Media-accelerated Global Information Carrier (MaGIC) is an

audio over Ethernet In audio and broadcast engineering, Audio over Ethernet (sometimes AoE—not to be confused with ATA over Ethernet) is the use of an Ethernet-based network to distribute real-time digital audio. AoE replaces bulky snake cables or audio-specific i ...

protocol developed by

Gibson Guitar Corporation Gibson Brands, Inc. (formerly Gibson Guitar Corporation) is an American manufacturer of guitars, other musical instruments, and professional audio equipment from Kalamazoo, Michigan, and now based in Nashville, Tennessee. The company was forme ...

in partnership with

3COM 3Com Corporation was an American digital electronics manufacturer best known for its computer network products. The company was co-founded in 1979 by Robert Metcalfe, Howard Charney and others. Bill Krause joined as President in 1981. Metcalfe ex ...

. It allows bidirectional transmission of multichannel audio data, control data, and instrument power. Revision 1.0 was introduced in 1999; the most current revision 3.0c was released in 2003. MaGIC is used in several guitar products such as Gibson Digital Guitar.

Capabilities

* Uses Category 5 UTP cables up to 100 m long * Frame-compatible with

Fast Ethernet In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. Fast Ethern ...

* 32 channels, 192 kHz sampling rate ** 32-bit integer audio ** 32-bit floating point audio ** 24-bit integer audio with 4-bit channel status and 4-bit channel command ** 32-bit raw data * Supports line network topology, star topology, and a combination of the two

Network protocol

In terms of

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

, MaGIC can use

physical Physical may refer to: *Physical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally co ...

and link layer ( MAC/ LLC) based on 100 Mbit

signalling specified in

IEEE 802.3 IEEE 802.3 is a working group and a collection standards defining the physical layer and data link layer's media access control (MAC) of wired Ethernet. The standards are produced by the working group of Institute of Electrical and Electronics Eng ...

/ IEEE 802.3af and

IEEE 802.2 IEEE 802.2 is the original name of the ISO/IEC 8802-2 standard which defines logical link control (LLC) as the upper portion of the data link layer of the OSI Model. The original standard developed by the Institute of Electrical and Electronics Engi ...

, however MaGIC implements proprietary

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

and application layers which can be used with different physical layers such as

Gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use i ...

or optical media. The frame consists of 1776 bytes. The network protocol encapsulates each frame application data (1506 bytes) into media payload (1024 bytes) and control payload (352 bytes) fields of the frame. The media payload is reserved for low-latency synchronous audio and video data, and control payload may encapsulate MaGIC control messages,

MIDI MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and re ...

data, and other protocols. Media streams are transmitted synchronously without re-sampling or buffering, ensuring minimal latency; each stream has one source and one or more destinations. Control messages are generally broadcast to the entire network each device processes the destination address and forwards to all neighbors if necessary.

Application protocol

A MaGIC device consists of the following logical entities: * Unit an access point that sends and receives control messages; * Components access points for control applications such as power on/off switches, volume controls, control surfaces, or graphical user interfaces; * Ports represent either physical connections or user applications which send media to the network; * Media slot routers route media data streams through the network. Individual control capabilities of the device are exposed through the MaGIC Control Protocol (MCP), which allow communication with Components in other devices (a maximum of 65535 per device). The network elects a System Timing Master (STM) which is the source of synchronization on for all devices. Timecode formats include MaGIC timecode and MIDI Time Code. The control data in consist of 12-bit Control Message Code (CMC) 4-bit status field, 32-bit Source (Unit and Component, 16-bit each) and 32-bit Destination, and may contain up to 32 Kbytes of data in multiple frames. The CMCs are defined into four classes: * Network Management Messages (0-127) * Well Known Application Protocols (128-511) used for encapsulation of well-known high-level protocols or for transporting messages with well-known format and structure (like MIDI). * User Control Messages (512-1023) - proprietary user messages * Reserved (1024-4095). Control links are bi-directional communication pipes between several MaGIC devices, intended for control applications. For example, a control link allows the knob on one device to regulate the remotely located volume on another device through the MaGIC network. Control links allow remote management from a computer with a sophisticated GUI which would act as a network supervisor that would manage other applications. Devices may also establish control links using proprietary mechanisms as long as they are compliant with this specification.

References

External links

* {{webarchive , url=https://web.archive.org/web/20100728213401/http://www.gibson.com/en-us/Divisions/Audio/MaGIC/ , title=MaGIC homepage at Gibson , date=2010-07-28 Audio network protocols Ethernet