  For 20 years, the gold standard to evaluate the performance of video codecs
is to calculate average differences between ratedistortion curves, also called
the "Bj{\o}ntegaard Delta". With the help of this tool, the compression
performance of codecs can be compared. In the past years, we could observe that
the calculus was also deployed for other metrics than bitrate and distortion in
terms of peak signal-to-noise ratio, for example other quality metrics such as
video multi-method assessment fusion or hardware-dependent metrics such as the
decoding energy. However, it is unclear whether the Bj{\o}ntegaard Delta is a
valid way to evaluate these metrics. To this end, this paper reviews several
interpolation methods and evaluates their accuracy using different
performancemetrics. As a result, we propose to use a novel approach based on
Akima interpolation, which returns the most accurate results for a large
variety of performance metrics. The approximation accuracy of this new method
is determined to be below a bound of 1.5%.
