Managing HDMI 2.1 related features is proving difficult for many manufacturers. The latest to run into issues of this kind is Sony with the XH90 TVs, one of two series marked “Ready for PlayStation 5”. The XH90s, announced at CES 2020, have recently been upgraded to support Ultra HD 120Hz input signals.
The greater availability of the new Nvidia RTX GPUs and the arrival in the editorial offices of the Xbox Series X (here our test) and PlayStation 5 (here our review) consoles have allowed us to carry out many more field tests precisely in the context of the functions of HDMI 2.1. According to what is reported by some sources (such as the tweet attached to the article but not only), the Sony XH90 would not seem able to manage Ultra HD at 120 Hz while maintaining the quality of the signal.
When you switch from Ultra HD at 60Hz to a higher refresh rate, the image becomes noticeably less detailed, as if it were lower definition than actually sent from the source. The cause apparently seems to be linked to signal processing: the HX90s are certainly capable of accepting a UHD / 120 Hz resolution in input but evidently rework it by scaling it down before actually showing it on screen.
What you see on the screen therefore looks like the result of an upscaling performed after the original quality has been lowered, a device that may be necessary to allow processing the large amount of data. Recall that a 120 Hz Ultra HD stream with HDR requires a bandwidth ranging from 40 to 48 Gbps (color sampling in 4: 4: 4 at 10-bit or 12-bit). In simpler words, the perceived resolution is not the native one but lower and simply readjusted to Ultra HD.
For the moment there are no reports for ZH8, the other “Ready for Playstation 5” series that supports 120 Hz. The motivation could be trivially linked to the spread of these televisions: the 8K, both for a matter of costs and for dimensions, are certainly much less common. However, the explanation could also be linked to the integrated processor: ZH8 mounts X1 Ultimate, Sony’s most performing electronics while XH90 uses the less powerful 4K HDR Processor X1.
The need to decrease the quality of the input signal could be due precisely to this component: the power made available by X1 may not be enough to manage 40 – 48 Gbps in real time. The compression of the band, the decrease of the detail and the consequent upscaling would therefore be a way to circumvent this limitation; the user is thus able to actually use the Ultra HD resolution at 120 Hz but with a lower video quality. However, it remains a supposition that, although perfectly logical and consistent with the problem, it will be officially confirmed by Sony.
We obviously await a communication from the manufacturer and to know the solution that will be proposed.
