Subjective evaluation conducted by JCT-VC (Joint Collaborative Team on Video Coding) members shows that H.265/HEVC achieves about 50% rate saving over H.264/AVC without sacrificing subjective quality. In this paper, we study 13 objective image and video quality assessment (IQA/VQA) metrics, including the recently proposed ones—FSIM , GMSD  and IWSSIM , in terms of coding gain prediction of HEVC over H.264. Experimental results on HEVC Class B and Class C test sequences show that most of the metrics underestimate the rate saving. Surprisingly, a relatively old metric—Noise Quality Measure (NQM)  index consists well with subjective evaluation. To verify the universality of the phenomenon, we carried out further tests on another ten video sequences with different levels of spatial and temporal complexities. The experimental results show that NQM still predicts rate saving more accurately than the other metrics.