Why 4K Streaming Isn’t Really 4K

| Analysis

Executive Summary

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

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Comments

ibuck

What gives?  Is TMO going for page clicks now? This story could have been on 2 webpages rather than 4.

Bryan Chaffin

Hey ibuck. The focus of our new pagination feature is readability, not extra clicks.

We’ve only paginated a few articles, and we’re still tweaking what we’re doing in search of the right length for our longer articles.  We appreciate the feedback.

John Martellaro

ibuck: It looked like, after all, pages 3 and 4 could be combined, so I fixed it. As Bryan said, we’re still experimenting.

geoduck

This just reaffirms my contention that the smart money will stay on the 4kTV sidelines for the next few years. Nobody is ready for it. Not to mention that there’s little content.

John Malone

18Gbps is with 60fps. Since movies use 24fps + they use lower bit audio/and color depth = that is how they can get 4K at 15mbit.

FlipFriddle

4k? Jeez, I have enough problem streaming 720p to my TV now. Which neighborhoods have pipes this big?

John Martellaro

Mr. Malone. I used 60 Hz as an example of pristine 4K at the outset.  But the Blu-ray data in the article is already based on 24p. Chris Heinonen says, “The Blu-ray data is taken from films that are encoded at 24p, so it’s Apples-to-Apples when you do that math. If you are using a 60i source (concert videos on Blu-ray typically, there isn’t anything that’s 60p really) then your bit rate will be around 25% higher. But the Netflix 4K vs. Blu-ray math should both be based on 24p data.”

vpndev

>4k? Jeez, I have enough problem streaming 720p to my TV now.
>Which neighborhoods have pipes this big?

I don’t know. I have FiOS and still get slow internet.

If we have a big pipe then it must be the sewer smile

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