This paper presents the issue of QP mapping in H.264 or AVS to MPEG-2 transcoding process. The theoretic QP mapping curve is deduced by analysis of H.264/AVS and MPEG-2 quantization schemes. Then
the mismatching between the theoretic curve and practical application is found. Based on the requirements of different applications
such as high fidelity video application
video transmission on limited bandwidth networks and video on demand with adaptive quality adjustment
a series of QP mapping curves is obtained by experiments and analysis. These curves are customized for predefined parameters
and they can be easily modified to meet specific applications.