HDfury Diva

HDMI signals

4K60

Resolutions and refresh rates the HDfury Diva handles

In short

Ultra HD at 3840x2160 pixels and 60 frames per second, the format that pushed HDMI links up to 18Gbps.

4K60 is easy to ask for and easy to lose. Whether it arrives at 4:4:4 or drops to 4:2:0 is bandwidth arithmetic, and on the Diva you can see exactly where it went.

4K60 means 3840 by 2160 pixels at 60 frames per second, progressive, and is usually called UHD. It is the format that forced HDMI 2.0 into existence: 1080p60 needs a pixel clock of 148.5MHz, and four times the pixels at the same refresh rate needs four times that. The link tops out at a 600MHz TMDS clock carrying 18Gbps, and 4K60 with 4:4:4 chroma at 8 bits per component sits at 594MHz, right against that ceiling.

Which is why the same resolution comes in several sizes. Halving the chroma resolution to 4:2:2, or quartering it to 4:2:0, frees enough room for 10 or 12 bit colour at the same refresh rate, so 4K60 4:2:2 12-bit fits inside 18Gbps while 4K60 4:4:4 12-bit does not. Dropping to 4K30 halves the clock to 300MHz and everything fits again. When a television advertises 4K60 without saying which variant, it often means 4:2:0 8-bit at 300MHz.

What the HDfury Diva accepts

The Diva takes four inputs at true full 4K60 4:4:4 600MHz 18Gbps, and that figure is the ceiling for the inputs and for TX0. In HDTV mode it handles all known SD, HD, Full HD and UHD formats, the manual listing everything from 480i50 through 2160p60 with 720p120, 1080p24, 1080p48, 1080p96 and 1440p60 among them, plus anything else that fits inside 600MHz. PC graphics modes are covered on the same basis, up to WQSXGA, QUXGA, QFHD and WQUXGA.

You do not set anything on the source. The Diva is detected as a 2160p60 4:4:4 capable device and accepts the best stream the source can produce, after which the EDID you present decides what the source actually sends. The predefined EDID tables are arranged by format for exactly this reason: banks 11 to 19 describe 4K60-444 600MHz, banks 38 to 46 describe 4K60-420 8-bit 300MHz, and banks 47 to 55 describe 4K30-444 300MHz, each in all sound, S/PDIF and stereo variants.

Where 4K60 gets lost

  • TX1 is a 1080p SDR downscale output by design, so anything sent there leaves at 1080p. That is the intended behaviour, not a fault.
  • TX0 upscales whenever it can under Auto Scaling. Tick NO UPSCALING if the display has the better scaler, or set 1080p60 upscale to remain at 1080p60 under Custom Scaling.
  • Most UHD televisions need their own setting enabled first. On a Samsung you enable UHD colour under settings and HDMI, then assign the port as PC in the tools menu, and only specific ports are 600MHz capable at all.
  • Cable. For 600MHz use cable certified or tested for 600MHz and 18Gbps, ideally between 6ft and 12ft.

Related terms

18Gbps and 600MHzThe data rate an HDMI link can carry, set by the pixel clock: 600MHz and 18Gbps are the HDMI 2.0b ceiling.ScalerThe stage that resamples a picture onto a different pixel grid, either upwards to fill a higher resolution panel or downwards to fit what a display can accept.DownscalingConverting a signal to a lower resolution, and often a lower dynamic range, so that equipment which cannot accept the original can display it.Chroma subsamplingA way of sending less colour information than brightness information, because the eye notices the difference far less.

In the manual

The pages of the HDfury Diva manual where this comes up.

All glossary terms