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Live Streaming Software

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

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

Today we'll be talking about the different types of SDI signals. So, when I started in video production I thought that there was just one type of SDI signal. Boy you have no idea how excited I was when I found out it wasn't just that simple. I guess nothing's really ever simple is it?


Okay so 12G, 3G, Blue G, Green G, What are we talking about here? It's actually quite simple. All the numbers before the G are just referring to bitrates of video. So 3G-SDI simply means it can transfer about 3 gigs of video data per second. 6G can transfer roughly 6 gigs per second, and 12G can transfer roughly 12 gigs per second. Okay, so in case you're still confused, or you need metaphors to understand things like me, let's talk about pipes. Pretend this pipe is 3G-SDI.

About 3 gallons of water can pass through it per second now pretend this pipe is 12G-SDI. About 12 gallons of water can passthrough per second. Make sense right? I'm pretty good with metaphors. Ok well then why would you need more water?

Or video data? Well, if you want higher quality video, then you're going to need a stronger signal. For example 6G and 12G SDI are better for 4k video, whereas 3G SDI is only optimized for HD video like 1080. This quick graph will show you what type of video quality you can expect out of each signal type.

So, if you're looking to stream 4k video you really only have three options 6G-SDI, 12G-SDI, and Quad Link SDI. Quad Link is like this weird monstrosity where you take four 3G SDI signals and you bond them together, equaling, you know, 12 G. Here at BoxCast, because we like to make life simple, we've developed the BoxCaster Pro which has an SDI input up to 12G. That means you don't need all that crazy mad science to get a 4k video out of a 3G SDI connection.


Final Thoughts + Further Reading

There's also a ton of other fancy stuff that it comes with, so if you're interested in learning more about it, you can click on the link at the end of this video. Anyway if you have any questions about SDI connections, SDI signals, or streaming 4k video, please contact me anytime here. Thanks for watching, and happy streaming!

Here are a few other resources you might find interesting:

HEVC (H.265) vs. AVC (H.264) - What’s the Difference?

HDMI vs. SDI Video Connections - What's the Difference?

This is Why Your Live Stream Lags: Intro to Streaming Latency

Hardware Video Encoder Comparison: BoxCaster vs Teradek VidiU vs Digicast DMB-8800A

Hardware Vs. Software Encoders: 6 Reasons Hardware Encoders Are Better

HEVC's Impact on Live Streaming