A new workaround has cropped up in Nvidia’s latest drivers for Kepler GPUs that allows the cards to output to 4K TV displays at 4K@60Hz over HDMI 1.4. This is instead of the 4K@30Hz that they were limited to before because of the HDMI bandwidth availability.
What’s surprising about this is that it’s something that wasn’t expected to happen until HDMI 2.0, which is not featured in current cards. It’s not magic; it’s just that a compromise has been made, lowering the image quality.
To see full support for 4K@60Hz, we’ll still need to wait for HDMI 2.0, but in the mean time, 4K TV manufacturers have decreased the image quality so that there’s less data that needs to be transmitted, allowing it to fit within the 8.16GBps bandwidth limit of HDMI 1.4.
Manufacturers such as Sony and Samsung have employed chroma subsampling, which reduces the amount of colour data being transmitted and frees up bandwidth to bump up the resolution from boring old 1080p to 4K.
Using 4:2:0 subsampling instead of normal 4:4:4, only a quarter of the colour data of a full resolution image is transmitted. For video, this isn’t a problem, since broadcasts, Blu-Ray and streaming are 4:2:0 anyway. Outside of video, the loss of quality is more noticeable.
But right now, with HDMI 2.0 not with us yet, and with 4:2:0 TVs already available and supported by Nvidia’s R340 drivers, it’s the only way to get 4K@60Hz without DisplayPort 1.2.
Have any of you lovely lot got 4K TVs yet? Tempted to use them as desktop monitors?
Cheers, AnandTech.
