Subjective testing confirms importance of frame rate for UHDTV

Wednesday, August 7th, 2013 
European Broadcasting Union logo

The impact of higher frame rates on the viewing experience is under investigation in Munich this week. The European Broadcasting Union (EBU)’s Broadcast Technology Futures (BTF) group, which is made up of the heads of the research labs of the BBC, IRT, RAI and NHK, is conducting a series of subjective tests at the IRT’s facilities. The BTF group is coordinated by the EBU Technology & Innovation department.

Last February, a set of subjective UHDTV resolution tests conducted at the EBU during the Production Technology Seminar revealed that higher resolutions would not be enough to create a clearly perceptible difference compared to HDTV. In the meantime the industry, with the EBU taking a leading role, has shifted towards supporting this notion. Significant work is now under way to investigate other parameters required to generate a more immersive experience with UHDTV. In addition to resolution, technical parameters that are likely to be crucial include higher dynamic range, extended colour space and, of course, the frame rate.

There are several open questions related to frame rates: will observers appreciate higher frame rates? What should the upper limit be for frame rates? And, given that the current UHDTV standard specified by the ITU includes only 120 Hz as a higher frame rate, is there a need for rates that are multiples of 50 Hz, i.e. 100, 150 Hz, etc?

The tests at the IRT will address some of the above questions, and represent a starting point for further necessary scientific investigations. Various frame rates up to 240 Hz with different content genres are being rated by observers. The sequences are in both uncompressed form and compressed with HEVC according to the ITU-R BT.500 DSCQS (double-stimulus continuous quality scale) test methodology.

Early results give a clear indication that higher frame rates are appreciated by the observers, to a significantly greater extent than increased resolution. This supports the position that future UHDTV systems should include higher frame rates. The detailed results will be examined in the BTF group and in the EBU’s Beyond HD strategic programme.