Gibson MaGIC
Encyclopedia
Media-accelerated Global Information Carrier (MaGIC) is an Audio over Ethernet
protocol developed by Gibson Guitar Corporation
in partnership with 3COM
. MaGIC 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.
, MaGIC can use physical
and link layer
(MAC
/LLC
) based on 100 Mbit Fast Ethernet
signalling specified in IEEE 802.3
/IEEE 802.3af and IEEE 802.2
, however MaGIC implements proprietary network
and application
layers which can be used with different psysical layers such as Gigabit Ethernet
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 synhronous audio and video data, and control payload may incapsulate MaGIC control messages, MIDI data, and other protocols.
Media streams are transmitted synchronously without resampling or buffering, ensuring minimal latency; each stream has one source and one or more destinations. Control messages are generally broadcast to entire network - each device processes the destination address and forwards to all neighbors if necessary.
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 includes 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:
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 remotele 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.
Audio over Ethernet
In audio engineering and broadcast engineering, Audio over Ethernet is the use of an Ethernet-based network to distribute real-time digital audio....
protocol developed by Gibson Guitar Corporation
Gibson Guitar Corporation
The Gibson Guitar Corporation, formerly of Kalamazoo, Michigan and currently of Nashville, Tennessee, manufactures guitars and other instruments which sell under a variety of brand names...
in partnership with 3COM
3Com
3Com was a pioneering digital electronics manufacturer best known for its computer network infrastructure products. The company was co-founded in 1979 by Robert Metcalfe, Howard Charney, Bruce Borden, and Greg Shaw...
. MaGIC 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 5Category 5Category 5 may refer to:*Category 5 , an album from rock band, FireHouse*Category 5 cable, used for carrying data*Category 5 computer virus, as classified by Symantec Corporation*Category 5 Records, a record label...
UTPUTPUTP may refer to:* Unlisted Trading Privileges - in finance - the statutory basis for, and by extension, an electronic network which carries quotes and trades for the New York-based NASDAQ stock_exchange....
cables up to 100 m long - Frame-compabitle with Fast EthernetFast EthernetIn computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the fast Ethernet standards 100BASE-TX is by far the most common and is supported by the...
- 32 channels, 192 kHz sampling rate
- 32-bit integer autio
- 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 OSI modelOSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
, MaGIC can use physical
Physical layer
The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....
and link layer
Data link layer
The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....
(MAC
Media Access Control
The media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
/LLC
Logical Link Control
The logical link control data communication protocol layer is the upper sub-layer of the data link layer in the seven-layer OSI reference model...
) based on 100 Mbit Fast Ethernet
Fast Ethernet
In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the fast Ethernet standards 100BASE-TX is by far the most common and is supported by the...
signalling specified in IEEE 802.3
IEEE 802.3
IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications...
/IEEE 802.3af and IEEE 802.2
IEEE 802.2
IEEE 802.2 is the IEEE 802 standard defining Logical Link Control , which is the upper portion of the data link layer of the OSI Model. The LLC sublayer presents a uniform interface to the user of the data link service, usually the network layer...
, however MaGIC implements proprietary network
Network Layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
and application
Application layer
The Internet protocol suite and the Open Systems Interconnection model of computer networking each specify a group of protocols and methods identified by the name application layer....
layers which can be used with different psysical layers such as Gigabit Ethernet
Gigabit Ethernet
Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
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 synhronous audio and video data, and control payload may incapsulate MaGIC control messages, MIDI data, and other protocols.
Media streams are transmitted synchronously without resampling or buffering, ensuring minimal latency; each stream has one source and one or more destinations. Control messages are generally broadcast to entire network - each device processes the destination address and forwards to all neighbors if necessary.
Application protocol
A MaGIC device consits 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 - oute media data streams between 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 includes 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 remotele 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.
Network Management Messages
| CMC | Name | Description |
| 0x01 | Operation Completion | Status Used for error reporting |
| 0x03 | Change of STM | Forces device resynchronization |
| 0x05 | Address Advertisement | Used for device address auto-configuration. Tentative address broadcast |
| 0x07 | Address Conflict | Reports an address conflict between two or more devices. |
| 0x09 | Neighbor Advertisement | Reports device symbolic name to neighbor devices |
| 0x11 | Add/Remove Link Record | Adds or removes a record to/from the control link table of a device component. |
| 0x13 | Establish/Drop Control Link | Establishes or disconnects a control link between two remote components. |
| 0x15 | Read/Clear Link Table | Reads or erases a control link table of a device component. |
| 0x17 | List of Linked Components | Provides list of addresses for linked components. |
| 0x19 | Read Link Parameters | Read parameters of a particular control link. |
| 0x1B | List of Link Parameters | Provides information about a control link. |
| 0x31 | Set routing table | Programs port routing table. |
| 0x33 | Read routing table | Accesses port routing table data. |
| 0x35 | Routing table data | Reports content of port routing table. |
| 0x41 | Mute | Transmits a list of data slot enable/disable masks. |
| 0x51 | Read Attribute | Requests an attribute value |
| 0x53 | Attribute Value | Transmits the requested attribute value. |
See also
- Audio over EthernetAudio over EthernetIn audio engineering and broadcast engineering, Audio over Ethernet is the use of an Ethernet-based network to distribute real-time digital audio....
- MIDI
- MADIMADIMultichannel Audio Digital Interface, MADI or AES10 is an industry-standard electronic communications protocol that defines the data format and electrical characteristics of an interface carrying multiple channels of digital audio. The Audio Engineering Society standard for MADI was originally...
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