A、VCEG 建议采用Bjontegaard metric described in [1] to provide relative gain between two methods,by measuring average difference between the two RD-curves.
参考[3]中的文档提供了这两种值的计算工具：the bitrate saving between two methods, for a given objective quality; and the PSNR-Y delta for a given bitrate .
由此可见 Bjøntegaard delta bit rate (BDBR) 表示了在同样的客观质量下，两种方法的码率节省情况(Rate/distortion curves 画一条水平线)
Bjøntegaard delta peak signal-to-noise rate (BD-PSNR)表示了在给定的同等码率下，两种方法的PSNR-Y的差异(Rate/distortion curves 画一条垂直线)。
B、在HEVC中，[4]提供另外一种使用五点来计算BD-PSNR/Rate的工具，
参考：
[1] G. Bjøntegaard, “Calculation of average PSNR differences between RD-Curves,” ITU-T SG16 Q.6 Document, VCEG-M33,Austin,US, April 2001
[2] G. Bjøntegaard, “Improvements of the BD-PSNR model,” ITU-T SG16 Q.6 Document, VCEG-AI11,Berlin,Germany, July 2008
[3] An excel add-in for computing Bjontegaard metric and its evolution,VCEG-AE07
[4] BD-PSNR/Rate computation tool for five data points,JCTVC-B055
[5] S. Pateux, Tools for proposal evaluations, JCTVC-A031, April 2010.