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http://www.anandtech.com/show/81 ... 0hz-support-kind-of

引用:

Lacking the available bandwidth to fully support 4K@60Hz until the arrival of HDMI 2.0, the latest crop of 4K TVs such as the Sony XBR 55X900A and Samsung UE40HU6900 have implemented what amounts to a lower image quality mode that allows for a 4K@60Hz signal to fit within HDMI 1.4’s 8.16Gbps bandwidth limit. To accomplish this, manufacturers are making use of chroma subsampling to reduce the amount of chroma (color) data that needs to be transmitted, thereby freeing up enough bandwidth to increase the image resolution from 1080p to 4K.

Specifically, manufacturers are making use of Y'CbCr 4:2:0 subsampling, a lower quality sampling mode that requires ¼ the color information of regular Y'CbCr 4:4:4 sampling or RGB sampling. By using this sampling mode manufacturers are able to transmit an image that utilizes full resolution luma (brightness) but a fraction of the chroma resolution, allowing manufacturers to achieve the necessary bandwidth savings.

引用:

In any case, with 4:2:0 4K TVs already on the market, NVIDIA has confirmed that they are enabling 4:2:0 4K output on Kepler cards with their R340 drivers. What this means is that Kepler cards can drive 4:2:0 4K TVs at 60Hz today, but they are doing so in a manner that’s only useful for video. For HTPCs this ends up being a good compromise and as far as we can gather this is a clever move on NVIDIA’s part. But for anyone who is seeing the news of NVIDIA supporting 4K@60Hz over HDMI and hoping to use a TV as a desktop monitor, this will still come up short. Until the next generation of video cards and TVs hit the market with full HDMI 2.0 support (4:4:4 and/or RGB), DisplayPort 1.2 will remain the only way to transmit a full resolution 4K image.

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