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45-502: CobraNet was designed for and is primarily used in large commercial audio installations such as convention centers, stadiums, airports, theme parks, and concert halls. It has applications where a large number of audio channels must be transmitted over long distances or to multiple locations. CobraNet is an alternative to analog audio , which suffers from signal degradation over long cable runs due to electromagnetic interference , high-frequency attenuation , and voltage drop . Additionally,

90-455: A network segment across the physical layer . The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer. The data link layer is concerned with local delivery of frames between nodes on the same level of the network. Data-link frames, as these protocol data units are called, do not cross

135-458: A MAC layer in combination with a different LLC layer. In the ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 Gigabit/s) local area network using existing home wiring ( power lines , phone lines and coaxial cables ), the data link layer is divided into three sub-layers (application protocol convergence, logical link control and media access control). The data link layer

180-488: A conductor. Four main types of packet are used in the transmission and synchronization of CobraNet: The buffering and transmission of audio data in Ethernet packets typically incurs a delay of 256 samples or 5 + 1 ⁄ 3  milliseconds. Additional delays are introduced through analog-to-digital and digital-to-analog conversion . Latency can be reduced by sending smaller packets more often. In most cases,

225-572: A function that computes the r (amount of redundant bits) corresponding to each string of N total number of bits. The simplest error detection code is the parity bit , which allows a receiver to detect transmission errors that have affected a single bit among the transmitted N + r bits. If there are multiple flipped bits then the checking method might not be able to detect this on the receiver side. More advanced methods than parity error detection do exist providing higher grades of quality and features. A simple example of how this works using metadata

270-432: A low-cost SoC implementation of CobraNet was developed and marketed. Using CobraNet and fast Ethernet, 64 channels of uncompressed digital audio are carried through a single category 5 cable . Using gigabit or fiber optic Ethernet variants, the cost of cabling per audio channel is reduced further compared to the fast Ethernet implementation. CobraNet data can coexist with data traffic over existing Ethernet networks so

315-534: A medium simultaneously, frame collisions occur. Data-link protocols specify how devices detect and recover from such collisions, and may provide mechanisms to reduce or prevent them. Examples of data link protocols are Ethernet , the IEEE 802.11 WiFi protocols, ATM and Frame Relay . In the Internet Protocol Suite (TCP/IP), the data link layer functionality is contained within the link layer ,

360-518: A network made up of people speaking, i.e. a conversation, they will each pause a random amount of time and then attempt to speak again, effectively establishing a long and elaborate game of saying "no, you first". The Media Access Control sublayer also performs frame synchronization , which determines the start and end of each frame of data in the transmission bitstream . It entails one of several methods: timing-based detection, character counting, byte stuffing, and bit stuffing. The services provided by

405-607: A single network infrastructure can serve audio distribution and other networking needs. Audio routing can be changed at any time with network commands, and does not require rewiring. Audio is transmitted in digital form, and provides reduced susceptibility to electromagnetic interference , crosstalk , coloration, and attenuation owing to cable impedance . Use of Ethernet by CobraNet offers many high availability features such as Spanning Tree Protocol , link aggregation , and network management . For critical applications, CobraNet devices can be wired with redundant connections to

450-409: A total of 184 bundles). If each device is transmitting four bundles, then only 105 transmitters can be active, although they would be producing a total of 421 active bundles. The use of private bundles does not require any additional data in the beat packet, so these network limitations can be sidestepped by using private bundles. The CobraNet network is synchronized to a single CobraNet device known as

495-510: A total of 8 bundles per device. Each bundle houses up to 8 channels of 48 kHz , 20-bit audio, for a total capacity of 64 channels. CobraNet is somewhat scalable, in that channel capacity increases when 16-bit audio is used, and channel capacity decreases when 24-bit audio is used. The number of channels allowed per bundle is limited by the 1,500-byte Ethernet MTU . There are three types of bundles: multicast, unicast, and private: As long as multicast bundles are used sparingly, it

