4K Webcast Workflow: Acquisition to Delivery

If you’re like me, then just when you think you have mastered your HD 1080/60P workflow for live production, you realize that you already need to move that workflow to UHD 4K. In this article, we’re going to take a first look at what it takes to work in 4K from acquisition to live webcast delivery, and everything in between.

Acquisition Resolution and Frame Rate

The first big consideration in your workflow is if you can settle for a 30P workflow or if you require a 60P one. This one question is likely to have a big impact on your equipment choices down the workflow line. On the acquisition end, most prosumer, entry-level professional, and early 4K/UHD video camera models are limited to 30P in 4K, even if they can also produce 60P in HD.

Delivering in 30P might be fine for most talking-head content where there is not much action, but sports content can benefit from a higher frame rate when you’re trying to avoid intraframe blurring. Content that you want to replay in slow motion is also a good candidate for a higher initial frame rate, especially when you consider than 60P is 2.5x faster than 24P footage. In other words, when you play back 60P footage on a 24P timeline, you can slow the footage down by 2.5x without duplicating any frames.

One big workflow consideration for all live video content is which video camera(s) you select for the job. I find that many creative producers often overlook live workflow considerations like the availability of a live 4K HDMI or HD-SDI output. Although I do wish that my Sony X70 and FS5 video cameras supported 4K output from the HD-SDI connection, both of these popular models only have 3G HD-SDI outputs, which are limited to 1080/60P. Going with 4K/UHD requires 6G HD-SDI for 30P and 12G HD-SDI for 60P, and Sony has not yet made it a priority to include this. 6G and 12G HD-SDI connections for 30P and 60P UHD signals are more common on 4K Blackmagic Design video cameras such as the new URSA Broadcast.

It isn’t the end of the world to be starting your 4K workflow from an HDMI connection, which is what both of my Sony cameras and many more support, but do be aware that you will be limited to 4K/30P. That is, unless you move to the Sony FS7 line of cameras or use the RAW output from a camera like the Sony FS5 at 4K/60P (only the RAW output supports 4K/60P) and pair it with monitor/recorder like the Atomos Ninja Assassin to convert the RAW signal into an output like 12G SDI or 4K HDMI (Figure 1, below).

Figure 1. Atomos Ninja Assassin

The Atomos Ninja Assassin is the first 4K monitor and recorder that can record RAW from Sony, Panasonic, and Canon video cameras to the new ProRes RAW codec. (ProRes RAW can be edited only in Final Cut Pro X.)

I would prefer to work with standard HD-SDI because it supports longer cable runs and has locking bayonet connectors. You can convert your 4K HDMI to either HD-SDI or fiber for longer runs. One other HDMI solution to overcome the 25′ HDMI limitation is to use the $39 Magewell HDMI 4K Mini Repeater to extend your HDMI cable run another 25′ (Figure 2, below). The Repeater can often draw sufficient power from the HDMI signal but can also be externally powered if needed.

Figure 2. The Magewell HDMI 4K Mini Repeater

If I have to work with HDMI, I prefer working with a full-size HDMI connector because they are more common and I have plenty of them and they are easy to replace in a pinch if you need to. I don’t like working with mini- or micro-HDMI cables, which is what some smaller mirrorless 4K video cameras like my Sony a7S II use. I dislike the smaller HDMI variants because I find the cables are much lower quality and need to be replaced far more frequently. My own experiences with bad micro- and mini-HDMI cables isn’t isolated—in fact, one of my local camera rental stores has a policy to always send two micro-HDMI cables with Sony a7S models they rent because the cable failure rate is much higher than with standard HDMI cables.

Also, I find that the micro-HDMI cables also generally come in shorter cable length runs of 3′ or less, which is fine for an on-camera monitor/recorder but not great when the camera is 5′ up on a tripod and you need to connect the short cable to some type of signal converter or distribution amplifier that you inevitably need to gaff tape to your tripod.

One final note on outputting a 4K HDMI signal from most Sony video cameras: Most models cannot record 4K internally at the same time as displaying video on the LCD/OLED viewfinder and outputting a 4K HDMI signal. If you need 4K from a Sony video camera and want to record the signal, you will need to add an external 4K monitor/recorder.