Calculation of average coding efficiency based on subjective quality scores

• We propose a model to calculate coding efficiency based on subjective scores (MOS).
• A logistic function is used to fit the rate–distortion (R–D) values.
• A confidence interval on the fitted R–D curve considers the reliability of MOS.
• The average MOS and bit rate differences are computed between the fitted R–D curves.
• The proposed model is expected to report more realistic coding efficiency.

The Bjøntegaard model is widely used to calculate the coding efficiency between different codecs. However, this model might not be an accurate predictor of the true coding efficiency as it relies on PSNR measurements. Therefore, in this paper, we propose a model to calculate the average coding efficiency based on subjective quality scores, i.e., mean opinion scores (MOS). We call this approach Subjective Comparison of ENcoders based on fItted Curves (SCENIC). To consider the intrinsic nature of bounded rating scales, a logistic function is used to fit the rate–distortion (R–D) values. The average MOS and bit rate differences are computed between the fitted R–D curves. The statistical property of subjective scores is considered to estimate corresponding confidence intervals on the calculated average MOS and bit rate differences. The proposed model is expected to report more realistic coding efficiency as PSNR is not always correlated with perceived visual quality.