基于MPEG压缩域的高速公路车辆检测方法

提出了一种从MPEG-2压缩数据流中提取高速公路车流量的方法．白天根据车辆运动的特点，利用宏块的运动矢量检测车辆，并给出了运动矢量噪声的滤除算法．夜间根据车灯的亮度高于背景区域的特点，利用图像块的DCT系数检测车辆的车灯，并介绍了P帧图像块的DCT系数的计算方法．为了防止道路外物体的移动以及镜头的移动对检测造成的影响，给出了车道定位的方法以及镜头移动检测的算法．采用此方法，白天的检测准确率可达97．4％，夜间的检测准确率可达95．4％．实验表明本检测方法是有效的．

Vehicle detection method for expressway by MPEG compressed domain

A method which extracts traffic information from an MPEG-2 compressed video is proposed.According to the features of vehicle motion,the motion vector of a macro-block is used to detect moving vehicles in daytime,and a filter algorithm for removing noises of motion vectors is given.As the brightness of the headlights is higher than that of the background in night images,discrete cosine transform (DCT)coefficient of image block is used to detect headlights of vehicles at night,and an algorithm for calculating the DCT coefficients of P-frames is introduced.In order to prevent moving objects outside the expressway and video shot changes from disturbing the detection,a driveway location method and a video-shot-change detection algorithm are suggested.The detection rate is 97.4% in daytime and 95.4% in nighttime by this method.The results prove that this vehicle detection method is effective.