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Review: Magewell USB Capture HDMI 4K Plus

Shawn Lam reviews the Magewell USB Capture HDMI 4K Plus video capture dongle for 4K cameras as part of a laptop-based webcast workflow

Over the last ten years, I have owned a lot of video capture cards for my various webcast systems. I have built many mobile webcast workstations in computer cases and most recently in road-rack cases. These builds all have had PCIe capture cards or external hardware connected to a PCIe card. I had been very happy with these solutions, but they aren’t as portable as a laptop-based solution.

Three years ago, I bought my first USB capture card, a Magewell USB 3.0 HDMI capture dongle, and paired with my old laptop, I had a truly portable webcast solution. Over the next two months I bought an SDI version and then a second HDMI version. These USB capture devices were fantastic for when I produced a one- or two-camera webcast without a video switcher or when I wanted to record or stream the program output from a video switcher. They also saw a lot of action on my mobile workstation solutions to add additional inputs or when I needed a device that was able to convert the video resolution and frame rate to something that was compatible with where the video was going. This was especially important when I used to produce webinars on Flash-based solutions that were limited to the video standard of 480p20, which isn’t a video standard that anything modern supports.

The beauty of a USB capture card is that the capture card hardware does all the heavy processing and it outputs over USB 3.0 a video signal that is Universal Video Codec-compliant. Or in other words, you don’t need to install any drivers with this protocol and your computer sees the signal as a webcam, which means it also works with services like webinars, video conferencing, and video chat, that won’t accept traditional PCIe video capture cards.

Capturing 4K

My most recent USB capture card is the Magewell USB Capture HDMI 4K Plus (Figure 1, below). It is a perfect companion to my Sony FS5 and X70 4K video cameras because these cameras output UHD 4K only over HDMI, whereas the 3G-SDI output is limited to HD resolutions.

Figure 1. The Magewell USB Capture HDMI 4K Plus

If you’re using a 4K video camera that supports 6G-HD-SDI, then you will want to consider the Magewell USB Capture SDI 4K Plus. In addition to taking a 2160p30 HDMI or SDI signal and converting it to a UVC signal over USB cable, both models also have a convenient HDMI or SDI Loop Thru (Figure 2, below).

Figure 2. HDMI and audio I/O USB Capture HDMI 4K Plus (left) and USB Capture SDI 4K Plus (right)

I use 4K workflows both when I want to record and webcast in 4K and when I want to create several HD virtual inputs from a single 4K video feed. Having a 4K camera set to wide allows me to have multiple virtual HD cameras with up to 2-3x lossless zoom each. This works because UHD video has 2x the vertical and horizontal resolution of 1080 HD video and 3x the resolution of 720 HD video. I can even use my recording software to zoom in or out and pan on the 4K image in pre-programmed movements.

It is important to note that, out of the box, these devices are set up to support both the YUY2 and NV12 capture formats. Other formats are available as well, but you have to enable them via the Magewell USB Capture Utility. I work in this space all the time, but I have to admit that these terms were new to me and I had to do a bit of research before I could understand the differences between the two formats and confidently know which one to use when.

When you’re working with 4K signals, you will want to be especially careful that your device is outputting the NV12 format. YUY2 works with a 4:2:2 color space, which is a common HD format in the video cameras that I use, while NV12 works with a 4:2:0 color space and is the UHD 4K format that my video cameras use. I found out the hard way not to leave my webcast and video recording software set to the “default” video format. Initially, I was very frustrated when I kept dropping frames in my 4K tests but thankfully Magewell support pointed me in the right direction. While I could force my capture card to work with only the NV12 format by using the USB Capture Utility, I decided it best to manually select NV12 within vMix so that when I used the same card with HD video, I would be in the proper color space (Figures 3 and 4, below).

Figure 3. Selecting the NV12 video format in vMix

Figure 4. No more dropped frames, as reported in the vMix Statistics screen

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