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The Many Languages Of Digital Audio Networking

A handy primer on terminology and where things stand in terms of protocols and interoperability

By Craig Leerman March 6, 2018

PSW Top 20 presented by Renkus-Heinz

While analog is still a popular and cost-effective method of signal distribution in pro audio, the benefits of going digital far outweigh the costs of switching from analog. No more electromagnetic interference (EMI) and high-frequency attenuation problems, and no more lugging around heavy multi-core analog snakes.

Still, digital’s not perfect. Latency (signal delay caused by converting the audio to/from analog and between various digital equipment) is not nearly the issue it used to be, but it can still be problematic. The more conversions and transport steps, the greater the latency.

In addition, there’s the lack of interoperability between various network protocols. Even hardware connections for some protocols can’t “speak” to each other – they may be the same at the protocol level but specify different electrical signal levels and/or use incompatible connectors or transport cabling.

For example, MADI over Cat-5 cannot directly interface with MADI over fiber optics. To solve this issue there are interface units called “bridges” that can covert from one protocol to another allowing different systems to coexist together. But a better solution is to upgrade the protocols to work together.

The Institute of Electrical and Electronics Engineers (IEEE) has developed technical standards and provide the specifications that will allow time-synchronized low latency audio and video networking. These Audio Video Bridging (AVB) standards have been well received. A group of professional and consumer electronics companies have formed the AVnu Alliance that provides testing and certification for submitted products ensuring they meet the AVB standards. Note, not all AVB products are submitted for testing as it’s a voluntary program.

Another group striving to help make various systems operate together is the Audio Engineering Society (AES) with the AES67 standard. This Layer 3 protocol suite is based on existing standards and is designed to allow interoperability between various IP-based audio networking systems.

Layer 1 protocols use Ethernet cables and switches but primarily employ proprietary media access control instead of the native Ethernet MAC. Examples include Riedel RockNet, Aviom A-Net, and Roland Pro A/V REAC.

Layer 2 protocols process audio by using the standard Ethernet packet approach. Two of the most well-known digital transfer approaches, CobraNet and EtherSound, use Layer 2, and it’s been adopted by numerous manufacturers.

Layer 3 protocols use IP packets for transmitting audio data over Ethernet cables. QSC Q-LAN, Axia Livewire, and Audinate Dante are a few of the transfer approaches that use Layer 3.


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About Craig

Craig Leerman
Craig Leerman

Senior Contributing Editor, ProSoundWeb & Live Sound International
 
Craig has worked in a wide range of roles in professional audio for more than 30 years in a dynamic career that encompasses touring, theater, live televised broadcast events and even concerts at the White House. Currently he owns and operates Tech Works, a regional production company that focuses on corporate events based in Reno.
http://techworksreno.com/

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Jon Wanez says

I am new to the world of audio - long time musician (drummer i never had to turn any dials lol).

Anyway, i am about a year into my Research/Studio build/Insanity. Originally I purchased my mixer to handle the live end of things. Well G.A.S took over and i decided to upgrade the plan of a "practice space" to a STUDIO.

It all started as: "I will put some acoustic panels up - to - ripping EVERYTHING down, sealing outside structure, building inner structure, green glue, over 5K in insulation (703 and Roxul included), Rewiring, adding another acoustic layer (but not a 3rd leaf), automating a few diffusers/absorbers, QRD's to be a ON THE FLY "tuneable" room, and on and on it goes!

Well i purchased the Soundcraft Si Impact in the beginning, 75 books and 9 million words of print ago!

I was patting myself on the back for that up until about a month and a half ago when it came time to start incorporating outboard gear, "dry fitting" if you will, the set up.

Well the Impact has NO LINE LEVEL inputs (sorry to yell) and NO INSERT RETURNS unless they are digital (again sorry for yelling). So how would one get ANYTHING except mic level into the signal chain?? (Not a rhetorical question if anyone has any advice i would be so very grateful!!)
I have 2 MADI/USB cards MADI is cat-5, and the stagebox mini16 with a MADI card in, Lenovo M900 Tiny i7, and another box but only i5 with jack for RAM and cant upgrade it - it was meant for quick books and Office nothing more really - use REAPER.

Sure I have run into the distressor and Transient Designer, run thru the API pre's (not in that order of course) and most of the outboard gear will "work".

But no headroom at all, sometimes it clips right at the input meter so bad you can not use the device at all (Pulteq EQ).

I thought about maybe in-line pads or even running backwards thru a DI, but figured that would sort of be pointless ( I dont know this to be fact as i am a complete newb, but Intuition tells me it is likely a ridiculous endeavor and i am unwilling to throw money at it.

So all this was to say THANK YOU - bc for the last week I have been yelling at my computer to the effect of "Can't someone just explain the plethora of digital protocols and connections and compatibility in one fell swoop (unreal that some have different cabling that is not compatible with the same protocol.

Lucky for me (sarcasm) Harmon is headstrong and they offer their HI-Q net and CAT-5 MADI (gotta sell that DIGI CO gear).

Fortunately they do have 2 expansion slots with a bunch of different protocols (again they could not have accidentally chosen the way they did - with Cat 5 where there should be coax, or BNC where there should be optical, etc. UNREAL!!)

Looks like AVB or DANTE may be the way around this for me, with the addition of a second CPU and either the multi digital card or the DANTE card, leanign towards the AVB route since the DANTE card is almost a grand and the multi digi card is about 300.

I am considering LAYER A on the Impact being the dry source from mics, LAYER B into the other box via aome other Audio Interface then into a separate instance of REAPER (REAPER will only allow 1 Audio Interface) coming back into to layer B as the "wet" tracks that will have plugins on them, but they will have to return via the AUDIO interface as digital signal, then LAYER C will give each instrument a blend of the 2 under the 14 MIX buses (wont be 14 but..), Then use the MTX mixes to mix the mixes and send to Mains, monitors, etc. Finally set up the 8 VCA's to control the blended signals (MIX 1-14) as well as the MTX mixes.

If anyone read that entire thing - wow - thank you!! If anyone had any advice or solutions that would not require me to purchase new cards and multiple interfaces and would keep everything as one cohesive unit - I am not opposed to paying for such a consultation!!

Thanks

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