Today we see what are the differences between an AVB endpoint (which are the AVB talkers and AVB listeners) versus an AVB compliant Network node (which connects those end-points to each other in an AVB network).
AVB is an Ethernet based Layer-2 Audio-Video bridging technology (from a Network perspective), however, any vanilla (or even high-end) Ethernet switch cannot be used to connect AVB devices, as it will not be able to provide the required Quality-of-Service though the network or be able to guarantee reservations required by AVB to operate. Let us first see how an AVB enabled Ethernet-switch is different
|Normal Ethernet Switch||AVB enabled Ethernet Switch|
|Provides Ethernet Switching capability|
Can have 2 or more ports with different port-speeds
Provides MAC learning, switching, filtering etc
Supports VLANs, priorities & Multicast capability
Basically provides Ethernet Layer-2 connectivity
|It needs to provide all the features |
that a normal Ethernet Switch provides
|Needs to provide stream delivery guarantee|
Has to synchronise and transfer clock
Support Stream Reservation protocol
Deliver Audio/Video payload without drops
Keep the latency within required margin
Communicate with other AVB nodes
As we see above, an AVB-enabled network gear is specialised in the way it operates and communicates with its peers. Now lets us see, how an AVB end-point is different from an AVB switch itself.
|AVB Switch||AVB endpoint (Talker/Listener)|
|Support gPTP (Time Synchronization)|
Support MSRP (Stream Reservation)
Support FQTSS (Delivery guarantees)
Support MAAP (MAC address acquisition)
Support MVRP (VLAN Registration)
|It needs to provide all the protocols|
that an AVB Switch provides
|N/A||Provide 1722 Talker/Listener support|
A2D/D2A or TDM conversion for MIC/Speakers etc
Packetization/De-packetization of media samples
AV Buffer Management
Support 1722.1 AVDECC (ADP, AECP, ACMP)
Clock Recovery and Media Clock conversion
In conclusion, while it may look like that an AVB end-point is more complex when compared to an AVB network switch, both have different complexities to deal with. While the end-point has to deal with TDM and A2D/D2A conversion and AVDECC for control, the AVB network device has to provide a “guaranteed” path with multiple port-speeds that may be carrying other priority and non-AVB traffic as well as support multicasting of frames to multiple destinations within the required latency margins over multiple network hops.
Hope this gives some insight into how AVB lets you connect, deliver and enjoy hi-fi audio/video.
- Audio Video Bridging Technology that is used to deliver Audio-Video streams on a Layer-2 Ethernet network with guaranteed delivery and quality
- Endpoints refer to Talker(s) and Listener(s) that are used to generate or consume Audio-Video streams on an AVB network
- It refers to layer-2 of OSI model of networking where communication is established using Ethernet source and destination MAC addresses and data-traffic is switched as well as broadcast in the physical or virtual LAN network.
- An AVB Listener is the consumer that joins an AV stream or streams that it is interested in
- Quality of Service defines the parameters and guarantees that the underlying infrastructure can provide, and covers things like priority, latency, bandwidth, shaping, policing etc
- Refers to an L2 networking device
- An AVB Talker is a source of Audio or Video that sends streams to one or more interested listeners