2 Cables and connector types need to support 4K/UHD. The cables you’re most likely to use are either a standard HDMI or, if you’re connecting a PC to a 4K/UHD monitor, DisplayPort. The primary factors that affect bandwidth are resolution, frame rate, color bit depth and chroma subsampling. HDMI v1.4a supports 4K/30 Hz for 8-bit color 4:4:4 or up to 12- bit color 4:2:2, at an aggregate data rate of 8.91 Gbps and bandwidth of 1.485 GHz. However, there are additional 4K format capabilities that are included in the HDMI 1.4 specification, all of which run at 8.91 Gbps, capping out at 10.2 Gbps. HDMI 2.0, at the same bandwidth of 1.485 GHz, supports 4K/60 Hz but at the cost of color, limiting to 8-bit 4:2:0 color depth. Blu-ray, DVD, and HDTV broadcast systems all use 4:2:0 color compression. So how is it possible to double the frame rate without doubling the bandwidth? The answer lies in the ‘8-bit 4:2:0’ chroma subsampling; they reduce the color data to half the bandwidth, allowing them to then double it again with frame rate. The human eye is far less sensitive to color than it is to brightness and greyscale, so the amount of color information in video can be reduced without being noticeable. Note that this trick only works with 8-bit 4:2:0. HDMI 2.0 doesn’t stop there, though, as there are additional 4K format capabilities that are included in the HDMI 2.0 specification. In the residential AV space we’re likely to cap out at 4K/60 Hz 12-bit 4:2:2, which increases bandwidth to a whopping 2.97 GHz. At 12- bit 4:4:4, 4K/60 Hz takes a big jump in data rate, doubling it from 8.9 Gbps up to a cap of 17.82 Gbps (rounded to 18 Gbps), and can go as high as 26 Gbps. The range above
2. Cables and Connector types need to support 4K/UHD 10.2 Gbps is referred to as “HDMI 2.0 mode” where the TMDS (Transition Minimized Differential Signaling) clock is slowed to 1/40th of the data rate to counter the effects of EMI at such high speeds. Other techniques such as data scrambling are also employed to improve stability. HDMI 2.0a has also added support for content with high dynamic range (HDR), which allows more leeway between bright and dark hues, so the viewer can see more realistic images by adjusting shadow and light. All the talk happening now about increasing to 8K won’t make as much difference to quality improvement as HDR, because your eyes can’t perceive any more detail than 4K/UHD. The quest for more realism then becomes putting better pixels on the screen, not more. However, the opinion of some suggests that HDR+ (HDR plus Wide Color Gamut) will not see much implementation before 2017-2018 or even 2019-2020, when 100/120 Hz frame rates are to be included. For HDMI 2.0, the best thing you can do is stick to high-quality, scalable, native HDMI cables and provide the ability to swap them out later. Native HDMI cables rely on the new 2.0 EQ profile in upcoming displays to boost shorter cables and likely will require additional active augmentation for longer lengths. If you need longer lengths now you can upgrade to Opticomm-EMCORE’s HDMI-fiber hybrid cable, which is available in various standard lengths up to 100 meters (330 feet). DisplayPort carries 4K image and audio signal from most high-end graphics cards to monitors without any noticeable artifacts or delays. DisplayPort 1.2 supports 4K/60 Hz but the new DisplayPort 1.3 has greater bandwidth for 4K/60 Hz.