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Choosing HD Video Switchers for Webcasting--UPDATED!


At its most basic level, the role of the video switcher is to accept multiple video camera inputs and to output a program video feed. But few video switchers are this limited in functionality. Live producers often rely on video switchers to accept a variety of inputs, including audio and computer inputs, and output multiple different video feeds.

Some even have internal recorders or USB outputs that can make live streaming easier, but the most import consideration with any video component--and especially video switchers--is how it integrates with your entire video production workflow. Just as a Mac-formatted hard drive doesn't play well on a Windows system and iPhones can't play Flash, a video switcher that accepts only HD-SDI inputs is of no use with video cameras that only has a composite video output.

Digital Video Inputs

Type and number of video inputs is usually the first place I start when I compare video switchers. This series is on HD webcasting, so I'm going to focus my efforts on HD video inputs, but if you have the need to mix both SD and HD video signals together, I will list two models that have internal upconverters.

You can also equip any of the models with external upconverters like the Blackmagic Design Teranex 2D Processor (below) or use an upconverting DVD player or Blu-ray player for get a compliant output from DVDs.

Blackmagic Design Teranex 2D Processor

Blackmagic Design Teranex 2D Processor

The main reason I bring up SD video inputs is that, even if you are planning on delivering a sub-HD webcast video signal, you should still start with an HD video input. Widescreen NTSC video is a non-square pixel video format, and its 720x480 video signal has a widescreen pixel aspect ratio, resulting in a 864x480 video when converted to a square pixel equivalent. Square pixels are the way that pretty much all modern video viewing takes place. An SD widescreen video will not look as nice as a downconverted HD video because of the pixel-averaging required to turn a widescreen pixel signal into a square-pixel signal.

In terms of video inputs, I recommend an entirely HD-SDI workflow. The bayonet connector on the SDI cable is more secure than the consumer HDMI equivalent, and the added benefit that HD-SDI doesn't interconnect each device along its path the way HDMI does means that if you lose power or connection with, say, a camera-mounted HDMI monitor, you won't lose the signal on the video switcher. This doesn't mean that if you have a video camera with an HDMI output, you can't use a video switcher with only HD-SDI inputs, because you can always use an HDMI-to-HD-SDI converter. But just be aware that you shouldn't split the HDMI signal before conversion (say, to give the camera operator an HDMI signal for their external camera monitor), and you should either equip them with HD-SDI monitors or convert the HD-SDI output back to an HDMI signal for this purpose. The goal is to avoid interconnecting HDMI devices at all costs.

You can also run greater lengths of HD-SDI cable than you can HDMI cable, but if you require lengths that exceed their maximum lengths, you can always convert the video signal and pass it through Ethernet cable or even fiber-optic cable. More on this in a future article in the series.

Video cameras don't output DVI signals, but computers often do, and it's very common to connect a computer to a video switcher so you can live-switch computer presentations (think PowerPoint). DVI converts to HDMI very easily so if you need computer inputs, an HDMI input on your video switcher will usually suffice.

Analog Video Inputs

On the analog side, component video inputs and VGA computer inputs can sometimes be found on video switchers, but I'm a bit frustrated that so many A/V companies still rely on the old VGA standard. You may need to equip yourself with a VGA-to-HDMI/DVI converter for these situations. No models on this list have support for both VGA and DVI/HDMI inputs. I'll cover workflow solutions for this in a future article. 

[Editor's note: See author's update on page 4 of this article for info on a new Roland switcher, scheduled to ship in January, which features VGA and DVI/HDMI support.]

Number of Inputs

The number of inputs is an important consideration--not only the maximum number of simultaneous inputs, but the maximum number of each type. For example, the Blackmagic Design Television Studio allows 6 simultaneous inputs, but you're limited to any combination of four HDMI and four HD-SDI inputs to equal six.

This isn't a big issue for most live producers, but if you're going to use one of the inputs for a computer HDMI input and plan on using more than three HDMI cameras, then you'll have to convert one to HD-SDI. This isn't a big deal and I have already recommended that you do so, especially when you require a longer length than 50'. HD-SDI cable can run around 300' before signal loss.

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