Ethernet AV – What could it mean for the home media network?
Will home networks bank on Ethernet?
One of the next points of research that will be appearing for the home network is “Ethernet AV” or “AV-optimised networking”. The main goal with this research is to deliver time-sensitive content like music or video over an Ethernet-based network so it appears at each endpoint at the same time with the bare minimum of jitter or latency.
This research is being pitched at any application where a data network may be used to transport AV information. In the home, this could include multi-room installations where the same programme may be available in different rooms or multi-channel setups where a Cat5 Ethernet, Wi-Fi or HomePlug network link may be used to distribute sound to the rear-channel speakers. In a vehicle or boat, the Cat5 Ethernet cable could be used as an alternative to analogue preamp-level or speaker-level cable runs to distribute audio signals to the back of the vehicle or through the craft. The same method of moving AV signals can appeal to live-audio setups as the digital equivalent of the “snake” – a large multi-core cable used to run audio signals between the stage and the mixing desk that is located at the back of the audience. It can also appeal to the use of IP networks as the backbone for broadcast applications, whether to deliver the signal to an endpoint installed in a home network like an Internet radio or IPTV set-top box; or to work as a backbone between the broadcast studios and multiple outputs like terrestrial radio/TV transmitters and/or cable/satellite services.
The main object of the research is to establish a “master clock” for each logical AV broadcast streams within the home network that represents a piece of programme material. This then allows the endpoints (displays, speakers) to receive the same signal packets at the same time no matter how many bridges or switches the packets travel between the source and themselves.
Once this goal is achieved at the Ethernet level of the OSI stack, it could permit one to implement software in a router to provide Internet broadcast synchronisation for endpoints in a logical network pointing to the same stream. This means that if, in the case of Internet radio, there are two or more Internet-radio devices pointing to one Internet broadcast stream, they appear to receive the stream in sync even if one of the devices is on the wireless segment and another is on the Cat5 Ethernet segment.
This issue will need to be resolved in conjunction with the quality-of-service issue so that time-sensitive VoIP and audio/video applications can have priority over “best-effort” bulk data applications like e-mail and file transfer. Similarly, the UPnP AV / DLNA standards need to implement a quality-of-service differentiation mechanism for bulk transfer compared to media playback because there is the idea of implementing these standards to permit media-file transfer applications like multi-location media-library synchronisation and portable-device-to-master-library media transfer. Here, bulk transfer can simply be based on simple “best-effort” file practices while the time-critical media synchronisation can take place using higher QoS setups.
The other issue that may need to be resolved over the years is the issue of assuring quality-of-service and AV synchronisation over “last-mile” networks like DOCSIS cable, ADSL and FTTH so that IP broadcasting can be in a similar manner to classic RF-based broadcasting technologies. This also includes using the cost-effective “last-mile” technologies for studio-transmitter backbone applications, especially if the idea is to serve “infill” transmitters that cover dead spots in a broadcaster’s coverage area or to feed small cable-TV networks.
Once these issues are sorted out, then the reality of using an IP network for transmitting media files can be achieved.
