When I had questions about 4K

4K television was still a pretty new thing in 2015. In fact, I think it’s fair to say it’s hardly well established today. The lion’s share of the “4K” content comes from streaming, where the quality rises and falls along with the amount of congestion on you local internet node.

In fact, even after all these years, only DIRECTV provides live 4K programming at a high quality level. No wonder, then, that I was skeptical when I wrote about a scheme that claimed to provide 4K content over a 7Mbps stream. Bandwidth was a bit more of a concern five years ago. Today it’s common to get at least 100Mbps as long as your neighbors aren’t trying to do the same thing, but back then if you got 20Mbps in a sustained stream you were thanking your lucky stars.

So how much bandwidth DO you need for 4K?

That’s an incredibly loaded question. As I’ve said before, 4K is a measure of resolution. It means that you’re providing an image 3840×2160 in size. It really doesn’t say anything about the quality of that image. You can create an incredibly ugly, blurry mess of an image and still call it 4K if you want it to. And really, that’s what most streaming services do. Pristine HD, such as you’ll find off a Blu-ray disc if you can still find one, usually beats streaming 4K by a long shot. Blu-ray was produced at a rate of 38Mbps and that was enough for a really beautiful HD picture even given the limits of the day’s technology.

Using the same technology as Blu-ray, you’d need about 160Mbps to produce a 4K picture. It’s generally agreed that you get a passable (still not pristine) 4K picture with about 40Mbps of bandwidth, and you can even get something that won’t embarrass you with 25Mbps.

But can you get there with 6-7Mbps?

Raw uncompressed 4K data would require something along the lines of 4 exabits per second, in other words 4,000,000,000 megabits per second. I get that number by multiplying the resolution of 4k by the number of colors in the color space (16.7 million) and then multiplying that by 60 frames per second. That speed is, simply, impossible. At least today. Another site suggests that the raw speed is actually “as low as” 1.4 gigabits per second.

The amount of compression we can apply and still have a usable picture is really pretty amazing. It takes very hardcore math to encode and decode it in real time. As our computers get more powerful, we can use ever-more complex algorithms to compress this video. It may someday be possible to compress video down to 6Mbps. But it’s never going to happen.

Internet speeds are continuing to rise and the need to get video down that small isn’t really there anymore. Building computers robust enough to get that compression to work isn’t likely to be cost-effective. Remember, most people prefer to pay under $100 for a streaming box.

My hope is that we can get to the point with changes in compression technology and hardware advances that we just won’t be embarrassed by streaming 4K. I’m guessing it would take about 50Mbps and a powerful decompressor. Maybe we’ll have that by the time I “throw back” to this article in five years.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 6,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.