURPOSE:To improve picture quality by accurately detecting the edge part of a picture at the time of compressing and encoding a video signal. CONSTITUTION:A blocking circuit 41 divides a video signal into plural blocks, an orthogonal transformation circuit 42 applies orthogonal transformation to each block and transformation coefficients are successively read out from a scanning circuit 43. A coefficient selecting circuit 44 selects a main coefficient from a low band area and a high band area and an evaluation value calculating circuit 45 calculates an evaluation value based upon the main coefficient and a detection circuit 46 detects a specific pattern in the video signal based upon the evaluation value. A quantizing step determining circuit 47 determines an optimum quantizing step based upon the specific pattern and a quantizer 48 applies adaptive quantization to the transformation coefficient to prevent the generation of deterioration in picture quality.