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540-510: A unique Ethernet protocol identifier (0x8819) assigned to Cirrus Logic. CobraNet is not designed to work over wireless networks. Bandwidth and reliability issues associated with typical 802.11 wireless networks tend to cause frequent dropouts and errors. However, wireless communication of CobraNet data can be accomplished reliably using lasers. CobraNet data is organized into channels and bundles. A typical CobraNet signal can contain up to 4 bundles of audio traveling in each direction, for

585-440: Is sampled and quantized to produce a digital signal which is represented, stored and transmitted as discrete numbers . This sound technology article is a stub . You can help Misplaced Pages by expanding it . Data link layer The data link layer , or layer 2 , is the second layer of the seven-layer OSI model of computer networking . This layer is the protocol layer that transfers data between nodes on

630-413: Is often divided into two sublayers: logical link control (LLC) and media access control (MAC). The uppermost sublayer, LLC, multiplexes protocols running at the top of the data link layer, and optionally provides flow control, acknowledgment, and error notification. The LLC provides addressing and control of the data link. It specifies which mechanisms are to be used for addressing stations over

675-456: Is the audio DSP . As self-powered speakers became more common, Cobranet was frequently used to distribute the audio signal from the DSP. These devices typically receive audio from CobraNet (and often from other digital or analog sources simultaneously), and process the audio using digital filters and effects (for example, volume control, EQ , compression , delay , crossovers , etc.) and then output

720-488: Is transmitting the word "HELLO", by encoding each letter as its position in the alphabet. Thus, the letter A is coded as 1, B as 2, and so on as shown in the table on the right. Adding up the resulting numbers yields 8 + 5 + 12 + 12 + 15 = 52, and 5 + 2 = 7 calculates the metadata. Finally, the "8 5 12 12 15 7" numbers sequence is transmitted, which the receiver will see on its end if there are no transmission errors. The receiver knows that

765-445: Is virtually impossible to exceed the bandwidth of a 100 Mbit network with CobraNet data. However, there are limitations to the maximum number of bundles that can be sent on a network, since the conductor must include data in its beat packets for every bundle on the network, and the beat packet is limited to 1,500 bytes. If each device is transmitting one bundle, there may be up to 184 transmitters active simultaneously (for

810-426: The conductor . A conductor priority can be configured to influence the selection of the conductor. Among devices with the same conductor priority, the first to establish itself on the network becomes is elected conductor. All other devices are known as performers . In the event that the conductor fails, another CobraNet device will be chosen to become the conductor within milliseconds. CobraNet cannot function without

855-480: The phonautograph and phonograph . Later, electronic techniques such as wire and tape recording were developed. Analog recording methods store analog signals directly in or on the media. The signal may be stored as a physical texture on a phonograph record , or a fluctuation in the field strength of a magnetic recording . Analog transmission methods use analog signals to distribute audio content. These are in contrast to digital audio where an analog signal

900-404: The physical layer . That transfer can be reliable or unreliable ; many data link protocols do not have acknowledgments of successful frame reception and acceptance, and some data link protocols might not even perform any check for transmission errors. In those cases, higher-level protocols must provide flow control , error checking, acknowledgments, and retransmission. The frame header contains

945-666: The CM-1 and the CM-2: Both cards are designed to be added to audio products by the manufacturer. Cirrus Logic provides a software application known as CobraCAD, which assists in the design of the network on which the CobraNet system will run. It helps to identify if there are too many routers between two CobraNet devices, if a certain latency is possible given the network configuration and other tasks. However, Cirrus Logic does not provide software to manipulate their hardware. In fact, in

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990-462: The CobraNet device may only be able to send and receive one bundle instead of the usual four. The bundle capacity of CobraNet devices are unique to the particular device and are not always the same. The Channels per bundle vs. test case latencies table illustrates the bundle capacity for a Biamp AudiaFLEX-CM DSP device. The Rx and Tx columns indicate the absolute maximum number of channels that can be received or transmitted. The Rx/Tx column represents

1035-439: The audio via CobraNet (or other digital or analog outputs). Some DSPs even have an integral telephone hybrid , and can incorporate CobraNet and other sources into a teleconferencing application. Amplifiers with integrated CobraNet help keep the signal chain digital for a longer span. Amplifiers with CobraNet inputs may also have limited DSP and network monitoring capabilities. Loudspeakers with integrated CobraNet help keep

