A new generation of audio/video coming to a network near you
Today, the majority of entertainment media that is produced is available in digital format and consumed in networked environments. As this trend continues, devices used in 802.1-compliant wired and wireless networks that support streaming audio and video are becoming mainstream consumer products. As a result, a new requirement for Audio/Video Bridging (AVB) standards has emerged, and new designs for wired and wireless networked components will be needed to implement these standards. In short, to meet consumers’ networking requirements and demands, mobile products that connect to wireless networks, access points and routers will require AVB.
Historically, many companies that developed these types of products resorted to proprietary formats. Although this approach can work well when targeting niche markets for techno-savvy consumers, moving into the mainstream commercial market requires standards. Beyond enabling products to interoperate, standards also simplify the support for networks containing these products in bridged local area networks (LANs). AVB standards therefore have become a necessity for home entertainment products that evolved from standalone components – the television, radio and turntable – to Internet-enabled entertainment and gaming systems with multiple devices connected via a LAN.
This transformation has made digital entertainment available to any device that can connect to the network. But to understand how we got here and the ongoing evolution of entertainment devices, a short history lesson is helpful. Early television configurations that included cable and VCR setups had what is known as a single–source/single-listener configuration. In this simple configuration, no AVB was required as the television could only receive the single stream provided and separated it into the audio and video streams. A more typical set-up today is known as a single–source/multiple-listener configuration. The different components, or listeners, such as the speakers in a surround sound system, have digital settings to set their location and extract the appropriate data for their location.
In today’s home networks an even more complex set-up is becoming increasingly common. A multiple–source/multiple-listeners configuration operates in a scenario, where there are multiple audio and video streams coming from multiple sources into the network. From a programmable decoder, users are able to direct the streams of the media data to different components, allowing them to watch and listen to audio and video anyplace in their home network. To make this possible it is essential, however, to have an efficient and reliable connection of the network components. That is where AVB standards come in.
Recognizing this new paradigm, the IEEE is in the process of releasing new standards that will support these demanding requirements. In fact many of these standards have now advanced to implementable versions of the draft specifications and are going into products today. The AVB updates are part of the IEEE 802.1 standards, which are responsible for the higher level services in 802-compliant networks. The IEEE 802.1 working groups developed updates to the specifications that are related to the architecture, link-level security, inter-networking and network bridging, as well as Layer 2 management of 802-compliant networks. The AVB updates are being undertaken to support multimedia networking, adding quality-of-service (QoS) features to support streaming traffic.
With the development of the new IEEE Audio/Video Bridging standards, interoperability among the bridges that supported audio and video streaming, as well as a standard way to setup or maintain such a service in an 802-compliant network, will be possible for the first time. In addition, these standards apply not only for consumer devices, but also for professional audio-video setups used in mixed-wired and wireless networks. These IEEE standards will help usher in a future of new media devices operating as part of an AVB network. However, within such networks all the components will be required to support the AVB specifications and adhere to the following:
- No transparent or non-AVB devices are allowed in the AVB cloud
- AVB only supports full duplex links
- Bandwidth reservation is made for end-to-end connections for AV traffic before actual AVB data transfer
- AVB end stations negotiate the AVB capabilities using LLDP
- Maximum of 75 percent / 25 percent ratio for AVB / non-AVB traffic allowed at any AVB node
- The total number of hops or bridges allowed in an AVB network are limited by the latency requirements of the AVB data and traffic
- Traffic scheduling is required for isochronous traffic
- Latency delay for isochronous traffic within each intermediate node is limited to 250us at 100Mbps and 125us for 1Gbps links
Companies are already beginning to begin to build a new generation of products that support real audio-video broadcasting in a LAN. This is based on the draft versions of these new specifications that were released in 2009 by several different working groups. The working groups developing AVB specifications include:
- IEEE 802.1-AS: Standard for Local and Metropolitan Area Networks - Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area Networks
- IEEE 802.1Qav: Standard for Local and Metropolitan Area Networks – Virtual Bridged Local Area Networks – Amendment: Forwarding and Queuing Enhancements for Time Sensitive Streams
- IEEE 802.1Qas: Standard for Local and Metropolitan Area Networks - Virtual Bridged Local Area Networks - Amendment: 9: Stream Reservation Protocol (SRP).
In addition to the IEEE 802.1 AVB activity, the IEEE 1588-2008 (also known as PTP Version 2) specification is an integral part of a quality audio-video network solution and is referenced by the IEEE 802.1AS working group. Also being developed is an early draft version of the IEEE 802.1BA standard for Local and Metropolitan Area Networks — Audio Video Bridging (AVB) Systems. The IEEE 1722 Layer 2 Transport Protocol working group for time-sensitive streams further builds on AVB by adapting the IEEE 1394 specifications rich suite of media formats, encapsulations and synchronizations mechanisms for use in AVB networks. And finally the IEEE 1733 Layer 3 Transport Layer for AVB working group species the protocol, data encapsulations and connection management, as well as the presentation time procedure, to ensure interoperability between the audio and video end stations using standard networking protocols defined in IEEE 802 networks. This standard leverages the Real-time Transport Protocol (RTP) and IEEE 802.1 AVB protocols.
The new IEEE 802.1 AVB specifications enable this synchronized home network environment to support all of the various types of digital media that are provided by external network sources, as well as internal network streaming. Along with having AVB standards however, designers must also be able to quickly update existing products and develop new products targeted for the next generation of wired and wireless networks. To meet this consumer-driven requirement, Synopsys has already introduced a new DesignWare® Ethernet QoS IP core that implements AVB standards and can be easily integrated into a new generation of wireless routers, set-top boxes with wired and wireless connectivity, as well as professional AV systems. Combined with a robust library of data converters, audio-video components, data path components and interface IP, designers will be able to not only quickly design products, but will also be able to easily make updates to the core as specifications evolve with time.
With all the pieces coming into place to enable the design of AVB products, this is a time of exciting opportunities for those companies leading the charge into more advanced, real time audio-video products. It’s also an exciting time for consumers. Consider a typical digital home. It receives Internet access from a land-line or cable provider, with TV possibly coming from the same cable provider or perhaps from a satellite provider. Then you add in satellite radio, wireless internet, etc. — the possibilities are endless. Consumers have a range of choices and will in the future be able to build their digital homes to synchronize with and enjoy this new age of media.
John Swanson is a Senior Manager for the Market and Business Development Group in the Solutions Group at Synopsys. John has worked in the verification, integration and implementation aspects of complex IP, in engineering methodology, as well as business development and marketing. In addition, John chaired the Verification Technical Working Group in the SPIRIT Consortium and represented Synopsys on the Power.org technical subcommittee.