AVB is an acronym for Audio Video Bridging. AVB packets are usually packets derived from the IEEE standards that enable the transmission of audio and video packets over standard Ethernet.
There are four primary differences between the proposed AVB architecture and existing 802 architectures:
- precise synchronization,
- traffic shaping for media streams,
- admission controls, and
- identification of non-participating devices
These are implemented using relatively small extensions to standard layer-2 MACs and bridges. This “minimal change” philosophy allows non-AVB and AVB devices to communicate using standard 802 frames. However, only AVB devices are able to: i) reserve a portion of network resources using admission control and traffic shaping and ii) send and receive the new timing-based frames.
For applications to take advantages of the features of AVB there needs to be some coordination with portions of the higher layer communication protocols in between. In addition, some transport protocols have been adapted to provide information for applications to use AVB. An application can implement synchronized distributed rendering using 802.1AS and higher layers. Specific audio samples and/or video frames carried by higher-layer protocols are given an associated presentation time (in terms of the shared 802.1AS clock) by the media source that is also an AVB talker. Each media renderer, that is also an AVB listener, renders the referenced audio sample or video frame at the 802.1AS presentation time.
Standards
An IEEE (Institute of Electrical and Electronics Engineers) 802 Task Group is defining AVB. You may be using one or more IEEE 802 standards right now: wired Ethernet is IEEE 802.3, WiFi is 802.11, WiMax is 802.16 and so on. AVB standards include IEEE 802.1Qav: Forwarding and Queuing for Time-Sensitive Streams, along with 802.1Qat: Stream Reservation Protocol, and 802.1AS: Timing and Synchronization for Time- Sensitive Applications. 802.1Qav was ratified and published in January.
An overview of the status is available at www.ieee802.org/1/files/public/docs2010/avb-prins-review-of-avb-v1-00-0610.pdf
Uses
The basic idea is to empower wired Ethernet to transport “professional quality audio video” - HDTV and multiple channels of uncompressed digital audio - using widely available products like off-the-shelf Ethernet routers and Cat 5 cable.
The Ethernet AVB Endpoint is ideally suited for endpoints in broadcast, profession or consumer audio and video, home networking, and automotive applications. Applications include professional cameras, surveillance cameras, professional mixers, projectors, and automotive head units and networking interface cards.
At the recent 2010 InfoComm show in Las Vegas, Harman Professional focused exclusively on the AVB protocol, with training sessions and discussion on its new AVB system, which demonstrates the benefits of the technology with an emphasis on house of worship applications. The system demonstrated the three interconnected elements of its system solution: next generation hardware, next generation software, and the next generation audio network.
The system is operated through next-generation software HiQnet System Architect version 2 with its new configuration and routing paradigms based on designing the system directly ‘into’ a floor plan of the venue; all audio running over the next-generation audio network, Ethernet AVB.
Big players
It is reported that currently billions being spent on software and chip development for AVB devices. The big players are all into AVB. Broadcom, Marvell, Intel, Cisco, Xilinx, Samsung and Apple are all in there. Even the new G4 mobile backhaul networks will be 802.1AS compliant (AVB protocol). Essentially the entire communications world is converging on one packet based (Ethernet) protocol which is AVB.
Broadcom is a founding member of the AVnu Alliance, an industry forum dedicated to the advancement of professional- quality audio video by promoting the adoption of the IEEE 802.1 Audio/Video Bridging (AVB) standards over various networking link-layers. The other AVnu founders are Harman, Cisco, Intel, Samsung and Xilinx, while ‘Promoter’ members include Analog Devices, Applied Micro, Audinate, Avid, Barco, Lab X Technologies, Marvell, Meyer Sound, Pelagicore, Sennheiser, Shure, Universal Media Access Networks (UMAN) and University of New Hampshire Interoperability Lab (UNH-IOL), a third-party laboratory dedicated to testing data networking technologies. AVB and the AVnu Alliance encompass consumer electronics, automotive and pro AV markets.
The industry hopes that when consumer electronics and automotive markets come on line, AVB network interfaces will become reasonably cheap.