Meyer Sound Documentation

IEEE 1722 is the standard for transporting audio, video, and control over a time-sensitive network.

An IEEE standard that enables interoperability between systems that stream time-sensitive media and data across local area networks which provide time synchronization and latency/bandwidth services. The standard specifies the protocol, device discovery, connection management, and device control procedures used to facilitate interoperability between systems that use IEEE 802 time-sensitive networking standards.

AAF is a technology specifically designed for digital nonlinear post-production and authoring, which in this case addresses the challenge of multi-vendor, cross-platform interoperability in computer-based digital video and audio production. It is defined in the AVTP standard.

An ASRC performs interpolation to fill in missing intermediate values, correcting small deviations between the clock frequencies of digital devices on a network that can cause occasional glitches.

AVB is the common name for a set of technical standards that provide improved synchronization, low latency, and reliability for switched Ethernet networks. AVB is now often referred to as AVB/TSN or simply TSN (Time-Sensitive Networking).

ATDECC is a system control protocol used for device discovery, connection management, and enumeration and control of parameters defined by IEEE 1722.

AVTP transmits the respective data in its payload area, as defined by IEEE 1722.

The container for an audio signal within a stream. AVB streams carry hundreds of channels. Milan AVB defines required channel counts that must be supported for interoperability between Milan devices.

AVB is defined by these components:

AVB controllers manage AVB networks. Routing, clock selection, and other features relevant to the AVB network can be controlled using these devices. An AVB controller can be software running on a computer connected to the AVB network, but it can also be built into the hardware of an AVB device. A Meyer Sound GALAXY processor is an example of an AVB device with a built-in controller.

There are four types of AVB devices:

A device that is capable of receiving AVB streams from an AVB talker. All available streams from all available AVB talkers on the network are selectable by the AVB listener as inputs.

AVB sink is another name for an AVB listener.

AVB source is another name for an AVB talker.

A unidirectional flow of AVTP frames with the same unique stream ID. AVB streams can vary in format, channel count, and other parameters.

A device that is an AVB source capable of transmitting AVB streams. This device will send AVB streams to AVB listeners. When an AVB talker is on the network, it advertises its presence and the streams or channels it is capable of transmitting.

The Avnu Alliance is a manufacturer consortium that creates an interoperable ecosystem, serving the precise timing and low-latency requirements of diverse applications using open standards through certification. Visit avnu.org for more details.

AAF AVTP Audio Format, as defined in AVTP, clause 7.

The BMCA is a crucial component of gPTP. It automatically determines which clock in the network is the most suitable to be the Grandmaster, considering factors like clock accuracy, stability, and priority. (For some devices, priority can be user-defined to influence the election of the gPTP Grandmaster.)

Channel names identify a specific channel within an AVB stream.

CRF is a format that only contains clock information, not audio. It can be used in AVB audio endpoints, along with the AM824 Stream Format or the AVTP Audio Format (AAF). CRF streams are a low-overhead way to distribute a "house clock" to AVB participants, allowing them to synchronize their media clocks before media streams are established. CRF streams contain clock edge timestamps that have occurred since the last CRF frame was transmitted, which gives them a lower transmit rate than standard media transport streams.

FQTSS defines traffic shaping using priority classes, as defined by IEEE 802.1Q.

gPTP precisely synchronizes distributed systems in time-critical applications. This is done through the high-precision, fast synchronization of the timers of all network participants in a distributed system as defined by IEE 801.1AS.

The gPTP Grandmaster Clock (GM) is the primary time source for a network, acting as the root of the synchronization hierarchy. It distributes time information to all other nodes in the gPTP domain, enabling precise time synchronization across the network. The Grandmaster is selected by the Best Master Clock Algorithm (BMCA) among all available clocks in the network.>

Associates multiple AVB devices connected to the same network.

The IEEE (pronounced "I-triple-E") produces technical standards, organizes conferences, publishes scientific journals, and provides certifications. The IEEE creates the standards that make technologies work together.

Notable IEEE network standards include:

A media clock is used to control the rate at which the media data is passed to or from the digital converter. For example, the GALAXY processor uses a 96 kHz media clock for audio signals. To keep all media inputs and outputs aligned in time, they need to reference the same media clock. Milan Endpoints can lock to an internal clock reference, recover the media clock from a received AVB stream, or lock to a CRF stream. A Listener must be set to use the same media clock as the Talker. Milan-certified devices use a 48 kHz CRF stream to transport the media clock stream, ensuring that the higher sample rates (96 kHz and 192 kHz) will correctly align with each other. This is independent of the sample rate of the audio stream.

Deterministic network protocol for professional audio/visual media with specification and certification led by the Avnu Alliance

The maximum amount of time it will take a signal to pass from the AVB talker to the AVB listener. This value is calculated when the stream reservation value is propagated from the AVB talker to the AVB listener.

MSRP provides a mechanism for endpoints to reserve network resources guaranteeing the sending and receiving of data streams across a network with the requested QoS. MSRP is one of the core protocols required on an AVB device (talker, listener, and switches).

MVRP is a standards-based Layer 2 network protocol for automatic configuration of VLAN information on switches. Within a layer 2 network, MVRP provides a method to dynamically share VLAN information and configure the needed VLANs. AVB automatically uses MSRP to set up the necessary stream reservations as the user makes connections.

In practice, the necessary VLANs for successful transport of AVB data are automatically configured by the AVB switch (which can also configure non-AVB devices). Users do not have to manually configure VLANs for the successful transport of AVB data.

AVB switch configures AVB and non-AVB devices

Persistent connection refers to a connection between Milan AVB devices (a talker and a listener) that remains established even if the network path is temporarily disrupted. This means that if a cable is unplugged, a switch is powered off, or an endpoint goes offline, the connection will be automatically reestablished once the interruption is resolved, without the need for manual reconfiguration.

Presentation time (also referred to as presentation time offset) ensures that audio data arrives at the listener device within the allocated time, preventing dropouts or synchronization issues. Meyer Sound Milan AVB systems use a default presentation time offset of 2ms, which is generally sufficient for most networks. This default can be adjusted, allowing for lower latency settings; however, network instability and audible dropouts can occur if the setting is set too low. The minimum presentation time offset depends on the number of switch hops and link speeds - the more switch hops, the longer the minimum presentation time offset.

A PDU is a single unit of information transmitted among entities of a network.

RSTP is a network protocol used to prevent loops in Ethernet networks introduced as part of the IEEE 802.1w standard in 2001 and is now widely used in modern networks due to its ability to quickly respond to changes in network topology.

An AVB listener has at least one sink, a virtual input. Each sink can receive one AVB stream.

SFP modules are compact, hot-swappable transceivers used in networking equipment to convert electrical signals into optical signals and vice versa. They facilitate communication between network devices, particularly for gigabit and 10-gigabit Ethernet, Fiber Channel, and other standards. SFP modules are designed for versatility, allowing different types of connections (copper or fiber optic) to be used in the same physical port.

An AVB talker has at least one source: a virtual output. Each source makes one AVB stream available on the network.

A transport protocol for time-sensitive applications in Bridged Local Area Networks.

The combination of samples per frame, channels per frame, sample rate, and bit depth of a data stream, which is specified in the IEEE 1722 standard.

SRP registers a stream and reserves the resources required through the entire path taken by the stream, as defined by IEEE 802.1Q.

TSN is a set of standards created by the Institute of Electrical and Electronics Engineers (IEEE) to enable traditional Ethernet networks to be used in deterministic, safety-critical applications.