What's the Difference in 3G, 6G, 12G, Quad Link & Other SDI Signals?

BoxCast Team • March 21, 2019

This post is a video explanation of the differences in SDI signals like 3G-SDI, 6G-SDI, 12G-SDI, and Quad Link SDI and talks about what they are used to accomplish. It's part of our series on video encoders.

Ever wondered what the numbers 3G, 6G, and 12G mean in the context of SDI signals? If you're new to video production, these terms might seem a bit overwhelming. But fear not, we're here to break it down for you.

The Basics of SDI Signals

SDI, or Serial Digital Interface, is a standard for transmitting high-definition video signals. The numbers preceding the "G" in SDI refer to the bitrate, essentially the amount of data that can be transmitted per second.

3G-SDI: Can transmit approximately 3 gigabits of video data per second.
6G-SDI: Can transmit approximately 6 gigabits of video data per second.
12G-SDI: Can transmit approximately 12 gigabits of video data per second.

Think of it like a pipe... a larger pipe can carry more water, just as a higher G-SDI signal can carry more video data.

When Do I Need More "G's" in My SDI?

The primary reason for using a higher G-SDI signal is to support higher video resolutions. For example, 4K video requires a much stronger signal than 1080p video.

Here's a quick breakdown:

3G-SDI: Optimized for HD video.
6G-SDI: Suitable for 4K video (30fps).
12G-SDI: Ideal for 4K video (60fps).

Choosing the Right Equipment

It's important when picking equipment for your video workflow, you choose the right gear that can support the video resolution you're planning to shoot, record, and stream in. Consider what inputs, outputs, and cabling you'll be using to make sure your workflow has consistent signal flow.

Often times, products will list their signal rating in the tech specs, as seen in the examples below:

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At BoxCast, we've made it easy to stream with your 4K workflow. Both our Spark Encoder and BoxCaster Pro have an SDI input up to 12G, meaning you can easily connect any video source up to 4K60.

So, the next time you encounter the terms 3G, 6G, or 12G-SDI, remember that they simply refer to the data-carrying capacity of the signal. Understanding these basics will help you make informed decisions when working with video equipment.

The Spark encoder has way more to offer, including an advanced video monitoring, a touchscreen, HEVC compression, and ultra-reliable streaming with BoxCast Flow. Check out the video below to see it in action: