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HD Webcast Production: Choosing Video Scalers and Converters

In this ongoing Streaming Media Producer series on webcast video production, Shawn Lam covers the video format converters he uses in his own HD webcast workflows, and one new converter that just might be the video converter, scaler, and distribution amplifier to rule them all.

Video Format Converters

Sooner or later you are going to have to convert VGA to something your video switcher can handle. I run into this challenge all the time as my primary video switchers are the Blackmagic ATEM 1 M/E and Production Studio 4K, and neither has a VGA or DVI-A or DVI-I video input.

My solution is a VGA-to-HDMI scan converter made by Atlona, the AT-HD510VGA (Figure 3, below). This converter sells for about $300 and features a convenient VGA pass-through so you can send a VGA output to the projector or presentation video switcher while you take the HDMI output. In addition to being a scan converter, it also has an internal scaler. I’ll cover scalers in more detail in the next section. Scaling is often required when working with computer connections; in my experience, these connections are rarely 1920x1080 or even 1280x720, which are the video formats that your video cameras output.

Figure 3. Atlona VGA-to-HDMI scaler with local VGA out. Click each image to see it at full size.

Unfortunately, the output that goes to me is HDMI, and to run that signal any length over 50’ I would first have to convert it to HD-SDI with a $300-400 HDMI-to-HD-SDI converter. For this reason some of my colleagues prefer the $1,000 Grass Valley ADVC G1 converter that has a DVI-I input (VGA with a simple converter) and HD-SDI output. Unfortunately, this model has no pass-through outputs--it has two HD-SDI outputs--so to return an output to the projector/presentation switcher you may need to convert the HD-SDI back to VGA or possibly HDMI in order to connect with the projector or presentation switcher.

Grass Valley does make a matching ADVC G2 converter for this HD-SDI to VGA conversion for $900, but $1,900 for this pair is an expensive solution. What this solution does point out is the value of those video switchers with internal DVI-I inputs, like the Sony MCS-8M and especially those with VGA Aux outputs, like the new Roland VR-50HD. I should take a step back in this workflow to note that you can also first split the VGA input using a distribution amplifier (Figure 4, below) and send one feed to the projector/presentation switcher and the other to your VGA-to-HDMI or HD-SDI scan converter.

Figure 4. VGA Distribution Amplifier. Click the image to see it at full size.

Does all this sound a bit complicated, and make you think there should be a single device that does it all? Me too. Especially one in the sub-$1,000 price range. Keep reading, because I will introduce one that I came across when researching this article. But first, I’d like to expand on scalers and DAs.

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