【摘要】 为了满足数字视频广播传输过程中对视频质量稳定性的要求,提出一种使视频质量保持在所需范围,并且满足带宽限制的应用方案。该方法使用离散余弦变换系数的均方差来评价图像质量损失,并建立二次量化参数与图像质量损失之间的对应关系模型,动态选择二次量化参数。该方法将视频质量作为主要控制对象,在转码过程中实时评估和控制图像质量损失,使得转码输出的视频质量保持平稳。与传统的像素域质量评估方法相比,全部操作可在频域完成,因而计算量小,调整速度快。仿真实验表明:该方法可有效地控制转码视频的质量损失。更多还原

【Abstract】 An adaptive transcoding scheme was developed for DVB(Digital Video Broadcasting) application with improved video quality control.The transcoding error is based on the mean square error of the DCT(Discrete Cosine Transform) coefficients in the frequency domain.The model is based on the quantization process where the quantization steps are adaptively selected to provide the desired video quality.Unlike previous schemes,this scheme focuses on video quality control and does not need to reconstruct the pictures into the pixel domain.Therefore,computations are not needed for the DCT transform in the quality evaluation process.Simulations show that the scheme greatly improves the efficiency of transcoding while maintaining video quality.更多还原