Whether or not your video strategy includes publishing in the latest ultra HD resolution, user expectations are already being set by the latest crop of TVs, monitors, and AV equipment. Consumers are looking for the best possible quality video and 4K promises just that. But filming something in 4K is only half the battle. The other half, delivery, needs to be aligned with the bandwidth and compute intensive requirements of ultra HD video as well. That’s why we’ve put together this blog post, to help you understand the ins and outs of 4K video as it stands right now.
Before we can get started, though, let’s get some basics out of the way, like, “what is 4K video?” First, 4K is not a “codec.” A codec, like h.264, is a way to encode and decode a video. Each codec has one or more “containers” into which the video can be encoded. For example, h.264 can produce .mp4 which is a very common format for online video. Most 4K encoding actually utilizes the h.264 codec. The difference between 4K video and other types of video (like HD and SD) is the number of pixels. There are 4 times as many pixels in a 4K video than there is in a 1080 HD video. That means a 4K video can be delivered in a much higher resolution and aspect ratio.
Okay, with that out of the way, let’s get down to what you really need to know about producing and delivering 4K video. I’ve decided to arrange this as a Q&A to make it easy to follow.
“Should I be filming in 4K?”
The simplest answer to this is, yes. By filming in 4K, you are ensuring that your master file is of a significantly high-enough quality that any variety of lower bitrates can be generated. And when it becomes easier to deliver 4K video online (i.e., users have more bandwidth, devices are better suited to decoding 4K), you will already have the assets to encode. There are a lot of cameras on the market that currently shoot in 4K. Although some of them are considerably expensive, you can get a relatively cheap solution by using the GoPro Hero4.
“How many bitrates should I produce from my 4K video?”
The first thing you have to keep in mind is that video quality, above all else, is your primary concern. That’s why today, you can’t just film in 4K and then deliver in 4K. You need to have a variety of bitrates at the ready to ensure that your users are getting the highest possible quality of video for their specific capabilities. A good suggestion is to cover each of the primary resolutions: High HD (1080p at 3.5mb/s), low HD (720p at 1.5mb/s), and SD (around 750kbp/s). Of course, if you plan on delivering your video to lots of small screens, you may want to have some additional lower bitrate options available.
“What is HEVC or h.265 and how will that help me deliver 4K?”
HEVC (High-efficiency video codec) or h.265 is the next generation codec. Built using h.264, this codec is intended to provide the same quality as h.264 but at smaller bitrates. This means that an Ultra HD video at 8mb/s might be encoded at 5.5mb/s (or smaller, depending upon the particulars of the video you are encoding) enabling you to deliver a much higher quality of video without using as much bandwidth or computing resources (memory and CPU) to decode the video. Unfortunately, in order to watch a h.265 encoded video, the user’s computer (browser, player, etc.) must have the h.265 codec installed in order to decode the video. At this time, there hasn’t been any deployment of h.265 to consumer devices (computers, TVs, smartphones, etc.) and it’s unclear when this will happen.
“Do I need to do anything with my player to deliver 4K content?”
Because 4K content is encoded using h.264, as long as your player can play common formats (i.e, .mp4, .mov, etc.) you won’t have any problems whether your content is 4K, HD, or SD.
“What impact will delivering 4K have on my users?”
Remember that decoding 4K is a lot more system intensive than HD. There's 4 times more data that has to go through storage, CPU, memory, and video decoding which could impact your user’s system responsiveness. So much so, that the player could request a different bitrate more suitable for the environment. And, if the user doesn’t have a native 4K display, there may be real-time scaling issues that will hinder playback smoothness.
“Can I deliver 4K to a smartphone?”
As long as the 4K content is delivered in a format that the smartphone can handle (most often .mp4), then absolutely. Remember, though, that smartphones are often bandwidth constrained. Whether on WiFi or a mobile network, there usually isn’t a lot of pipe for delivering high bitrate content. What’s more, in order to decode h.264-encoded content, the target device will need to have dedicated decoding hardware. Although most of today’s modern smartphones have such, older phones will not.
“Are we ready for 4K delivery today?”
Although some would disagree, I don’t think we are quite ready for 4K delivery. There are lots of reasons for saying this. First is the availability of consumer bandwidth. Although more and more people are signing up for fiber or “gigaethernet,” the percentage of people with enough available bandwidth to support 4K delivery is still significantly low. If you were to try, 1% of your audience might be able to view it. The rest would, hopefully, see the highest quality video they could (because you would be delivering it in multiple bitrates). Second is the lack of compute resources on many of the handheld devices to support the compute-intensive requirements of decoding 4K video. Finally, there is the lack of 4K native displays. And even though a lack of native display that won't prevent users from watching 4K content, it will hinder the overall quality of the experience.
“Can Limelight handle 4K?”
The short answer is, absolutely. First, 4K video, like I’ve already said, is just more bits at a higher throughput. Instead of delivering 1mb/s, you are delivering 8mb/s for example. Limelight’s network was built specifically to deliver and stream large video files. Second, Limelight’s video delivery services support adaptive bitrate meaning you can provide us multiple bitrates and we do the switching at the server level when we receive a request to switch from a user’s player.
As you can see, there are a lot of considerations to make before choosing to deliver 4K content. Even though your CDN, like Limelight, might be built for pushing the extra bits to all those endpoints, you have to take into account where the content is being consumed (i.e., if the device has the appropriate amount of CPU, memory, and hardware to decode such a high bitrate video well) and how much bandwidth is available. In most cases, your 4K content in today’s environment will be “downshifted” by the player to a lower bitrate. But that doesn’t mean you should shun the higher bitrate qualities of ultra HD. Your best bet is to start producing content in 4K now so that you are ready with high quality files when it becomes easier to deliver ultra HD video.