Originally featured on BroadcastEngineering.com
High frame rates improve experience says EBU
The European Broadcasting Union (EBU) has reported early findings from tests suggesting that higher frame rates boost the TV viewing experience significantly. The tests are being conducted in the light of earlier subjective findings based on feedback from the EBU’s the Production Technology Seminar in February 2013, suggesting that higher resolutions on their own do not yield a perceptible quality improvement compared with existing HD. This was especially true on screens smaller than 60in, leading to the growing perception that only users of very large screens will be willing to pay extra for UHDTV.
But some broadcasters, such as the BBC, had already conducted their own tests indicating that higher frame rates, combined with other improvements, such as 10-bit rather than 8-bit color, made at least as big a difference to quality of viewing as higher resolutions. The EBU then decided to conduct its own more rigorous tests within its Broadcast Technology Futures (BTF) group, comprising the heads of the research labs of the BBC, IRT, RAI and NHK. This involves a series of subjective but thorough tests at IRT's facilities in Munich, Germany, coordinated by the EBU Technology & Innovation department.
The preliminary conclusion is that higher frame rates are much appreciated by the observers and to a significantly greater extent than increased resolution. This leads to several open related questions that the EBU is now considering, such as what the upper limit might be for frame rates, above which no further improvement in quality will be discerned. Another question is whether the current UHDTV standard should be extended to allow multiples of 50Hz, rather than just the 120MHz rates currently supported. This would be helpful for European broadcasters, which use 50Hz transmission in line with the oscillation frequency of the power supply. For them, use of 120Hz frame rate would require sophisticated and expensive motion-compensated format converters to avoid UHD material appearing as “judder” if used in HDTV programs and vice versa.
The tests at the IRT are addressing these questions, and providing a starting point for more in-depth scientific investigations. One question not being looked at is whether it makes sense, given bandwidth constraints, to increase frame instead of, rather than as well as, resolution, at least beyond “full HD” at 1080p. On the other hand, it may be that with the help of higher resolutions, UHDTV may make a significant difference to the experience even for screens substantially smaller than 60in.