提出了一种新的基于DCT域的MPEG-2码流转换算法，该算法与现有算法，即通过解码、空域采样率转换来设定新的码流参数，再编码的算法相比，无需IDCT、DCT操作，便可在DCT域实现码流转换，而且省去了运动矢量估值和运动补偿过程，不仅节省了大量帧存和减少了运算量，而且更具有实时性的优点，对MPEG-2 MP@ML到4：2：2Profile@ML码流转换算法实例的分析和现实表明：该算法能简单有效的实现压缩域码流转换，其思想同样可广泛用于其他基于DCT压缩图象的采样率转换、线性滤波等任务。

In this paper a novel MPEG-2 transcoder based on DCT domain is proposed. After analyzing the differences between MPEG-2 MP@ML and 4∶2∶2 Profile as well as the properties of discrete cosine transform and some spatial domain filters, the upsampling and linear filter algorithm in DCT domain is derived. The new transcoder has low buffer requirement and results in low delay. Compared with common decoder-encoder cascade methods, the current algorithm can reduce the computation and hardware complexity dramatically due to its omission on DCT(IDCT), ME(motion estimation) and MC(motion compensation) procedures,which are very time consuming. The simulation results demonstrate,the new approach only suffers slighter quality degradation than the pixel domain method on basis of the conventional decode/re-encode schema, and it is more appropriate to be used in real time environment.