So how does AVB work?
Timing is everything in AV. . In your office or conference room, you have become accustomed to video and audio that behave in a certain way. You will not, for example, put up with video that takes 10 seconds to begin playing, nor would you accept video if it’s audio was delayed even a fraction of a second. So if someone could replace all that AV infrastructure with a single computer network, cool, right? Not if it’s all weird and glitchy. Problem up to now has been: How to get AVB connected devices to act exactly the same way our existing devices act.
AVB has taken years to get that point – same equipment, standard networks, same performance. And it’s now working fairly well.
Devices now talk to each other, sharing timing information; at some point one device is chosen as the master clock. How tight is the timing? The latency of AVB provides 2ms over 7 switch hops in a 100Mbit Ethernet network. We are talking about one gigabit hops, with 1ms TOTAL latency.
The secret to this is something called stream reservation protocol (SRP), which keeps the system from over committing itself, thus running out of bandwidth. That’s called oversubscription, and is exactly like double booking your appointments for tomorrow, which ensures you will make someone angry, am I right?
In this case, AVB ensures quality of service (QoS) through the use of admission control and traffic shaping, along with queuing and forwarding rules that ensure AV streams pass through the network with the delay specified. There is even some protection against lost streams when the system gets overloaded.
So how many channels can you run, assuming your network will support it? So far, channel count is 420 x 420. And this is all over existing Ethernet infrastructure with proper switches. Get this: you can even sync multiple flows of media from different places, and they will all arrive at their end point simultaneously. So not just point-to-point, but point-to-multi point.
Can AVB devices identify and communicate with non-AVB devices? Sure, using standard 802 frames, just can’t send AVB data streams through non-AVB switches.
So, to sum up: An IEEE open network standard will give us market stability and consistency for end-users, integrators, and manufacturers alike. Once the standard is completely baked into place, it’s modularity will allow for the creation of different system configurations including centralized, hybrid and distributed systems. Your situation changes? Expand or reconfigure the existing network. No need to install a completely new system.
That’s the promise of AVB.