1080-435: The boundaries of a local area network. Inter-network routing and global addressing are higher-layer functions, allowing data-link protocols to focus on local delivery, addressing, and media arbitration. In this way, the data link layer is analogous to a neighborhood traffic cop; it endeavors to arbitrate between parties contending for access to a medium, without concern for their ultimate destination. When devices attempt to use

1125-429: The conversions between analog and digital . Licensing the technology or purchasing the required CobraNet interfaces, which encode and decode the CobraNet signal, can be expensive. CobraNet is transmitted using standard Ethernet packets. Instead of using TCP/IP packets, CobraNet transfers data using data link layer packets, which travel quickly through hubs , bridges and switches , and are not as susceptible to

1170-436: The data link layer are: In addition to framing, the data link layer may also detect and recover from transmission errors. For a receiver to detect transmission errors, the sender must add redundant information as an error detection code to the frame sent. When the receiver obtains a frame it verifies whether the received error detection code matches a recomputed error detection code. An error detection code can be defined as

1215-556: The data link layer is described in more detail with media access control (MAC) and logical link control (LLC) sublayers; this means that the IEEE 802.2 LLC protocol can be used with all of the IEEE 802 MAC layers, such as Ethernet, Token Ring , IEEE 802.11 , etc., as well as with some non-802 MAC layers such as FDDI . Other data-link-layer protocols, such as HDLC , are specified to include both sublayers, although some other protocols, such as Cisco HDLC , use HDLC's low-level framing as

1260-401: The data link layer. In the Internet Protocol Suite (TCP/IP), OSI's data link layer functionality is contained within its lowest layer, the link layer . The TCP/IP link layer has the operating scope of the link a host is connected to, and only concerns itself with hardware issues to the point of obtaining hardware (MAC) addresses for locating hosts on the link and transmitting data frames onto

1305-472: The last number received is the error-detecting metadata and that all data before is the message, so the receiver can recalculate the above math and if the metadata matches it can be concluded that the data has been received error-free. Though, if the receiver sees something like a "7 5 12 12 15 7" sequence (first element altered by some error), it can run the check by calculating 7 + 5 + 12 + 12 + 15 = 51 and 5 + 1 = 6, and discard

1350-489: The latency and QoS problems commonly found in streaming protocols using a higher transport layer . However, since CobraNet does not use IP protocol , its packets cannot travel through routers , and therefore it is limited to use on a LAN ; CobraNet cannot be used over the Internet. The network over which CobraNet is transmitted must be able to operate at a minimum of 100 Mbit/s . All CobraNet packets are identified with

1395-492: The link. The link-layer functionality was described in RFC 1122 and is defined differently than the data link layer of OSI, and encompasses all methods that affect the local link. The TCP/IP model is not a top-down comprehensive design reference for networks. It was formulated for the purpose of illustrating the logical groups and scopes of functions needed in the design of the suite of internetworking protocols of TCP/IP, as needed for

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1440-462: The lowest layer of the descriptive model, which is assumed to be independent of physical infrastructure. The data link provides for the transfer of data frames between hosts connected to the physical link. Within the semantics of the OSI network architecture, the protocols of the data link layer respond to service requests from the network layer , and perform their function by issuing service requests to

1485-601: The maximum number of channels that can be received and transmitted simultaneously. CobraNet interfaces come in several varieties, some of which can support more channels than others. Additionally, CobraNet interfaces have two Ethernet ports labelled "primary" and "secondary". Only the primary Ethernet port needs to be connected, but if both ports are connected the latter acts as a fail-safe . Careful network design and topology which takes advantage of this feature can provide extremely high reliability in critical applications. The typical CobraNet interfaces provided by Cirrus Logic are

1530-430: The network. In this configuration, if one CobraNet device, cable, or Ethernet switch fails, the other takes over almost immediately. Delays over the CobraNet transmission medium itself are at least 1 + 1 ⁄ 3 milliseconds per network traversal. For some applications, these delays can be unacceptable – especially when combined with further delays resulting from propagation time , digital signal processing and

