Best Practices for Affordable Multicam 4K Live Streaming

So when picking a camera for 4K live streaming, the key consideration is how you're going to connect it to your production system. HDMI output seems to be the most common standard for 4K video over cables right now.

SDI support for 4K is still relatively new, with Blackmagic being pretty much the only manufacturer currently offering cameras that can do 4K over SDI. The Panasonic and the Sony have SDI outputs as well, but those are limited to HD formats for output.

So that's another cabling standard as well in the consumer space is HDBaseT, which allows you to convert back and forth between SDI and HDMI for those long cable lengths, and it also supports 4K. HDBaseT standard uses a standard Cat6 cable, the same sort of cable you might use for a network.

Software

At vMix, we do live streaming production software, and our software supports 4K. This enables producers to deliver multicam streams using a single PC. vMix 4K (Figure 4, below) is a complete live streaming and production software tool for the PC, so it supports everything from switching your cameras to graphics, pre-recorded videos, and much more. And it has a built-in encoder, so everything you need to do 4K live streaming but the PC and the camera is in this single piece of software.

Figure 4. vMix 4K

On the vMix website, we have recommended PC specifications. We have PCs that are capable of doing HD multi-camera productions, 4K multi-camera productions, instant replay, and all of the different requirements you might have for your live stream. For a 4K-ready, multi-camera production PC, you can build one, or you can contact a system builder or a resell to build one for you to your specifications. You could find these for under $4,000.

So if you factor in that the system is going to do all of your production, it's going to do all of the encoding that you need, and the cameras, as I've mentioned, range from $4,000 and under. You can do three $4,000 cameras plus the system, and you're still under the $20,000 mark to purchase things such as cabling, lighting, accessories like that. But you literally don't need anything else; you just need the cables, the cameras, and the PC, and the vMix software to bring everything all together.

Capture Cards

The key part of building the PC is choosing a capture card that supports 4K. Capture cards are basically add-on cards for the computer that can accept the video signal that your cameras are sending, either HDMI or SDI. There are a number of vendors out there offering cards that support 4K, such as AJA, Blackmagic Design, and Magewell.

Basically, you just choose your cameras, choose whatever cabling you want, and buy multiple capture cards, depending on how many cameras you want to incorporate into your production. That's the production system all taken care of.

Encoding

And now we get into the nitty-gritty of the encoding and the bitrates you will need for 4K live streaming. As I mentioned earlier, you’re going to use H.264 to encode for 4K live streaming today. It's supported by all browsers across mobile and desktop devices. This is what most viewers are going to be able to watch 4K in, so this is what you'll want to use for encoding.

Those with slow internet connections should stop reading now, because streaming 4K is bandwidth-intensive. For 4K live streaming, you want to set the bitrate in your encoder (or in this setup, vMix) anywhere from 13-50 megabits per second (Mbps). This is the recommended bandwidth range for high-quality 4K streaming. Choosing the right bitrate within that range is a combination of how fast is the internet of your viewers, and how fast is the action in your live stream.

If you're streaming 4K sports, you're going to choose a bitrate between 30 and 50 Mbps. If you're just going to have static shots, talking heads, and PowerPoint presentations, you can get away with as low as 13 Mbps for 4K video. For comparison, Netflix, when they do 4K livestreaming of their content, ranges between 15 and 18 Mbps. They have the advantage, though, of spending a lot of time encoding at that bitrate to the highest possible quality. To achieve similar quality to what they are targeting for live streaming, you're probably looking at around 20-30 Mbps recommended, but as I said, it comes down to the content you're streaming, and what you can expect your viewers to have access to, as far as their own internet speeds are concerned.

HEVC and AV1

As I mentioned earlier, there are two emerging formats, HEVC and AV1, that will allow you to stream at lower bitrates. HEVC and AV1 will allow you to do the same quality at up to half the bandwidth of H.264.

But we’re still at the early stages of getting these standards adopted in all of the devices and televisions that your viewers might be using. Both have pros and cons: HEVC is available now, AV1 is intended to be an open standard without any royalty or patent fees, both for the device manufacturers and the content creators, so that's one of those encoding formats to look out for in the next twelve months.