AVEM Classroom 08 - Digital Audio Network Protocols

Digital Audio Network Protocols

Digital audio signals can be transmitted from one source to multiple endpoint over standard networks. Over the years, many proprietary protocols such as CobraNet and Ethersound for transporting audio directly over Ethernet (but not TCI/IP) were developed, and some were fairly widely adopted. However, the introduction of the AES67 interoperability standard has simplified the choice of equipment and protocols used for networked audio. The following are among the more popular network audio protocols:

• Audio Video Bridging (AVB)  is an IEEE standard protoco that transports uncompressed video and up to 200 channels of 48/24-bit audio on real time, plus embedded control and monitoring,using Ethernet frames. It requires specialized, and relatively costly, AVB-enabled switches and network components but does not require separate network infrastucture or dedicated bandwidth.

• Dante operates over TCP/IP networks and is not dependant on an underlying Ethernet network. Over Gigabit Ethernet (1Gbps), Dante transports up to 10,24 channels of 48kHz/24-bit of audio, or 48 channels at 96kHz/24 bit. Danteis fully routable over IP networks using standard Ethernet switches, routers, and other components. It requires no separate infrastructure.

• AES67: is an interoperability standard that allows different AoIP networks to communicate with each other. It aims to provide a common language for various AoIP protocols, enhancing flexibility and reducing vendor lock-in.

• MADI (Multichannel Audio Digital Interface): is a standard for transmitting multiple channels of digital audio over a single connection, often using coaxial or optical cables. It's commonly used in broadcast and professional audio environments.

• Unicast streaming is a one-to-one connection between the streaming server sending out the AV data and client device listening to the stream. Each client has a direct relationship with the server. The client sends a request to the server, and the server sends the client a stream in response. Since the server is sending out a separate stream for each client, each additional client takes up more bandwidth. Streaming media to three clients at 100kbps actually uses 300kbps of bandwidth. Unicast streams may be sent between networks, but there will always be some buffering.

• Multicast streaming is a one-to-many transmissions: one server sends out a single stream that can then be accessed by multiple clients. Class D IP addresses (224.0.0.0 to 239.255.255.255) are set aside for multicast transmissions. In multicast streaming:

            A server sends the stream to a designated Class D IP address, called the host address. The clients subscribe to the host address. Routers send the stream to all clients subscribing to the host address. Multicast streams can only be sent across LANs or private networks: they cannot be sent over the open Internet.