1575-673: The programmer can choose the desired CobraNet latency for a particular CobraNet device ( 5 + 1 ⁄ 3 , 2 + 2 ⁄ 3 , or 1 + 1 ⁄ 3  milliseconds). However, reducing audio latency has consequences: It may seem from the Latency vs. Channels per bundle table that more information can be sent at a lower latency. However, that is not the case. More channels can be sent per bundle, but fewer bundles can be processed simultaneously by one device. So, while eight 24-bit, 96 kHz channels can be sent in one bundle at 1 + 1 ⁄ 3 ms latency, due to processing constraints,

1620-402: The received data as defective since 6 does not equal 7. More sophisticated error detection and correction algorithms are designed to reduce the risk that multiple transmission errors in the data would cancel each other out and go undetected. An algorithm that can even detect if the correct bytes are received but out of order is the cyclic redundancy check or CRC. This algorithm is often used in

1665-449: The signal chain digital for an even longer span. In a typical unpowered speaker application, the amplifier would be housed far away from the speaker, and a long speaker cable (analog) would be run between the speaker and the amplifier. The speaker cable would be subject to interference and signal loss from electrical resistance. However, a powered speaker , powered by an electrical cable and fitted with integrated CobraNet inputs, eliminates

1710-498: The simplest of cases, no software is required by the end user. For instance, a simple breakout box which converts a CobraNet signal to eight analog audio signals would require little or no configuration by the end user apart from possibly selecting the bundle number. If configuration is required (for example, in a DSP box with integrated CobraNet I/O), then the manufacturer of the device typically supplies proprietary software for that purpose. One type of device that integrates CobraNet

1755-426: The source and destination addresses that indicate which device originated the frame and which device is expected to receive and process it. In contrast to the hierarchical and routable addresses of the network layer, layer 2 addresses are flat, meaning that no part of the address can be used to identify the logical or physical group to which the address belongs. In some networks, such as IEEE 802 local area networks,

1800-512: The speaker cable and replaces it with a network cable. Since a speaker will only use one audio channel out of the bundle, many speakers with CobraNet will also have a number of analog outputs for the rest of the channels in the bundle, which is useful in speaker cluster applications. Many digital mixing consoles are available with optional CobraNet interfaces for increased channel capacity and reduced cabling. Manufacturers who wish to integrate CobraNet connectivity into their devices either license

1845-425: The technology or purchase CobraNet interface modules or chips from Cirrus Logic. Many audio equipment manufacturers have included CobraNet in their products. Below is a partial list: Analog audio Analog recording is a category of techniques used for the recording of analog signals . This enables later playback of the recorded analog audio . Analog audio recording began with mechanical systems such as

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1890-467: The transmission medium and for controlling the data exchanged between the originator and recipient machines. MAC may refer to the sublayer that determines who is allowed to access the media at any one time (e.g. CSMA/CD ). Other times it refers to a frame structure delivered based on MAC addresses inside. There are generally two forms of media access control: distributed and centralized. Both of these may be compared to communication between people. In

1935-459: The use of digital multiplexing allows audio to be transmitted using less cabling than analog audio. CobraNet was developed in 1996 by Boulder, Colorado -based Peak Audio. Initial demonstrations were of a 10 Mbit/s point-to-point system with limited channel capacity. The first permanent installation of CobraNet in this early form was to provide background music throughout Disney's Animal Kingdom theme park. The first commercial use of CobraNet

1980-502: Was during the halftime show at Super Bowl XXXI in 1997. CobraNet was first introduced as an interoperable standard in collaboration with manufacturer QSC Audio Products . QSC was the first to license the technology from Peak Audio and marketed it under the RAVE brand. At this point CobraNet had graduated to fast Ethernet and used a unique collision avoidance technique to carry up to 64 channels per Ethernet collision domain . CobraNet

2025-438: Was subsequently enhanced to support and eventually require a switched Ethernet network. An SNMP agent was added for remote control and monitoring. Support for higher sample rates , increased bit resolutions and lowered latency capabilities were later introduced in an incremental and backward-compatible manner. In May 2001, Cirrus Logic announced that it had acquired the assets of Peak Audio. Leveraging Cirrus DSP technology,

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