VMAF Score for Subjectively Lossless Video Quality on TVs, Tablets and Smartphones

The use of over-the-top (OTT) video streaming services applying adaptive bit rate (ABR) streaming is growing continuously. In ABR streaming, digital video signals are encoded at various bit rates and associated qualities and provided to a wide range of end-user devices via the internet using a content delivery network (CDN). Each end-user device can request and stream the video signals from the CDN at a bit rate suiting the individual transmission rate of the user's internet connection. The quality of encoded video can be judged by the objective metric Video Multi-Method Assessment Fusion (VMAF). For OTT video streaming services, which aim at providing subjectively lossless video of very high quality, it is important to know the lowest VMAF score being associated with subjectively lossless quality as this allows to deliver the desired quality at a minimum bit rate and thus at minimum costs. In this paper, this VMAF score is determined individually for each of the three most important classes of end-user devices, i.e. TV, tablet, and smartphone. Extensive subjective tests following the international recommendations, such as ITU-R BT.500, reveal that this VMAF score is 95 for the applied 4K TV, 95 for the applied tablet, and 92 for the applied smartphone.