The bandwidth requirement for a full-fledged 4K video signal, including audio, is enormous — nearly 18 gigabits per second. Therefore, superior compression technology is required to transmit a 4K signal into the home with current Internet technology. Every tech giant is up against extreme limits to make 4K video the Next Big Thing, and compromises will be necessary.
Because a 4K stream is so demanding, some sleight of hand marketing will be necessary to convince customers that they're receiving full 4K video. It will be called "4K," but it may not be the real thing for awhile. Here's why.
The 4K Picture Basics
There are lots of engineering details in broadcast TV, and they can get complex. I'm going to cover just the basics here. The links I've provided below have many more details.
The transmission of a 4K signal for a picture at 4096 x 2160 at 60 fps, when combined with audio requires, a 4400 x 2250 x 60 frame. Plus, while each pixel requires 8 bits of color information for red, green and blue, the actual transcoding for HDMI 2.0 uses 10 bits per color. The resulting bandwidth from the video hardware to the display is:
4400 x 2250 x 60 Hz x 30 bits/pix = 17.82 Gbps (gigabits per second.)
That's enormous, and now we know why Thunderbolt 2, with a capability of 20 Gbps, or HDMI 2.0 with a capability of 18 Gbps is required to handle 4K on a local connection from a device to the display.
Next: Compression to the Rescue