Apparatus and method for encoding video stream using property of background in video

摘要

PURPOSE: An image coding system and method using background characteristic of an image are provided to control a quantization step size for a background region to encode the background region, thereby improving the picture quality of the background image. CONSTITUTION: A image coding system(100) includes a spatial/temporal prediction coding unit(110), a background processing unit(120), a transform coding unit(130), an adaptive quantizer(140), and an entropy coding unit(150). The background processing unit includes a motion judgement part(121), a memory(122) and a background pre-processor(123). The spatial/temporal coding unit carries out motion estimation and motion compensation for an input image to detect a motion vector and carries out spatial/temporal prediction coding for the detected motion vector. The background processing unit compares the prediction-coded image with a previous image and stores temporal continuity of macro-blocks having no motion in the memory. The transform coding unit discrete-cosine-transforms the video data received from the spatial/temporal prediction coding unit. The adaptive quantizer quantizes video data recognized as a background region and video data that is not recognized as a background region. The entropy coding unit variable-length-codes the data output from the adaptive quantizer.