I’ve had another Video Production Idea

An SDI Multi-Core for Audio

Future Jim Note: Since writing this post, I’ve done some research into Dante and the price difference between the setup below and a Dante system. Check out my next post to see my findings.

I had a bit of a shower thought the other day: How much would it cost for me to bring audio from a venue’s sound desk to my future video production system? I don’t just want the main Left/Right mix from the sound desk; I’d like separate channels—for example, the drum kit on one, the bass on another, the guitar on another, and so on.

When I’ve streamed live events previously, I’ve been stuck with whatever the sound desk gave me. This might sound amazing in the venue, but vocals can get overpowered or the house engineer might leave music running that shouldn't be on the stream. By having individual channels, I can make sure the live stream or recording sounds exactly as it should for the client.

The Connectivity Problem

There are two ways to get this audio: either split it before it hits the mixing desk using microphone signal splitters, or use spare outputs on the venue's desk. Since I’m basing this on my ATEM Mini Pro setup, I’m going with the second option to avoid unnecessary complications.

Did you know that SDI can carry 16 channels of audio? I knew, but I didn't know how to utilize it, as Blackmagic’s ATEM switchers only allow you to control the first two channels of an SDI input. Furthermore, I couldn't find a device that takes 16 XLR inputs and converts them to a single SDI output. I’ve come up with a workaround, though: using four Blackmagic converters (which take four audio feeds to SDI) together to provide 16 channels over a single SDI cable.

The "Master Plan"

If I could, I would remove a lot of cabling by using Blackmagic’s Micro Converters at each camera, but HDMI-to-SDI converters strip out the ATEM Mini Pro’s camera control ability.

I’m also unsure if the audio flow is restricted to one direction. I have an Audio-to-SDI converter at the switcher so I can send any VT audio over the SDI to the in-house audio engineer. If audio is strictly unidirectional, my plan is to route everything from the audio mixer into rack-mountable Audio-to-SDI converters, then to an SDI distributor via an "SDI Multicore," and finally out to the cameras. I’ve added an extra four SDI-to-Audio converters so I have four channels for the ATEM and four to send elsewhere if needed.

Future Hopes

It would be great if Blackmagic or someone else made a single device that could take 16 audio channels at one end and break them out at the other—or a mix of 12-in/4-out or 8-in/8-out. Ideally, they would add an extra SDI port on the switchers that acts as an audio-only interface, working directly with the Fairlight audio engine built into the ATEMs.

Side Note: I’d love it if Blackmagic made a version of the Fairlight console that had SDI audio inputs. If there were a 16-channel stage box that ran audio to the console via SDI, the time and money saved in cabling would be massive. As a lighting technician, I’d also be interested to see what they could do with lighting control. They’ve nailed video and audio—why leave out lighting? Imagine being able to run an entire venue with the products of one company, knowing they would all work together to put on amazing live events.

I suppose I could probably do everything mentioned here with fiber and Ethernet using Dante stage boxes, but again, I’m left with the problem of the ATEM not having a way of putting those feeds straight into its internal Fairlight engine.

Do you like having a separate audio mix for your productions? What solutions do you use, and what would you change in my master plan? Let me know in the comments below!